Intelligent transport systems (ITS) — Location referencing for geographic databases — Part 1: General requirements and conceptual model

The ISO 17572 series specifies location referencing methods (LRMs) that describe locations in the context of geographic databases and that are intended for use in locating transport-related phenomena both in an encoder system and from the decoder side. This document defines what is meant by such objects and describes the reference in detail, including whether or not components of the reference are mandatory or optional, and their characteristics. The ISO 17572 series specifies three different LRMs: — pre-coded LRM (pre-coded profile); — dynamic LRM (dynamic profile); — precise relative LRM (precise relative profile). The ISO 17572 series does not define a physical format for implementing the LRM. However, the requirements for physical formats are defined. The ISO 17572 series does not define details of the location referencing system (LRS), i.e. how the LRMs are to be implemented in software, hardware or processes. This document specifies the following general LRM-related subjects: — requirements of an LRM; — conceptual data model for LRMs; — inventory LRMs (see Annex A). This document also provides: — examples of conceptual model use (see Annex B); — a comparison of definitions with ISO/TC 211 (see Annex C).

Systèmes de transport intelligents (ITS) — Localisation pour bases de données géographiques — Partie 1: Exigences générales et modèle conceptuel

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Publication Date
21-Jul-2022
Current Stage
6060 - International Standard published
Due Date
19-Oct-2022
Completion Date
22-Jul-2022
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INTERNATIONAL ISO
STANDARD 17572-1
Third edition
2022-07
Intelligent transport systems (ITS) —
Location referencing for geographic
databases —
Part 1:
General requirements and conceptual
model
Systèmes de transport intelligents (ITS) — Localisation pour bases de
données géographiques —
Partie 1: Exigences générales et modèle conceptuel
Reference number
ISO 17572-1:2022(E)
© ISO 2022
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ISO 17572-1:2022(E)
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© ISO 2022

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© ISO 2022 – All rights reserved
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ISO 17572-1:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 7

5 Objectives and requirements for a location referencing method ...................................................................7

5.1 Objectives for an optimal location referencing method .................................................................................... 7

5.2 Requirements of the location referencing method ................................................................................................ 8

6 Conceptual data model for location referencing methods ...................................................................................... 9

6.1 Role of conceptual model............................................................................................................................................................... 9

6.2 Components of conceptual model .......................................................................................................................................... 9

6.3 Description of the conceptual model ............................................................................................................................... 10

6.4 Location categories ......................................................................................................................................................................... 10

6.5 Conceptual model of a road network ............................................................................................................................... 11

6.6 Conceptual model of area locations ..................................................................................................................................12

Annex A (informative) Inventory of location referencing methods ................................................................................14

Annex B (informative) Examples of location referencing methods in use (mapping to

conceptual data model for location referencing systems) ...................................................................................18

Annex C (informative) Comparison of definitions with ISO/TC 211 ...............................................................................20

Bibliography .............................................................................................................................................................................................................................21

iii
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ISO 17572-1:2022(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

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

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

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/

iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

This third edition cancels and replaces second edition (ISO 17572-1:2015), which has been technically

revised.
The main changes are as follows:
— Annex C has been significantly reduced;
— Annex D, Annex E and Annex F have been deleted;

— cross-references have been updated throughout the document to refer to the most recent edition of

the relevant publication;
— various minor editorial modifications have been made throughout.
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.
© ISO 2022 – All rights reserved
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ISO 17572-1:2022(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 location reference 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,

location references are often coded. This is especially significant if the location reference is used to

define the location for information about various objects between different systems. For intelligent

transport systems (ITS), many different types of real-world objects are addressed. Amongst these,

location referencing of the road network, or components thereof, is a particular focus.

Communication of a location reference for specific geographic phenomena, corresponding to objects

in geographic databases, in a standardized, unambiguous manner is a vital part of an integrated ITS

system in which different applications and sources of geographic data are 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 standardized location referencing method 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, it is necessary for data referencing across various applications to be possible. Information

prepared on one system, such as traffic messages, needs to be interpretable by all receiving systems. A

standardized method to refer to specific object instances is essential in achieving such objectives.

LR activities are currently supported by Japanese, Korean, Australian, Canadian, US and European ITS

bodies. Japan has developed a link specification for vehicle information and communication systems

(VICS). In Europe, the radio data system – traffic message channel (RDS-TMC) traffic messaging system

has been developed. In addition, methods have been developed and refined in the EVIDENCE and

AGORA projects based on intersections identified by geographic coordinates and other intersection

descriptors. In the US, standards for location referencing have been developed to accommodate several

different location referencing methods.

This document provides specifications for location referencing for ITS systems (although other

committees or standardization bodies can subsequently consider extending it to a more generic

context). Other LR methods for transport protocol experts group (TPEG) and geographic information

are defined in the following documents:

— ISO/TS 21219-21, Intelligent transport systems — Traffic and travel information via transport protocol

experts group, generation 2 (TPEG2) — Part 21: Geographic location referencing (TPEG-GLR)

— ISO/TS 21219-22, Intelligent transport systems — Traffic and travel information (TTI) via transport

protocol experts group, generation 2 (TPEG2) — Part 22: OpenLR location referencing (TPEG2-OLR)

— ISO 19148, Geographic information — Linear referencing
© ISO 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO 17572-1:2022(E)
Intelligent transport systems (ITS) — Location referencing
for geographic databases —
Part 1:
General requirements and conceptual model
1 Scope

The ISO 17572 series specifies location referencing methods (LRMs) that describe locations in the

context of geographic databases and that are intended for use in locating transport-related phenomena

both in an encoder system and from the decoder side. This document defines what is meant by such

objects and describes the reference in detail, including whether or not components of the reference are

mandatory or optional, and their characteristics.
The ISO 17572 series specifies three different LRMs:
— pre-coded LRM (pre-coded profile);
— dynamic LRM (dynamic profile);
— precise relative LRM (precise relative profile).

The ISO 17572 series does not define a physical format for implementing the LRM. However, the

requirements for physical formats are defined.

The ISO 17572 series does not define details of the location referencing system (LRS), i.e. how the LRMs

are to be implemented in software, hardware or processes.
This document specifies the following general LRM-related subjects:
— requirements of an LRM;
— conceptual data model for LRMs;
— inventory LRMs (see Annex A).
This document also provides:
— examples of conceptual model use (see Annex B);
— a comparison of definitions with ISO/TC 211 (see Annex C).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
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ISO 17572-1:2022(E)
3.1
accuracy

measure of closeness of results of observations, computations, or estimates to the true values or the

values accepted as being true
3.2
area
two-dimensional, geographical region on the surface of the Earth

Note 1 to entry: An area can be represented as an implicit area or an explicit area.

3.3
area location

two-dimensional location, representing a geographical region on the surface of the Earth

3.4
attribute
characteristic property of a real-world feature

Note 1 to entry: This property allows the identification of a specific feature by its attributes. An attribute has a

defined type and contains a value. Attributes can be either simple, consisting of one atomic value, or composite

(see composite attribute).
3.5
coordinate

one of an ordered set of N numbers designating the position of a point in N-dimensional space

Note 1 to entry: N would be 1, 2 or 3.
3.6
complex intersection

intersection that consists at least of two or more junctions and one or more road elements

3.7
datum

parameter or set of parameters that realize the position of the origin, the scale, and the orientation of a

coordinate system

[SOURCE: ISO 19111:2019, 3.1.15, modified — admitted term ("reference frame") removed.]

3.8
descriptor
characteristic of a geographic object, usually stored as an attribute
EXAMPLE Road names or road numbers.
3.9
digital map database

structured set of digital and alphanumeric data portraying geographic locations and relationships of

spatial features

Note 1 to entry: Typically, such structures represent, but are not limited to, the digital form of hard copy maps.

For example, drawings can be imported into a geographic information system (GIS) and considered as a form of

digital map.
3.10
dynamic location reference

location reference generated on-the-fly based on geographic properties in a digital map database

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ISO 17572-1:2022(E)
3.11
explicit area

two-dimensional face on the surface of the earth, with a specified outline either being a simple

geometric figure or an irregular outline/polygon
3.12
geodetic reference frame

reference frame or datum describing the relationship of a two- or three-dimensional coordinate system

to the Earth
[SOURCE: ISO 19111:2019, 3.1.34, modified — Note 1 to entry has been removed.]
3.13
implicit area

selection of road segments to be referenced belonging to a certain area (subnetwork)

Note 1 to entry: One implicit area can be built up of multiple subnetworks that are geographically connected.

3.14
international terrestrial reference frame
ITRF

Earth-centred global reference frame, including an Earth model, based on satellite and terrestrial data;

realization of the international terrestrial reference system (ITRS)

Note 1 to entry: The ITRF is a realization of the international terrestrial reference system (ITRS). It contains

primary parameters defining the shape, angular velocity and the earth mass of an Earth ellipsoid, and secondary

parameters defining a gravity model of the Earth. Primary parameters are used to derive latitude-longitude

coordinates (horizontal datum). The ITRF94 reference frame is defined in ISO 19161-1.

3.15
international terrestrial reference system
ITRS

reference system for the Earth derived from precise and accurate space geodesy measurements,

not restricted to GNSS Doppler measurements, which is periodically tracked and revised by the

International Earth Rotation and Reference Service

Note 1 to entry: The basic information and the requirements related to the ITRS are defined in ISO 19161-1.

3.16
intersection
crossing and/or connection of two or more roads

Note 1 to entry: In the ISO 20524 series (Geographic Data Files, GDF), an intersection is a level 2 representation of

a junction which bounds a road or a ferry. It is a complex feature, composed of one or more level 1 junctions, road

elements and enclosed traffic areas. The definition in this document is different from that of the ISO 20524 series

because the location referencing system refers to real-world objects rather than a database definition, as defined

in the ISO 20524 series.

Note 2 to entry: Crossings can be at-grade or grade-separated. Crossings that are grade-separated where no

connection between the road segments exists are excluded from this definition.
3.17
road junction
junction
elementary element in the road network, connecting two or more road elements

Note 1 to entry: In the ISO 20524 series (Geographic Data Files, GDF), a junction is a level 1 feature that bounds

a road element or ferry connection. Junctions that represent real crossings are at least trivalent (having three

roads connected). A bivalent junction can only be defined if an attribute change occurs along the road (e.g. road

name change). A junction is also coded at the end of a dead-end road, to terminate it.

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ISO 17572-1:2022(E)
3.18
linear location
location that has a one-dimensional character
EXAMPLE A road segment.
3.19
link
edge

direct topological connection between two nodes that has a unique link ID in a given digital map

database

Note 1 to entry: A link can contain additional intermediate coordinates (shape points) to better represent the

shape of curved features. A link can be directed or undirected.
3.20
link identifier
link ID
identifier that is uniquely assigned to a link

Note 1 to entry: A link identifier can be arbitrary or can be assigned by convention to ensure that no multiple

occurrences of the same identifier will be used within one instance of a network or map database.

3.21
link location

location identifiable by a part of the road network database having one identifier or having a uniquely

identifiable combination of attributes throughout the continuous stretch
Note 1 to entry: One link location can consist of multiple links.
3.22
location
particular place or position

Note 1 to entry: A location is matched to database objects by location definitions, which specify what is meant

by a particular location. Without any explicit remark, it is intended to be a linear stretch in terms of topology in

the database network without any loops or discontinuities in between (linear location). It can also be only a point

in the network as a specialization of a linear stretch with length zero. In addition to that, a location can also be

a set of road elements representing an area. This area is expressible by a polygon or a list of linear locations. For

further description of different categories of locations, refer to 6.4.

[SOURCE: ISO 19112:2019, 3.1.3, modified — The original Note to entry and Example have been

removed. A new Note 1 to entry has been added.]
3.23
location reference
label assigned to a location

Note 1 to entry: With a single location referencing method (LRM), one reference defines unambiguously and

exactly one location in the location referencing system as defined in 5.2. The location reference is the string of

data which is passed between different implementations of a location referencing system to identify the location.

3.24
location definition

actual delineation of exactly what is meant, and therefore what is not meant, by a particular location

within a specific database

Note 1 to entry: It is the precise location definition of the database object, or set of database objects, which is

referenced.

EXAMPLE GDF road elements that make up a particular instance of an ALERT-C location.

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ISO 17572-1:2022(E)
3.25
location referencing
action to assign a label to a location
3.26
location referencing method
LRM
methodology of assigning location references to locations
3.27
location referencing system
LRS

complete system by which location references are generated, according to a location referencing

method, and communicated, including standards, definitions, software, hardware, and databases

3.28
matching

translation of a location reference to a specific object in a given map database to attempt

recognition of the same identified object in both the sender's and the receiver's map database

Note 1 to entry: Matching is seen as a subsequent part to the method of decoding a location reference adhering to

the defined LRM.
3.29
node

zero-dimensional element that is a topological junction of two or more edges or an end point of an edge

Note 1 to entry: A node is created for topologically significant points, such as simple intersections of roads or

other linear features including boundaries, but also for locations such as electric beacons, kilometre-posts, or

sensors detecting traffic flows, these being significant points specified in a map.

3.30
point
zero-dimensional element that specifies geometric location
Note 1 to entry: One coordinate pair or triplet specifies the location.
3.31
point location
location with a zero-dimensional character
EXAMPLE A simple crossing.
3.32
precision

closeness of agreement between indications or measured quantity values obtained by replicate

measurements on the same or similar objects

Note 1 to entry: Alternatively, the closeness of measurements of the same phenomenon repeated under exactly

the same conditions and using the same techniques.

[SOURCE: ISO/IEC Guide 99:2007, 2.15, modified — The Note to entry and Example have been removed.

A new Note 1 to entry has been added.]
3.33
pre-coded location reference

location reference using a unique identifier that is agreed upon in both a sender and receiver system to

select a location from a set of pre-coded locations
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ISO 17572-1:2022(E)
3.34
quad tree

hierarchical data structure which, on a next lower level, subdivides a given area into four quadrants of

the same size where any level has knowledge of its four sublevels and its parent level

3.35
relationship

semantic or topological interrelation or dependency between locations in the location referencing

system (LRS)

Note 1 to entry: Relationships can exist between locations in the LRS. These relationships will generally

be structured to allow more sophisticated use of the location reference, such as a topological or hierarchical

structure. For example, a county location can be defined as an aggregate of several city locations or a long

stretch of road can be an aggregate of several smaller road segments. Referencing the county can be easier than

referencing all the cities which make up the county. This allows scalability and ease of use in the LRSs using the

location referencing method (LRM).

Note 2 to entry: The term definition in ISO/TC 211 is different because of the difference in conceptual level

between the groups.
3.36
road

part of the road network which is generally considered as a whole and which can be addressed by a

single identification like a road name or road number throughout

Note 1 to entry: In general, it is a connection within the road network, with or without crossings, which

functionally can be considered as a unity. A road with multiple (associated) carriageways can be considered as

one road. Within the ISO 17572 series, the term also covers the natural language term "street".

Note 2 to entry: The subsequent parts of this document intentionally do not make direct use of this term because

under different circumstances it is not always possible to define exactly where a road ends. For this reason,

reference is made to artificial but more precisely-definable road elements or road sections of the road network.

3.37
road crossing
location where two or more roads connect or intersect

Note 1 to entry: A road crossing can be “simple”, corresponding to one junction, or “complex”, including internal

road elements and junctions.
3.38
road element

linear section of the road network which is designed for vehicular movement having a junction at each

end

Note 1 to entry: It serves as the smallest unit of the road network at GDF level 1 that is independent.

3.39
road section

road segment that is bounded by two intersections and has the same attributes throughout

Note 1 to entry: Generally, the two intersections are different, only in some specific cases are the intersections

the same, e.g. a tear-drop street or slip roads inside of complex intersections.
3.40
road segment
part of a road, having its start and end along that road

Note 1 to entry: An important difference between a road section and road segment is that the segment does not

necessarily end at intersections.
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ISO 17572-1:2022(E)
3.41
shape point
intermediate coordinate pair to represent the shape of curved features
3.42
subnetwork

plurality of road segments lying in geographical or topological conjunction to each other

3.43
topology
properties of spatial configuration invariant under continuous transformation

Note 1 to entry: In a digital map database, this means the logical relationships among map features. It can be

used to characterize spatial relationships such as connectivity and adjacency.
4 Abbreviated terms
AGORA implementation of global location referencing approach
(name of a European Union project 2000–2002)
ALERT-C advice and problem location for European road traffic-compact
EVIDENCE extensive validation of identification concepts in Europe
(name of a European Union project 1998–1999)
GDF geographic data file
GIS geographic information system
GNSS global navigation satellite system
ITS intelligent transport systems
POI point of interest
RDS radio data system
TPEG transport protocol expert group
TMC traffic message channel
TTI traffic and traveller information
UML unified modelling language
UTM universal transverse mercator
VICS vehicle information and communication system

NOTE The ISO 17572 series uses unified modelling language (UML) to express specific circumstances. As

such, graphical elements are used to express specific constraints and structural relationships. A full definition

can be found in the ISO/IEC 19505 series.
5 Objectives and requirements for a location referencing method
5.1 Objectives for an optimal location referencing method

ITS applications have different objectives regarding location referencing, which from their

contradictory nature, cannot be fulfilled completely. In theory, an ideal location referencing method

would require every LRS to have at a given time the same, completely accurate map and all locations

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ISO 17572-1:2022(E)

would be identifiable without any additional computational effort. Even though this is not achievable,

the following goals should guide the definition and optimization of a location referencing method. The

circumstances of the specific location referencing system can give different weight to the following

goals.
1) The LRM should be simple enough to be implemented in a resource- and
performance-efficient way.

This first goal states that processing power in any case is a cost factor to be minimized.

2) The LRM should not unduly add to the volume of data to be transferred.

Location referencing implies at least two systems communicating with each other. Communication

also causes costs and therefore needs to be minimized.

3) The LRM should provide location references with the highest accuracy possible.

This means that the aim should be to use the exact location, both in the sender and the receiver

system. In many cases, it will be up to the receiver to decode the location reference as well as

possible. To help the receiver to do so, it shall be implied that the sending system sends the location

reference as accurately as possible.
5.2 Requirements of the location referencing method

In addition to the goals, a number of minimal requirements shall make the different location referencing

methods feasible for the foreseen categories of locations (see 6.4).

One of the most important data characteristics for ITS applications is spatial accuracy. Spatial accuracy

is an aspect of data quality and is described in ISO 20524-1 in the following way: "The shape of a level

0 edge including all positions on the segment as a whole shall not have any position that diverges from the

real shape more than an allowed error." Spatial data accuracy requirements for ITS vary accordi

...

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