ISO 17438-3:2024

International
Standard
ISO 17438-3
First edition
Intelligent transport systems —
2024-09
Indoor navigation for personal and
vehicle ITS stations —
Part 3:
Requirements and specification for
indoor positioning reference data
Systèmes de transport intelligents — Navigation interne pour
station personnelle et véhicule ITS —
Partie 3: Exigences et spécification pour les données de référence
de positionnement intérieur
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms and definitions .1
3.2 Abbreviated terms .4
4 Requirement and conformance. 5
4.1 Requirements .5
4.2 Conformance .5
5 Conventions . 5
6 Indoor positioning references for positioning at P/V-ITS-stations . 5
6.1 Overview .5
6.2 Scope of indoor positioning references .6
6.3 Use cases of indoor positioning references .6
7 Definition of indoor positioning references . 6
Annex A (normative) ASN.1 module . 14
Annex B (informative) An example of indoor positioning references — WiFi .16
Bibliography .18

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
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Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
With the spread of nomadic and mobile devices such as smart phones and the rapid expansion of indoor
spaces, many of the services and facilities related to the transport system have become accessible to indoor
spaces. Consequently, navigation in indoor space is considered a new killer application in the transport
industry.
The objective of this document is to provide a basic data model and encoding format for indoor positioning
reference data required for indoor navigation functionality for ITS applications. This document is intended
to be used by designers, developers and providers of indoor navigation services. When implemented, this
document is intended to:
1) provide developers and designers with concepts and appropriate information to implement indoor
navigation services;
2) provide developers and designers with interoperable ways to use indoor navigation data from various
sources for indoor navigation;
3) enable the provision of indoor navigation services to users;
4) provide developers and designers with an extendable base for indoor navigation.

v
International Standard ISO 17438-3:2024(en)
Intelligent transport systems — Indoor navigation for
personal and vehicle ITS stations —
Part 3:
Requirements and specification for indoor positioning
reference data
1 Scope
This document defines requirements and specifications for indoor positioning references, which can be
referenced for positioning in indoor space, for supporting indoor navigation functionality of a personal/
vehicle (P/V) ITS station.
This document defines:
a) the composition of indoor positioning references for use in obtaining indoor positions for indoor
navigation of P/V-ITS-stations;
b) the schema and encoding format of indoor positioning references for P/V-ITS-stations.
This document focuses on indoor positioning references. The following issues which are adjunctive but
essential for commercial navigation services are beyond the scope of this document:
— authorized and authenticated access of users and services, including security;
— payment;
— preparation of indoor data which are necessary for indoor navigation;
— low-level communication protocols required to transfer and share data from and to a roadside ITS station
or a central ITS station;
— other issues dependent on implementation of an instance of indoor navigation.
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 13184-2, Intelligent transport systems (ITS) — Guidance protocol via personal ITS station for advisory
safety systems — Part 2: Road guidance protocol (RGP) requirements and specification
ISO 17438-1, Intelligent transport systems — Indoor navigation for personal and vehicle ITS station — Part 1:
General information and use case definition
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13184-2 and ISO 17438-1 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
nomadic device
ND
implementation of a personal ITS station which provides communication connectivity via portable
equipment such as cellular telephones, wireless communication network (3G, 4G and 5G), mobile wireless
broadband (WIMAX, HC-SDMA, etc.), etc. and includes short range links, such as IEEE 802.11x, etc. to connect
portable devices to the motor vehicle communications system network
Note 1 to entry: Nomadic devices that have hardware security modules and have been certified to be ITS-trusted are
called a personal ITS station.
[SOURCE: ISO 23795-2:2024, 3.1.1, modified — Note 1 to entry has been added.]
3.1.2
navigation
combination of routing, route transversal and tracking
Note 1 to entry: This is essentially the common term "navigation", but the definition decomposes the process in terms
used in the packages defined in ISO 19133.
[SOURCE: ISO 19133:2005, 4.15, modified — “this International Standard” has been replaced by “ISO 19133”
in the definition.]
3.1.3
indoor navigation
navigation provided in indoor space
[SOURCE: ISO 17438-4:2019, 3.1.2]
3.1.4
indoor navigation data
data needed for indoor navigation, which includes indoor maps and indoor positioning infrastructure
information
[SOURCE: ISO 17438-4:2019, 3.1.13]
3.1.5
indoor space
space within artificial structures such as buildings and facilities connected with transport corridors or roads
EXAMPLE A building or indoor parking lot.
[SOURCE: ISO 17438-1:2016, 3.1.2]
3.1.6
ITS station
ITS-S
entity in a communication network, comprised of application, facilities, networking and access layer
components specified in ISO 21217 that operate within a bounded secure management domain
[SOURCE: ISO 13184-2:2016, 3.5]

3.1.7
personal/vehicle ITS station
P/V-ITS-S
ITS station implemented in a vehicle or personal mobile device
[SOURCE: ISO 17438-4:2019, 3.1.4, modified — "personal mobile device" has been replaced by "mobile
device" in the definition.]
3.1.8
roadside ITS station
R-ITS-S
system that receives and processes vehicular and pedestrian information within a certain zone
Note 1 to entry: The system is installed at the roadside.
[SOURCE: ISO 13184-2:2016, 3.9, modified — "and determines the situation, in order to provide the safety
warning and parking guide service to vehicles and pedestrians" has been removed from the definition.]
3.1.9
central ITS station
central ITS-S
C-ITS-S
implementation of an ITS-S in a central ITS subsystem
[SOURCE: ISO 17438-4:2019, 3.1.6]
3.1.10
indoor positioning
determination of a location in an indoor space
[SOURCE: ISO 17438-4:2019, 3.1.7]
3.1.11
client-based indoor positioning
indoor positioning executed at a personal/vehicle ITS station (P/V-ITS-S)
[SOURCE: ISO 17438-4:2019, 3.1.8]
3.1.12
server-based indoor positioning
indoor positioning executed at a central ITS station (C-ITS-S)
[SOURCE: ISO 17438-4:2019, 3.1.9]
3.1.13
indoor positioning infrastructure
infrastructure used to determine locations of personal/vehicle ITS stations (P/V-ITS-S) in an indoor space
EXAMPLE Wi-Fi, Bluetooth, etc.
[SOURCE: ISO 17438-4:2019, 3.1.11]
3.1.14
indoor positioning reference
information to support indoor positioning
Note 1 to entry: Detailed specifications and contents of indoor positioning references depend on the specific indoor
positioning technologies.
EXAMPLE A good example of an indoor positioning reference is information about indoor positioning
infrastructure. For Wi-Fi based positioning, the indoor positioning infrastructure information includes the Wi-Fi APs
information, such as location, SSID, and RSSI values of APs.

[SOURCE: ISO 17438-4:2019, 3.1.12, modified — Example 1 and Example 2 have been combined into a single
Example.]
3.1.15
fingerprint map
map including information about specific positioning resources at target locations.
Note 1 to entry: Examples of positioning resources are WiFi, BLE, LTE, etc.
Note 2 to entry: For Wi-Fi based positioning, WiFi fingerprint map can be defined.
Note 3 to entry: The concrete concept of a fingerprint map for indoor positioning can be a form of the indoor positioning
reference.
3.1.16
WGS84 coordinate system
reference system used in the satellite-based positioning system, Global Positioning System (GPS)
Note 1 to entry: The World Geodetic System (WGS) is a standard for use in cartography, geodesy and navigation. The
latest version is WGS84.
[SOURCE: ISO 13184-2:2016, 3.11, modified — "NAVSTAR Global Positioning System" has been updated to
"Global Positioning System" in the definition.]
3.2 Abbreviated terms
AP access point
ASN abstract syntax notation
BLE bluetooth low energy
BS base station
C-ITS-S central ITS station
CID cell identifier
CRS coordinate reference system
EPSG European Petroleum Survey Group
GNSS global navigation satellite system
GPS global positioning system
ITS intelligent transport systems
ITS-S ITS station
LTE long term evolution
M/O mandatory/optional
MBR minimum bounding rectangle
MCC mobile country code
MNC mobile network code
MO maximum occurrence
P/V-ITS-S personal/vehicle its station
R-ITS-S roadside its station
RSSI received signal strength indicator
SSID service set identifier
TA timing advance
UUID universally unique identifier
WGS World Geodetic System
4 Requirement and conformance
4.1 Requirements
This document defines use cases and message interfaces between a P/V-ITS-S and a C-ITS-S for supporting
client-based indoor positioning functionality. In the definitions of data types for supporting the client-
based indoor positioning, there are mandatory, optional or conditional fields. Mandatory fields shall be
provided and conditions for conditional fields shall be satisfied. These are the requirements embedded in
the definition of data types for supporting client-based positioning.
Specific encoding of each data type can be adapted for implementation. There can be additional requirements
for specific encoding.
4.2 Conformance
For the purpose of conformance to the client-based indoor positioning for which messages are defined in
Clause 7, multiplicity of the elements in a message should be observed through their implementations.
5 Conventions
This document is based on the conventions of ASN.1 (Abstract Syntax Notation One) formats.
6 Indoor positioning references for positioning at P/V-ITS-stations
6.1 Overview
The GNSS signal which is generally used to calculate the positions of mobile devices outdoor cannot be
acquired in indoor space. Therefore, for positioning in indoor spaces, other positioning technologies are
needed. For indoor positioning, various technologies and infrastructures can be used and information
for supporting the indoor positioning should be constructed in advance according to the types of indoor
positioning. The indoor positioning references are shared between a P/V-ITS-S and a C-ITS-S, according to
the architecture of the indoor navigation implemented.
Indoor positioning can be categorized into two groups, depending on where it runs:
a) client-based indoor positioning; and
b) server-based indoor positioning.
In the client-based indoor positioning architecture, the positioning, i.e. the calculation of a P/V-ITS-S, is
executed in the P/V-ITS-S. Therefore, the P/V-ITS-S needs to obtain the indoor positioning references
from a C-ITS-S, which normally maintains them. In the server-based indoor positioning architecture, a
C-ITS-S calculates the position of a P/V-ITS-S dependent on the request for positioning from the P/V-ITS-S.
Therefore, the P/V-ITS-S does not need to obtain the indoor positioning references. This document defines

the specification, requirements and messages for the indoor positioning references directly used in the
client-based indoor positioning.
Further to this, client-based indoor positioning can be categorized into another two groups:
1) positioning using information regarding the positioning infrastructure installation; and
2) positioning using indoor positioning references, such as a fingerprint map, constructed from indoor
positioning resources obtained in advance in the target indoor space.
Positioning as described in point 1) requires the installation coordinates of the positioning infrastructure,
such as the installation coordinates of WiFi APs when WiFi indoor positioning is used for calculating the
current position of a P/V-ITS-S, which is generally based on concepts of the triangulation. However, due to
privacy and security reasons, such installation coordinates are not normally open, so they are often not
available.
Positioning as described in point 2) requires pre-acquired resources, i.e. indoor positioning references,
such as the signal strength (RSSI) map of WiFi APs when WiFi indoor positioning is used for calculating the
current positioning of a P/V-ITS-S. Such information can be shared with appropriate permissions.
6.2 Scope of indoor positioning references
The scope of indoor positioning references depends on the type of indoor positioning technologies or
methods available. In this document, the scope of indoor positioning references is limited to the fingerprint
map format using the following positioning resources, taking into consideration the public availability of
indoor positioning methods, the spread of indoor positioning infrastructure, and the possibility of obtaining
related information:
— WiFi;
— BLE;
— LTE;
— Geomagnetic.
In addition to the resources for indoor positioning, other types of positioning resources may be additionally
considered according to the configuration of systems and services to be implemented and the type of indoor
positioning to be used.
6.3 Use cases of indoor positioning references
Use cases regarding indoor positioning references for P/V-ITS-S (client)-based positioning are described in
ISO 17438-4:2019, UC 2.4 – Retrieving an indoor positioning reference.
This use case describes the sequence by which a P/V-ITS-S requests an indoor positioning reference and a
C-ITS-S returns it. The message definition and the flow of messages are also defined in ISO 17438-4.
7 Definition of indoor positioning references
Indoor positioning references in the form of a fingerprint map include values to be used for the indoor
positioning, such as WiFi RSSI and BLE RSSI, that can be obtained at a specific location in an indoor space.
The indoor positioning references are transferred to a P/V-ITS-S from a C-ITS-S using the “reference”
attribute of the “indoor-positioning-reference” message defined in ISO 17438-4:2019, 8.13.
Although the data type of the “reference” attribute wit
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