CEN/TR 17297-1:2019

SLOVENSKI STANDARD
01-september-2019
Inteligentni transportni sistemi (ITS) - Uskladitev navajanja lokacije za mestni ITS -
1. del: Stanje tehnike in smernice
Intelligent transport systems - Location referencing harmonization for Urban ITS - Part 1:
State of the art and guidelines
Intelligente Verkehrssysteme - Ortsreferenzierungsharmonisieung für Urbane ITS - Teil
1: Stand der Technik und Richtlinien
Ta slovenski standard je istoveten z: CEN/TR 17297-1:2019
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.

CEN/TR 17297-1
TECHNICAL REPORT
RAPPORT TECHNIQUE
May 2019
TECHNISCHER BERICHT
ICS 35.240.60
English Version
Intelligent transport systems - Location referencing
harmonization for Urban ITS - Part 1: State of the art and
guidelines
Intelligente Verkehrssysteme -
Ortsreferenzierungsharmonisieung für Urbane ITS -
Teil 1: Stand der Technik und Richtlinien

This Technical Report was approved by CEN on 1 April 2019. It has been drawn up by the Technical Committee CEN/TC 278.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17297-1:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and abbreviations . 6
5 Overview . 7
6 Introduction to location referencing . 8
6.1 Maps . 8
6.2 Basic concepts of location referencing . 8
7 Profiles of location referencing methods . 10
7.1 General . 10
7.2 Location referencing by coordinates . 10
7.2.1 General . 10
7.2.2 Coordinates, coordinate tuples and coordinate sets . 10
7.2.3 Coordinate systems and coordinate reference systems . 11
7.2.4 Map projections . 12
7.2.5 Commonly used coordinate reference systems . 13
7.2.6 TPEG-GLR . 15
7.3 Pre-coded location referencing . 15
7.3.1 General . 15
7.3.2 Methods . 16
7.4 Dynamic location referencing . 19
7.4.1 Basic concepts . 19
7.4.2 Methods . 20
8 Usage of location referencing methods in some standards for ITS . 22
8.1 General . 22
8.2 DATEX II . 22
8.3 TPEG . 22
8.4 Geographic Data Files (GDF) . 23
8.5 TN-ITS . 23
8.6 INSPIRE . 24
8.7 Rail – Telematics Applications for Passengers/Freight (TAP/TAF) . 24
8.8 Air . 24
8.9 Multimodal public transport standards: Transmodel and NeTEx . 24
9 Data exchange between actors . 25
9.1 Scenarios . 25
9.1.1 General . 25
9.1.2 Scenario 1: Bi-lateral exchange . 25
9.1.3 Scenario 2: Data-warehousing – data aggregation . 25
9.2 Use cases . 26
9.2.1 General . 26
9.2.2 Sharing between centres . 26
9.2.3 On board dynamic routing for a vehicle . 28
9.2.4 Person centred dynamic trip planning . 29
9.2.5 Vehicle detection and monitoring in public transport . 29
9.2.6 Updating of persistent data . 32
10 Problem statements . 32
10.1 General . 32
10.2 Location accuracy . 33
10.2.1 Overview . 33
10.2.2 Examples concerning location accuracy . 33
10.3 Timeliness and currency . 35
11 Expected demands of future applications . 36
11.1 Emerging applications . 36
11.1.1 General . 36
11.1.2 Actual trip plan provision . 36
11.1.3 Dynamic car-pooling . 37
11.1.4 Driver Guidance . 37
11.1.5 Car-sharing and bicycle-sharing or on demand services . 38
11.1.6 Smart parking . 38
11.1.7 Electronic management and exchange of traffic regulations . 38
11.2 Main concerns of public transport . 39
11.2.1 Demands . 39
11.2.2 Issues and problem description: aggregation platforms . 39
11.2.3 Issues and problem description: cross-sector interoperability . 41
12 Approaches for improvement . 42
12.1 Objectives . 42
12.2 General approaches for improvement . 42
12.3 Existing EU approaches concerning transport-related data set access . 44
12.3.1 Overview . 44
12.3.2 The context of multimodal information provision: EU priority action A . 45
12.3.3 The INSPIRE directive . 47
12.3.4 The context of real-time traffic information provision: priority action B . 48
12.4 Preliminary conclusions . 49
12.5 Quality. 49
Bibliography . 52

European foreword
This document (CEN/TR 17297-1:2019) has been prepared by Technical Committee CEN/TC 278
“Intelligent transport systems”, the secretariat of which is held by NEN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Introduction
Location is an ever-present feature of travel-related data and information services. Systems and services
are deployed and evolve using a myriad of ways of defining and describing locations. As we move towards
more sophisticated ITS services benefits will be accrued in the urban environment by the provision of
multimodal offerings to the traveller. This often combines data from the different modes, which in turn
will involve the harmonization of location referencing. Further strong trends are emerging with the drive
towards greater levels of open data, regulated obligations for access to travel data under various
European Union initiatives, and the almost ubiquitous expectation on instant access to travel data by
users via the smartphone or other connected devices. Historically, it is appreciated that many of the
services will have their bespoke location referencing systems that suit their applications well, and that it
would never be successful to oblige city authorities to change their legacy systems, without significant
cost, disruption and risk. Therefore, it is preferable to set out a vision towards greater integration,
including encouraging cities to consider a standardized location referencing system when they develop
or commission new services but support them integrating all systems, both legacy and new.
This document pulls together the many existing referencing systems, classifies them, and then describes
them in selected scenarios with use cases, looking at the advantages and disadvantages and the
challenges. The primary intended purpose of this document is to act as a kind of “handbook” or “primer”
for city engineers and urban administrators who need to combine data from all the transport services
that are in the city domain and those transport services that come into the city, to allow a truly multimodal
offering, be it traveller information, traffic control, urban logistics, public transport, etc. However this
document can be of high interest for every actor dealing with location referencing.
This document has been produced by the CEN/TC 278/WG 17 Project Team 1703 - Location Referencing
Harmonization. The project was formed because in the CEN/TC 278/WG 17 PT 1701 report on U-ITS
(PD CEN/TR 17143), in which location referencing harmonization was the most supported requirement
among the stakeholders consulted. Despite the name of this project, its purpose is not to invent new
location referencing systems or to create a “super set” of location references to achieve harmonization;
that would not be worthwhile. This document is complemented by a Part 2 that normatively specifies
methods for managing the identified challenges, e.g. translating between selected location referencing
methods.
Development of this document was based on an outreach to organizations across Europe to identify what
is being presently used and to ensure that today's requirements are captured; this document also reflects
on emerging application and service requirements and potential foreseeable future needs.
Due to evolving standardization works on indoor location determination and referencing, reference to
these are not yet included in this document. Indoor location determination and referencing are likely to
be considered in future standards.
At the time of production of this document, referencing to precise road-related location referencing,
which is sometimes referred to as lane level referencing, is not yet mature enough to be included.
The audience of this document is those who need to combine data which use different location
referencing methods due to their different applications, modes or vendors.
1 Scope
This document presents:
— a concise tutorial on location referencing methods;
— applicable location referencing specifications, standards and directives;
— an introduction into challenges given by a multiplicity of different location referencing systems.
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 terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
data set
set of road and traffic data (provided by the data owner)
[SOURCE: SPA - Coordinated Metadata Catalogue]
3.2
geographic identifier
identifier of a geographic location, e.g. a street name with house number
4 Symbols and abbreviations
AVM automatic vehicle monitoring
CRS coordinate reference system
CS coordinate system
EPSG European Petroleum Survey Group
ETRS European terrestrial reference system
EU European Union
GALILEO name of the European satellite navigation and time reference system
GIS geographic information system
GLONASS Global Navigation Satellite System
NOTE 1 Russian: globalnaja nawigazionnaja sputnikowaja sistema.
NOTE 2 Name of the satellite navigation and time reference system of the Russian
Federation.
GLR geographic location referencing
GML geography markup language
GNSS global navigation satellite system
GPS global positioning system
NOTE 3 Name of the satellite navigation and time reference system of the United States of
America.
INSPIRE infrastructure for spatial information in Europe
NOTE 4 Name of a directive of the EC; aims at creating a European Union spatial data
infrastructure.
IOGP International association of oil and gas producers
ITRS international terrestrial reference system
ITS intelligent transport systems
LRM location referencing method
LRS location referencing system
OEM original equipment manufacturer
OGC open geospatial consortium
TN-ITS transport networks for ITS
U-ITS urban ITS
UTM universe transverse Mercator
5 Overview
The CEN/TC 278 PT1701 final technical report recommended over 100 actions needed to support the
coordination of “Intelligent Transport Systems” (ITS) services in the urban environment. The most
requested action concerned location referencing and the need to be able to combine both real-time,
historic and planned data to provide coordinated multi-modal services in an urban environment.
Nearly all ITS applications need some form of location determination and referencing to put the data or
information into a spatial context. Unfortunately, the historical technical evolution of services resulted in
existing legacy systems based on different location referencing methods (LRMs), each of them being
optimized for the specific purposes. These silo approaches impose challenges to the users, e.g. urban
administrators, where data from different silos need to be merged together, or where data from one silo
needs to be used in another silo, as direct transformation between location referencing systems (LRSs)
are not necessarily possible with sufficient location accuracy.
NOTE The terms LRM and LRS are explained in 6.2. Classes of LRMs are presented in Clause 7.
A way to face these challenges is, first to identify the characteristics of location referencing and then
evolve:
a) a conversion strategy for short term usage, and
b) a migration strategy for the long-term usage;
with constant pressure on budgets in urban administrations, this represents a major challenge.
This document presents:
— a tutorial on location referencing covering:
1) basics of location referencing, i.e. LRMs, and the difference to location mapping;
2) LRSs of the identified LRMs;
3) identification of standards and industry specifications on LRMs and LRSs;
— a description of the data exchange scenarios that typify the need for location referencing
transformations:
1) bi-lateral exchange between two actors;
2) data-warehousing – data aggregation;
— a description of use cases with a linkage to LRSs.
6 Introduction to location referencing
6.1 Maps
Before discussing location referencing, it is helpful to make a distinction between location references and
maps.
NOTE “Location referencing” is a process whilst “map” is an object.
Most of us have exposure to various forms of maps throughout our daily lives. Although historically maps
were typically drawn or printed on paper, the greatest exposure to maps for many people today is in the
form of a digital spatial data set that provides some spatial context, against which things are referenced
by some form of location referencing – these maps are often rendered on the screens of smartphones,
digital devices and computers.
The nature of maps will differ dependent on their intended purpose, the expectation of how they will be
rendered and used, which organization creates and distributes them, how they are created and
maintained, as well as their geographic coverage and data content, e.g. is this a road map, a map of
waterways, a topological land features map, etc.?
As the creation of spatial data sets can be expensive and time-consuming, there are often costs associated
with the purchase, use or distribution of map content. For the local authority transportation officer, the
nature and scale of these costs is often a deciding factor in which data set to use.
6.2 Basic concepts of location referencing
Nearly all ITS applications need some form of description of the location of features (physical objects,
restrictions, events, etc.) in a spatial context, both in absolute relationship to the surface of the Earth, and
in relation to other features. 6.2 describes the basics of such location referencing.
The term “location” has been defined in various ways, e.g. in several standards and deliverables from ISO
and CEN. A very basic definition is provided by EN ISO 19111 as “identifiable geographic place”. A “place”
is defined in ISO 19155:2012, 4.8 as an “identifiable part of any space”. Such a part may be a single point,
a segment, an area, a volume or any other part that the space in question may be divided into. The terms
“location” and “position” can also be confusing. According to ISO 19155, a “place” is referred to as a
“position” when that place is identified using coordinates, while a “place” is referred to as a “location”
when that place is identified using geographic identifiers. Note that a location with a given shape will also
have a position, i.e. the reference position of the shape. In this document, the term “location” will be used
as defined in ISO 19155. In comparison, ISO 17572-1:2015, 2.1.23 defines in a more general way a
location as a “simple or compound geographic object to be referenced by a location reference”.
EN ISO 19111 or other standards from ISO/TC 211 do not have a definition of the term “location
reference”, but the term “spatial reference” is defined as a “description of position in the real-world”
(EN ISO 19111:2007, 4.43). Based on this and the definition of the term “location”, a definition of the term
“location referencing” would be “description of an identifiable geographic place”. ISO 17572-1:2015,
2.1.25 defines a location reference as a “label which is assigned to a location”, while ISO/TS 21219-7:2017,
3.3 TPEG2-LRC defines location referencing as “means to provide information that allows a system to
identify accurately a location”.
Furthermore, a location reference is described using a location referencing method (LRM), and within a
location referencing system (LRS) based on the LRM. These terms are well defined in ISO 17572-1:2015,
2.1.26 and 2.1.27; a “location referencing method” is a “methodology of assigning location references to
locations”, and a “location referencing system” is a “complete system by which location references are
generated, according to a location referencing method (…)”.
From these definitions, it follows that location referencing is about describing a location within an LRS,
according to an LRM. Applying location referencing to a feature results in a description of that feature's
location.
Figure 1 illustrates the concepts of location referencing. In Figure 1, two LRMs are given, i.e. LRM and
A
LRM , each with two LRSs, i.e. LRS and LRS according to LRM , and LRS and LRS according to LRM .
B A1 A2 A B1 B2 B
Two real-world locations are described, i.e. L and L . As shown in Figure 1, the same location can be
α β
described with location references in different LRSs. Both, LR and LR with different LRSs and LRMs,
A1,α B2,α
describe location L ; and both, LR and LR , describe location L . Of course, different locations can be
α A1,β B1,β β
described with location references from the same LRS; Both L and L are described with location
α β
references (LR and LR ) from LRS .
A1,α A1,β A1
Figure 1 — Location referencing concepts
In the ITS domain, a feature can be a physical object like a vehicle, a pedestrian, a road side unit or a road
sign; it can be a restriction or regulation such as speed limits or access restrictions; it can be an event like
a traffic incident or a road closure; it can be a physical road condition such as black-ice, and so on. Location
referencing of these features results in descriptions where these features are in relation to each other
and in relation to the real world.
7 Profiles of location referencing methods
7.1 General
Three profiles of location reference methods containing various methods are distinguished in this
document:
— location referencing by coordinates, see 7.2;
— pre-coded location referencing, see 7.3;
— dynamic location referencing, see 7.4.
7.2 Location referencing by coordinates
7.2.1 General
The most common, well-known and understood methods for describing locations probably are by using
names by humans, and by using coordinates by machines. The concepts for using coordinates are defined
in EN ISO 19111 and EN ISO 6709.
7.2.2 Coordinates, coordinate tuples and coordinate sets
Three basic elements in location referencing by coordinates are coordinates, coordinate tuples and
coordinate sets. According to EN ISO 19111:2007, 4.5 and 4.12, a coordinate is “one of a sequence of n
numbers designating the position of a point in n-dimensional space”, and a coordinate tuple is a “tuple
composed of a sequence of coordinates”. The number of coordinates in the coordinate tuple equals the
dimension of the coordinate system defined in 7.2.3; the order of coordinates in the coordinate tuple is
identical to the order of the axes of the coordinate system. In other words, a coordinate tuple can be used
to describe the position of a point in one to several dimensions, from a one-dimensional position on a line
to a three-dimensional position, or even more complex systems adding also a time reference. If the
location to be described is a line, area, volume, etc., rather than a single point, a set of coordinates may be
used. A coordinate set is defined as a “collection of coordinate tuples related to the same coordinate
reference system”, and can for example be a collection of two coordinate tuples representing the
coordinates at two points of a line.
Figure 2 illustrates the concepts of coordinates, coordinate tuples and coordinate sets and how they
relate to coordinate reference systems defined in 7.2.3. A coordinate reference system is defined, and all
coordinates in Figure 2 are given in this system. A single coordinate tuple with three coordinates
represents a point, and a coordinate set with n coordinate tuples represents a line with n points.
Figure 2 — The concepts of coordinates, coordinate tuples and coordinate sets
7.2.3 Coordinate systems and coordinate reference systems
Coordinates have no meaning unless the system to which they are related to has been defined. Therefore,
EN ISO 19111:2007, 4.10 and 4.8 defines the terms “Coordinate system” and “Coordinate reference
system”. A coordinate system is defined as “set of mathematical rules for specifying how coordinates are
to be assigned to points” while a coordinate reference system is a “coordinate system that is related to an
object by a datum”. With this definition, also a “datum” needs to be defined, being a “parameter or set of
parameters that define the position of the origin, the scale, and the orientation of a coordinate system”. A
datum will then relate the coordinate reference system to the Earth or to another object. For example;
ETRS89 is a geographic 2-dimensional coordinate reference system. It is related to the Earth through the
datum European Terrestrial System 1989, that defines the shape of the Earth as an ellipsoid, and with
positions “fixed to the stable part of the Eurasian continental plate and consistent with ITRS at the epoch
1989.0”, and it is using an ellipsoidal two-dimensional coordinate system with coordinates in
latitude/longitude.
Figure 3 shows how this coordinate reference system is based on a datum and a coordinate system.
Figure 3 — Relations between a coordinate reference system, a datum and a coordinate system
NOTE In this example, the names of the datum and of the coordinate reference system are similar, but they are
different concepts, as shown in Figure 3.
7.2.4 Map projections
The Earth is almost a sphere, but with a very irregular surface. For calculations and presentations of
location, it is considerably easier to work in plane rectangular coordinates than with complex spherical
coordinates. For this purpose, coordinates in relation to the Earth are often presented in a projected
coordinate reference system, where a selected area of the Earth is considered as flat. Coordinates in a
projected coordinate system are given in a Cartesian coordinate system, with perpendicular axes. A
projected coordinate reference system is defined in EN ISO 19111:2007, 4.39 as “coordinate reference
system derived from a [geographic] coordinate reference system by applying a map projection”, and a map
projection is defined in EN ISO 19111:2007, 4.33 as a “coordinate conversion from an ellipsoidal
coordinate system to a plane”.
Map projections involve some degree of deviation from real locations related to the Earth, as it is not
possible to map the curved surface of an ellipsoid onto a plane map surface without deformation. Several
approaches exist for preserving areas, shapes, directions, bearings, distances or scales. For location
references at large scales, which is most relevant for ITS, the most common compromise is to preserve
angles and distance ratios, which can be done with a conformal projection. Two commonly used
conformal projections are Transverse Mercator and Lambert. When applied on relatively small portions
of the Earth, projected coordinate reference systems calculated with these projections have deviations
that are considered acceptable for most purposes. However, there are still deviations, and these will
increase with the distance from the central axis of the projection. If a projected coordinate reference
system is to be used for the most accurate operations, like bridge construction, the covered area is
typically smaller than for commonly used topographic maps.
Figure 4 illustrates how a projected coordinate reference system, i.e. ETRS89 / UTM (universe transverse
Mercator) Zone 33N, with two-dimensional coordinates in a Cartesian coordinate system is derived from
a Geographic two-dimensional coordinate reference system, i.e. ETRS89 (the base coordinate reference
system).
NOTE ETRS89 / UTM Zone 33N is used as an example, as it is a projected coordinate reference system that is
considered suitable for large and medium scale topographic mapping and engineering surveys, in a restricted
geographic zone – such that this projection is considered suitable for the intended purpose within the zone. This
zone is between 12°E and 18°E, northern hemisphere between equator and 84°N, onshore and offshore. Projections
to other UTM zones derived from the same base CRS are by definition other coordinate reference systems, as the
projection parameters are different.

Figure 4 — Example of a projected coordinate reference system
7.2.5 Commonly used coordinate reference systems
The “International Association of Oil and Gas Producers” (IOGP) maintains a registry of coordinate
reference systems known as the “EPSG Geodetic Parameter Registry”. The registry is based on the
conceptual model from EN ISO 19111:2007. Coordinate reference systems are often identified by their
identifier from the registry – the EPSG code.
Examples of coordinate reference systems among the most commonly used in Europe are listed in
Table 1.
Table 1 — Examples of coordinate reference systems
Coordinate Description Comment
reference
system
ITRS The International Terrestrial Reference In principle, all points on the Earth
System: have variable coordinates because of
the drift of the tectonic plates.
— Global geocentric coordinate
reference system. The ITRS is realized at fixed years
with coordinates for a global set of
— CS: Cartesian three-dimensional.
stations, based on observations by
— Axes: X, Y, Z, with the origin in the
several precise satellite-based
mass middle point of the Earth, and
geodesy technologies.
the z-axis through the North Pole.
Coordinate Description Comment
reference
system
WGS 84 World Geodetic System 1984: Core system used for global
navigation satellite systems (GNSS)
a
(EPSG: 4326) — CRS: Geodetic.
GPS.
— Datum: World Geodetic System
1984.
— CS: Ellipsoidal two-dimensional.
— Axes: latitude, longitude.
— Orientations: north, east.
— Unit of measure: degree.
— CRS: Projected.
WGS84 / Pseudo- Used for Google Maps, Open Street
Mercator Map, Bing maps, etc.
— Base CRS: WGS 84 (EPSG 4326).
(EPSG: 3857)
— Conversion: Popular Visualization
Pseudo Mercator.
— CS: Cartesian two-dimensional.
— Axes: X, Y.
— Orientations: east, north.
— Unit of measure: metre.
— CRS: Projected.
ETRS89 / UTM Based on the Universe Transverse
Mercator projection, widely used for
— Base CRS: ETRS89 (EPSG 4258).
(Example zone:
base maps, several zones across
EPSG: 25833)
— Conversion: Transverse Mercator.
Europe.
— CS: Cartesian two-dimensional.
— Axes: E, N.
— Orientations: east, north.
— Unit of measure: metre.
— CRS: Projected.
Lambert-93 Large and medium scale topographic
mapping and engineering survey.
— Base CRS: RGF 93 (EPSG 4171).
(Example zone:
EPSG 2154)
— Conversion: Lambert Conic
Conformal.
— CS: Cartesian two-dimensional.
— Axes: easting, northing (X, Y).
— Orientations: east, north.
— Unit of measure: metre.
Coordinate Description Comment
reference
system
— CRS: Compound
ETRS89 / UTM Used for three-dimensional base data.
zone 32 + Combination of a horizontal and a
— Base CRS: ETRS89 / UTM zone 32N
NN2000 height vertical CRS; used in Norway
(EPSG 25832) and Norway Normal
Null 2000 (EPSG 1096)
(EPSG 5972)
— CS: Cartesian two-dimensional and
Vertical
— Axes: easting, northing, height (E, N,
H)
— Orientations: east, north, up
— Unit of measure: metre.
a
Specific coordinate reference systems are indicated by numbers, e.g. EPSG: 4326, and are registered in the
EPSG geodetic parameter registry.
7.2.6 TPEG-GLR
Geographic location referencing (GLR) defined in ISO/TS 21219-21 is a special type of location
referencing by coordinates.
Geographic locations in TPEG-GLR can be referenced as:
— points, i.e. one coordinate tuple,
— lines, i.e. two or more coordinate tuples,
— areas, i.e. three or more coordinate tuples,
— bounding boxes, i.e. extent – two coordinate tuples representing diagonal corners, or
— sectors of circles, i.e. one coordinate tuple for centre point, a radius and a start and end angle for the
sector).
Coordinates are always given in the WGS84 (EPSG: 4326) coordinate reference system, unless the service
is explicitly describing that it uses another coordinate reference system.
7.3 Pre-coded location referencing
7.3.1 General
Methods for pre-coded location referencing, also referred to as indirect location referencing, are LRMs
that use pre-coded unique location identifiers to describe locations. The identifiers are defined in a data
set, and are identical for all applications using the location references. ISO 17572-2 describes three steps
that are performed to implement a pre-coded LRS:
1) create and update the location database;
2) provide the location database to applications and devices using the LRS;
3) use the location database to create location references to the location identifiers;
see also EN ISO 14819-3. TPEG 2 can also use an extended version of EN ISO 14819-3 and is defined in
ISO 17572-2.
In simple terms, each real-word location is identified by a coded reference in a particular system and a
synchronized application receives that reference and decodes it back to a real-world location using the
same location database.
Location referencing methods using pre-coded location referencing are described in 7.3.2.
7.3.2 Methods
7.3.2.1 Location referencing by geographic identifiers
The conceptual model for location referencing by geographic identifiers is described in EN ISO 19112. In
EN ISO 19112:2005, 4.3, the unique location identifiers are described as “geographic identifiers”, defined
as “spatial reference in the form of a label or code that identifies a location”. Examples of geographic
identifiers can be a country name or code (Spain or ES), a property address (Parkgata 81, Hamar, Norway)
or a road link (E6 – see also linear referencing).
When a feature is located based on a location reference to a geographic identifier, it implies that the real-
world location of the feature is in a relationship with the real-world location identified with the
geographic identifier, e.g. the feature is:
— contained within a country or a municipality,
— located on a road link, or
— located close to an address.
A spatial referencing system based on location referencing by geographic identifiers is a collection of
“location classes” (country, town, address, road, etc.), with geographic identifiers, while a “gazetteer”
contains the information on each location, including its real-world position. This is illustrated in Figure 5.
One spatial referencing system (Norwegian address system) is defined, with one location class (address).
The address class has a geographic identifier – street address. The gazetteer Addresses contains a set of
locations (addresses), each with an extent and a representation point. The location reference (Parkgata
81, Hamar) is based on the Norwegian address system, with the location defined in the gazetteer.
Figure 5 — Illustration of the concepts of location referencing by geographic identifiers
7.3.2.2 Linear referencing
Linear referencing is a method for pre-coded location referencing that uses a combination of references
to predefined identifiers representing linear features and coordinates on the referred features. The
concepts for linear referencing are defined in EN ISO 19148:2012, 4.10, where the basic term “linear
referencing” is defined as a “specification of a location relative to a linear element as a measurement along
(and optionally offset from) that element”.
Two of the basic concepts in linear referencing are
— a “linear feature”, defined as a “one-dimensional object that serves as the axis along which linear
referencing is performed”, and
— a “linearly located event”, defined as an “occurrence along a feature of an attribute value or another
feature”.
A linearly referenced location is specified with a reference to a linear feature and a measurement
(coordinate) along the feature. Point locations (“at locations”) are specified with one single linearly
referenced location (a coordinate), while segments (“from/to locations”) are specified with one linearly
referenced location (coordinate) for the start point and either a linearly referenced location (coordinate)
for the end point or a length from the start point coordinate.
Furthermore, locations are referenced according to a “linear referencing method”, within a “linear
referencing system”. Linear referencing methods can be interpolative (values ranging from 0 to 1 or
percentages along the linear features), absolute (using a unit of measure, e.g. km) or relative (distance
from a reference milepost, kilometre post, hectometre post, etc.). The linear referencing system can, for
example, be the road network in a national road database, using an interpolative line
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