SIST EN 302 890-2 V2.1.1:2020

Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)

EUROPEAN STANDARD
Intelligent Transport Systems (ITS);
Facilities Layer function;
Part 2: Position and Time management (PoTi);
Release 2
2 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)

Reference
DEN/ITS-00182
Keywords
facility, ITS, time-stamping
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3 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 10
4 Position and Time entity introduction . 11
4.1 Introduction . 11
4.2 Service provided by the PoTi entity . 12
5 PoTi functional description . 12
5.1 PoTi in the ITS Domain . 12
5.2 ITS Constellation . 12
5.3 PoTi in the ITS Station (ITS-S) architecture . 13
hitecture . 14
5.4 PoTi entity functional arc
5.4.1 General . 14
5.4.2 Position information Management . 14
5.4.3 Position Augmentation . 15
5.4.4 Reference coordinate System Conversion . 15
5.4.5 Time information Management . 15
5.4.6 Time synchronization . 15
5.4.7 Time reference system conversion Service . 15
5.5 PoTi Interfaces . 16
5.5.1 Interface to ITS applications (FA-SAP). 16
5.5.2 Interfaces to the Networking and Transport Layer (NF-SAP) . 17
5.5.3 Interfaces to the Management entity (MF-SAP) . 17
5.5.4 Interfaces to the Security entity (SF-SAP) . 17
5.5.5 Interfaces to other Facility layer entities . 18
6 Position and time requirements . 18
6.1 Requirements related to PoTi functions . 18
6.2 ITS-S reference position . 20
6.2.1 Introduction. 20
6.2.2 ITS-S reference position for passenger cars . 20
6.2.3 ITS-S reference position for Trucks . 22
6.2.4 ITS-S reference position for Busses . 28
6.2.5 ITS-S reference position for Motorcycles, mopeds and bicycles . 29
6.2.6 ITS-S reference position for Pedestrians . 31
6.2.7 ITS-S reference position for Special Vehicles . 31
6.2.8 ITS-S reference position for City-Tram . 31
6.2.9 ITS-S reference position for Roadside ITS Stations (R-ITS-Ss) . 32
6.3 Position and time confidence. 32
6.3.1 General requirements related to confidence . 32
6.3.2 Confidences related to Position Information Management . 33
6.3.2.1 Horizontal Position confidence . 33
6.3.2.2 Vertical Position confidence . 33
6.3.2.3 Horizontal Speed confidence . 33
6.3.2.4 Heading confidence . 33
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4 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
6.3.2.5 Confidence of other quantities . 34
6.3.2.6 Other accuracy estimations . 34
6.3.3 Confidences related to Reference Coordinate System Conversion Management . 34
6.3.3.1 Relative Position confidence . 34
6.3.4 Confidences related to Time Information Management . 34
7 Augmentation services . 35
7.1 Introductions . 35
7.2 GNSS Positioning Correction (GPC) Augmentation Service . 35
7.2.1 Introduction. 35
7.2.2 GPC requirements . 36
7.2.3 GPC Data processing by the V-ITS-S during transition between R-ITS-S service areas . 36
7.3 R-ITS-S ranging augmentation Service . 37
7.3.1 Introduction. 37
7.3.2 Ranging service announcements . 38
7.3.2.1 Introduction . 38
7.3.2.2 Ranging Service Application Data . 39
7.3.3 Measurement. 40
7.3.4 Ranging Rate . 40
7.3.5 Security . 40
Annex A (normative): ASN.1 specification of messages . 41
A.1 ASN.1 specification of ranging service application data . 41
History . 42
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5 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This final draft European Standard (EN) has been produced by ETSI Technical Committee Intelligent Transport
Systems (ITS), and is now submitted for the Vote phase of the ETSI standards EN Approval Procedure.
The present document is part 2 of a multi-part deliverable covering Facilities Layer function, as identified below:
Part 1: "Services Announcement (SA) specification";
Part 2: "Position and Time management (PoTi); Release 2".
The present document is based on inputs provided by various European projects including AutoNet, Concorda,
Ensemble, Hights, PRoPART, Dutch-Germany-Austria Corridor, Scope@F, A58 (NL), PRE-DRIVE C2X, DRIVE
C2X, SafeSpot, CVIS, CoVeL, SCOR@F, simTD, etc.
Proposed national transposition dates
Date of latest announcement of this EN (doa): 3 months after ETSI publication
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 6 months after doa
Date of withdrawal of any conflicting National Standard (dow): 6 months after doa
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
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6 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
Introduction
Intelligent Transportation Systems Cooperative, Connected and Automated Mobility (CCAM) related use cases in the
ITS environment as specified in the ETSI ITS architecture (ETSI EN 302 665 [i.1]) can be distributed over multiple ITS
stations (ITS-Ss). ITS-Ss interact in the ITS system to exchange sensor data and traffic related information to make each
other aware of traffic safety or traffic efficiency circumstances and situations by which each ITS-S equipped road user,
whether automated or not, can improve their safety and efficiency related decisions.
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7 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
1 Scope
The present document provides the specification of the Position and Time (PoTi) services. It includes functional and
operational requirements for the position and time data to support ITS Applications. In addition, it includes the
definition of syntax and semantics of messages exchanged between ITS Stations (ITS-Ss) to augment the position and
time accuracy. Finally, it specifies the facilities layer protocol in support of such message exchanges.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 103 301: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of
Applications; Facilities layer protocols and communication requirements for infrastructure
services".
[2] RTCM 10402.3: "Recommended Standards for Differential GNSS (Global Navigation Satellite
Systems) Service".
[3] RTCM 10403.3: "Differential GNSS (Global Navigation Satellite Systems) Services - Version 3".
[4] ETSI EN 302 663 (V1.3.1) (01-2020): "Intelligent Transport Systems (ITS); ITS-G5 Access layer
specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
[5] ETSI EN 302 890-1 (V1.2.1) (07-2019): "Intelligent Transport Systems (ITS); Facilities layer
function; Part 1: Services Announcement (SA) specification".
[6] World Geodetic System 1984 (WGS84).
NOTE: Available at http://earth-info.nga.mil/GandG/update/index.php?dir=wgs84&action=wgs84#tab_wgs84-
res.
[7] ISO 8855 (2011): "Road Vehicles -- Vehicle dynamics and road-holding ability -- Vocabulary".
[8] ETSI TS 103 248: "Intelligent Transport Systems (ITS); GeoNetworking; Port Numbers for the
Basic Transport Protocol (BTP)".
[9] ISO 5725-1 (1994): "Accuracy (trueness and precision) of measurement methods and results --
Part 1: General principles and definitions".
[10] ETSI TS 102 894-2: "Intelligent Transport Systems (ITS); Users and applications requirements;
Part 2: Applications and facilities layer common data dictionary".
[11] ETSI EN 302 931 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Geographical Area Definition".
[12] ISO/TS 16460:2016: "Intelligent transport systems -- Communications access for land mobiles
(CALM) -- Communication protocol messages for global usage".
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[13] Recommendation ITU-T X.691/ISO/IEC 8825-2:2015: "Information technology - ASN.1 encoding
rules: Specification of Packed Encoding Rules (PER)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[i.2] ETSI TR 102 638 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Definitions".
[i.3] ETSI EN 302 637-2: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[i.4] ETSI EN 302 637-3: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 3: Specifications of Decentralized Environmental Notification Basic
Service".
[i.5] ETSI TS 102 894-1 (V1.1.1): "Intelligent Transport Systems (ITS); Users and applications
requirements; Part 1: Facility layer structure, functional requirements and specifications".
[i.6] ETSI TR 103 299: "Intelligent Transport System (ITS); Cooperative Adaptive Cruise Control
(CACC); Pre-standardization study".
[i.7] ETSI TS 103 324: "Intelligent Transport Systems (ITS); Cooperative Perception Services".
[i.8] ETSI TS 103 246-1 (V1.2.1) (03-2017): "Satellite Earth Stations and Systems (SES); GNSS based
location systems; Part 1: Functional requirements".
[i.9] EUREF: European Terrestrial Reference System 89 (ETRS89).
NOTE: Available at http://etrs89.ensg.ign.fr.
[i.10] ETSI TR 101 607 (V1.1.1) (05-2013): "Intelligent Transport Systems (ITS); Cooperative ITS
(C-ITS); Release 1".
[i.11] ISO 3534-1 (10-2009): "Statistics - Vocabulary and symbols - Part 1: General statistical terms and
terms".
[i.12] ETSI TS 136 305 (V11.2.0): "LTE; Evolved Universal Terrestrial Radio Access Network (E-
UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN
(3GPP TS 36.305 version 11.2.0 Release 11)".
[i.13] IETF RFC 5905 (June 2010): "Network Time Protocol Version 4: Protocol and Algorithms
Specification".
[i.14] IEC 60050: "International Electrotechnical Vocabulary", 113-01-08 (instant), 113-01-10 (time
interval), 113-01-13 (duration).
[i.15] IS-QZSS-L6-001: "Quasi-Zenith Satellite System Interface Specification Centimeter Level
Augmentation Service".
NOTE: Available at https://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-l6-001.pdf.
[i.16] IETF RFC 8173 (June 2017): "Precision Time Protocol Version 2 (PTPv2) Management
Information Base".
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[i.17] EN ISO 22418: "Intelligent transport systems - Fast service announcement protocol (FSAP) for
general purposes in ITS" (produced by CEN).
TM
1609.3: "IEEE Standard for Wireless Access in Vehicular Environments (WAVE) --
[i.18] IEEE
Networking Services".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
accuracy: closeness of a measured value to a standard or known value
heading: orientation of the horizontal velocity vector with respect to the WGS84 [6] North (clockwise), unless
otherwise noted
horizontal speed: magnitude of horizontal velocity-vector of the reference position point
horizontal velocity vector: projection of the 3D velocity vector on the WGS84 [6] ellipsoid
integrity risk: probability, per unit of time, of having a Parameter Failure without issuing an alert within the
Time-to-Alert
ITS constellation: group of ITS-Ss which are exchanging ITS data among themselves
ITS time: time based on TAI
st
NOTE: Epoch of this time is set to 2004-01-01T00:00:00Z, that is 0 seconds on 1 of January 2004 UTC.
parameter failure: failure occurring when the position and time entity is unable to estimate parameters with an error
less than the maximum tolerable error (err > err_max)
position integrity: measure of the trust that can be placed in the correctness of the estimated Parameters supplied by the
Position and Time entity
NOTE: Integrity includes the ability of the equipment (at the Position and Time entity and/or User level) to
compute timely and valid alerts when the estimated Parameters do not need to be used for the operation of
interest.
protection level: estimated bound on the Parameter Error from the Position and Time entity at a defined confidence
level such as 50 %, 75 %, 95 %, 99 %, etc., delivered with the Parameters
station clock: clock representing ITS time in an ITS Station
Time-to-Alert: maximum allowable elapsed time from the onset of a Parameter Failure until the equipment annunciates
the alert
velocity: vector indicating speed in a particular direction
vertical velocity vector: projection of the 3D velocity vector on the normal vector of the WGS84 [6] Ellipsoid
3.2 Symbols
For the purposes of the present document, the following symbols apply:
Tsys ITS Station Time
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10 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3D 3 Dimensional
ACC Automatic Crouse Control
ACK Acknowledgement
ASN Abstract Syntax Notation
BSA Basic Set of Applications
CA Cooperative Awareness (service)
CACC Cooperative Adaptive Cruise Control
CAM Cooperative Awareness Message
CCAM Cooperative, Connected and Automated Mobility
CDD Common Data Dictionary
CP Collective Perception (service)
CVIS Cooperative Vehicle-Infrastructure Systems
DEN Decentralized Environmental Notification
DENM Decentralized Environmental Notification Message
D-GNSS Differential Global Navigation Satellite System
ECU Electronic Control Unit
EDAS EGNOS Data Access Service
EGNOS European Geostationary Navigation Overlay Service
EU European Union
FA-SAP Facilities to Applications Service Access Point
GLONASS GLObal NAvigation Satellite System
GNSS Global Navigation Satellite Systems
GPC GNSS Positioning Correction
GPS Global Positioning System
GRM GPS Raw data Message
IEC International Electrotechnical Commission
IETF Internet Engineering Task Force
ISO International Organization for Standardization
ITRF International Terrestrial Reference Frame
ITS Intelligent Transport Systems
ITS-C ITS Constellation
ITS-S ITS Station
ITU-T International Telecommunication Union - Telecommunication standardization sector
MAC Media Access Control
NA Not Applicable
NF-SAP Network to Facilities Service Access Point
NGA National Geospatial-intelligence Agency
NRTK Network Real Time Kinematic
NTP Network Time Protocol
PDU Protocol Data Unit
PoTi Position and Time
PPP Precise Point Positioning
PSID Provider Service Identifier
RAN Radio Access Network
RF Radio Frequency
RFC Request For Comment
R-ITS-S Roadside ITS Station
RTCM Radio Technical Commission for Maritime services
RTCMEM Radio Technical Commission for Maritime services Environmental Message
RTK Real Time Kinematic
SA Service Announcement
SAM Service Announcement Message
SF-SAP Security to Facilities Service Access Point
SI Standard International
SIFS Short InterFrame Space
SLR Satellite Laser Ranging
SPATEM Signal Phase And Timing Extended Message
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SSR Sirius Satellite Radio
TAI International Atomic Time scale
TCU Transmission Control Unit
ToF Time-of-Flight
UE User Equipment
UPER Unaligned Packet Encoding Rules
UTC Coordinated Universal Time
UWB Ultra Wide Band
VLBI Very-Long-Baseline Interferometry
VRU Vulnerable Road User
WGS World Geodetic System
WGS84 World Geodetic System 1984
4 Position and Time entity introduction
4.1 Introduction
ITS applications such as specified in the Basic Set of Applications specification (BSA) ETSI TR 102 638 [i.2] require
the exchange of position and time information as part of the information exchange among ITS-Ss. As initial ITS
location based services, the Cooperative Awareness (CA) basic service ETSI EN 302 637-2 [i.3] and similar, the road
traffic event Decentralized Environmental Notification (DEN) basic service ETSI EN 302 637-3 [i.4] are developed.
These services and their data exchanges are dependent on position and time information. In this and the following
clauses it is understood that "position" means kinematic and attitude state as defined in clause 5.4.1 which includes
attitude and movement parameters including velocity, heading, horizontal speed and optionally others.
In order to realize road ITS safety related applications, ITS-Ss need to have an absolute knowledge about their position
and have a common synchronized knowledge about time to be able to value information received from another ITS-Ss.
To realize this absolute knowledge about position and time, an ITS-S may be equipped with a Global Navigation
Satellite Systems (GNSS) making use of Galileo or GPS and/or other satellite navigation technologies, providing
satellite positioning information to the PoTi entity.
Depending on the applications supported by an ITS-S, the qualitive requirements on the accuracy, integrity and
reliability of the position and time references may vary. As the CA basic service (ETSI EN 302 637-2 [i.3]) specifies,
road safety applications may require the ITS-S to transmit position and time information at intervals of about 10 times a
second, while new applications such as Platooning requires intervals of ≥ 20 times a second.
ITS applications are based on the exchange of information among ITS-Ss and therefore ITS applications operating in
one ITS-S are depending on the information provided by other ITS-Ss, a set of minimum requirements to be supported
by all ITS-Ss needs to be agreed. As new ITS applications are constantly being developed these minimum requirements
need to be set for a selective set of (grouped) ITS applications. At the current state an ETSI Release 1 set of ITS
standards (ETSI TR 101 607 [i.10]) is the reference for the Release 1 equipment and therefore it provides the
requirements for the Release 1 PoTi requirements.
Based on the current developments of new services and related analyses by EU projects further optional requirements
are included.
The position and time (PoTi) service as identified in ETSI TS 102 894-1 [i.5] residing in the facility layer is an essential
part of the ITS; it provides time and position information to all ITS applications and services.
In order to satisfy the application requirements and different Releases of application sets, the PoTi entity may include
various methods to ensure the accuracy, integrity and reliability of the position and time references as required by the
ITS applications supported by the ITS-S.
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12 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
4.2 Service provided by the PoTi entity
The facility layer PoTi entity manages the position and time information for use by ITS applications, facility, network,
management and security layers. For this purpose, it gets information from sub-system entities such as GNSS, sensors
and other sub-system entities. Given the ITS application requirements in terms of position and time accuracy, PoTi may
use augmentation services to improve the position and time accuracy. Various augmentation methods may be applied.
PoTi may support these augmentation services by providing messages services broadcasting augmentation data. For
instance, a roadside ITS-S may broadcast correction information for GNSS to oncoming vehicle ITS-S; ITS-Ss may
exchange raw GPS data or may exchange terrestrial radio position and time relevant information. PoTi maintains and
provides the position and time reference information according to the application and facility and other layer service
requirements in the ITS-S.
5 PoTi functional description
5.1 PoTi in the ITS Domain
The ITS reference architecture is defined in ETSI EN 302 665 [i.1]. It defines the ITS Station (ITS-S) architecture as
part of the ITS domain. In the ITS domain, at a particular time an ITS-S may be in a situation when no other ITS-Ss are
active within its communication range, while at another moment it may be in a situation in which there are many ITS-Ss
active within its communication range. An ITS Constellation (ITS-C) is a group of ITS-Ss that communicate with each
other. ITS-Cs may overlap, and an ITS-S may be active in several ITS-Cs but in general not necessary in all as not all
ITS-Cs need to overlap (see Figure 1).

Figure 1: Momentary ITS-Cs in the ITS domain
5.2 ITS Constellation
ITS services are based on sharing information between ITS-Ss. Applications in ITS-Ss receive messages containing
information from neighbouring ITS-Ss and use this to provide services in the receiving ITS-S. It is therefore essential
that receiving ITS-Ss can identify the time and position relevance of the content of each message. ITS-Ss in the same
ITS-C shall have a consistent understanding of position and time for the services they support. When ITS-C overlap,
only those in the overlapping area shall have an understanding of position and time, of both constellations but other
ITS-Ss not (see Figure 1).
ITS applications and services may have different time and position requirements. Depending on the ITS services to be
supported by an ITS-S, the time and position accuracy requirements toward the facility service PoTi may differ but are
required to be commonly agreed. To ensure that the existing ITS-Ss in an ITS-C can support each other's active ITS
services, common minimum requirements are agreed based on the ITS Releases. Currently Release 1 and Release 2 ITS
services are distinguished. Minimum common requirements for the Release 1 set of applications are defined in ETSI
TR 102 638 [i.2]. Minimum requirements for Release 2 cannot be set at this time.
The PoTi entity of any ITS-S in a given ITS-C should ensure that Tsys ≈ T (T is the ITS Time) within this ITS-C.
n
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13 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
IT S- S4
IT S-S2
IT S-S6
PoTi
ITS- S1
PoTi
PoTi
ITS-S 3 ITS- S5
Tsys ≈T
PoTi
Tsys ≈T
2 Po Ti PoTi
Tsys ≈T
Tsys ≈T
Tsys ≈T Tsys ≈T
3 5
Figure 2: Momentary ITS-C
5.3 PoTi in the ITS Station (ITS-S) architecture
PoTi is a facilities layer entity that manages the Position and Time information required by the application, facility,
network, management and security layers. It ensures ITS time synchronicity between the ITS-Ss in the ITS system, it
maintains the data quality (e.g. by monitoring time deviation) and manages updates of the kinematic and attitude state
and time. The PoTi entity may include augmentation services to improve the position and time accuracy, integrity, and
reliability. Among these methods, communication technologies may be used to provide positioning assistance from
mobile to mobile ITS-Ss and infrastructure to mobile ITS-Ss.
The PoTi entity interfaces with ITS applications and other facility layer entities in order to provide position and time
information, such as CA basic service described in ETSI EN 302 637-2 [i.3] and DEN basic service described in ETSI
EN 302 637-3 [i.4], C-ACC described in ETSI TR 103 299 [i.6] and CP described in ETSI TS 103 324 [i.7] basic
service. Figure 3 presents PoTi in the ITS-S architecture according to ETSI EN 302 665 [i.1].

Figure 3: The PoTi entity its interfaces to other facilities entities via the FA-SAP,
and its interfaces in the ITS-S architecture according to ETSI EN 302 665 [i.1]
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5.4 PoTi entity functional architecture
5.4.1 General
Figure 4 illustrates functions and interfaces of the PoTi entity.

Figure 4: PoTi entity functional architecture
The functions are described in the following clauses. The interfaces are described in clause 5.5.
5.4.2 Position information Management
• The kinematic and attitude state of the rigid body contained in the ITS-S included position, velocity,
acceleration, orientation, angular velocity and possible other motion related information. The position
information at a specific moment in time is referred to as the kinematic and attitude state including time, of the
rigid body.
NOTE 1: If not otherwise stated all these quantities are provided in 3D.
• In addition to the kinematic and attitude state, PoTi should also maintain information on the confidence of the
kinematic and attitude state variables.
An ITS-S should at least be functional when the system of which it is part of is in operation. The PoTi entity should be
functional when the ITS-S is operating.
NOTE 2: As for many implementations it takes time for the PoTi entity to provide proper information. The PoTi
entity may be functional for a period of time when the system of which it is part of is not operational.
Once the system is reactivated, the PoTi entity should validate the kinematic and attitude state and
confidences whether it still meets the system requirements.
An ITS-S may use multiple means of positioning if they are available (e.g. GNSS, inertial sensors, odometer, cameras,
terrestrial radio ranging, map matching, etc.). Depending on the applications and services an ITS-S needs to support an
ITS-S could use single or multiple augmentation services to improve its position and time accuracy.
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15 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
5.4.3 Position Augmentation
• The Position augmentation function uses externally sourced assistance data or measurements in order to
improve positioning performance by eliminating system errors common to many ITS-Ss.
• Satellite based augmentation: in Europe, European Geostationary Navigation Overlay Service (EGNOS) is
provided to improve GNSS position accuracy. RTK and SSR services are also augmentation services that can
be used by GNSS receivers; they may be distributed across satellite channels or terrestrial communication
links including from other ITS-Ss.
• Cooperative positioning: ITS-Ss may exchange information to improve the relative positioning. Ground based
augmentation such as EGNOS, RTCM or SSR based (PPP-RTK) services can be distributed over terrestrial
communications channels to augment GNSS data. R-ITS-S could transmit RTCM or SSR correction
information to vehicle ITS-Ss, as specified in ETSI TS 103 301 [1].
5.4.4 Reference coordinate System Conversion
The reference coordinate System Conversion function converts the kinematic and attitude state between different
reference systems, e.g. to and from local (vehicle) coordinate systems or ITRF14 or ETRS89. Relative positioning is a
sub function of Reference coordinate System Conversion and involves the conversion from the WGS84 [6] coordinate
system to local coordinates systems, as e.g. used in DENM traces.
The Reference coordinate System Conversion is used for instance to describe relevance areas:
• Where the relevance area is an ellipse or a rectangle, the Cartesian coordinates of the area center and of the
current position shall be calculated as specified in the ETSI EN 302 931 [11]. For this purpose, the 'local
tangent plane' method is recommended, or another method delivering the same accuracy.
5.4.5 Time information Management
ITS time shall be defined as a time based on TAI. Epoch of ITS time is set to 2004-01-01T00:00:00Z, that is 0 seconds
st
on 1 of January 2004 UTC. ITS time is the general time base for all ITS-Ss. An ITS-S's representation of ITS Time is
referred to as the station clock. A moment in time, or instant, after the epoch can be represented by a timestamp.
A timestamp is the duration of the time interval between the epoch and the instant, derived from the station clock
according to IEC 60050 [i.14].
Time Information Management manages the quality of the station clock, handles updates of the ITS-S time information
and provides the time information to other entities in the ITS-S.
For the ITS-S time information the same activation requirements are valid as for ITS-S position information as
identified in clause 5.4.2.
5.4.6 Time synchronization
The ITS Station should synchronize its station clock by means of one or more external time services (GNSS, NTP),
taking into account accuracy, integrity and reliability of the external service.
NOTE: ITS-Time is based on TAI, and therefore has no special treatments of leap-seconds that are introduced in
UTC at specific moments in time. UTC itself is based on counting SI seconds since an epoch, similar to
ITS-Time. However, several time synchronization protocols, like NTP, modify the clock that counts the
number of SI seconds since the epoch, to facilitate easier conversion from clock counter values to UTC
date/time. Therefore, care should be taken when using such synchronization services to correctly treat the
insertion of UTC leap seconds, specifically also during the insertion of the leap second.
5.4.7 Time reference system conversion Service
• The time reference system conversion takes care of converting from ITS Time to other time reference systems.
PoTi should support the conversion between ITS Time and UTC and vice versa when required by applications.
Support for other time reference systems can also be supported.
ETSI
16 Final draft ETSI EN 302 890-2 V2.1.1 (2020-08)
NOTE: UTC is used as the time basis for time information in several messages, like SPATEM in ETSI
TS 103 301 [1].
5.5 PoTi Interfaces
5.5.1 Interface to ITS applications (FA-SAP)
PoTi provides position and time information to ITS applications residing in the ITS-S via the interface IF.Appl as
illustrated in Figure 4. In one possible implementation, the interface IF.Appl may be implemented as SF-SAP as
illustrated in Figure 3.
In one possible implementation of this interface, the position and time information (including confidence values) may
be provided by the PoTi module upon request or automatically upon a given trigger, e.g. when the system receives an
update.
Via the FA-SAP interface security and integrity information could be provided by the PoTi service originating source
entity (such as on-board sensors or GNSS).
Although PoTi specifies checks for integrity and security, however these checks are also done by misbehaviour
detection functions.
Interfaces to local sensor in an ITS station may exist. PoTi could provide an interface to functions harmonizing local
sensor data input.
An Application layer function may receive data from POTI using the parameters shown in Table 1.
The following minimum data set may be made available via IF.App. Additional data may be made available. All data
shall refer to reference point 0, see clause 6.2. Data for other reference points may be provided. All data provided need
to fulfil the specifications and requirements stipulated in clause 5.4 and clause 6.
Table 1: FA-SAP minimum data set
Category Data Data requirement Mandatory/Optional
Reference point Reference point identifier See clause 6.2 Conditional: mandatory only when
data for multiple reference points
are provided
Time Timestamp See clause 5.4.4 Mandatory
Position Latitude See clause 6.1 Mandatory
Longitude See clause
...

EUROPEAN STANDARD
Intelligent Transport Systems (ITS);
Facilities Layer function;
Part 2: Position and Time management (PoTi);
Release 2
2 ETSI EN 302 890-2 V2.1.1 (2020-10)

Reference
DEN/ITS-00182
Keywords
facility, ITS, time-stamping
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ETSI
3 ETSI EN 302 890-2 V2.1.1 (2020-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 10
4 Position and Time entity introduction . 11
4.1 Introduction . 11
4.2 Service provided by the PoTi entity . 12
5 PoTi functional description . 12
5.1 PoTi in the ITS Domain . 12
5.2 ITS Constellation . 12
5.3 PoTi in the ITS Station (ITS-S) architecture . 13
5.4 PoTi entity functional architecture . 14
5.4.1 General . 14
5.4.2 Position information Management . 14
5.4.3 Position Augmentation . 15
5.4.4 Reference coordinate System Conversion . 15
5.4.5 Time information Management . 15
5.4.6 Time synchronization . 15
5.4.7 Time reference system conversion Service . 15
5.5 PoTi Interfaces . 16
5.5.1 Interface to ITS applications (FA-SAP). 16
5.5.2 Interfaces to the Networking and Transport Layer (NF-SAP) . 17
5.5.3 Interfaces to the Management entity (MF-SAP) . 17
5.5.4 Interfaces to the Security entity (SF-SAP) . 17
5.5.5 Interfaces to other Facility layer entities . 18
6 Position and time requirements . 18
6.1 Requirements related to PoTi functions . 18
6.2 ITS-S reference position . 20
6.2.1 Introduction. 20
6.2.2 ITS-S reference position for passenger cars . 20
6.2.3 ITS-S reference position for Trucks . 22
6.2.4 ITS-S reference position for Busses . 28
6.2.5 ITS-S reference position for Motorcycles, mopeds and bicycles . 29
6.2.6 ITS-S reference position for Pedestrians . 31
6.2.7 ITS-S reference position for Special Vehicles . 31
6.2.8 ITS-S reference position for City-Tram . 31
6.2.9 ITS-S reference position for Roadside ITS Stations (R-ITS-Ss) . 32
6.3 Position and time confidence. 32
6.3.1 General requirements related to confidence . 32
6.3.2 Confidences related to Position Information Management . 33
6.3.2.1 Horizontal Position confidence . 33
6.3.2.2 Vertical Position confidence . 33
6.3.2.3 Horizontal Speed confidence . 33
6.3.2.4 Heading confidence . 33
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4 ETSI EN 302 890-2 V2.1.1 (2020-10)
6.3.2.5 Confidence of other quantities . 34
6.3.2.6 Other accuracy estimations . 34
6.3.3 Confidences related to Reference Coordinate System Conversion Management . 34
6.3.3.1 Relative Position confidence . 34
6.3.4 Confidences related to Time Information Management . 34
7 Augmentation services . 35
7.1 Introductions . 35
7.2 GNSS Positioning Correction (GPC) Augmentation Service . 35
7.2.1 Introduction. 35
7.2.2 GPC requirements . 36
7.2.3 GPC Data processing by the V-ITS-S during transition between R-ITS-S service areas . 36
7.3 R-ITS-S ranging augmentation Service . 37
7.3.1 Introduction. 37
7.3.2 Ranging service announcements . 38
7.3.2.1 Introduction . 38
7.3.2.2 Ranging Service Application Data . 39
7.3.3 Measurement. 40
7.3.4 Ranging Rate . 40
7.3.5 Security . 40
Annex A (normative): ASN.1 specification of messages . 41
A.1 ASN.1 specification of ranging service application data . 41
History . 42

ETSI
5 ETSI EN 302 890-2 V2.1.1 (2020-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Intelligent Transport Systems (ITS).
The present document is part 2 of a multi-part deliverable covering Facilities Layer function, as identified below:
Part 1: "Services Announcement (SA) specification";
Part 2: "Position and Time management (PoTi); Release 2".
The present document is based on inputs provided by various European projects including AutoNet, Concorda,
Ensemble, Hights, PRoPART, Dutch-Germany-Austria Corridor, Scope@F, A58 (NL), PRE-DRIVE C2X, DRIVE
C2X, SafeSpot, CVIS, CoVeL, SCOR@F, simTD, etc.

National transposition dates
Date of adoption of this EN: 19 October 2020
Date of latest announcement of this EN (doa): 31 January 2021
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 July 2021
Date of withdrawal of any conflicting National Standard (dow): 31 July 2021

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 302 890-2 V2.1.1 (2020-10)
Introduction
Intelligent Transportation Systems Cooperative, Connected and Automated Mobility (CCAM) related use cases in the
ITS environment as specified in the ETSI ITS architecture (ETSI EN 302 665 [i.1]) can be distributed over multiple ITS
stations (ITS-Ss). ITS-Ss interact in the ITS system to exchange sensor data and traffic related information to make each
other aware of traffic safety or traffic efficiency circumstances and situations by which each ITS-S equipped road user,
whether automated or not, can improve their safety and efficiency related decisions.

ETSI
7 ETSI EN 302 890-2 V2.1.1 (2020-10)
1 Scope
The present document provides the specification of the Position and Time (PoTi) services. It includes functional and
operational requirements for the position and time data to support ITS Applications. In addition, it includes the
definition of syntax and semantics of messages exchanged between ITS Stations (ITS-Ss) to augment the position and
time accuracy. Finally, it specifies the facilities layer protocol in support of such message exchanges.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 103 301: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of
Applications; Facilities layer protocols and communication requirements for infrastructure
services".
[2] RTCM 10402.3: "Recommended Standards for Differential GNSS (Global Navigation Satellite
Systems) Service".
[3] RTCM 10403.3: "Differential GNSS (Global Navigation Satellite Systems) Services - Version 3".
[4] ETSI EN 302 663 (V1.3.1) (01-2020): "Intelligent Transport Systems (ITS); ITS-G5 Access layer
specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
[5] ETSI EN 302 890-1 (V1.2.1) (07-2019): "Intelligent Transport Systems (ITS); Facilities layer
function; Part 1: Services Announcement (SA) specification".
[6] World Geodetic System 1984 (WGS84).
NOTE: Available at http://earth-info.nga.mil/GandG/update/index.php?dir=wgs84&action=wgs84#tab_wgs84-
res.
[7] ISO 8855 (2011): "Road Vehicles -- Vehicle dynamics and road-holding ability -- Vocabulary".
[8] ETSI TS 103 248: "Intelligent Transport Systems (ITS); GeoNetworking; Port Numbers for the
Basic Transport Protocol (BTP)".
[9] ISO 5725-1 (1994): "Accuracy (trueness and precision) of measurement methods and results --
Part 1: General principles and definitions".
[10] ETSI TS 102 894-2: "Intelligent Transport Systems (ITS); Users and applications requirements;
Part 2: Applications and facilities layer common data dictionary".
[11] ETSI EN 302 931 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Geographical Area Definition".
[12] ISO/TS 16460:2016: "Intelligent transport systems -- Communications access for land mobiles
(CALM) -- Communication protocol messages for global usage".
ETSI
8 ETSI EN 302 890-2 V2.1.1 (2020-10)
[13] Recommendation ITU-T X.691/ISO/IEC 8825-2:2015: "Information technology - ASN.1 encoding
rules: Specification of Packed Encoding Rules (PER)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[i.2] ETSI TR 102 638 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Definitions".
[i.3] ETSI EN 302 637-2: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[i.4] ETSI EN 302 637-3: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 3: Specifications of Decentralized Environmental Notification Basic
Service".
[i.5] ETSI TS 102 894-1 (V1.1.1): "Intelligent Transport Systems (ITS); Users and applications
requirements; Part 1: Facility layer structure, functional requirements and specifications".
[i.6] ETSI TR 103 299: "Intelligent Transport System (ITS); Cooperative Adaptive Cruise Control
(CACC); Pre-standardization study".
[i.7] ETSI TS 103 324: "Intelligent Transport Systems (ITS); Cooperative Perception Services".
[i.8] ETSI TS 103 246-1 (V1.2.1) (03-2017): "Satellite Earth Stations and Systems (SES); GNSS based
location systems; Part 1: Functional requirements".
[i.9] EUREF: "European Terrestrial Reference System 89 (ETRS89)".
NOTE: Available at http://etrs89.ensg.ign.fr.
[i.10] ETSI TR 101 607 (V1.1.1) (05-2013): "Intelligent Transport Systems (ITS); Cooperative ITS
(C-ITS); Release 1".
[i.11] ISO 3534-1 (10-2009): "Statistics - Vocabulary and symbols - Part 1: General statistical terms and
terms".
[i.12] ETSI TS 136 305 (V11.2.0): "LTE; Evolved Universal Terrestrial Radio Access Network
(E-UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN
(3GPP TS 36.305 version 11.2.0 Release 11)".
[i.13] IETF RFC 5905 (June 2010): "Network Time Protocol Version 4: Protocol and Algorithms
Specification".
[i.14] IEC 60050: "International Electrotechnical Vocabulary", 113-01-08 (instant), 113-01-10 (time
interval), 113-01-13 (duration).
[i.15] IS-QZSS-L6-001: "Quasi-Zenith Satellite System Interface Specification Centimeter Level
Augmentation Service".
NOTE: Available at https://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-l6-001.pdf.
[i.16] IETF RFC 8173 (June 2017): "Precision Time Protocol Version 2 (PTPv2) Management
Information Base".
ETSI
9 ETSI EN 302 890-2 V2.1.1 (2020-10)
[i.17] EN ISO 22418: "Intelligent transport systems - Fast service announcement protocol (FSAP) for
general purposes in ITS" (produced by CEN).
TM
1609.3: "IEEE Standard for Wireless Access in Vehicular Environments (WAVE) --
[i.18] IEEE
Networking Services".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
accuracy: closeness of a measured value to a standard or known value
heading: orientation of the horizontal velocity vector with respect to the WGS84 [6] North (clockwise), unless
otherwise noted
horizontal speed: magnitude of horizontal velocity-vector of the reference position point
horizontal velocity vector: projection of the 3D velocity vector on the WGS84 [6] ellipsoid
integrity risk: probability, per unit of time, of having a Parameter Failure without issuing an alert within the
Time-to-Alert
ITS constellation: group of ITS-Ss which are exchanging ITS data among themselves
ITS time: time based on TAI
st
NOTE: Epoch of this time is set to 2004-01-01T00:00:00Z, that is 0 seconds on 1 of January 2004 UTC.
parameter failure: failure occurring when the position and time entity is unable to estimate parameters with an error
less than the maximum tolerable error (err > err_max)
position integrity: measure of the trust that can be placed in the correctness of the estimated Parameters supplied by the
Position and Time entity
NOTE: Integrity includes the ability of the equipment (at the Position and Time entity and/or User level) to
compute timely and valid alerts when the estimated Parameters do not need to be used for the operation of
interest.
protection level: estimated bound on the Parameter Error from the Position and Time entity at a defined confidence
level such as 50 %, 75 %, 95 %, 99 %, etc., delivered with the Parameters
station clock: clock representing ITS time in an ITS Station
Time-to-Alert: maximum allowable elapsed time from the onset of a Parameter Failure until the equipment annunciates
the alert
velocity: vector indicating speed in a particular direction
vertical velocity vector: projection of the 3D velocity vector on the normal vector of the WGS84 [6] Ellipsoid
3.2 Symbols
For the purposes of the present document, the following symbols apply:
Tsys ITS Station Time
ETSI
10 ETSI EN 302 890-2 V2.1.1 (2020-10)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3D 3 Dimensional
ACC Automatic Crouse Control
ACK Acknowledgement
ASN Abstract Syntax Notation
BSA Basic Set of Applications
CA Cooperative Awareness (service)
CACC Cooperative Adaptive Cruise Control
CAM Cooperative Awareness Message
CCAM Cooperative, Connected and Automated Mobility
CDD Common Data Dictionary
CP Collective Perception (service)
CVIS Cooperative Vehicle-Infrastructure Systems
DEN Decentralized Environmental Notification
DENM Decentralized Environmental Notification Message
D-GNSS Differential Global Navigation Satellite System
ECU Electronic Control Unit
EDAS EGNOS Data Access Service
EGNOS European Geostationary Navigation Overlay Service
EU European Union
FA-SAP Facilities to Applications Service Access Point
GLONASS GLObal NAvigation Satellite System
GNSS Global Navigation Satellite Systems
GPC GNSS Positioning Correction
GPS Global Positioning System
GRM GPS Raw data Message
IEC International Electrotechnical Commission
IETF Internet Engineering Task Force
ISO International Organization for Standardization
ITRF International Terrestrial Reference Frame
ITS Intelligent Transport Systems
ITS-C ITS Constellation
ITS-S ITS Station
ITU-T International Telecommunication Union - Telecommunication standardization sector
MAC Media Access Control
NA Not Applicable
NF-SAP Network to Facilities Service Access Point
NGA National Geospatial-intelligence Agency
NRTK Network Real Time Kinematic
NTP Network Time Protocol
PDU Protocol Data Unit
PoTi Position and Time
PPP Precise Point Positioning
PSID Provider Service Identifier
RAN Radio Access Network
RF Radio Frequency
RFC Request For Comment
R-ITS-S Roadside ITS Station
RTCM Radio Technical Commission for Maritime services
RTCMEM Radio Technical Commission for Maritime services Environmental Message
RTK Real Time Kinematic
SA Service Announcement
SAM Service Announcement Message
SF-SAP Security to Facilities Service Access Point
SI Standard International
SIFS Short InterFrame Space
SLR Satellite Laser Ranging
SPATEM Signal Phase And Timing Extended Message
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11 ETSI EN 302 890-2 V2.1.1 (2020-10)
SSR Sirius Satellite Radio
TAI International Atomic Time scale
TCU Transmission Control Unit
ToF Time-of-Flight
UE User Equipment
UPER Unaligned Packet Encoding Rules
UTC Coordinated Universal Time
UWB Ultra Wide Band
VLBI Very-Long-Baseline Interferometry
VRU Vulnerable Road User
WGS World Geodetic System
WGS84 World Geodetic System 1984
4 Position and Time entity introduction
4.1 Introduction
ITS applications such as specified in the Basic Set of Applications specification (BSA) ETSI TR 102 638 [i.2] require
the exchange of position and time information as part of the information exchange among ITS-Ss. As initial ITS
location based services, the Cooperative Awareness (CA) basic service ETSI EN 302 637-2 [i.3] and similar, the road
traffic event Decentralized Environmental Notification (DEN) basic service ETSI EN 302 637-3 [i.4] are developed.
These services and their data exchanges are dependent on position and time information. In this and the following
clauses it is understood that "position" means kinematic and attitude state as defined in clause 5.4.1 which includes
attitude and movement parameters including velocity, heading, horizontal speed and optionally others.
In order to realize road ITS safety related applications, ITS-Ss need to have an absolute knowledge about their position
and have a common synchronized knowledge about time to be able to value information received from another ITS-Ss.
To realize this absolute knowledge about position and time, an ITS-S may be equipped with a Global Navigation
Satellite Systems (GNSS) making use of Galileo or GPS and/or other satellite navigation technologies, providing
satellite positioning information to the PoTi entity.
Depending on the applications supported by an ITS-S, the qualitive requirements on the accuracy, integrity and
reliability of the position and time references may vary. As the CA basic service (ETSI EN 302 637-2 [i.3]) specifies,
road safety applications may require the ITS-S to transmit position and time information at intervals of about 10 times a
second, while new applications such as Platooning requires intervals of ≥ 20 times a second.
ITS applications are based on the exchange of information among ITS-Ss and therefore ITS applications operating in
one ITS-S are depending on the information provided by other ITS-Ss, a set of minimum requirements to be supported
by all ITS-Ss needs to be agreed. As new ITS applications are constantly being developed these minimum requirements
need to be set for a selective set of (grouped) ITS applications. At the current state an ETSI Release 1 set of ITS
standards (ETSI TR 101 607 [i.10]) is the reference for the Release 1 equipment and therefore it provides the
requirements for the Release 1 PoTi requirements.
Based on the current developments of new services and related analyses by EU projects further optional requirements
are included.
The position and time (PoTi) service as identified in ETSI TS 102 894-1 [i.5] residing in the facility layer is an essential
part of the ITS; it provides time and position information to all ITS applications and services.
In order to satisfy the application requirements and different Releases of application sets, the PoTi entity may include
various methods to ensure the accuracy, integrity and reliability of the position and time references as required by the
ITS applications supported by the ITS-S.
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12 ETSI EN 302 890-2 V2.1.1 (2020-10)
4.2 Service provided by the PoTi entity
The facility layer PoTi entity manages the position and time information for use by ITS applications, facility, network,
management and security layers. For this purpose, it gets information from sub-system entities such as GNSS, sensors
and other sub-system entities. Given the ITS application requirements in terms of position and time accuracy, PoTi may
use augmentation services to improve the position and time accuracy. Various augmentation methods may be applied.
PoTi may support these augmentation services by providing messages services broadcasting augmentation data. For
instance, a roadside ITS-S may broadcast correction information for GNSS to oncoming vehicle ITS-S; ITS-Ss may
exchange raw GPS data or may exchange terrestrial radio position and time relevant information. PoTi maintains and
provides the position and time reference information according to the application and facility and other layer service
requirements in the ITS-S.
5 PoTi functional description
5.1 PoTi in the ITS Domain
The ITS reference architecture is defined in ETSI EN 302 665 [i.1]. It defines the ITS Station (ITS-S) architecture as
part of the ITS domain. In the ITS domain, at a particular time an ITS-S may be in a situation when no other ITS-Ss are
active within its communication range, while at another moment it may be in a situation in which there are many ITS-Ss
active within its communication range. An ITS Constellation (ITS-C) is a group of ITS-Ss that communicate with each
other. ITS-Cs may overlap, and an ITS-S may be active in several ITS-Cs but in general not necessary in all as not all
ITS-Cs need to overlap (see Figure 1).

Figure 1: Momentary ITS-Cs in the ITS domain
5.2 ITS Constellation
ITS services are based on sharing information between ITS-Ss. Applications in ITS-Ss receive messages containing
information from neighbouring ITS-Ss and use this to provide services in the receiving ITS-S. It is therefore essential
that receiving ITS-Ss can identify the time and position relevance of the content of each message. ITS-Ss in the same
ITS-C shall have a consistent understanding of position and time for the services they support. When ITS-C overlap,
only those in the overlapping area shall have an understanding of position and time, of both constellations but other
ITS-Ss not (see Figure 1).
ITS applications and services may have different time and position requirements. Depending on the ITS services to be
supported by an ITS-S, the time and position accuracy requirements toward the facility service PoTi may differ but are
required to be commonly agreed. To ensure that the existing ITS-Ss in an ITS-C can support each other's active ITS
services, common minimum requirements are agreed based on the ITS Releases. Currently Release 1 and Release 2 ITS
services are distinguished. Minimum common requirements for the Release 1 set of applications are defined in ETSI
TR 102 638 [i.2]. Minimum requirements for Release 2 cannot be set at this time.
The PoTi entity of any ITS-S in a given ITS-C should ensure that Tsys ≈ T (T is the ITS Time) within this ITS-C.
n
ETSI
13 ETSI EN 302 890-2 V2.1.1 (2020-10)
IT S- S4
IT S-S2
IT S-S6
PoTi
ITS- S1
PoTi
PoTi
ITS-S 3 ITS- S5
Tsys ≈T
PoTi
Tsys ≈T
2 Po Ti PoTi
Tsys ≈T
Tsys ≈T
Tsys ≈T Tsys ≈T
3 5
Figure 2: Momentary ITS-C
5.3 PoTi in the ITS Station (ITS-S) architecture
PoTi is a facilities layer entity that manages the Position and Time information required by the application, facility,
network, management and security layers. It ensures ITS time synchronicity between the ITS-Ss in the ITS system, it
maintains the data quality (e.g. by monitoring time deviation) and manages updates of the kinematic and attitude state
and time. The PoTi entity may include augmentation services to improve the position and time accuracy, integrity, and
reliability. Among these methods, communication technologies may be used to provide positioning assistance from
mobile to mobile ITS-Ss and infrastructure to mobile ITS-Ss.
The PoTi entity interfaces with ITS applications and other facility layer entities in order to provide position and time
information, such as CA basic service described in ETSI EN 302 637-2 [i.3] and DEN basic service described in ETSI
EN 302 637-3 [i.4], C-ACC described in ETSI TR 103 299 [i.6] and CP described in ETSI TS 103 324 [i.7] basic
service. Figure 3 presents PoTi in the ITS-S architecture according to ETSI EN 302 665 [i.1].

Figure 3: The PoTi entity its interfaces to other facilities entities via the FA-SAP,
and its interfaces in the ITS-S architecture according to ETSI EN 302 665 [i.1]
ETSI
14 ETSI EN 302 890-2 V2.1.1 (2020-10)
5.4 PoTi entity functional architecture
5.4.1 General
Figure 4 illustrates functions and interfaces of the PoTi entity.

Figure 4: PoTi entity functional architecture
The functions are described in the following clauses. The interfaces are described in clause 5.5.
5.4.2 Position information Management
• The kinematic and attitude state of the rigid body contained in the ITS-S included position, velocity,
acceleration, orientation, angular velocity and possible other motion related information. The position
information at a specific moment in time is referred to as the kinematic and attitude state including time, of the
rigid body.
NOTE 1: If not otherwise stated all these quantities are provided in 3D.
• In addition to the kinematic and attitude state, PoTi should also maintain information on the confidence of the
kinematic and attitude state variables.
An ITS-S should at least be functional when the system of which it is part of is in operation. The PoTi entity should be
functional when the ITS-S is operating.
NOTE 2: As for many implementations it takes time for the PoTi entity to provide proper information. The PoTi
entity may be functional for a period of time when the system of which it is part of is not operational.
Once the system is reactivated, the PoTi entity should validate the kinematic and attitude state and
confidences whether it still meets the system requirements.
An ITS-S may use multiple means of positioning if they are available (e.g. GNSS, inertial sensors, odometer, cameras,
terrestrial radio ranging, map matching, etc.). Depending on the applications and services an ITS-S needs to support an
ITS-S could use single or multiple augmentation services to improve its position and time accuracy.
ETSI
15 ETSI EN 302 890-2 V2.1.1 (2020-10)
5.4.3 Position Augmentation
• The Position augmentation function uses externally sourced assistance data or measurements in order to
improve positioning performance by eliminating system errors common to many ITS-Ss.
• Satellite based augmentation: in Europe, European Geostationary Navigation Overlay Service (EGNOS) is
provided to improve GNSS position accuracy. RTK and SSR services are also augmentation services that can
be used by GNSS receivers; they may be distributed across satellite channels or terrestrial communication
links including from other ITS-Ss.
• Cooperative positioning: ITS-Ss may exchange information to improve the relative positioning. Ground based
augmentation such as EGNOS, RTCM or SSR based (PPP-RTK) services can be distributed over terrestrial
communications channels to augment GNSS data. R-ITS-S could transmit RTCM or SSR correction
information to vehicle ITS-Ss, as specified in ETSI TS 103 301 [1].
5.4.4 Reference coordinate System Conversion
The reference coordinate System Conversion function converts the kinematic and attitude state between different
reference systems, e.g. to and from local (vehicle) coordinate systems or ITRF14 or ETRS89. Relative positioning is a
sub function of Reference coordinate System Conversion and involves the conversion from the WGS84 [6] coordinate
system to local coordinates systems, as e.g. used in DENM traces.
The Reference coordinate System Conversion is used for instance to describe relevance areas:
• Where the relevance area is an ellipse or a rectangle, the Cartesian coordinates of the area center and of the
current position shall be calculated as specified in the ETSI EN 302 931 [11]. For this purpose, the 'local
tangent plane' method is recommended, or another method delivering the same accuracy.
5.4.5 Time information Management
ITS time shall be defined as a time based on TAI. Epoch of ITS time is set to 2004-01-01T00:00:00Z, that is 0 seconds
st
on 1 of January 2004 UTC. ITS time is the general time base for all ITS-Ss. An ITS-S's representation of ITS Time is
referred to as the station clock. A moment in time, or instant, after the epoch can be represented by a timestamp.
A timestamp is the duration of the time interval between the epoch and the instant, derived from the station clock
according to IEC 60050 [i.14].
Time Information Management manages the quality of the station clock, handles updates of the ITS-S time information
and provides the time information to other entities in the ITS-S.
For the ITS-S time information the same activation requirements are valid as for ITS-S position information as
identified in clause 5.4.2.
5.4.6 Time synchronization
The ITS Station should synchronize its station clock by means of one or more external time services (GNSS, NTP),
taking into account accuracy, integrity and reliability of the external service.
NOTE: ITS-Time is based on TAI, and therefore has no special treatments of leap-seconds that are introduced in
UTC at specific moments in time. UTC itself is based on counting SI seconds since an epoch, similar to
ITS-Time. However, several time synchronization protocols, like NTP, modify the clock that counts the
number of SI seconds since the epoch, to facilitate easier conversion from clock counter values to UTC
date/time. Therefore, care should be taken when using such synchronization services to correctly treat the
insertion of UTC leap seconds, specifically also during the insertion of the leap second.
5.4.7 Time reference system conversion Service
• The time reference system conversion takes care of converting from ITS Time to other time reference systems.
PoTi should support the conversion between ITS Time and UTC and vice versa when required by applications.
Support for other time reference systems can also be supported.
ETSI
16 ETSI EN 302 890-2 V2.1.1 (2020-10)
NOTE: UTC is used as the time basis for time information in several messages, like SPATEM in ETSI
TS 103 301 [1].
5.5 PoTi Interfaces
5.5.1 Interface to ITS applications (FA-SAP)
PoTi provides position and time information to ITS applications residing in the ITS-S via the interface IF.Appl as
illustrated in Figure 4. In one possible implementation, the interface IF.Appl may be implemented as SF-SAP as
illustrated in Figure 3.
In one possible implementation of this interface, the position and time information (including confidence values) may
be provided by the PoTi module upon request or automatically upon a given trigger, e.g. when the system receives an
update.
Via the FA-SAP interface security and integrity information could be provided by the PoTi service originating source
entity (such as on-board sensors or GNSS).
Although PoTi specifies checks for integrity and security, however these checks are also done by misbehaviour
detection functions.
Interfaces to local sensor in an ITS station may exist. PoTi could provide an interface to functions harmonizing local
sensor data input.
An Application layer function may receive data from POTI using the parameters shown in Table 1.
The following minimum data set may be made available via IF.App. Additional data may be made available. All data
shall refer to reference point 0, see clause 6.2. Data for other reference points may be provided. All data provided need
to fulfil the specifications and requirements stipulated in clause 5.4 and clause 6.
Table 1: FA-SAP minimum data set
Category Data Data requirement Mandatory/Optional
Reference point Reference point identifier See clause 6.2 Conditional: mandatory only when
data for multiple reference points
are provided
Time Timestamp See clause 5.4.4 Mandatory
Position Latitude See clause 6.1 Mandatory
Longitude See clause 6.1 Mandatory
Altitude See clause 6.1 Optional
Motion Horizontal Speed See clause 6.1 Optional
Vertical Horizontal Speed See clause 6.1 Optional
Heading See clause 6.1 Optional
Confiden
...

SLOVENSKI STANDARD
01-december-2020
Inteligentni transportni sistemi (ITS) - Funkcija zmogljivostne plasti - 2. del:
Upravljanje položaja in časa (PoTi) - Izdaja 2
Intelligent Transport Systems (ITS) - Facilities Layer function - Part 2: Position and Time
management (PoTi) - Release 2
Ta slovenski standard je istoveten z: ETSI EN 302 890-2 V2.1.1 (2020-10)
ICS:
35.240.60 Uporabniške rešitve IT v IT applications in transport
prometu
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
Intelligent Transport Systems (ITS);
Facilities Layer function;
Part 2: Position and Time management (PoTi);
Release 2
2 ETSI EN 302 890-2 V2.1.1 (2020-10)

Reference
DEN/ITS-00182
Keywords
facility, ITS, time-stamping
ETSI
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ETSI
3 ETSI EN 302 890-2 V2.1.1 (2020-10)
Contents
Intellectual Property Rights . 5
Foreword. 5
Modal verbs terminology . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 10
4 Position and Time entity introduction . 11
4.1 Introduction. 11
4.2 Service provided by the PoTi entity . 12
5 PoTi functional description . 12
5.1 PoTi in the ITS Domain . 12
5.2 ITS Constellation . 12
5.3 PoTi in the ITS Station (ITS-S) architecture . 13
5.4 PoTi entity functional architecture . 14
5.4.1 General . 14
5.4.2 Position information Management . 14
5.4.3 Position Augmentation . 15
5.4.4 Reference coordinate System Conversion . 15
5.4.5 Time information Management . 15
5.4.6 Time synchronization . 15
5.4.7 Time reference system conversion Service . 15
5.5 PoTi Interfaces . 16
5.5.1 Interface to ITS applications (FA-SAP) . 16
5.5.2 Interfaces to the Networking and Transport Layer (NF-SAP) . 17
5.5.3 Interfaces to the Management entity (MF-SAP) . 17
5.5.4 Interfaces to the Security entity (SF-SAP) . 17
5.5.5 Interfaces to other Facility layer entities . 18
6 Position and time requirements . 18
6.1 Requirements related to PoTi functions . 18
6.2 ITS-S reference position . 20
6.2.1 Introduction . 20
6.2.2 ITS-S reference position for passenger cars . 20
6.2.3 ITS-S reference position for Trucks . 22
6.2.4 ITS-S reference position for Busses . 28
6.2.5 ITS-S reference position for Motorcycles, mopeds and bicycles . 29
6.2.6 ITS-S reference position for Pedestrians . 31
6.2.7 ITS-S reference position for Special Vehicles . 31
6.2.8 ITS-S reference position for City-Tram . 31
6.2.9 ITS-S reference position for Roadside ITS Stations (R-ITS-Ss) . 32
6.3 Position and time confidence . 32
6.3.1 General requirements related to confidence . 32
6.3.2 Confidences related to Position Information Management . 33
6.3.2.1 Horizontal Position confidence. 33
6.3.2.2 Vertical Position confidence . 33
6.3.2.3 Horizontal Speed confidence . 33
6.3.2.4 Heading confidence . 33
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4 ETSI EN 302 890-2 V2.1.1 (2020-10)
6.3.2.5 Confidence of other quantities . 34
6.3.2.6 Other accuracy estimations . 34
6.3.3 Confidences related to Reference Coordinate System Conversion Management . 34
6.3.3.1 Relative Position confidence . 34
6.3.4 Confidences related to Time Information Management . 34
7 Augmentation services . 35
7.1 Introductions . 35
7.2 GNSS Positioning Correction (GPC) Augmentation Service . 35
7.2.1 Introduction . 35
7.2.2 GPC requirements . 36
7.2.3 GPC Data processing by the V-ITS-S during transition between R-ITS-S service areas . 36
7.3 R-ITS-S ranging augmentation Service . 37
7.3.1 Introduction . 37
7.3.2 Ranging service announcements . 38
7.3.2.1 Introduction . 38
7.3.2.2 Ranging Service Application Data . 39
7.3.3 Measurement . 40
7.3.4 Ranging Rate . 40
7.3.5 Security . 40
Annex A (normative): ASN.1 specification of messages . 41
A.1 ASN.1 specification of ranging service application data . 41
History . 42

ETSI
5 ETSI EN 302 890-2 V2.1.1 (2020-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Intelligent Transport Systems (ITS).
The present document is part 2 of a multi-part deliverable covering Facilities Layer function, as identified below:
Part 1: "Services Announcement (SA) specification";
Part 2: "Position and Time management (PoTi); Release 2".
The present document is based on inputs provided by various European projects including AutoNet, Concorda,
Ensemble, Hights, PRoPART, Dutch-Germany-Austria Corridor, Scope@F, A58 (NL), PRE-DRIVE C2X, DRIVE
C2X, SafeSpot, CVIS, CoVeL, SCOR@F, simTD, etc.

National transposition dates
Date of adoption of this EN: 19 October 2020
Date of latest announcement of this EN (doa): 31 January 2021
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 July 2021
Date of withdrawal of any conflicting National Standard (dow): 31 July 2021

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 302 890-2 V2.1.1 (2020-10)
Introduction
Intelligent Transportation Systems Cooperative, Connected and Automated Mobility (CCAM) related use cases in the
ITS environment as specified in the ETSI ITS architecture (ETSI EN 302 665 [i.1]) can be distributed over multiple ITS
stations (ITS-Ss). ITS-Ss interact in the ITS system to exchange sensor data and traffic related information to make each
other aware of traffic safety or traffic efficiency circumstances and situations by which each ITS-S equipped road user,
whether automated or not, can improve their safety and efficiency related decisions.

ETSI
7 ETSI EN 302 890-2 V2.1.1 (2020-10)
1 Scope
The present document provides the specification of the Position and Time (PoTi) services. It includes functional and
operational requirements for the position and time data to support ITS Applications. In addition, it includes the
definition of syntax and semantics of messages exchanged between ITS Stations (ITS-Ss) to augment the position and
time accuracy. Finally, it specifies the facilities layer protocol in support of such message exchanges.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 103 301: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of
Applications; Facilities layer protocols and communication requirements for infrastructure
services".
[2] RTCM 10402.3: "Recommended Standards for Differential GNSS (Global Navigation Satellite
Systems) Service".
[3] RTCM 10403.3: "Differential GNSS (Global Navigation Satellite Systems) Services - Version 3".
[4] ETSI EN 302 663 (V1.3.1) (01-2020): "Intelligent Transport Systems (ITS); ITS-G5 Access layer
specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
[5] ETSI EN 302 890-1 (V1.2.1) (07-2019): "Intelligent Transport Systems (ITS); Facilities layer
function; Part 1: Services Announcement (SA) specification".
[6] World Geodetic System 1984 (WGS84).
NOTE: Available at http://earth-info.nga.mil/GandG/update/index.php?dir=wgs84&action=wgs84#tab_wgs84-
res.
[7] ISO 8855 (2011): "Road Vehicles -- Vehicle dynamics and road-holding ability -- Vocabulary".
[8] ETSI TS 103 248: "Intelligent Transport Systems (ITS); GeoNetworking; Port Numbers for the
Basic Transport Protocol (BTP)".
[9] ISO 5725-1 (1994): "Accuracy (trueness and precision) of measurement methods and results --
Part 1: General principles and definitions".
[10] ETSI TS 102 894-2: "Intelligent Transport Systems (ITS); Users and applications requirements;
Part 2: Applications and facilities layer common data dictionary".
[11] ETSI EN 302 931 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Geographical Area Definition".
[12] ISO/TS 16460:2016: "Intelligent transport systems -- Communications access for land mobiles
(CALM) -- Communication protocol messages for global usage".
ETSI
8 ETSI EN 302 890-2 V2.1.1 (2020-10)
[13] Recommendation ITU-T X.691/ISO/IEC 8825-2:2015: "Information technology - ASN.1 encoding
rules: Specification of Packed Encoding Rules (PER)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[i.2] ETSI TR 102 638 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Definitions".
[i.3] ETSI EN 302 637-2: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[i.4] ETSI EN 302 637-3: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 3: Specifications of Decentralized Environmental Notification Basic
Service".
[i.5] ETSI TS 102 894-1 (V1.1.1): "Intelligent Transport Systems (ITS); Users and applications
requirements; Part 1: Facility layer structure, functional requirements and specifications".
[i.6] ETSI TR 103 299: "Intelligent Transport System (ITS); Cooperative Adaptive Cruise Control
(CACC); Pre-standardization study".
[i.7] ETSI TS 103 324: "Intelligent Transport Systems (ITS); Cooperative Perception Services".
[i.8] ETSI TS 103 246-1 (V1.2.1) (03-2017): "Satellite Earth Stations and Systems (SES); GNSS based
location systems; Part 1: Functional requirements".
[i.9] EUREF: "European Terrestrial Reference System 89 (ETRS89)".
NOTE: Available at http://etrs89.ensg.ign.fr.
[i.10] ETSI TR 101 607 (V1.1.1) (05-2013): "Intelligent Transport Systems (ITS); Cooperative ITS
(C-ITS); Release 1".
[i.11] ISO 3534-1 (10-2009): "Statistics - Vocabulary and symbols - Part 1: General statistical terms and
terms".
[i.12] ETSI TS 136 305 (V11.2.0): "LTE; Evolved Universal Terrestrial Radio Access Network
(E-UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN
(3GPP TS 36.305 version 11.2.0 Release 11)".
[i.13] IETF RFC 5905 (June 2010): "Network Time Protocol Version 4: Protocol and Algorithms
Specification".
[i.14] IEC 60050: "International Electrotechnical Vocabulary", 113-01-08 (instant), 113-01-10 (time
interval), 113-01-13 (duration).
[i.15] IS-QZSS-L6-001: "Quasi-Zenith Satellite System Interface Specification Centimeter Level
Augmentation Service".
NOTE: Available at https://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-l6-001.pdf.
[i.16] IETF RFC 8173 (June 2017): "Precision Time Protocol Version 2 (PTPv2) Management
Information Base".
ETSI
9 ETSI EN 302 890-2 V2.1.1 (2020-10)
[i.17] EN ISO 22418: "Intelligent transport systems - Fast service announcement protocol (FSAP) for
general purposes in ITS" (produced by CEN).
TM
[i.18] IEEE 1609.3: "IEEE Standard for Wireless Access in Vehicular Environments (WAVE) --
Networking Services".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
accuracy: closeness of a measured value to a standard or known value
heading: orientation of the horizontal velocity vector with respect to the WGS84 [6] North (clockwise), unless
otherwise noted
horizontal speed: magnitude of horizontal velocity-vector of the reference position point
horizontal velocity vector: projection of the 3D velocity vector on the WGS84 [6] ellipsoid
integrity risk: probability, per unit of time, of having a Parameter Failure without issuing an alert within the
Time-to-Alert
ITS constellation: group of ITS-Ss which are exchanging ITS data among themselves
ITS time: time based on TAI
st
NOTE: Epoch of this time is set to 2004-01-01T00:00:00Z, that is 0 seconds on 1 of January 2004 UTC.
parameter failure: failure occurring when the position and time entity is unable to estimate parameters with an error
less than the maximum tolerable error (err > err_max)
position integrity: measure of the trust that can be placed in the correctness of the estimated Parameters supplied by the
Position and Time entity
NOTE: Integrity includes the ability of the equipment (at the Position and Time entity and/or User level) to
compute timely and valid alerts when the estimated Parameters do not need to be used for the operation of
interest.
protection level: estimated bound on the Parameter Error from the Position and Time entity at a defined confidence
level such as 50 %, 75 %, 95 %, 99 %, etc., delivered with the Parameters
station clock: clock representing ITS time in an ITS Station
Time-to-Alert: maximum allowable elapsed time from the onset of a Parameter Failure until the equipment annunciates
the alert
velocity: vector indicating speed in a particular direction
vertical velocity vector: projection of the 3D velocity vector on the normal vector of the WGS84 [6] Ellipsoid
3.2 Symbols
For the purposes of the present document, the following symbols apply:
Tsys ITS Station Time
ETSI
10 ETSI EN 302 890-2 V2.1.1 (2020-10)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3D 3 Dimensional
ACC Automatic Crouse Control
ACK Acknowledgement
ASN Abstract Syntax Notation
BSA Basic Set of Applications
CA Cooperative Awareness (service)
CACC Cooperative Adaptive Cruise Control
CAM Cooperative Awareness Message
CCAM Cooperative, Connected and Automated Mobility
CDD Common Data Dictionary
CP Collective Perception (service)
CVIS Cooperative Vehicle-Infrastructure Systems
DEN Decentralized Environmental Notification
DENM Decentralized Environmental Notification Message
D-GNSS Differential Global Navigation Satellite System
ECU Electronic Control Unit
EDAS EGNOS Data Access Service
EGNOS European Geostationary Navigation Overlay Service
EU European Union
FA-SAP Facilities to Applications Service Access Point
GLONASS GLObal NAvigation Satellite System
GNSS Global Navigation Satellite Systems
GPC GNSS Positioning Correction
GPS Global Positioning System
GRM GPS Raw data Message
IEC International Electrotechnical Commission
IETF Internet Engineering Task Force
ISO International Organization for Standardization
ITRF International Terrestrial Reference Frame
ITS Intelligent Transport Systems
ITS-C ITS Constellation
ITS-S ITS Station
ITU-T International Telecommunication Union - Telecommunication standardization sector
MAC Media Access Control
NA Not Applicable
NF-SAP Network to Facilities Service Access Point
NGA National Geospatial-intelligence Agency
NRTK Network Real Time Kinematic
NTP Network Time Protocol
PDU Protocol Data Unit
PoTi Position and Time
PPP Precise Point Positioning
PSID Provider Service Identifier
RAN Radio Access Network
RF Radio Frequency
RFC Request For Comment
R-ITS-S Roadside ITS Station
RTCM Radio Technical Commission for Maritime services
RTCMEM Radio Technical Commission for Maritime services Environmental Message
RTK Real Time Kinematic
SA Service Announcement
SAM Service Announcement Message
SF-SAP Security to Facilities Service Access Point
SI Standard International
SIFS Short InterFrame Space
SLR Satellite Laser Ranging
SPATEM Signal Phase And Timing Extended Message
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11 ETSI EN 302 890-2 V2.1.1 (2020-10)
SSR Sirius Satellite Radio
TAI International Atomic Time scale
TCU Transmission Control Unit
ToF Time-of-Flight
UE User Equipment
UPER Unaligned Packet Encoding Rules
UTC Coordinated Universal Time
UWB Ultra Wide Band
VLBI Very-Long-Baseline Interferometry
VRU Vulnerable Road User
WGS World Geodetic System
WGS84 World Geodetic System 1984
4 Position and Time entity introduction
4.1 Introduction
ITS applications such as specified in the Basic Set of Applications specification (BSA) ETSI TR 102 638 [i.2] require
the exchange of position and time information as part of the information exchange among ITS-Ss. As initial ITS
location based services, the Cooperative Awareness (CA) basic service ETSI EN 302 637-2 [i.3] and similar, the road
traffic event Decentralized Environmental Notification (DEN) basic service ETSI EN 302 637-3 [i.4] are developed.
These services and their data exchanges are dependent on position and time information. In this and the following
clauses it is understood that "position" means kinematic and attitude state as defined in clause 5.4.1 which includes
attitude and movement parameters including velocity, heading, horizontal speed and optionally others.
In order to realize road ITS safety related applications, ITS-Ss need to have an absolute knowledge about their position
and have a common synchronized knowledge about time to be able to value information received from another ITS-Ss.
To realize this absolute knowledge about position and time, an ITS-S may be equipped with a Global Navigation
Satellite Systems (GNSS) making use of Galileo or GPS and/or other satellite navigation technologies, providing
satellite positioning information to the PoTi entity.
Depending on the applications supported by an ITS-S, the qualitive requirements on the accuracy, integrity and
reliability of the position and time references may vary. As the CA basic service (ETSI EN 302 637-2 [i.3]) specifies,
road safety applications may require the ITS-S to transmit position and time information at intervals of about 10 times a
second, while new applications such as Platooning requires intervals of  20 times a second.
ITS applications are based on the exchange of information among ITS-Ss and therefore ITS applications operating in
one ITS-S are depending on the information provided by other ITS-Ss, a set of minimum requirements to be supported
by all ITS-Ss needs to be agreed. As new ITS applications are constantly being developed these minimum requirements
need to be set for a selective set of (grouped) ITS applications. At the current state an ETSI Release 1 set of ITS
standards (ETSI TR 101 607 [i.10]) is the reference for the Release 1 equipment and therefore it provides the
requirements for the Release 1 PoTi requirements.
Based on the current developments of new services and related analyses by EU projects further optional requirements
are included.
The position and time (PoTi) service as identified in ETSI TS 102 894-1 [i.5] residing in the facility layer is an essential
part of the ITS; it provides time and position information to all ITS applications and services.
In order to satisfy the application requirements and different Releases of application sets, the PoTi entity may include
various methods to ensure the accuracy, integrity and reliability of the position and time references as required by the
ITS applications supported by the ITS-S.
ETSI
12 ETSI EN 302 890-2 V2.1.1 (2020-10)
4.2 Service provided by the PoTi entity
The facility layer PoTi entity manages the position and time information for use by ITS applications, facility, network,
management and security layers. For this purpose, it gets information from sub-system entities such as GNSS, sensors
and other sub-system entities. Given the ITS application requirements in terms of position and time accuracy, PoTi may
use augmentation services to improve the position and time accuracy. Various augmentation methods may be applied.
PoTi may support these augmentation services by providing messages services broadcasting augmentation data. For
instance, a roadside ITS-S may broadcast correction information for GNSS to oncoming vehicle ITS-S; ITS-Ss may
exchange raw GPS data or may exchange terrestrial radio position and time relevant information. PoTi maintains and
provides the position and time reference information according to the application and facility and other layer service
requirements in the ITS-S.
5 PoTi functional description
5.1 PoTi in the ITS Domain
The ITS reference architecture is defined in ETSI EN 302 665 [i.1]. It defines the ITS Station (ITS-S) architecture as
part of the ITS domain. In the ITS domain, at a particular time an ITS-S may be in a situation when no other ITS-Ss are
active within its communication range, while at another moment it may be in a situation in which there are many ITS-Ss
active within its communication range. An ITS Constellation (ITS-C) is a group of ITS-Ss that communicate with each
other. ITS-Cs may overlap, and an ITS-S may be active in several ITS-Cs but in general not necessary in all as not all
ITS-Cs need to overlap (see Figure 1).

Figure 1: Momentary ITS-Cs in the ITS domain
5.2 ITS Constellation
ITS services are based on sharing information between ITS-Ss. Applications in ITS-Ss receive messages containing
information from neighbouring ITS-Ss and use this to provide services in the receiving ITS-S. It is therefore essential
that receiving ITS-Ss can identify the time and position relevance of the content of each message. ITS-Ss in the same
ITS-C shall have a consistent understanding of position and time for the services they support. When ITS-C overlap,
only those in the overlapping area shall have an understanding of position and time, of both constellations but other
ITS-Ss not (see Figure 1).
ITS applications and services may have different time and position requirements. Depending on the ITS services to be
supported by an ITS-S, the time and position accuracy requirements toward the facility service PoTi may differ but are
required to be commonly agreed. To ensure that the existing ITS-Ss in an ITS-C can support each other's active ITS
services, common minimum requirements are agreed based on the ITS Releases. Currently Release 1 and Release 2 ITS
services are distinguished. Minimum common requirements for the Release 1 set of applications are defined in ETSI
TR 102 638 [i.2]. Minimum requirements for Release 2 cannot be set at this time.
The PoTi entity of any ITS-S in a given ITS-C should ensure that Tsys ≈ T (T is the ITS Time) within this ITS-C.
n
ETSI
13 ETSI EN 302 890-2 V2.1.1 (2020-10)
ITS-S4
ITS-S2
ITS-S6
PoTi
ITS-S1
PoTi
PoTi
ITS-S3 ITS-S5
Tsys ≈T
PoTi
Tsys ≈T
2 PoTi PoTi
Tsys ≈T
Tsys ≈T
Tsys ≈T Tsys ≈T
3 5
Figure 2: Momentary ITS-C
5.3 PoTi in the ITS Station (ITS-S) architecture
PoTi is a facilities layer entity that manages the Position and Time information required by the application, facility,
network, management and security layers. It ensures ITS time synchronicity between the ITS-Ss in the ITS system, it
maintains the data quality (e.g. by monitoring time deviation) and manages updates of the kinematic and attitude state
and time. The PoTi entity may include augmentation services to improve the position and time accuracy, integrity, and
reliability. Among these methods, communication technologies may be used to provide positioning assistance from
mobile to mobile ITS-Ss and infrastructure to mobile ITS-Ss.
The PoTi entity interfaces with ITS applications and other facility layer entities in order to provide position and time
information, such as CA basic service described in ETSI EN 302 637-2 [i.3] and DEN basic service described in ETSI
EN 302 637-3 [i.4], C-ACC described in ETSI TR 103 299 [i.6] and CP described in ETSI TS 103 324 [i.7] basic
service. Figure 3 presents PoTi in the ITS-S architecture according to ETSI EN 302 665 [i.1].

Figure 3: The PoTi entity its interfaces to other facilities entities via the FA-SAP,
and its interfaces in the ITS-S architecture according to ETSI EN 302 665 [i.1]
ETSI
14 ETSI EN 302 890-2 V2.1.1 (2020-10)
5.4 PoTi entity functional architecture
5.4.1 General
Figure 4 illustrates functions and interfaces of the PoTi entity.

Figure 4: PoTi entity functional architecture
The functions are described in the following clauses. The interfaces are described in clause 5.5.
5.4.2 Position information Management
• The kinematic and attitude state of the rigid body contained in the ITS-S included position, velocity,
acceleration, orientation, angular velocity and possible other motion related information. The position
information at a specific moment in time is referred to as the kinematic and attitude state including time, of the
rigid body.
NOTE 1: If not otherwise stated all these quantities are provided in 3D.
• In addition to the kinematic and attitude state, PoTi should also maintain information on the confidence of the
kinematic and attitude state variables.
An ITS-S should at least be functional when the system of which it is part of is in operation. The PoTi entity should be
functional when the ITS-S is operating.
NOTE 2: As for many implementations it takes time for the PoTi entity to provide proper information. The PoTi
entity may be functional for a period of time when the system of which it is part of is not operational.
Once the system is reactivated, the PoTi entity should validate the kinematic and attitude state and
confidences whether it still meets the system requirements.
An ITS-S may use multiple means of positioning if they are available (e.g. GNSS, inertial sensors, odometer, cameras,
terrestrial radio ranging, map matching, etc.). Depending on the applications and services an ITS-S needs to support an
ITS-S could use single or multiple augmentation services to improve its position and time accuracy.
ETSI
15 ETSI EN 302 890-2 V2.1.1 (2020-10)
5.4.3 Position Augmentation
• The Position augmentation function uses externally sourced assistance data or measurements in order to
improve positioning performance by eliminating system errors common to many ITS-Ss.
• Satellite based augmentation: in Europe, European Geostationary Navigation Overlay Service (EGNOS) is
provided to improve GNSS position accuracy. RTK and SSR services are also augmentation services that can
be used by GNSS receivers; they may be distributed across satellite channels or terrestrial communication
links including from other ITS-Ss.
• Cooperative positioning: ITS-Ss may exchange information to improve the relative positioning. Ground based
augmentation such as EGNOS, RTCM or SSR based (PPP-RTK) services can be distributed over terrestrial
communications channels to augment GNSS data. R-ITS-S could transmit RTCM or SSR correction
information to vehicle ITS-Ss, as specified in ETSI TS 103 301 [1].
5.4.4 Reference coordinate System Conversion
The reference coordinate System Conversion function converts the kinematic and attitude state between different
reference systems, e.g. to and from local (vehicle) coordinate systems or ITRF14 or ETRS89. Relative positioning is a
sub function of Reference coordinate System Conversion and involves the conversion from the WGS84 [6] coordinate
system to local coordinates systems, as e.g. used in DENM traces.
The Reference coordinate System Conversion is used for instance to describe relevance areas:
• Where the relevance area is an ellipse or a rectangle, the Cartesian coordinates of the area center and of the
current position shall be calculated as specified in the ETSI EN 302 931 [11]. For this purpose, the 'local
tangent plane' method is recommended, or another method delivering the same accuracy.
5.4.5 Time information Management
ITS time shall be defined as a time based on TAI. Epoch of ITS time is set to 2004-01-01T00:00:00Z, that is 0 seconds
st
on 1 of January 2004 UTC. ITS time is the general time base for all ITS-Ss. An ITS-S's representation of ITS Time is
referred to as the station clock. A moment in time, or instant, after the epoch can be represented by a timestamp.
A timestamp is the duration of the time interval between the epoch and the instant, derived from the station clock
according to IEC 60050 [i.14].
Time Information Management manages the quality of the station clock, handles updates of the ITS-S time information
and provides the time information to other entities in the ITS-S.
For the ITS-S time information the same activation requirements are valid as for ITS-S position information as
identified in clause 5.4.2.
5.4.6 Time synchronization
The ITS Station should synchronize its station clock by means of one or more external time services (GNSS, NTP),
taking into account accuracy, integrity and reliability of the external service.
NOTE: ITS-Time is based on TAI, and therefore has no special treatments of leap-seconds that are introduced in
UTC at specific moments in time. UTC itself is based on counting SI seconds since an epoch, similar to
ITS-Time. However, several time synchronization protocols, like NTP, modify the clock that counts the
number of SI seconds since the epoch, to facilitate easier conversion from clock counter values to UTC
date/time. Therefore, care should be taken when using such synchronization services to correctly treat the
insertion of UTC leap seconds, specifically also during the insertion of the leap second.
5.4.7 Time reference system conversion Service
• The time reference system conversion takes care of converting from ITS Time to other time reference systems.
PoTi should support the conversion between ITS Time and UTC and vice versa when required by applications.
Support for other time reference systems can also be supported.
ETSI
16 ETSI EN 302 890-2 V2.1.1 (2020-10)
NOTE: UTC is used as the time basis for time information in several messages, like SPATEM in ETSI
TS 103 301 [1].
5.5 PoTi Interfaces
5.5.1 Interface to ITS applications (FA-SAP)
PoTi provides position and time information to ITS applications residing in the ITS-S via the interface IF.Appl as
illustrated in Figure 4. In one possible implementation, the interface IF.Appl may be implemented as SF-SAP as
illustrated in Figure 3.
In one possible implementation of this interface, the position and time information (including confidence values) may
be provided by the PoTi module upon request or automatically upon a given trigger, e.g. when the system receives an
update.
Via the FA-SAP interface security and integrity information could be provided by the PoTi service originating source
entity (such as on-board sensors or GNSS
...

SLOVENSKI STANDARD
01-december-2020
Inteligentni transportni sistemi (ITS) - Funkcija zmogljivostne plasti - 2. del:
Upravljanje položaja in časa (PoTi) - Izdaja 2
Intelligent Transport Systems (ITS) - Facilities Layer function - Part 2: Position and Time
management (PoTi) - Release 2
Ta slovenski standard je istoveten z: ETSI EN 302 890-2 V2.1.1 (2020-10)
ICS:
35.240.60 Uporabniške rešitve IT v IT applications in transport
prometu
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
Intelligent Transport Systems (ITS);
Facilities Layer function;
Part 2: Position and Time management (PoTi);
Release 2
2 ETSI EN 302 890-2 V2.1.1 (2020-10)

Reference
DEN/ITS-00182
Keywords
facility, ITS, time-stamping
ETSI
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ETSI
3 ETSI EN 302 890-2 V2.1.1 (2020-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 10
4 Position and Time entity introduction . 11
4.1 Introduction . 11
4.2 Service provided by the PoTi entity . 12
5 PoTi functional description . 12
5.1 PoTi in the ITS Domain . 12
5.2 ITS Constellation . 12
5.3 PoTi in the ITS Station (ITS-S) architecture . 13
5.4 PoTi entity functional architecture . 14
5.4.1 General . 14
5.4.2 Position information Management . 14
5.4.3 Position Augmentation . 15
5.4.4 Reference coordinate System Conversion . 15
5.4.5 Time information Management . 15
5.4.6 Time synchronization . 15
5.4.7 Time reference system conversion Service . 15
5.5 PoTi Interfaces . 16
5.5.1 Interface to ITS applications (FA-SAP). 16
5.5.2 Interfaces to the Networking and Transport Layer (NF-SAP) . 17
5.5.3 Interfaces to the Management entity (MF-SAP) . 17
5.5.4 Interfaces to the Security entity (SF-SAP) . 17
5.5.5 Interfaces to other Facility layer entities . 18
6 Position and time requirements . 18
6.1 Requirements related to PoTi functions . 18
6.2 ITS-S reference position . 20
6.2.1 Introduction. 20
6.2.2 ITS-S reference position for passenger cars . 20
6.2.3 ITS-S reference position for Trucks . 22
6.2.4 ITS-S reference position for Busses . 28
6.2.5 ITS-S reference position for Motorcycles, mopeds and bicycles . 29
6.2.6 ITS-S reference position for Pedestrians . 31
6.2.7 ITS-S reference position for Special Vehicles . 31
6.2.8 ITS-S reference position for City-Tram . 31
6.2.9 ITS-S reference position for Roadside ITS Stations (R-ITS-Ss) . 32
6.3 Position and time confidence. 32
6.3.1 General requirements related to confidence . 32
6.3.2 Confidences related to Position Information Management . 33
6.3.2.1 Horizontal Position confidence . 33
6.3.2.2 Vertical Position confidence . 33
6.3.2.3 Horizontal Speed confidence . 33
6.3.2.4 Heading confidence . 33
ETSI
4 ETSI EN 302 890-2 V2.1.1 (2020-10)
6.3.2.5 Confidence of other quantities . 34
6.3.2.6 Other accuracy estimations . 34
6.3.3 Confidences related to Reference Coordinate System Conversion Management . 34
6.3.3.1 Relative Position confidence . 34
6.3.4 Confidences related to Time Information Management . 34
7 Augmentation services . 35
7.1 Introductions . 35
7.2 GNSS Positioning Correction (GPC) Augmentation Service . 35
7.2.1 Introduction. 35
7.2.2 GPC requirements . 36
7.2.3 GPC Data processing by the V-ITS-S during transition between R-ITS-S service areas . 36
7.3 R-ITS-S ranging augmentation Service . 37
7.3.1 Introduction. 37
7.3.2 Ranging service announcements . 38
7.3.2.1 Introduction . 38
7.3.2.2 Ranging Service Application Data . 39
7.3.3 Measurement. 40
7.3.4 Ranging Rate . 40
7.3.5 Security . 40
Annex A (normative): ASN.1 specification of messages . 41
A.1 ASN.1 specification of ranging service application data . 41
History . 42

ETSI
5 ETSI EN 302 890-2 V2.1.1 (2020-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Intelligent Transport Systems (ITS).
The present document is part 2 of a multi-part deliverable covering Facilities Layer function, as identified below:
Part 1: "Services Announcement (SA) specification";
Part 2: "Position and Time management (PoTi); Release 2".
The present document is based on inputs provided by various European projects including AutoNet, Concorda,
Ensemble, Hights, PRoPART, Dutch-Germany-Austria Corridor, Scope@F, A58 (NL), PRE-DRIVE C2X, DRIVE
C2X, SafeSpot, CVIS, CoVeL, SCOR@F, simTD, etc.

National transposition dates
Date of adoption of this EN: 19 October 2020
Date of latest announcement of this EN (doa): 31 January 2021
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 July 2021
Date of withdrawal of any conflicting National Standard (dow): 31 July 2021

Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 302 890-2 V2.1.1 (2020-10)
Introduction
Intelligent Transportation Systems Cooperative, Connected and Automated Mobility (CCAM) related use cases in the
ITS environment as specified in the ETSI ITS architecture (ETSI EN 302 665 [i.1]) can be distributed over multiple ITS
stations (ITS-Ss). ITS-Ss interact in the ITS system to exchange sensor data and traffic related information to make each
other aware of traffic safety or traffic efficiency circumstances and situations by which each ITS-S equipped road user,
whether automated or not, can improve their safety and efficiency related decisions.

ETSI
7 ETSI EN 302 890-2 V2.1.1 (2020-10)
1 Scope
The present document provides the specification of the Position and Time (PoTi) services. It includes functional and
operational requirements for the position and time data to support ITS Applications. In addition, it includes the
definition of syntax and semantics of messages exchanged between ITS Stations (ITS-Ss) to augment the position and
time accuracy. Finally, it specifies the facilities layer protocol in support of such message exchanges.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 103 301: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set of
Applications; Facilities layer protocols and communication requirements for infrastructure
services".
[2] RTCM 10402.3: "Recommended Standards for Differential GNSS (Global Navigation Satellite
Systems) Service".
[3] RTCM 10403.3: "Differential GNSS (Global Navigation Satellite Systems) Services - Version 3".
[4] ETSI EN 302 663 (V1.3.1) (01-2020): "Intelligent Transport Systems (ITS); ITS-G5 Access layer
specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
[5] ETSI EN 302 890-1 (V1.2.1) (07-2019): "Intelligent Transport Systems (ITS); Facilities layer
function; Part 1: Services Announcement (SA) specification".
[6] World Geodetic System 1984 (WGS84).
NOTE: Available at http://earth-info.nga.mil/GandG/update/index.php?dir=wgs84&action=wgs84#tab_wgs84-
res.
[7] ISO 8855 (2011): "Road Vehicles -- Vehicle dynamics and road-holding ability -- Vocabulary".
[8] ETSI TS 103 248: "Intelligent Transport Systems (ITS); GeoNetworking; Port Numbers for the
Basic Transport Protocol (BTP)".
[9] ISO 5725-1 (1994): "Accuracy (trueness and precision) of measurement methods and results --
Part 1: General principles and definitions".
[10] ETSI TS 102 894-2: "Intelligent Transport Systems (ITS); Users and applications requirements;
Part 2: Applications and facilities layer common data dictionary".
[11] ETSI EN 302 931 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Geographical Area Definition".
[12] ISO/TS 16460:2016: "Intelligent transport systems -- Communications access for land mobiles
(CALM) -- Communication protocol messages for global usage".
ETSI
8 ETSI EN 302 890-2 V2.1.1 (2020-10)
[13] Recommendation ITU-T X.691/ISO/IEC 8825-2:2015: "Information technology - ASN.1 encoding
rules: Specification of Packed Encoding Rules (PER)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[i.2] ETSI TR 102 638 (V1.1.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Definitions".
[i.3] ETSI EN 302 637-2: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[i.4] ETSI EN 302 637-3: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 3: Specifications of Decentralized Environmental Notification Basic
Service".
[i.5] ETSI TS 102 894-1 (V1.1.1): "Intelligent Transport Systems (ITS); Users and applications
requirements; Part 1: Facility layer structure, functional requirements and specifications".
[i.6] ETSI TR 103 299: "Intelligent Transport System (ITS); Cooperative Adaptive Cruise Control
(CACC); Pre-standardization study".
[i.7] ETSI TS 103 324: "Intelligent Transport Systems (ITS); Cooperative Perception Services".
[i.8] ETSI TS 103 246-1 (V1.2.1) (03-2017): "Satellite Earth Stations and Systems (SES); GNSS based
location systems; Part 1: Functional requirements".
[i.9] EUREF: "European Terrestrial Reference System 89 (ETRS89)".
NOTE: Available at http://etrs89.ensg.ign.fr.
[i.10] ETSI TR 101 607 (V1.1.1) (05-2013): "Intelligent Transport Systems (ITS); Cooperative ITS
(C-ITS); Release 1".
[i.11] ISO 3534-1 (10-2009): "Statistics - Vocabulary and symbols - Part 1: General statistical terms and
terms".
[i.12] ETSI TS 136 305 (V11.2.0): "LTE; Evolved Universal Terrestrial Radio Access Network
(E-UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN
(3GPP TS 36.305 version 11.2.0 Release 11)".
[i.13] IETF RFC 5905 (June 2010): "Network Time Protocol Version 4: Protocol and Algorithms
Specification".
[i.14] IEC 60050: "International Electrotechnical Vocabulary", 113-01-08 (instant), 113-01-10 (time
interval), 113-01-13 (duration).
[i.15] IS-QZSS-L6-001: "Quasi-Zenith Satellite System Interface Specification Centimeter Level
Augmentation Service".
NOTE: Available at https://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-l6-001.pdf.
[i.16] IETF RFC 8173 (June 2017): "Precision Time Protocol Version 2 (PTPv2) Management
Information Base".
ETSI
9 ETSI EN 302 890-2 V2.1.1 (2020-10)
[i.17] EN ISO 22418: "Intelligent transport systems - Fast service announcement protocol (FSAP) for
general purposes in ITS" (produced by CEN).
TM
1609.3: "IEEE Standard for Wireless Access in Vehicular Environments (WAVE) --
[i.18] IEEE
Networking Services".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
accuracy: closeness of a measured value to a standard or known value
heading: orientation of the horizontal velocity vector with respect to the WGS84 [6] North (clockwise), unless
otherwise noted
horizontal speed: magnitude of horizontal velocity-vector of the reference position point
horizontal velocity vector: projection of the 3D velocity vector on the WGS84 [6] ellipsoid
integrity risk: probability, per unit of time, of having a Parameter Failure without issuing an alert within the
Time-to-Alert
ITS constellation: group of ITS-Ss which are exchanging ITS data among themselves
ITS time: time based on TAI
st
NOTE: Epoch of this time is set to 2004-01-01T00:00:00Z, that is 0 seconds on 1 of January 2004 UTC.
parameter failure: failure occurring when the position and time entity is unable to estimate parameters with an error
less than the maximum tolerable error (err > err_max)
position integrity: measure of the trust that can be placed in the correctness of the estimated Parameters supplied by the
Position and Time entity
NOTE: Integrity includes the ability of the equipment (at the Position and Time entity and/or User level) to
compute timely and valid alerts when the estimated Parameters do not need to be used for the operation of
interest.
protection level: estimated bound on the Parameter Error from the Position and Time entity at a defined confidence
level such as 50 %, 75 %, 95 %, 99 %, etc., delivered with the Parameters
station clock: clock representing ITS time in an ITS Station
Time-to-Alert: maximum allowable elapsed time from the onset of a Parameter Failure until the equipment annunciates
the alert
velocity: vector indicating speed in a particular direction
vertical velocity vector: projection of the 3D velocity vector on the normal vector of the WGS84 [6] Ellipsoid
3.2 Symbols
For the purposes of the present document, the following symbols apply:
Tsys ITS Station Time
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10 ETSI EN 302 890-2 V2.1.1 (2020-10)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3D 3 Dimensional
ACC Automatic Crouse Control
ACK Acknowledgement
ASN Abstract Syntax Notation
BSA Basic Set of Applications
CA Cooperative Awareness (service)
CACC Cooperative Adaptive Cruise Control
CAM Cooperative Awareness Message
CCAM Cooperative, Connected and Automated Mobility
CDD Common Data Dictionary
CP Collective Perception (service)
CVIS Cooperative Vehicle-Infrastructure Systems
DEN Decentralized Environmental Notification
DENM Decentralized Environmental Notification Message
D-GNSS Differential Global Navigation Satellite System
ECU Electronic Control Unit
EDAS EGNOS Data Access Service
EGNOS European Geostationary Navigation Overlay Service
EU European Union
FA-SAP Facilities to Applications Service Access Point
GLONASS GLObal NAvigation Satellite System
GNSS Global Navigation Satellite Systems
GPC GNSS Positioning Correction
GPS Global Positioning System
GRM GPS Raw data Message
IEC International Electrotechnical Commission
IETF Internet Engineering Task Force
ISO International Organization for Standardization
ITRF International Terrestrial Reference Frame
ITS Intelligent Transport Systems
ITS-C ITS Constellation
ITS-S ITS Station
ITU-T International Telecommunication Union - Telecommunication standardization sector
MAC Media Access Control
NA Not Applicable
NF-SAP Network to Facilities Service Access Point
NGA National Geospatial-intelligence Agency
NRTK Network Real Time Kinematic
NTP Network Time Protocol
PDU Protocol Data Unit
PoTi Position and Time
PPP Precise Point Positioning
PSID Provider Service Identifier
RAN Radio Access Network
RF Radio Frequency
RFC Request For Comment
R-ITS-S Roadside ITS Station
RTCM Radio Technical Commission for Maritime services
RTCMEM Radio Technical Commission for Maritime services Environmental Message
RTK Real Time Kinematic
SA Service Announcement
SAM Service Announcement Message
SF-SAP Security to Facilities Service Access Point
SI Standard International
SIFS Short InterFrame Space
SLR Satellite Laser Ranging
SPATEM Signal Phase And Timing Extended Message
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11 ETSI EN 302 890-2 V2.1.1 (2020-10)
SSR Sirius Satellite Radio
TAI International Atomic Time scale
TCU Transmission Control Unit
ToF Time-of-Flight
UE User Equipment
UPER Unaligned Packet Encoding Rules
UTC Coordinated Universal Time
UWB Ultra Wide Band
VLBI Very-Long-Baseline Interferometry
VRU Vulnerable Road User
WGS World Geodetic System
WGS84 World Geodetic System 1984
4 Position and Time entity introduction
4.1 Introduction
ITS applications such as specified in the Basic Set of Applications specification (BSA) ETSI TR 102 638 [i.2] require
the exchange of position and time information as part of the information exchange among ITS-Ss. As initial ITS
location based services, the Cooperative Awareness (CA) basic service ETSI EN 302 637-2 [i.3] and similar, the road
traffic event Decentralized Environmental Notification (DEN) basic service ETSI EN 302 637-3 [i.4] are developed.
These services and their data exchanges are dependent on position and time information. In this and the following
clauses it is understood that "position" means kinematic and attitude state as defined in clause 5.4.1 which includes
attitude and movement parameters including velocity, heading, horizontal speed and optionally others.
In order to realize road ITS safety related applications, ITS-Ss need to have an absolute knowledge about their position
and have a common synchronized knowledge about time to be able to value information received from another ITS-Ss.
To realize this absolute knowledge about position and time, an ITS-S may be equipped with a Global Navigation
Satellite Systems (GNSS) making use of Galileo or GPS and/or other satellite navigation technologies, providing
satellite positioning information to the PoTi entity.
Depending on the applications supported by an ITS-S, the qualitive requirements on the accuracy, integrity and
reliability of the position and time references may vary. As the CA basic service (ETSI EN 302 637-2 [i.3]) specifies,
road safety applications may require the ITS-S to transmit position and time information at intervals of about 10 times a
second, while new applications such as Platooning requires intervals of ≥ 20 times a second.
ITS applications are based on the exchange of information among ITS-Ss and therefore ITS applications operating in
one ITS-S are depending on the information provided by other ITS-Ss, a set of minimum requirements to be supported
by all ITS-Ss needs to be agreed. As new ITS applications are constantly being developed these minimum requirements
need to be set for a selective set of (grouped) ITS applications. At the current state an ETSI Release 1 set of ITS
standards (ETSI TR 101 607 [i.10]) is the reference for the Release 1 equipment and therefore it provides the
requirements for the Release 1 PoTi requirements.
Based on the current developments of new services and related analyses by EU projects further optional requirements
are included.
The position and time (PoTi) service as identified in ETSI TS 102 894-1 [i.5] residing in the facility layer is an essential
part of the ITS; it provides time and position information to all ITS applications and services.
In order to satisfy the application requirements and different Releases of application sets, the PoTi entity may include
various methods to ensure the accuracy, integrity and reliability of the position and time references as required by the
ITS applications supported by the ITS-S.
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12 ETSI EN 302 890-2 V2.1.1 (2020-10)
4.2 Service provided by the PoTi entity
The facility layer PoTi entity manages the position and time information for use by ITS applications, facility, network,
management and security layers. For this purpose, it gets information from sub-system entities such as GNSS, sensors
and other sub-system entities. Given the ITS application requirements in terms of position and time accuracy, PoTi may
use augmentation services to improve the position and time accuracy. Various augmentation methods may be applied.
PoTi may support these augmentation services by providing messages services broadcasting augmentation data. For
instance, a roadside ITS-S may broadcast correction information for GNSS to oncoming vehicle ITS-S; ITS-Ss may
exchange raw GPS data or may exchange terrestrial radio position and time relevant information. PoTi maintains and
provides the position and time reference information according to the application and facility and other layer service
requirements in the ITS-S.
5 PoTi functional description
5.1 PoTi in the ITS Domain
The ITS reference architecture is defined in ETSI EN 302 665 [i.1]. It defines the ITS Station (ITS-S) architecture as
part of the ITS domain. In the ITS domain, at a particular time an ITS-S may be in a situation when no other ITS-Ss are
active within its communication range, while at another moment it may be in a situation in which there are many ITS-Ss
active within its communication range. An ITS Constellation (ITS-C) is a group of ITS-Ss that communicate with each
other. ITS-Cs may overlap, and an ITS-S may be active in several ITS-Cs but in general not necessary in all as not all
ITS-Cs need to overlap (see Figure 1).

Figure 1: Momentary ITS-Cs in the ITS domain
5.2 ITS Constellation
ITS services are based on sharing information between ITS-Ss. Applications in ITS-Ss receive messages containing
information from neighbouring ITS-Ss and use this to provide services in the receiving ITS-S. It is therefore essential
that receiving ITS-Ss can identify the time and position relevance of the content of each message. ITS-Ss in the same
ITS-C shall have a consistent understanding of position and time for the services they support. When ITS-C overlap,
only those in the overlapping area shall have an understanding of position and time, of both constellations but other
ITS-Ss not (see Figure 1).
ITS applications and services may have different time and position requirements. Depending on the ITS services to be
supported by an ITS-S, the time and position accuracy requirements toward the facility service PoTi may differ but are
required to be commonly agreed. To ensure that the existing ITS-Ss in an ITS-C can support each other's active ITS
services, common minimum requirements are agreed based on the ITS Releases. Currently Release 1 and Release 2 ITS
services are distinguished. Minimum common requirements for the Release 1 set of applications are defined in ETSI
TR 102 638 [i.2]. Minimum requirements for Release 2 cannot be set at this time.
The PoTi entity of any ITS-S in a given ITS-C should ensure that Tsys ≈ T (T is the ITS Time) within this ITS-C.
n
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13 ETSI EN 302 890-2 V2.1.1 (2020-10)
IT S- S4
IT S-S2
IT S-S6
PoTi
ITS- S1
PoTi
PoTi
ITS-S 3 ITS- S5
Tsys ≈T
PoTi
Tsys ≈T
2 Po Ti PoTi
Tsys ≈T
Tsys ≈T
Tsys ≈T Tsys ≈T
3 5
Figure 2: Momentary ITS-C
5.3 PoTi in the ITS Station (ITS-S) architecture
PoTi is a facilities layer entity that manages the Position and Time information required by the application, facility,
network, management and security layers. It ensures ITS time synchronicity between the ITS-Ss in the ITS system, it
maintains the data quality (e.g. by monitoring time deviation) and manages updates of the kinematic and attitude state
and time. The PoTi entity may include augmentation services to improve the position and time accuracy, integrity, and
reliability. Among these methods, communication technologies may be used to provide positioning assistance from
mobile to mobile ITS-Ss and infrastructure to mobile ITS-Ss.
The PoTi entity interfaces with ITS applications and other facility layer entities in order to provide position and time
information, such as CA basic service described in ETSI EN 302 637-2 [i.3] and DEN basic service described in ETSI
EN 302 637-3 [i.4], C-ACC described in ETSI TR 103 299 [i.6] and CP described in ETSI TS 103 324 [i.7] basic
service. Figure 3 presents PoTi in the ITS-S architecture according to ETSI EN 302 665 [i.1].

Figure 3: The PoTi entity its interfaces to other facilities entities via the FA-SAP,
and its interfaces in the ITS-S architecture according to ETSI EN 302 665 [i.1]
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5.4 PoTi entity functional architecture
5.4.1 General
Figure 4 illustrates functions and interfaces of the PoTi entity.

Figure 4: PoTi entity functional architecture
The functions are described in the following clauses. The interfaces are described in clause 5.5.
5.4.2 Position information Management
• The kinematic and attitude state of the rigid body contained in the ITS-S included position, velocity,
acceleration, orientation, angular velocity and possible other motion related information. The position
information at a specific moment in time is referred to as the kinematic and attitude state including time, of the
rigid body.
NOTE 1: If not otherwise stated all these quantities are provided in 3D.
• In addition to the kinematic and attitude state, PoTi should also maintain information on the confidence of the
kinematic and attitude state variables.
An ITS-S should at least be functional when the system of which it is part of is in operation. The PoTi entity should be
functional when the ITS-S is operating.
NOTE 2: As for many implementations it takes time for the PoTi entity to provide proper information. The PoTi
entity may be functional for a period of time when the system of which it is part of is not operational.
Once the system is reactivated, the PoTi entity should validate the kinematic and attitude state and
confidences whether it still meets the system requirements.
An ITS-S may use multiple means of positioning if they are available (e.g. GNSS, inertial sensors, odometer, cameras,
terrestrial radio ranging, map matching, etc.). Depending on the applications and services an ITS-S needs to support an
ITS-S could use single or multiple augmentation services to improve its position and time accuracy.
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5.4.3 Position Augmentation
• The Position augmentation function uses externally sourced assistance data or measurements in order to
improve positioning performance by eliminating system errors common to many ITS-Ss.
• Satellite based augmentation: in Europe, European Geostationary Navigation Overlay Service (EGNOS) is
provided to improve GNSS position accuracy. RTK and SSR services are also augmentation services that can
be used by GNSS receivers; they may be distributed across satellite channels or terrestrial communication
links including from other ITS-Ss.
• Cooperative positioning: ITS-Ss may exchange information to improve the relative positioning. Ground based
augmentation such as EGNOS, RTCM or SSR based (PPP-RTK) services can be distributed over terrestrial
communications channels to augment GNSS data. R-ITS-S could transmit RTCM or SSR correction
information to vehicle ITS-Ss, as specified in ETSI TS 103 301 [1].
5.4.4 Reference coordinate System Conversion
The reference coordinate System Conversion function converts the kinematic and attitude state between different
reference systems, e.g. to and from local (vehicle) coordinate systems or ITRF14 or ETRS89. Relative positioning is a
sub function of Reference coordinate System Conversion and involves the conversion from the WGS84 [6] coordinate
system to local coordinates systems, as e.g. used in DENM traces.
The Reference coordinate System Conversion is used for instance to describe relevance areas:
• Where the relevance area is an ellipse or a rectangle, the Cartesian coordinates of the area center and of the
current position shall be calculated as specified in the ETSI EN 302 931 [11]. For this purpose, the 'local
tangent plane' method is recommended, or another method delivering the same accuracy.
5.4.5 Time information Management
ITS time shall be defined as a time based on TAI. Epoch of ITS time is set to 2004-01-01T00:00:00Z, that is 0 seconds
st
on 1 of January 2004 UTC. ITS time is the general time base for all ITS-Ss. An ITS-S's representation of ITS Time is
referred to as the station clock. A moment in time, or instant, after the epoch can be represented by a timestamp.
A timestamp is the duration of the time interval between the epoch and the instant, derived from the station clock
according to IEC 60050 [i.14].
Time Information Management manages the quality of the station clock, handles updates of the ITS-S time information
and provides the time information to other entities in the ITS-S.
For the ITS-S time information the same activation requirements are valid as for ITS-S position information as
identified in clause 5.4.2.
5.4.6 Time synchronization
The ITS Station should synchronize its station clock by means of one or more external time services (GNSS, NTP),
taking into account accuracy, integrity and reliability of the external service.
NOTE: ITS-Time is based on TAI, and therefore has no special treatments of leap-seconds that are introduced in
UTC at specific moments in time. UTC itself is based on counting SI seconds since an epoch, similar to
ITS-Time. However, several time synchronization protocols, like NTP, modify the clock that counts the
number of SI seconds since the epoch, to facilitate easier conversion from clock counter values to UTC
date/time. Therefore, care should be taken when using such synchronization services to correctly treat the
insertion of UTC leap seconds, specifically also during the insertion of the leap second.
5.4.7 Time reference system conversion Service
• The time reference system conversion takes care of converting from ITS Time to other time reference systems.
PoTi should support the conversion between ITS Time and UTC and vice versa when required by applications.
Support for other time reference systems can also be supported.
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NOTE: UTC is used as the time basis for time information in several messages, like SPATEM in ETSI
TS 103 301 [1].
5.5 PoTi Interfaces
5.5.1 Interface to ITS applications (FA-SAP)
PoTi provides position and time information to ITS applications residing in the ITS-S via the interface IF.Appl as
illustrated in Figure 4. In one possible implementation, the interface IF.Appl may be implemented as SF-SAP as
illustrated in Figure 3.
In one possible implementation of this interface, the position and time information (including confidence values) may
be provided by the PoTi module upon request or automatically upon a given trigger, e.g. when the system receives an
update.
Via the FA-SAP interface security and integrity information could be provided by the PoTi service originating source
...