EN ISO 19148:2021

SLOVENSKI STANDARD
01-julij-2021
Nadomešča:
SIST EN ISO 19148:2012
Geografske informacije - Linearno georeferenciranje (ISO 19148:2021)
Geographic information - Linear referencing (ISO 19148:2021)
Geoinformation - Lineares Bezugssystem (ISO 19148:2021)
Information géographique - Référencement linéaire (ISO 19148:2021)
Ta slovenski standard je istoveten z: EN ISO 19148:2021
ICS:
07.040 Astronomija. Geodezija. Astronomy. Geodesy.
Geografija Geography
35.240.70 Uporabniške rešitve IT v IT applications in science
znanosti
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 19148
EUROPEAN STANDARD
NORME EUROPÉENNE
April 2021
EUROPÄISCHE NORM
ICS 35.240.70 Supersedes EN ISO 19148:2012
English Version
Geographic information - Linear referencing (ISO
19148:2021)
Information géographique - Référencement linéaire Geoinformation - Lineares Bezugssystem (ISO
(ISO 19148:2021) 19148:2021)
This European Standard was approved by CEN on 10 March 2021.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, 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
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19148:2021 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 19148:2021) has been prepared by Technical Committee ISO/TC 211
"Geographic information/Geomatics" in collaboration with Technical Committee CEN/TC 287
“Geographic Information” the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by October 2021, and conflicting national standards shall
be withdrawn at the latest by October 2021.
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.
This document supersedes EN ISO 19148:2012.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 19148:2021 has been approved by CEN as EN ISO 19148:2021 without any modification.

INTERNATIONAL ISO
STANDARD 19148
Second edition
2021-04
Geographic information — Linear
referencing
Information géographique — Référencement linéaire
Reference number
ISO 19148:2021(E)
©
ISO 2021
ISO 19148:2021(E)
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
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Email: copyright@iso.org
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Published in Switzerland
ii © ISO 2021 – All rights reserved

ISO 19148:2021(E)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms and UML notation . 5
4.1 Abbreviated terms . 5
4.2 UML notation . 5
5 Conformance . 5
5.1 Conformance overview . 5
5.2 Conformance classes . 6
5.2.1 General. 6
5.2.2 Data type conformance . 6
5.2.3 Operation conformance . 6
6 Linear referencing . 7
6.1 Background . 7
6.1.1 Linear referencing concepts . 7
6.1.2 Linear referencing packages .17
6.2 Package: Linear Referencing System .18
6.2.1 Semantics .18
6.2.2 PositionExpression .19
6.2.3 LinearElement . .20
6.2.4 LinearElementType .21
6.2.5 ILinearElement .21
6.2.6 IFeature .22
6.2.7 ISpatial .23
6.2.8 LinearReferencingMethod .24
6.2.9 DistanceAlongDirection .25
6.2.10 LRMType .25
6.2.11 DistanceExpression .26
6.2.12 Referent .27
6.2.13 ReferentType .28
6.2.14 ValueExpression .29
6.3 Package: Linear Referencing Towards Referent .30
6.3.1 Semantics .30
6.3.2 LRMWithTowardsReferent .30
6.3.3 DistanceExpression .31
6.4 Package: Linear Referencing Offset .31
6.4.1 Semantics .31
6.4.2 LRMWithOffset .33
6.4.3 LateralOffsetDirection .34
6.4.4 VerticalOffsetDirection .34
6.4.5 LateralOffsetDistanceExpression .34
6.4.6 LateralOffsetExpression .35
6.4.7 LateralOffsetReferent . .36
6.4.8 VerticalOffsetExpression .37
6.4.9 VerticalOffsetReferent .38
6.4.10 ICrossSectionalConvention .38
6.4.11 ICrossSectionalConventionPart .39
6.5 Package: Linear Referencing Offset Vector .40
6.5.1 Semantics .40
6.5.2 VectorOffsetDistanceExpression .40
ISO 19148:2021(E)
6.5.3 VectorOffsetExpression .41
6.6 Package: Linearly Located Event .42
6.6.1 Semantics .42
6.6.2 Linearly located event .43
6.6.3 Event .44
6.6.4 AttributeEvent.45
6.6.5 FeatureEvent .46
6.6.6 EventLocation .47
6.6.7 AtLocation .47
6.6.8 FromToLocation .47
6.6.9 EventTime .48
6.6.10 EventInstant .49
6.6.11 EventPeriod .49
6.7 Package: Linear Segmentation .49
6.7.1 Semantics .49
6.7.2 SegmentableFeature .50
6.7.3 LinearSegmentSet .51
6.7.4 LinearSegment .52
Annex A (normative) Abstract test suite .54
Annex B (informative) Generalized Model for Linear Referencing .58
Annex C (informative) Commonly used linear referencing methods and models .61
Annex D (informative) Application Schema example .84
Annex E (informative) Event and segmentation examples .87
Annex F (informative) Backwards compatibility with ISO 19148:2012 .96
Bibliography .98
iv © ISO 2021 – All rights reserved

ISO 19148:2021(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 211, Geographic information/Geomatics,
in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/
TC 287, Geographic Information, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 19148:2012), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— revision of the definition of the term linear element, removing a circular reference with the definition
for the term linear referencing;
— introduction of the definition of the term referent;
— revision of the conceptual schema to meet current standards and harmonize with other ISO/TC 211
International Standards;
— refactoring of the core Linear Referencing System package, abstracting implementation classes into
a new Application Schema package which is now presented as an example in Annex D;
— introduction of an approach addressing broken-chainage;
— introduction of an enumeration addressing directionality of measurements;
— introduction of an approach addressing Cross-Sectional Positioning (XSP) conventions;
— introduction of an approach addressing Measures with Uneven Distribution;
— refactoring of the Linearly Located Event package dropping the previous assumption that the Linear
Element was always of a Feature type;
— introduction of simplifications of the conceptual schema;
ISO 19148:2021(E)
— additional example illustrating Measures with Uneven Distribution in Annex C;
— introduction of information about some standards implementing the conceptual schema described
in this document in Annex C;
— additional example illustrating Secondary Linear Referencing Systems in Annex E;
— the correction of minor errors;
— introduction of a detailed overview regarding changes and backwards compatibility in Annex F.
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.
vi © ISO 2021 – All rights reserved

ISO 19148:2021(E)
Introduction
This document is a description of the data and operations required to support linear referencing. This
includes Linear Referencing Systems, linearly located events and linear segments.
Linear Referencing Systems enable the specification of positions along linear objects. The approach is
[12]
based upon the Generalized Model for Linear Referencing first standardized within ISO 19133:2005.
This document extends that which was included in ISO 19133, both in functionality and explanation.
ISO 19109 supports features representing discrete objects with attributes with values which apply to
the entire feature. ISO 19123 allows the attribute value to vary, depending upon the location within a
feature, but does not support the assignment of attribute values to a single point or length along a linear
feature. Linearly located events provide the mechanism for specifying attribution of linear objects
when the attribute value varies along the length of a linear feature. A Linear Referencing System is used
to specify where along the linear object each attribute value applies. The same mechanism can be used
to specify where along a linear object another object is located, such as guardrail or a traffic accident.
It is common practice to segment a linear object with linearly located events, based upon one or
more of its attributes. The resultant linear segments are attributed with just the attributes used in
the segmentation process, ensuring that the linear segments are homogeneous in value for these
segmenting attributes.
In accordance with the ISO/IEC Directives, Part 2, 2018, Rules for the structure and drafting of
International Standards, in International Standards the decimal sign is a comma on the line. However,
the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures) at its
meeting in 2003 passed unanimously the following resolution:
“The decimal marker shall be either a point on the line or a comma on the line.” In practice, the choice
between these alternatives depends on customary use in the language concerned. In the technical areas
of geodesy and geographic information it is customary for the decimal point always to be used, for all
languages. That practice is used throughout this document.
INTERNATIONAL STANDARD ISO 19148:2021(E)
Geographic information — Linear referencing
1 Scope
This document specifies a conceptual schema for locations relative to a one-dimensional object as
measurement along (and optionally offset from) that object. It defines a description of the data and
operations required to use and support linear referencing.
This document is applicable to transportation, utilities, environmental protection, location-based
services and other applications which define locations relative to linear objects. For ease of reading,
most examples discussed in this document come from the transportation domain.
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 19103, Geographic information — Conceptual schema language
ISO 19107, Geographic information — Spatial schema
ISO 19108, Geographic information — Temporal schema
ISO 19111, Geographic information — Referencing by coordinates
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:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
attribute event
value of an attribute of a feature (3.4) that can apply to only part of the feature
Note 1 to entry: An attribute event includes the linearly referenced location (3.16) where the attribute value
applies along the attributed feature (3.2).
Note 2 to entry: An attribute event can be qualified by the instant (3.8) in which, or period (3.20) during which,
the attribute value applied.
3.2
attributed feature
feature (3.4) along which an attribute event (3.1) applies
3.3
direct position
position (3.21) described by a single set of coordinates within a coordinate reference system
[SOURCE: ISO 19136-1:2020, 3.1.20]
ISO 19148:2021(E)
3.4
feature
abstraction of real-world phenomena
[SOURCE: ISO 19101-1:2014, 4.1.11]
3.5
feature event
information about the occurrence of a located feature (3.17) along a locating feature (3.18)
Note 1 to entry: A feature event includes the linearly referenced location (3.16) of the located feature along the
locating feature.
Note 2 to entry: A feature event can be qualified by the instant (3.8) in which, or period (3.20) during which, the
feature event occurred.
3.6
geometric primitive
geometric object representing a single, connected, homogeneous (isotropic) element of space
Note 1 to entry: Geometric primitives are non-decomposed objects that present information about geometric
configuration. They include points, curves, surfaces and solids. Many geometric objects behave like primitives
(supporting the same interfaces defined for geometric primitives) but are actually composites composed of some
number of other primitives. General collections can be aggregates and incapable of acting like a primitive (such
as the lines of a complex network, which is not connected and thus incapable of being traceable as a single line).
By this definition, a geometric primitive is topological open, since the boundary points are not isotropic to the
interior points. Geometry is assumed to be closed. For points, the boundary is empty.
[SOURCE: ISO 19107:2019, 3.50]
3.7
height
h, H
distance of a point from a chosen reference surface positive upward along a line perpendicular to
that surface
Note 1 to entry: A height below the reference surface will have a negative value.
Note 2 to entry: Generalization of ellipsoidal height (h) and gravity-related height (H).
[SOURCE: ISO 19111:2019, 3.1.38]
3.8
instant
0-dimensional geometric primitive (3.6) representing position (3.21) in time
Note 1 to entry: The geometry of time is discussed in ISO 19108:2002, 5.2.
[SOURCE: ISO 19108:2002, 4.1.17]
3.9
linear element
one-dimensional object that serves as the axis along which measurements are made
Note 1 to entry: Also known as curvilinear element.
EXAMPLE Feature (3.4), such as “road”; curve geometry; directed edge topological primitive.
3.10
linear referencing
specification of a location (3.19) relative to a linear element (3.9) as a measurement along (and optionally
offset from) that element
Note 1 to entry: An alternative to specifying a location as a two- or three- dimensional spatial position (3.23).
2 © ISO 2021 – All rights reserved

ISO 19148:2021(E)
3.11
linear referencing method
LRM
manner in which measurements are made along (and optionally offset from) a linear element (3.9)
3.12
linear referencing system
LRS
set of linear referencing methods (3.11) and the policies, records and procedures for implementing them
Note 1 to entry: Adapted from Reference [10].
3.13
linear segment
part of a linear feature (3.4) that is distinguished from the remainder of that feature by a subset of
attributes, each having a single value for the entire part
Note 1 to entry: A linear segment is a one-dimensional object without explicit geometry.
Note 2 to entry: The implicit geometry of the linear segment can be derived from the geometry of the parent
feature.
3.14
linearly located
located using a linear referencing system (3.12)
3.15
linearly located event
occurrence along a feature (3.4) of an attribute value or another feature
Note 1 to entry: The event location (3.19) is specified using linearly referenced locations (3.16).
Note 2 to entry: A linearly located event can be qualified by the instant (3.8) in which, or period (3.20) during
which, the linearly located event occurred.
Note 3 to entry: ISO 19108 limits events to a single instant in time and does not include the specification of a
location.
3.16
linearly referenced location
location (3.19) whose position (3.21) is specified using linear referencing (3.10)
3.17
located feature
linearly located feature
feature (3.4) that is linearly located (3.14) along an associated (locating) feature
EXAMPLE A feature “bridge” can be a located feature along the feature “railway” [a locating feature (3.18)].
3.18
locating feature
linearly locating feature
feature (3.4) that is used to identify the location (3.19) of linearly located (3.14) features
EXAMPLE A feature “road” can be the locating feature for a feature “pedestrian crossing” [a located feature
(3.17)].
3.19
location
particular place or position (3.21)
Note 1 to entry: A location identifies a geographic place.
ISO 19148:2021(E)
Note 2 to entry: “Madrid”, “California”.
Note 3 to entry: Additionally, in this document, a location is represented by one of a set of data types that describe
a position (3.21), along with metadata about that data, including coordinates (from a coordinate reference
system), a measure (from a linear referencing system (3.12)), or an address (from an address system).
[SOURCE: ISO 19112:2019, 3.1.3]
3.20
period
one-dimensional geometric primitive (3.6) representing extent in time
Note 1 to entry: A period is bounded by two different temporal positions (3.24).
[SOURCE: ISO 19108:2002, 4.1.27]
3.21
position
data type that describes a point or geometry potentially occupied by an object or person
Note 1 to entry: A direct position (3.3) is a semantic subtype of position. Direct positions as described can define
only a point and, therefore, not all positions can be represented by a direct position. That is consistent with the
“is type of” relation. An ISO 19107 geometry is also a position, just not a direct position.
[SOURCE: ISO 19133:2005, 4.18]
3.22
referent
known location (3.19) along a linear element (3.9) from which relative measurements are made
EXAMPLE Milepost, kilopost or reference post.
3.23
spatial position
direct position (3.3) that is referenced to a two- or three-dimensional coordinate reference system
Note 1 to entry: An alternative to specifying a location (3.19) as a linearly referenced location (3.16).
3.24
temporal position
location (3.19) relative to a temporal reference system (3.25)
[SOURCE: ISO 19108:2002, 4.1.34]
3.25
temporal reference system
reference system against which time is measured
[SOURCE: ISO 19108:2002, 4.1.35]
3.26
valid time
time when a fact is true in the abstracted reality
[SOURCE: ISO 19108:2002, 4.1.39]
4 © ISO 2021 – All rights reserved

ISO 19148:2021(E)
4 Abbreviated terms and UML notation
4.1 Abbreviated terms
CRS coordinate reference system
GIS geographic information systems
IFC industry foundation classes
LandInfra land and infrastructure conceptual model
NCHRP national cooperative highway research program
RDF resource description framework
REST representational state transfer
SOAP single object access protocol
SPARQL SPARQL protocol and RDF query language
SQL structured query language
UML unified modelling language
XSP cross-sectional positioning
4.2 UML notation
In this document, conceptual schemas are presented in the UML. ISO 19103 presents the specific profile
of UML used in this document.
5 Conformance
5.1 Conformance overview
Clause 6 of this document uses the UML to present conceptual schemas for describing the constructs
required for Linear Referencing. These schemas define conceptual classes that shall be used in
application schemas, profiles and implementation specifications. This document concerns only
externally visible interfaces and places no restriction on the underlying implementations other than
what is required to satisfy the interface specifications in the actual situation, such as:
— interfaces to software services using techniques such as SOAP, REST and SPARQL end points;
— interfaces to databases using techniques such as SQL;
— data interchange using encoding as defined in ISO 19118.
Few applications require the full range of capabilities described by this conceptual schema. Clause 6,
therefore, defines a set of conformance classes that support applications whose requirements range
from the minimum necessary to define data structures to full object implementation. This flexibility is
controlled by a set of UML concepts that can be implemented in a variety of manners. Implementations
that define full object functionality shall implement all operations defined by the types of the chosen
conformance class, as is common for UML designed object implementations. It is not necessary for
implementations that choose to depend on external “free functions” for some or all operations, or
forgo them altogether, to support all operations, but they shall always support a data type sufficient for
recording the state of each of the chosen UML types as defined by its member variables. It is acceptable
to use common names for concepts that are the same but have technically different implementations.
ISO 19148:2021(E)
The UML model in this document defines abstract types, application schemas define conceptual classes,
various software systems define implementation classes or data structures, and the XML from the
encoding standard (ISO 19118) defines entity tags. All of these references the same information content.
There is no difficulty in allowing the use of the same name to represent the same information content
even though at a deeper level there are significant technical differences in the digital entities being
implemented. This “allows” types defined in the UML model to be used directly in application schemas.
5.2 Conformance classes
5.2.1 General
Conformance to this document shall consist of either data type conformance or both data type and
operation conformance. The related tests are provided in the abstract test suite in Annex A.
5.2.2 Data type conformance
Data type conformance includes the usage of data types in application schemas or profiles that
instantiate types in this document. In this context, “instantiate” means that there is a correspondence
between the types in the appropriate part of this document, and the data types of the application schema
or profile in such a way that each standard type can be considered as a supertype of the application
schema data type. This means that an application schema or profile data type corresponding to a
standard type contains sufficient data to recreate that standard type's information content.
Table 1 assigns conformance tests, detailed in Annex A, to each of the packages in Clause 6. Each row
in the table represents one conformance class. A specification claiming data type conformance to a
package in the first column of the table shall satisfy the requirements specified by the tests given in the
remaining columns to the right.
Table 1 — Data type conformance tests
Conformance test
Package
A.1.1 A.1.2 A.1.3 A.1.4 A.1.5 A.1.6
Linear Referencing System X — — — — —
Linear Referencing Towards Referent X X — — — —
Linear Referencing Offset X — X — — —
Linear Referencing Offset Vector X — X X — —
Linearly Located Event X — — — X —
Linear Segmentation X — — — X X
5.2.3 Operation conformance
Operation conformance includes both the consistent use of operation interfaces and data type
conformance for the parameters, and return values used by those operations. Operation conformance
also includes get and set operations for attributes.
Table 2 assigns conformance tests, detailed in Annex A, to each of the packages in Clause 6. Each row
in the table represents one conformance class. A specification claiming operation conformance to a
package in the first column of the table shall satisfy the requirements specified by the tests given in the
remaining columns to the right.
6 © ISO 2021 – All rights reserved

ISO 19148:2021(E)
Table 2 — Operation conformance tests
Conformance test
Package
A.1.1 A.1.2 A.1.3 A.1.4 A.1.5 A.1.6
A.2.1 A.2.2 A.2.3 A.2.4 A.2.5 A.2.6
Linear Referencing System X — — — — —
Linear Referencing Towards Referent X X — — — —
Linear Referencing Offset X — X — — —
Linear Referencing Offset Vector X — X X — —
Linearly Located Event X — — — X —
Linear Segmentation X — — — X X
6 Linear referencing
6.1 Background
6.1.1 Linear referencing concepts
6.1.1.1 General
LRSs are in wide use in transportation but are also appropriate in other areas such as utilities. They
allow for the specification of positions along linear elements by using measured distances along (and
optionally offset from) the element. This is in contrast to using spatial positions that use two- or three-
dimensional coordinates, consistent with a particular CRS.
Linearly referenced locations are significant for several reasons. First, a significant amount of
information is currently held in huge databases from legacy systems that pre-date GISs. Many useful
applications can and have been built on these data with no understanding of where on the earth's
surface the data are located. Knowing where they are located relative to a linear element such as a
roadway route or pipeline is sufficient to support these applications and can be used as a means of
integrating data from multiple, disparate sources.
In some situations, having a linearly referenced location along a known linear element is more
advantageous than knowing its spatial position. Consider a crash in need of emergency assistance.
Knowing the linear element (e.g. Northbound I-95) and the approximate linear location is superior to
having a potentially more precise spatial GPS location that is not of significant accuracy to determine
whether it is northbound or southbound I-95, especially if an impassable barrier separates the two
carriageways.
The linearly referenced location as specified in this document as a position expression, therefore,
has many uses. It can be used to tie information about a linear facility to a specific location along that
facility. It can also be used to find a position on the face of the earth by specifying how far along the
position is (and optionally offset from) on a particular linear element.
This document proposes a consistent specification for describing linearly referenced locations that also
enables translation between different referencing methods and/or linear elements. It also specifies
how these position expressions can be used to specify how information that pertains to only a part of a
linear element can be specified as linearly located events.
A LRS is a set of LRMs and the policies, records and procedures for implementing them. There are
numerous, seemingly disparate, LRMs in use today. There is no single, best method, as each has
advantages in certain situations. It is, therefore, unreasonable to propose a single standard LRM. The
[12]
Generalized Model for Linear Referencing has been developed which instead categorizes LRMs
into a basic set of common concepts. The additional advantage of this approach is that it also enables
a singular method for translating linearly referenced locations into locations specified by another
method or along an alternative linear element. This translation method is both closed and transitive,
ISO 19148:2021(E)
ensuring round-tripping and translation chaining. The Generalized Model for Linear Referencing has
been summarized in Annex B.
The Generalized Model for Linear Referencing standardizes the content of a linearly referenced
...