ISO/TR 14825:1996

TECHNICAL ISOTTR
REPORT 14825
First edition
1996-11-15
Geographic Data Files (GDF)
Fichiers de don&es ggographiques
Reference number
ISOTTR 14825: 1996(E)
ISOmR 14825:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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-
in liaison with ISO, also take part in the work. IS0
governmental,
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International
Standards. In exceptional circumstances a technical committee may
propose the publication of a Technical Report of one of the following types:
the required S upport cannot
- type 1, when be obtai ned for the
publication of an Internationa IS tandard, despite eated efforts;
rep
- type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility of
an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is normally published as an International
Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years
of publication, to decide whether they can be transformed into International
Standards. Technical Reports of type 3 do not necessarily have to be
reviewed until the data they provide are considered to be no longer valid or
useful.
ISOTTR 14825, which is a Technical Report of type 2, was prepared by the
European Committee for Standardization (CEN) in collaboration with IS0
Technical Committee ISOmC 204, Transport information and control
systems, in accordance with the Agreement on technical cooperation
between IS0 and CEN (Vienna Agreement).
This document is being issued in the Technical Report (type 2) series of
publications (according to subclause G.3.2.2 of part 1 of the ISO/IEC
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All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ isocs.iso.ch
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Printed in Switzerland
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lSO/TR 14825: 1996(E)
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Directives, 1995) as a “prospective standard for provisional application” in
the field of transport information and control systems because there is an
urgent need for guidance on how standards in this field should be used to
meet an identified need.
This document is not to be regarded as an “International Standard”. It is
proposed for provisional application so that information and experience of
its use in practice may be gathered. Comments on the content of this
document should be sent to the lSO/TC 204 Secretariat.
A review of this Technical Report (type 2) will be carried out not later than
three years after its publication with the options of: extension for another
three years; conversion into an International Standard; or withdrawal.

ISO/TR 14825: 1996(E)
INTRODUCTION
The Geographic Data Files (GDF) standard has been developed to meet the needs of professionals and
organizations involved in the creation, update, supply and application of referenced and structured road network
data.
It has been created in order to improve the efficiency of the capture, the production and handling of road related
geographic information. This increase in efficiency is obtained by supplying a common reference model on which
users can base their requirements and producers can base their product definition. In addition to this, the standard
facilitates the exchange of information, defined according to this reference model. For this it contains the definition
of an exchange format which avoid compatibility problems at both the users and the producersS side of the
information flow. In this respect, producers and users should not be viewed as two totally distinct groups- It is
envisaged that an important application of the standard will be the combination of information present in already
existing geographic information data bases into one, more comprehensive source of road-related information”
To ensure maximum compatibility with these already existing sources and also to make use of the strengths of the
structure in which these sources have been defined, the basic foundation of the standard is based on a general,
non-application specific data model. On top of this data model, a road network specific application model has been
built. Together they make up the GDF standard. Due to its general character, the data model also is able to support
other types of applications, thus facilitating the future creation of a wide variety of geographic information sources
which can be combined with maximum flexibility.
The standard consists of twelve chapters, of which six (chapter 5 to 10) together form the reference model. They
each contain the elaboration and definition of one clearly identifiable aspect of road related information. Chapter 4
contains a more general description of the standard. It contains the definition of the general data model as well as
the definition of the basic components of the standard, thus explaining the structure of the rest of the standard.
Chapter 11 describes the logical data structure by which the conceptual models as defined in the previous chapters
can be represented.
Chapter 12 defines the exchange format by which the information can be exchanged.

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ISO/TR 14825: 1996(E)
I. SCOPE
This standard specifies a system for the interchange of digital road related geographic information. It
takes into account all the requirements of applications in the road transport and traffic telematics
(RTTT) field. Within this field, the standard is application independent. The standard contains the
following detailed specifications :
a) A reference model according to which the information covered by the standard shall be defined.
The core of the reference model is formed by a data model and a data dictionary in which the
individual information components and their interrelations are defined.
A specification of ways of representation of the information components contained.
) The specification how to define meta information. An important aspect is the quality of the
information defined according to the standard. This aspect is dealt with separately in the sense that
the methodology is defined with which the quality of the information components contained can be
measured.
A specification for an exchange format reflecting the reference model.

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2 R REFERENCES
21 . Normative References
Working Party to Produce National Standards for the Transfer of Digital Map Data; National
II
Transfer Format, Release 1 .I ; Ordnance Survey; Southampton, U.K.; January 1989
National Committee for Digital Cartographic Data Standards et al.; Spatial Data Transfer Standard;
U.S. Geological Survey, National Mapping Division; Columbus, Ohio, USA; June 1990
International Federation of Library Associations and Institutions, Joint Working Group on the
International Standard Bibliographic Description for Cartographic Materials; ISBD(CM):
International Standard Bibliographic Description for Cartographic Materials; IFLA International
Office for UBC; London, U.K.; 1977
Bibliographic Systems Office, Working Group on Bibliographic Codes; Revised List of Languages
and Language Codes; Library of Congress, Bibliographic SystemsOffice; Washington D.C., U.S.A;
ISO; International Standard IS0 690, Documentation -Bibliographic references - Content, form and
structure; International Organisation for Standardisation; 1987
ISO; International Standard IS0 6709, Standard representation of latitude, longitude and altitude
for geographic point locations; International Organisation for Standardisation; 1983
ISO; International Standard IS0 3166; Codes for the representation of names of countries.;
International Organisation for Standardisation; 1993
ISO; International Standard IS0 2108, Information and documentation - International Standard
Book Numbering (ISBN); International Organisation for Standardisation; 1992
ISO; International Standard IS0 3297; Documentation - International Standard Serial Numbering
(ISSN); International Organisation for Standardisation; 1986
lSO/IEC; International Standard 8859-I) Information processing - 8-bit single-byte coded graphic
character sets - Part 1: Latin alphabet No. 1; International Organisation for Standardisation; 1987
ISO; International Standard 2859, Sampling procedures for inspection by attributes; International
Organisation for Standardization; 1985-l 995 (all parts)
AFNOR; Norme expkrimentale: Echanges de donneirs informatisees dans le domaine de
I’lnformation Geographique - EDlG&O; Association Franc;aise de Normalisation;Paris, 1991;
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ISO/TR 14825: 1996(E)
2.2 Digital Geographic Information Working Group; Digital Geographic
Information Exchange Standard (DIGEST); December 1989; Other references
131 FIG; Technical Dictionary, terms and definitions as used in surveying and mappingin Germany;
lnstitute for Applied Geodesy; Frankfurt am Main; 1971
141 ICA; Multilingual Dictionary of Technical Terms in Cartography; InternationalCartographic
Association; Wiesbaden; 1973
151 DTV; DTV-Lexikon; Deutscher Taschenbuchen-Verlag; 1975
161 The Shorter Oxford English Dictionary
171 Claude Berge; Graphs; North-Holland Mathematical Library, Volume 6 - Part 1; North Holland;
Amsterdam, New York, Oxford; 1985
181 Mehdi Behzad, Gary Chartrand; Introduction to the Theory of Graphs; Allyn and Bacon Inc.;
Boston, Massachusetts; 1971
191 Nijssen G.M, Halpin T.A.; Conceptual Schema and Relational Database Design - A fact oriented
approach; Prentice Hall, Sydney; 1989

ISO/TR 14825: 1996(E)
3. DEFINITIONS
The numbers between square brackets refer to the reference documents mentioned in 2.
3.1 General terms
3.3 .I Accuracy
The closeness of results of observations, computations or estimates to the true values or the values as
accepted as being true [2]
3.1.2 Cartography
The art, science and technology of making maps, together with their study as scientific documents and
works of art[l5]
3.1.3 Cartographic Primitive
Atomic construction element in a cartographic representation, i.e. Node, Edge and Face.
3.1.4 Data Fiie
A collection of related data records.[2] The records shall have a homogeneous structure.
3.1.5 Data Retard
A record containing feature related data
3.1 x6 Data set
A large set of data covering a particular geographic area
3.1.7 Entity
A real world phenomenon that is not subdivided into phenomena of the same kind (e.g. a bridge) [2]
3.1.8 Error Rate
The percentage of falsehoods
3.1.9 Field
A specified part of a record containing a unit of data. The unit of data may be a data element or a data
item [I]
3.1 .I0 Geudesy
Science of determination of the shape and gravity field of the earth and of survey and mapping of the
physical surface of the earth [14]
3.1 .I 1 Geography
Science of phenomena of the earth’s surface, its being and growing and its manifold relations [16]
3.1 .I 2 Geumetry
Science of the characteristics of spatial figures [16]
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3.1 .I3 Global Record
A record that logically precedes the data records and contains control parameters, data definition and
documentation necessary to interpret companion data records [ISO 821 I]
3.1 .+I4 information Unit
A collection of information that may be regarded as an undivided whole, e.g. 1 data set, I section, 1
layer
3.1 .I5 Logical Dumain
The range of attribute values to which a meaning has been assigned.
3.1 .I6 Logical Unit
A collection of data that may be regarded as a logically undivided whole, e.g. 1 logical record.
3.1.17 Medium Unit
An object for data storage that can be considered as a physically undivided whole, e.g. 1 floppy disk, 1
magnetic tape etc.
3.1 .I8 Physical Unit
A unit of data storage that may be regarded as physically undividable.
3.1 .I 9 Precision
The closeness of measurements of the same phenomenon repeated under exactly the same
conditions and using the same techniques.
3.1.20 Primitive
Fundamental form from which all other forms can be derived [17]
3.121 Repeating Attribute Type
An attribute type that may have multiple values associated to one and the same instance of a particular
feature type.
3.1.22 Resolution
The smallest unit which can be detected. It fixes a limit to precision and accuracy.
3.1.23 Spatial Domain
The description of the limits of a geographical area to which a particular set of data spatially belongs to.
3.124 Source Material
The origin of data in analogue or digital representation, stored on any kind of data medium.
3.1.25 Topography
The technical and conceptual registration of the terrain, its features and properties of the landscape
.
WI
3.1.26 Topology
The field of mathematics that deals with characteristics of geometric structures that keep preserved
after continual variation [ 161

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3.1.27 Transcription
Render ,ing of geographic na ,mes from a non-alphabetic script into an alphabetic one or vice versa. The
term is also applied to initial reco rding script of hitherto unwritten names [15]
3.1.28 Up-to-dateness
The closeness in time of the (geographic) data to the present reality.

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3.2 Mathematical terms
3.2.1 Area Feature
A two dimensional feature. An area feature is defined by one or more faces.’
3.2.2 Edge
A directed sequence of non-intersecting line segments with nodes at each end [2]
3.2.3 Encfave
Small part of an area enclosed by another area seen from the area to which that part belongs [ 141
3.2A Excfave
Small part of an area enclosed by another area seen from the enclosing area [14]
3.2.5 Face
or more non-
A two-dimensional element bounded by a closed set of edges and zerc
dimensional
intersection inner closed set of edges. The face is the atomic two element.
3.2.6 Graph
A set of points and a set of arrows, with each arrow joining one point to another. The points are called
nodes of the graph, and the arrows are called the edges of the graph [18].
3.2.7 Intermediate
A Point, not being a Node, that bounds the line segments belonging to an Edge
3.2,8 Line Featwe
A one-dimensional feature. A line feature is defined by one or more edges.
3.2.9 Luup
An edge which is bounded at both ends by one and the same node.
3.2.10 Nude
A zero-dimensional element that is a topological junction of two or more edges, or an end point of an
edge PI
3.2.1 I Non planar graph
A graph which is not planar
3.2.12 Path
A finite, alternating sequence of nodes and edges, such that every arc is immediately preceded and
succeeded by the two vertices with which it is incident and in which no vertex is repeated, except
(possibly) the first and the last one. [I 81
3.2.13 Planar Graph
A graph G is planar if it can be embedded in a plane. That means that it can be drawn on the plane so
that edges intersect only at a node mutually incident with them.
3.2A4 Plane Graph
A planar graph embedded in the plane
3.2.15 Point
A zero-dimensional element that specifies geometric location. One coordinate pair or triplet specifies
the location [2]
3.2.16 Segment
The direct connection between exactly 2 Intermediate Points
3.2.17 Valency (or Degree)
The number of edges which are incident with a particular Node.

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3.3 Geodetical terms
3.3.1 Cuntrul Points
Points in the real world that are identical with points in a map or aerial photograph.
3.3.2 Ellipsoidal Height
The distance between a point and the reference ellipsoid (measured along the ellipsoidal normal).
3.3.3 Geudetic datum
The position and orientation of a particular reference ellipsoid.
3.3=4 Geuid
A model of the figure of the earth, that coincides with the mean sea level over the oceans and
continues in continental areas as an imaginary sea level surface, defined by spirit level.
At every place it is perpendicular to the pull of gravity. The shape is irregular, but can for most
purposes be approximated by an oblate ellipsoid.
3.3.5 Geuid Ondulation
The difference between the orthometric height and the ellipsoidal height, measured along the ellipsoid
normal.
3.3.6 Height
The (vertical) distance between a point and the reference height level or the reference ellipsoid. On
land maps the reference level is commonly the mean sea level.
3.3.7 Horizontal Reference System
A reference system for positions
3.3.8 Magnetic Declination
Angle between Magnetic North and True North [14]
3.3.9 Map Projectian
The transformation method used to represent the curved earth surface on a plane
3.3.10 offset
A pair of values, subtracted from all coordinate values in order to shorten these coordinate values.
3.3.1 I Orthumetric Height
The distance between a point and the geoid (measured along the perpendicular line.
3.3.12 Reference Ellipsoid
An oblate ellipsoid of revolution that is used to approximate the figure of the geoid. It is specified by two
parameters: a semi-major axis “a” (equatorial radius of the earth) and a semi-minor axis “b” (polar
radius).
The flattening ‘7 is defined as: f = (a-b).a
3.3.13 Reference Height Level
The level to which all terrestrial heights are referred. It changes from country to country and it forms
part of the national coordinate system for surveying and mapping.

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3.3.14 Reference System
A coordinate system on which a national survey is based 1141
3.3.A 5 Vertical Reference System
A reference system for elevations
3.3.16 World Geodetic System (WGS)
A three-dimensional Cartesian coordinate system, its origin being the geocentre. WGS is related to a
specified gravity model.
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3.4 GDF Terms
Note: All feature classes mentioned below are defined in the Feature Catalogue (Chapter 5)
3.4.1 Album
A collection of related Volumes.
3.4.2 Attribute
A characteristic of a feature which is independent of other features[2]
3.4,3 Attribute Code
An alphanumeric identifier for an attribute type [I]
3.4.4 Attribute Name
A name associated to an attribute type [I]
3.4.5 Attribute Type
A defined characteristic of a Feature, which is independent of the other features.
3.4.6 Attribute Value
A specific quality or quantity assigned to an attribute [2]
3.4.7 Completeness
Extent to which all specified features are present.
3.4.8 correctness
Indication of whether a data item is correctly recorded according to a specified data catalogue.
3.4.9 Data Set
A collection of related data files
3x4.1 0 Feature
A database representation of a real world object. ( see feature catalogue)
3.4.11 Feature Category
Type of representation of a feature. I.e. Point, Line, Area or Complex Feature.
3.4.12 Feature Class
An alphanumeric identifier for a feature class.
3.4.13 Feature Code
An alphanumeric identifier for a feature class [I]
3.4.14 Feature Name
A name associated with a feature class [2]
3.4.15 Feature Theme
A specified group of related features.
lSO/T=R 14825:1996(E)
3.4A 6 Field
A set of characters representing one unit of data
3.4.17 Layer
A certain subset of a section based upon information contents. The collection of level-0 elements
present in a layer together should form one planar graph.
3x4.l 8 Manoeuvre
An ordered sequence of a Road Element, a Juncfion and one or more Road Elements.
3.4.19 Record
An implementation dependent construct that consists of an identifiable collection of one or more
related fields [2]
3.4.20 Semantic Relationship
A characteristic of a feature involving other features.
3.4.21 Section
A certain subset of a dataset based on geographical co-ordinates
3.4.22 Relationship
Semantic relationship
3.4.23 Relationship Code
An alphanumerical identifier for a (Semantic) Relationship.
3.4.24 Refationship Name
A name associated to a relationship type [2]
3.4.25 Relationship Type
A defined characteristic of a feature which is depenedent of ofther features.
3.4.26 Trarrsportation Element
A Road Element, Railway Element, Water Boundary Element, Junction, Rail Junction and Water
Boundary Junction
3.4.27 Turn
An ordered sequence of a Road Elemenf, a Juncfion and a Road Element
3.4.28 Volume
The smallest physical unit of medium. For example a magnetic tape, a floppy disk etc. A single
Volume may contain one or more GDF Datasets depending on Dataset size.
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4. GENERAL DATA MODEL
4.1 GDF History
The first version of the draft GDF standard was released in October 1988 (Geographic Data Files
Release 1 .O; 1988-10-01). A product of the EUREKA project DEMETER, it was designed to specify the
data content, means of data representation and structure of data supply for vehicle navigation systems.
Based on a comprehensive data model (derived from the UK National Transfer Format [NTF] Model)
the first draft standard was used extensively in the EUREKA project CARMINAT and in the DRIVE
projects PANDORA and Task Force European Digital Road Map (EDRM). Both the DRIVE-1 projects
put forward requests for changes to GDF 1 .O.
GDF 2.0 has been developed under work package 3532 of the Task Force EDRM. The GDF 2.0
Working Group consisted of representatives of EDRM partners Daimler Benz (Prime Contractor),
Bosch, Philips, Renault, Tele Atlas and Intergraph and MVA Systematica, a participant of the
PANDORA project. The other PANDORA project partners were Philips, Bosch, Ordnance Survey and
the Automobile Association.
In parallel with DRIVE projects, an informal working group of mapping organizations (both state and
private), electronics and vehicle manufacturers, academics and other experts has been developing a
conceptual data model upon which to standardize the exchange of geographical data in Europe.
Termed the “European Transfer Format” (ETF) model, it diverges from the GDF 1.0 data model in
certain key areas. The second release of GDF endorses the ETF conceptual data model, and is
therefore the first exchange format to be compliant with the ETF model.
GDF 2.0 differs from GDF I .O both in its treatment of the architecture of certain data structures and in
its use of terminology. It is also far more extensive in specification. It defines standards for the
description, classification and encoding of features of the road environment, suitable to support a
family of application areas. These include requirements for Vehicle Navigation Systems, Highway
Maintenance Systems, Road Transport Informatics, and Advanced Road Transport Telematics (ATT).
RTI and ATT are known in the US as Intelligent Vehicle Highway Systems (IVHS). Accommodation of
other applications in the future is envisaged.
GDF 2.1 was released in October 1992 and consists of a revision of Volume 3, the Attribute Catalogue
and Volume 9, the Media Record Specifications. The major differences with respect to 2.0 are the
introduction of the Segmented Attribute concept and the Time Domain concept.
GDF 2.2 was released in November 1994. The Feature, Attribute and Relationship Catalogue have
been considerably extended. The changes mainly consisted of the introduction of new information
items. GDF 2.2 was at the time of release , officially submitted to CEN TC278 for approval as a prENV.
For this, the CEN member countries reviewed the document during a three months period. The
comments received were subsequentely incorporated. The result of this was published in July 1995 as
GDF 2.3.
GDF 2.3 was subject to a final editorial review in September 1995.
GDF 3.0 was the result of the incorporation of comments from this review and submitted to CEN
TC278 for official approval as ENV in October 1995.
The work was undertaken by EDRM2 project partners and the members of CEN TC278 WG 7 with
considerations given to the needs of highway authorities in the later stages.
ISO/TR 14825: 1996(E)
4.2 Structure of GDF
GDF is divided into 12 chapters :
Scope, Normative References and Definitions
4 . General Data Model
5. The GDF Feature Catalogue
6 . The GDF Attribute Catalogue
7. The GDF Relationship Catalogue
8 . The GDF Feature Representation Scheme
9 . Quality Description Specifications
Global Data Catalogue
10 .
11 . Logical Data Structures
Media Record Specifications
12 .
Throughout each chapter, /talks are used to indicate a reserved meaning.
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lSO/TR 14825: 1996(E)
4.3 Contents of GDF
The Feature Catalogue provides a definition of the “real world objects” such as Roads, Buildings’
Administrative Areas and Settlements that have significance in the broad area of applications for this
standard. They all relate to the road environment. Suppliers of data destined for Vehicle Navigation
Systems, Highway Maintenance Systems and other applications will find a concise description and
classification of features in this catalogue.
The Attribute Catalogue defines a number of characteristics of features and possibility of
relationships. Some attributes are dedicated to one particular feature class. Other attributes may be
more generally applied. Some attributes themselves describe a certain characteristic completely.
Others have to be combined to reach this goal.
The Relationship Catalogue describes relations between features that may be used to convey
information in a realistic manner. For example, a relationship may exist between Road Elements and
Buildings such that a Building “is along” a Road Element. This serves to enrich the model to represent
the real world.
In the Feature Representation Scheme, instruction is given on how to represent an object: as a Point,
Line, Area or Complex Feature.
The Quality Measuring Specifications describe rules and methods on how to measure the quality of
and validate a GDF dataset.
In the Global Data Catalogue, a description is given on how meta information such as geodetic
references and data sources must be modelled. Data dictionary specifications are also provided in this
catalogue so that GDF will be able to meet diverse needs in the future.
The Volume Logical Data Structures describe how the information modelled according to the rules
described in the previous volumes, can be represented by a nested set of data types. This specification
is independent of any particular media record specification.
Finally, information needed to supply GDF data as physical data records is provided in the Media
Record Specification.
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4.4 Data Models in GDF
Many of the concepts relevant to GDF are best expressed diagrammatically. Those concepts
concerned with the data models of GDF are represented using a variant of Entity-Relation Modelling
referred to as NIAM (see section 4.5).
Where required, detailed sub-schema’s are given to reduce the complexity of the figures. The
complete data model and views pertinent to each of the volumes are presented and explained in detail
in 4.5.
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4.5 Understanding the NIAM diagrams
Figure 4.2 gives a diagram of the Conceptual Data Model. The diagram has been constructed
according to the conventions of NIAM modelling (Nijssens Information Analysis Method) [20].
Figure 4.1 provides the key to figure 4.2 and all other data models contained in this standard.
In the centre of the model resides “the feature” which is a geographic object that has a location’ such
as a road or a building. Note that in this diagram with “feature” is meant feature instance’ i.e. an
individual occurrence of a geographic object, such as the Eiffel Tower in Paris.
Each feature belongs to a certain feature class, i.e. a set of feature instances of the same class. Each
feature belongs to not more than one feature class: hybrid features are not allowed. This constraint is
indicated by the arrow above “belongs to”. Each feature also must belong to a feature class: classless
features are not allowed. This constraint is indicated by the black dot at the location where “belongs to”
is attached to “feature”.
The diagram shows furthermore that each feature may have zero, one or more attributes and may be
related to one or more other features.
It can also be seen that each feature is of exactly one feature category (Point, Line, Area or Complex).
The consequences of being of a particular category is illustrated in the lower part of the diagram. The
single side arrows indicate a subtype constraint: a Point feature is a subtype of a Simple Feature,
which in turn is a subtype of Feature.
The diagram shows that a Point feature is always represented by not more than one Node, a Line
feature by one or more Edges and an Area feature by one or more Faces. The lowest part of the
diagram illustrates how the “cartographic primitives” Face, Edge and Node are mutually related.
Entity type “A” has data type
“Data type” and domain
“Domain”
“A” plays role “x” to “B”
X
Y f
Uniqueness constraint
Exclusivity constraint
Mandatory role
“A” is subtype of “B”
Figure 4.1 Key to NIAM diagrams for GDF data models.
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The Feature Catalogue
This Catalogue defines only feature classes, not the individual feature instances. For that reason the
Feature Catalogue uses the term “feature” as a synonym for “feature class”.
The diagram shows that each feature must belong to exactly one feature class and exactly one feature
theme. The diagram also shows that feature classes and feature themes are uniquely referenced by a
Name and a Code. The dotted lines around these indicate that they are only used for referencing.
The diagram shows furthermore that certain features are composed of one or more other features.
These are called Complex Features. For example, a Road may contain Road Elements.
The Attribute Catalogue
The Attribute Catalogue defines a set of attribute types and a corresponding reference name and code
as shown in Figure 4.3. It defines the feature class that a particular attribute type may be attached to.
The diagram shows that an attribute may be an aggregation of other attributes. Such an attribute is
called a Composite Attribute. Some Attribute types that are used in a Composite Attribute may never
be directly attached to a feature. This is indicated by the exclusion constraint (the “X”) between the
roles “belongs to” and “is part of’ of Attribute Type.
The Relationship Catalogue
A semantic relationship is a meaningful link between two or more features, which are not necessarily of
different classes.
Semantic relationships with a common structure (e.g. linking feature A to feature B, where the
instances of A are always of the same class and where the instances of B are always of the same
class) and with a common meaning, are grouped into a relationship type.
A particular relationship type is uniquely referred to by a relationship name or a relationship code (see
figure 4.4).
Relationships are in most cases binary, i.e. involving two features. However there are instances when
three or more features are involved in a relationship. For example, the relationship Prohibited
Manoeuvre requires a Road Element, a Junction and at least one other Road Element. The order in
which these feature instances occur is significant. That is why Figure 4.4 shows a “Partner No.” which
specifies the order in which the individual feature types should occur in the relationship.
The Feature Representation Scheme
The Feature Catalogue, the Attribute Catalogue and the Relationship Catalogue can be considered as
being valid for a wide range of applications. With the Feature Representation Scheme however, we
enter the world of a more restricted group of applications that share the same representation needs.
In this Feature Representation Scheme for instance’ it is defined that a Road Element shall always be
considered as a Line feature. Another FRS however, possibly may specify that a Road Element should
be considered as an Area feature.
The most important role of the Feature Representation Scheme is to specify two what Feature
category or categories a particular feature class must or may belong. Four different categories are
distinguished: Point, Line, Area and Complex features.
Figure 4.5 illustrates that two different possibilities exist for a particular feature class:
all instances must be of one and the same category
some instances may be of one category, other instances of another one.
2)
In the latter case, the FRS describes when a particular instance must be considered as one category
and when as the other.
A representation of a feature by means of Points, Lines and Areas, is called a LeveM representation,
where as a representation by means of Complex features is called a Level-2 representation.
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ISO/TR 14825: 1996(E)
Depending to what category it belongs, a simple feature is represented by a Node, one or more Edges
or one or more Faces. All Nodes, Edges and Faces of the feature instances of a particular layer form
together a so-called Level-O representation. An important requirement is that this representation must
be plane, i.e. should contain Nodes where Edges meet each other in the plane.
Furthermore the FRS gives guidelines how the geometry for a particular feature class has to be
constructed and how curved lines have to be represented by Segments.
f CATEGORY 1
FEATURE
IS mm
contains
in
WI
n NODE
I IS bounded 1
\ I left
Figure 4.2. The overall Data Model
TYPE
[NAME,
elation of
Figure 4.3. The Data Model for Attributes

lSO/TR 14825: 1996(E)
Figure 4.4. The Data Model for Relationships between Features
represented by represent
Figure 4.5. The Data Model for Feature Representation
5. FEATURE CATALOGUE
5.1 Generic Specifications
51.1 Features and Feature Themes
In GDF, real world objects, such as roads and buildings are represented by ‘features’. Features such
as Roads’ and ‘Ferries’ may be grouped together into ‘feature themes’ (for example ‘Roads and
Ferries’).
All features and feature themes in the GDF are referenced throughout the manual by a feature name
or feature theme name. Most of these names are derived from terms commonly used in daily life (for
In order to distinguish a GDF feature name from these commonly-used
example road, building).
terms, the names of the features and feature themes are written in italics with an uppercase character
at the beginning of each word (for example ‘Road Elemenf versus ‘road element’).
5.1.2 Feature Class Names
For data exchange the features and feature themes are not referenced by their names but by a
numeric code. A four digit code is used for features and a two digit code for feature themes. A strict
I:1 relationship exists between feature class name and feature class code and between feature theme
names and feature theme codes. A full list of codes is given in Appendix Al. 1.
51.3 Simple and Complex Features
GDF makes a distinction between simple and complex features. A simple feature is a feature
composed only from geometrical primitives. In GDF, these are nodes, edges and faces. A complex
feature is composed of other simple or complex features. For example, a ‘Road Elemenf is a simple
feature constructed only of edges, and an ‘Intersection’ is a complex feature, made up of a set of
features such as ‘Road Elements’ and ‘Junctions’.
5.1.4 Data Model for the Feature Catalogue
Figure 5.1 shows that part of the data model which is relevant for the Feature Catalogue. The relations
between features and attributes have been left out for simplicity. They will be shown in the sub-
schemes of the Attribute Catalogue. Also, there are relationships which exist, which are not part of a
feature’s definition. These are described in the Relationship Catalogue.
ISOnR 14825: 1996(E)
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5.1.5 Overview Of Feature Themes
In the current Feature Catalogue the following feature themes are defined:
l Roads and Ferries
l Administrative Areas
l Settlements and Named Areas
Land Cover and Use
l Brunnels
Railways
l Watenfvays
Road Furniture
l Services
0 Public Transport
l General Features
These will be discussed in the following sections.
5.1.6 User-defined Features
The standard supports the ability for a user to define features which are not already defined. For these,
special Feature Class Codes have been reserved. (See appendix A 1 .l).
ISO/TR 14825: 1996(E)
Elective 1
I
Water
Element
xl
x
1 “““““J ‘\
Line
contains
@
Service
I
contains
Figure 5.1. Data Model of Feature Catalogue
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lSO/TR 14825: 1996(E)
5.2 Roads and Ferries
5.2.1 General Overview
The road network is seen here primarily from the viewpoint of transportation and traffic. Ferry
connections are therefore placed together with road network elements in one theme.
The road network can be represented at two different levels, Level I and Level 2. Level 1 describes all
the simple features such as Road Element, Junction, Ferry Connecfion, Enclosed Traffic Area,
Address area Boundary Element and Address Area, whereas Level 2 describes the complex features
Road, Infersecfion, Ferry and Aggregafed Way.
For example, in a vehicle navigation system application Level 1 can be used by the system to calculate
routes. Level 2 may be used to give guidance instructions to the driver.
The Data Model for Roads and Ferries is given in Figure 5.2 which describes relationships between
features within and between Levels 1 and 2.
ISO/TR 14825: 1996(E)
. I
’ starts at bounds bounds starts at
L
Road
(ID)
‘:ndsqbounds : ( 1 bounds ends at
Y
z
r
iz
tn
.- bounds ends at
UY
c
.-
RI
z
Figure 5.2 Data Model for Roads and Ferries

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52.2 Road Element
5.2.2.1 Definition
A linear section of the earth which is designed for or the result of vehicular movement. It serves as the
smallest unit of the road network at Level 1 that is independent and having a Junction at each end.
5.2.2.2 Independence of Road Elements
Individual Road Elements must be independent of one another. A change in the status of one Road
Hemenf must not affect a change in another. In Figure 5.3 for example, AB, BE, ED, DC and CA are
all Road Nemenfs. Their independence is illustrated by the fact that a barrier placed on Road Element
CD creates a no through road CD, but does not affect the status of the other Road Nemenfs.
Road Nemenfs may also have a distinguishing set of attributes. For example, in Figure 5.4, Road
Elements AF, FB have different names. AD, DE and EC have different restrictions. Within the context
of the attributes Official Name and Direction of Traffic Flow, the elements AF, FB, AD, DE, EC and BC
may be considered as being the smallest independent units and can consequently be considered as
individual Road Elements. Alternatively, changes in attributes along a single road element can be
described by stating the starting and ending positions along the road element for which the attribute is
valid. This procedure is further described in the Attribute Catalogue (see chapter 6.1 .lO, Relation
between attributes and features: Segmented Attributes)
5.2.2.3 Agqreqation Rules
Any additions to the attributes of a Road Hemenf, such as a restriction, or another name, may require
it to be split into two or more separate Road Elements. In the example of Figure 5.4, the addition of a
width restriction can cause the Road Element BC to be split into three new elements in order to be able
to distinguish the influence of the narrow bridge from the other parts of the road. Alternatively, the
limits for which attributes are valid along a road element may be described together with the attribute
value.
In Figures 5.5 and 5.6, both carriageways are considered as being independent and consequently are
treated as two individual Road Elements. A road with a physical separation between two parts of a
road can be represented by two different Road Elements. Alternatively, the physical separation can be
indicated by attributes.
/ \ I /
Queens’ Road King’s Road
Road Element AF and BF differ in an attribute
(their names) and therefore may be
independent. AD, DE and EC are differentiated
by traffic restrictions.
Road ElemenKD is independent of other
Road Elements. When CD is blocked,
traffic can still flow on other elements
Figure 5.3. Independence of Road Elements by Figure 5.4. Independence of Road Elements by
function
Attribute
_-----__--_--_--------------------------------------
Two separated parts of a road can be
Carriageways are physically separated along
represented as separate road elements.
their length and so may be represented
as two road elements.
Figure 5.5. Road Elements as Physically Figure 5.6. Road Elements as separated
Separated Carriageways carriageways
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ISO/rR 14825:1996(E)
5.2.3 Enclosed Traffic Area
5.2.3.1 Definition
fined area within which unstructured traffic movements are allowed.
Any con
5.2.3.2 Description
Examples of Enclosed Traffic Areas are: Industrial Sites, Car Parks, Harbour areas, Camp Sites,
Military Areas, Unstructured Traffic Squares
5.2.4 Junction
5.2.4. ‘I Definition
A feature that bounds a Road Elemenf or a Ferry Connection. A Road Element or Ferry Connecfion
always forms a connection between two Junctions and, a Road Elemenf or Ferry Connecfion is always
bounded by exactly two Junctions. A Junction feature represents the physical connection between it’s
adjoining Road Elements and Ferry Connections.
5.2.4.2 Relation between Junction, Road Element, Enclosed Traffic Area, Ferry Connection and
Address Area
Road Elements, Ferry Connections and Juncfions are mutually dependent: a change in the first set will
cause a change in the second one and vice versa.
is located at the ntersection of two or more road centrelines. If the road centrelines
A Juncfion
in tersect in two differen t points the situation has to be interpreted as two different Junctions.
A Juncfion is also located at the end of a dead end road or at the intersection of a Road Element and
an Enclosed Traffic A
...