ISO 17572-4:2020

INTERNATIONAL ISO
STANDARD 17572-4
First edition
2020-04
Intelligent transport systems (ITS) —
Location referencing for geographic
databases —
Part 4:
Precise relative location references
(precise relative profile)
Reference number
ISO 17572-4:2020(E)
©
ISO 2020

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ISO 17572-4:2020(E)

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ISO 17572-4:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Abbreviated terms . 2
5 Conformance . 2
6 Requirements for a location referencing standard . 2
7 Conceptual data model for LFMs . 3
7.1 Role of conceptual model . 3
7.2 Components of conceptual model . 3
7.3 Description of the conceptual model . 3
7.4 Location categories . 3
7.5 Conceptual model of a road network. 4
7.6 Conceptual model of area locations . 5
8 Specification of LRs for precise relative information . 5
8.1 General concept . 5
8.1.1 Methods to be defined in this document . 5
8.1.2 Concept of Method 1: Lane number counting . 5
8.1.3 Concept of Method 2: Displacement from a reference point . 6
8.2 Specification for contents delivering message . 7
8.2.1 Structure of the message . 7
8.2.2 Definition of the components . 8
8.3 Use cases and examples of contents for location referencing messages .11
Annex A (normative) Abstract test suite .12
Annex B (informative) Basic lane model of a road .13
Annex C (informative) Use cases for Precise Relative Location Referencing Method .14
Annex D (informative) Use cases for elements of Precise Relative Location Referencing Method.17
Annex E (informative) Implementation examples of Precise Relative Location Referencing
Method .25
Bibliography .28
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ISO 17572-4:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
A list of all parts in the ISO 17572 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 17572-4:2020(E)

Introduction
A Location Reference (LR) is a unique identification of a geographic object. In a digital world, a real-
world geographic object can be represented by a feature in a geographic database. An example of a
commonly known LR is a postal address of a house. Examples of object instances include a particular
exit ramp on a particular motorway, a road junction or a hotel. For efficiency reasons, LRs are often
coded. This is especially significant if the LR is used to define the location for information about
various objects between different systems. For ITS, many different types of real-world objects will be
addressed. Amongst these, the LR of the road network, or components thereof, is a particular focus.
Communication of a LR for specific geographic phenomena, corresponding to objects in geographic
databases, in a standard, unambiguous manner is a vital part of an integrated ITS system in which
different applications and sources of geographic data will be used. Location Referencing Methods
(LRM), methods of referencing object instances, differ by applications, by the data model used to create
the database, or by the enforced object referencing imposed by the specific mapping system used to
create and store the database. A standard LRM allows for a common and unambiguous identification
of object instances representing the same geographic phenomena in different geographic databases
produced by different vendors, for varied applications, and operating on multiple hardware/software
platforms. If ITS applications using digital map databases are to become widespread, data reference
across various applications and systems must be possible. Information prepared on one system, such as
traffic messages, need to have LRs that are interpretable by all receiving systems. A standard method
to refer to specific object instances is essential to achieving such objectives.
Japanese, Korean, Australian, Canadian, North American and European ITS bodies all support LR
activities . In Japan, precise location referencing is needed due to the increasing introduction of
C-ITS and automated driving systems such as SIP-adus. Due to the mechanisms for the creation of
digital maps, even with high accuracies, representation of a real-world position will differ between
maps. Additionally, because of crustal movement over time, discrepancies would occur for locations
determined simply by measurements from ground-based objects if only latitude and longitude were
utilized.
Location referencing at the precise relative level is needed to describe exact positions and exchange
LRs accordingly. Location referencing at the precise relative level requires referencing to a position
that is sufficiently detailed and accurate to distinguish the lane in which the object exists, and to
distinguish the position within a lane or a lane junction. This does not imply the need to provide an
absolute position with a high accuracy.
This document provides specifications for location referencing for ITS systems (although other
committees or standardization bodies may subsequently consider extending it to a more generic
context).
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INTERNATIONAL STANDARD ISO 17572-4:2020(E)
Intelligent transport systems (ITS) — Location referencing
for geographic databases —
Part 4:
Precise relative location references (precise relative
profile)
1 Scope
This document describes and lists the characteristics of the Precise Relative Location Referencing
Method (PRLRM) which describes precise relative locations in the context of geographic databases and
is used to locate transport-related objects in an encoder system as well as in the decoder side.
This document does not define a physical format for implementing the PRLRM. However, the
requirements for physical formats are defined. This document does not define details of the Precise
Relative Location Referencing System (PRLRS), i.e. how the PRLRM is to be implemented in software,
hardware or processes.
This document specifies PRLRM, comprising:
— conceptual data model for Location Referencing Methods (LFMs);
— specification of location referencing for precise relative information;
— use cases for Precise Relative Location References (informative Annex C);
— use cases for elements of Precise Relative Location References (informative Annex D);
— implementation of Precise Relative Location References (Japanese example) (informative Annex E).
This document defines methods that enable exchange location information of the object to be referenced
in the lane or the lane junction. This document does not specify the road (link) on which the object of
reference exists.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 17572-1:2015, Intelligent transport systems (ITS) — Location referencing for geographic databases —
Part 1: General requirements and conceptual model
ISO 17572-2:2018, Intelligent transport systems (ITS) — Location referencing for geographic databases —
Part 2: Pre-coded location references (pre-coded profile)
ISO 17572-3:2015, Intelligent transport systems (ITS) — Location referencing for geographic databases —
Part 3: Dynamic location references (dynamic profile)
ISO 19148:2012, Geographic information — Linear referencing
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3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 17572-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
lane
strip of carriageway intended to accommodate a single line of moving vehicles, frequently defined by
carriageway marks
3.2
lane junction
area of roadway common to two or more lanes, whether in the same or different directions, frequently
without carriageway marks and where it may be difficult to count lanes
3.3
reference point
point which is used as a starting point for referencing
4 Abbreviated terms
C-ITS Cooperative Intelligent Transport Systems
GNSS Global Navigation Satellite System
ID Identifier
LR Location Referencing (or Reference)
LP Location Point
LRM Location Referencing Method
PRLRM Precise Relative Location Referencing Method
PRLRS Precise Relative Location Referencing System
SIP-adus Cross-ministerial Strategic Innovation Promotion Program Innovation of Automated
Driving for Universal Services (Japan)
5 Conformance
A location referencing message shall be provided as specified in Clause 8.
Any location referencing message claiming conformance with this document shall pass the requirements
presented in the abstract test suite in Annex A.
6 Requirements for a location referencing standard
For details, see ISO 17572-1:2015, Clause 4.
NOTE For an inventory of LRMs, see ISO 17572-1:2015, Annex A.
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Additional requirements for this document are defined as follows.
— A Precise Relative Location Reference shall have a sufficiently high accuracy to distinguish the lane,
or the position within/close to the intersection, in which the referenced object exists.
— A Precise Relative Location Reference shall support the definition of 3-dimension positional
information.
— A Precise Relative Location Reference shall not wholly be reliant on geographic coordinates.
Due to the mechanisms for the creation of digital maps, even with high accuracy, a coordinate
representation of a real-world position can differ between maps. Additionally, there is a(n)
(Earth’s) crustal movement of 20 cm/year in some points in Japan, for example, so there may be
discrepancies between the true location determined in real-time with a high-accurate GNSS and
the location on a map created in the past.
— A reference point shall be defined to reference within an intersection.
Because there is no lane information within an intersection, a reference point which is used as a
basis for reference shall be defined.
— A road section shall have a direction.
In order to distinguish the left and right sides of the lanes, a road section shall have a direction.
7 Conceptual data model for LFMs
7.1 Role of conceptual model
See ISO 17572-1:2015, 5.1.
7.2 Components of conceptual model
See ISO 17572-1:2015, 5.2.
7.3 Description of the conceptual model
See ISO 17572-1:2015, 5.3.
7.4 Location categories
General location categories for LR are defined in ISO 17572-1:2015, 5.4.
Locations for precise relative location reference shall be categorized as point locations, linear locations,
area locations, and solid volume locations. These location categories represent real world objects which
can be described as follows:
— a single position (point location);
— between two points in the same lane (linear location);
— between two points in different lanes (linear location);
— between two points with no lane-specific definition (linear location);
— a bounded area on the same lane (area location);
— a bounded area on different lanes (area location);
— a bounded area with no lane-specific definition (area location);
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— an object position (solid volume location).
7.5 Conceptual model of a road network
One purpose of PRLRS is to be able to locate an object on a road within a specific lane. For this reason,
this subclause expands on the conceptual model of a road network described in ISO 17572-1:2015, 5.5
and adds the concept of a lane. The conceptual model of the road network is, therefore, depicted in
Figure 1 and described in this subclause to give a clear understanding of the different terms and their
relationships. The definition of each word is described in ISO 17572-1:2015, Clause 2 and Clause 4.
Figure 1 shows the conceptual model of a road network.
In general, the road network consists of roads and intersections. A road is generally identified by a
name (or number) and consists of a set of road sections. A road element consists of one or more lanes.
On a road, a very large (but countable) number of road segments can be defined (and referenced).
A road section consists of nodes and edges, is bounded by intersections, and can have intermediate
intersections (where the road name does not change, for example). An intersection is a connection or
crossing of roads. The simplest intersection consists of just one node (i.e. junction). The data model
of a lane may be formed with the addition of location referencing related items to the lane model of
ISO 14296. A basic lane model is shown in Annex B.
Figure 1 — Conceptual model for the physical road network
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7.6 Conceptual model of area locations
See ISO 17572-1:2015, 5.6.
8 Specification of LRs for precise relative information
8.1 General concept
8.1.1 Methods to be defined in this document
The methods to be defined in this document are being adopted for Precise Relative Location References
which allows for location referencing within lanes as defined in 7.5.
There are two ways to reference a location using this method:
— (Method 1) Lane number counting;
— (Method 2) Displacement from a reference point.
Either method is selected by road segment type and/or usage. As a general rule, Method 1 is used to
represent events in lanes (excluding an intersection) and Method 2 is used to represent events in a
junction. However, Method 2 can also be used to represent events in lanes.
This document defines how to express the representative point of each object. It does not explain how
to express the real shape of line, area and solid volume.
Figure 2 shows the two methods for PRLRM.
Figure 2 — Methods for PRLRM
8.1.2 Concept of Method 1: Lane number counting
8.1.2.1 General concept of Method 1
The linearly referenced location shall be referenced by using a distance on a road section and lane
number counting rule. The distance on a road section references the longitudinal location on a road and
the lane number references the lateral location. The distance on a road section may be expressed as a
percentage along the road section or a distance from a start point. The expression shall be consistent
with the definition defined in ISO 19148:2012, 6.2. The vertical location shall be expressed as a relative
height from the road surface. The expression shall be consistent with the definition provided in
ISO 19148:2012, 6.2.
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This method is used for:
— road segments that have lane information;
— specifying the lane.
Figure 3 demonstrates Method 1.
Figure 3 — Explanation of Method 1
8.1.2.2 Procedure to use Method 1
The sender of the location information sends the objective road section, distance from start point, and
object lane for the objective location.
A method provided by ISO17572 -2: 2018 or ISO 17572-3:2015 shall be used to identify the objective road
section. Use the ID in ISO 17572-2:2018, Clause 7 to identify the objective road section. To define the
location of a LP, use ISO 17572-3:2015, 7.2.2.
The start point shall be shared by the sender and the receiver. The start point may be set at any location
within the road section and any location on roadway.
Object lane includes lane counting convention, total number of lanes, object lane number, and specific
lane flag. Specific lane flag is used when the targeting object exists on a specific lane, e.g. specialty lanes
and road shoulders, e.g. bus lanes and emergency parking areas.
The receiver of the location information identifies the road section on its own map from the objective
road section received and the location of the sender from the percentage along distance from start
point, lane counting convention, total number of lanes, object lane number, and specific lane flag.
8.1.3 Concept of Method 2: Displacement from a reference point
8.1.3.1 General concept of Method 2
The location shall be referenced by using the distance from a reference point (dx, dy, dh). The X axis
represents east/west and the Y axis represents north/south. The H axis represents the height.
This method is used for:
— the road segments of lane junctions;
— specifying the relative position within a road (e.g. σ < 25 cm accuracy).
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In order to achieve an accuracy with location measurement errors of σ < 25 cm when using this method,
the following condition shall apply:
— The method is used within a radius of no more than 200 m from the reference point.
Figure 4 demonstrates Method 2.
Figure 4 — Explanation of Method 2
8.1.3.2 Procedure to use Method 2
The sender of the location information sends the object reference point and the distance, in metres,
from the object reference point.
The ID as in 17572-2:2018, Clause 7 is used to identify the object reference point.
The object reference point shall be shared by the sender and the receiver.
The receiver of the location information identifies the reference point on its own map from the object
reference point received and the relative location of the sender from the distance, in metres, from the
object reference point.
8.2 Specification for contents delivering message
8.2.1 Structure of the message
The data structure of Precise Relative Location References is shown in Figure 5.
The process to determine which method to use and the procedure for each method is described in 8.1.
The data structure of the message is defined as below.
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Figure 5 — Data structure for delivering messages
8.2.2 Definition of the components
8.2.2.1 Data type: BasicDescription
BasicDescription is a data type used to represent the LFM and content type of the object.
Table 1 shows the constructional elements of this class.
Table 1 — Data type: BasicDescription
Name Description
LocationReferencingMethod LFM to be used (See Table 2)
Content Type Type of the content to be referred (See Table 8)
8.2.2.2 Enumeration: LocationReferencingMethod
LocationReferencingMethod is an enumeration used to represent which method applies to location
referencing messages.
Table 2 shows the constructional elements of this enumeration.
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Table 2 — Enumeration: LocationReferencingMethod
Name Description
LaneNumberCounting LFM which is defined in 8.1.2 (Method 1)
DisplacementFromAReferencePoint LFM which is defined in 8.1.3 (Method 2)
8.2.2.3 Data type: LaneNumberCounting
LaneNumberCounting is a data type for Method 1. This class is composed of a sub-class
RoadSectionInformation.
8.2.2.4 Data type: RoadSectionInformation
RoadSectionInformation is a data type used to represent the distance from the start point to the object.
Table 3 shows constructional elements of this class.
Table 3 — Data type: RoadSectionInformation
Name Description
LR_PositionExpression See the definition in ISO 19148:2012, 6.2.2.
LROV_VectorOffsetDistanceExpression See the definition in ISO 19148:2012, 6.5.2.
LocationInformationOnLane See LocationInformationOnLane class definition.
8.2.2.5 Data type: LocationInformationOnLane
LocationInformationOnLane is a data type used to distinguish the lane where the object exists.
Table 4 shows constructional elements of this class.
Table 4 — Data type: ObjectiveLane
Name Description
LaneCountingConvention The direction in which the lane number is counted (See Table 5).
TotalNumberOfLanes The total number of lanes within the carriageway.
ObjectiveLaneNumber The lane number of the objective lane.
“ObjectiveLaneNumber =2” denotes the second lane and “ObjectiveL-
aneNumber =2.3” denotes the space between the second and third lane.
“ObjectiveLaneNumber =<0” and “ObjectiveLaneNumber > TotalNum-
berOfLanes” denote areas outside of the road used for regular travel.
SpecificLaneType Special-purpose lane (See Table 6).
This attribute is optional.
More than two of the items may be chosen.
8.2.2.6 Enumeration: LaneCountingConvention
LaneCountingConvention is an enumeration used to represent a convention of lane counting.
Table 5 shows constructional elements of this enumeration.
Table 5 — Enumeration: LaneCountingConvention
Name Description
FromLeft Lane number is counted from the left side of the road area. The direc-
tion of the road section shall be defined.
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Table 5 (continued)
Name Description
FromRight Lane number is counted from the right side of the road area. The direc-
tion of the road section shall be defined.
FromCentre Lane number is counted from the area established in the centre to di-
vide the traffic flow bi-directionally, such as the central reservation.
FromRoadShoulder Count the road shoulder as a lane. Road shoulders are areas outside
of the road used for regular travel, on the opposite side of the central
reservation.
Figure 6 illustrates the lane counting convention.
Figure 6 — Illustration of lane counting convention
8.2.2.7 Enumeration: SpecificLaneType
SpecificLaneType is an enumeration used to represent lanes that are designated for some specific
purpose.
Table 6 shows constructional elements of this enumeration.
Table 6 — Enumeration: SpecificLaneType
Name Description
Bus Bus lane
HOV High-Occupancy Vehicle lane
Bicycle Bicycle lane
Pedestrian Pedestrian lane
Reversible Reversible lane
Auxiliary Extra lane constructed between on and off ramps
Overtaking Overtaking lane
SlowVehicle Slow vehicle lane
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Table 6 (continued)
Name Description
Other Areas outside of the road used for regular travel, such as road shoul-
ders and emergency parking areas; specialty lanes besides those men-
tioned above
8.2.2.8 Data type: DisplacementFromAReferencePoint
Displacemen
...