EN ISO 19144-1:2012
(Main)Geographic information - Classification systems - Part 1: Classification system structure (ISO 19144-1:2009)
Geographic information - Classification systems - Part 1: Classification system structure (ISO 19144-1:2009)
ISO 19144-1:2009 establishes the structure of a geographic information classification system, together with the mechanism for defining and registering the classifiers for such a system. It specifies the use of discrete coverages to represent the result of applying the classification system to a particular area and defines the technical structure of a register of classifiers in accordance with ISO 19135.
Geoinformation - Klassifizierungssysteme - Teil 1: Struktur des Klassifizierungssystems (ISO 19144-1:2009)
Information géographique - Systèmes de classification - Partie 1: Structure de système de classification (ISO 19144-1:2009)
L'ISO 19144-1:2009 établit la structure d'un système de classification d'informations géographiques, ainsi que le mécanisme de définition et d'enregistrement des classificateurs pour un tel système. Elle spécifie l'utilisation de couvertures discrètes pour représenter le résultat de l'application du système de classification à une zone particulière et définit la structure technique d'un registre de classificateurs, conformément à l'ISO 19135.
Geografske informacije - Klasifikacijski sistemi - 1. del: Struktura klasifikacijskega sistema (ISO 19144-1:2009)
Ta del standarda ISO 19144 vzpostavlja strukturo klasifikacijskega sistema geografskih informacij z mehanizmom za določanje in registracijo klasifikatorjev za tak sistem. Določa uporabo diskretnega pokritja za predstavitev rezultatov uporabe klasifikacijskega sistema na določenem območju ter določa tehnično strukturo registra ali klasifikatorjev v skladu s standardom ISO 19135. Struktura se lahko uporablja za razvoj specifičnih klasifikacijskih sistemov, ki obravnavajo posamezna področja uporabe in so opredeljeni v drugih delih standarda ISO 19144.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-junij-2012
Geografske informacije - Klasifikacijski sistemi - 1. del: Struktura klasifikacijskega
sistema (ISO 19144-1:2009)
Geographic information - Classification systems - Part 1: Classification system structure
(ISO 19144-1:2009)
Geoinformation - Normierte Klassifizierungssysteme - Teil 1: Struktur des
Klassifizierungssystems (ISO 19144-1:2009)
Information géographique - Systèmes de classification - Partie 1: Structure de système
de classification (ISO 19144-1:2009)
Ta slovenski standard je istoveten z: EN ISO 19144-1:2012
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.
EUROPEAN STANDARD
EN ISO 19144-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2012
ICS 35.240.70
English Version
Geographic information - Classification systems - Part 1:
Classification system structure (ISO 19144-1:2009)
Information géographique - Systèmes de classification - Geoinformation - Klassifizierungssysteme - Teil 1: Struktur
Partie 1: Structure de système de classification (ISO des Klassifizierungssystems (ISO 19144-1:2009)
19144-1:2009)
This European Standard was approved by CEN on 9 March 2012.
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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19144-1:2012: E
worldwide for CEN national Members.
Contents Page
Foreword .3
Foreword
The text of ISO 19144-1:2009 has been prepared by Technical Committee ISO/TC 211 “Geographic
information/Geomatics” of the International Organization for Standardization (ISO) and has been taken over
as EN ISO 19144-1:2012 by 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 2012, and conflicting national standards shall be withdrawn at
the latest by October 2012.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
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, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 19144-1:2009 has been approved by CEN as a EN ISO 19144-1:2012 without any
modification.
INTERNATIONAL ISO
STANDARD 19144-1
First edition
2009-08-15
Geographic information — Classification
systems —
Part 1:
Classification system structure
Information géographique — Systèmes de classification —
Partie 1: Structure de système de classification
Reference number
ISO 19144-1:2009(E)
©
ISO 2009
ISO 19144-1:2009(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2009
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 either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Conformance .1
2.1 Classes .1
2.2 Conformance of a classification system.1
2.3 Conformance of a register of classifiers.1
2.4 Representation of classification results .1
3 Normative references.1
4 Terms, definitions and abbreviated terms.2
4.1 Terms and definitions .2
4.2 Abbreviated terms.4
5 Classification systems.5
5.1 Concept .5
5.2 Classification and legend .7
5.3 Hierarchical versus non-hierarchical systems.8
5.4 A priori and a posteriori classification systems .8
5.5 Structure of classified data .9
5.6 A classification data set.13
6 Management of classifiers .14
6.1 General .14
6.2 Concept dictionary register for a classification scheme .15
6.3 Management of classifiers through registration.15
6.4 Register structure.15
Annex A (normative) Abstract test suite .24
Annex B (informative) A priori and a posteriori classification systems .26
Bibliography.30
ISO 19144-1:2009(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 19144-1 was prepared jointly by the Food and Agriculture Organization (FAO) of the United Nations and
Technical Committee ISO/TC 211, Geographic information/Geomatics under a cooperative agreement
between the two organizations.
ISO 19144 consists of the following parts, under the general title Geographic information — Classification
systems:
⎯ Part 1: Classification system structure
The following part is under preparation:
⎯ Part 2: Land cover classification system (LCCS)
iv © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
Introduction
This part of ISO 19144 is based on publications of the Food and Agriculture Organization (FAO) of the United
[1][2]
Nations . The first in a series of International Standards related to geographic classification systems, it
defines the structure of such systems, together with the mechanism for defining and registering classifiers.
Since there are many different possible application areas, there is no single classification system that will
serve all needs. The method by which classifiers are defined depends upon the application area. In addition,
the classifiers used within a particular application area might not be adequate for all situations encountered
within that application area and could need to be augmented over time. To facilitate extension of the set of
classifiers in a particular application area, classifiers are registered in a register structure compliant with
ISO 19135. This allows the set of classifiers to be maintained. The use of the ISO 19135 registration
mechanism allows for separate registers to be defined for different sets of classifiers within multiple
information communities, thereby satisfying application needs. This approach allows for independence
between information communities, but also allows relationships to be developed between different
classification systems that potentially allow the conversion, or partial conversion, of data from one
classification system to another, or the fusion of data from two separate sources.
The concept of classification systems is well known in the geographic information community. A classification
system can be used to subdivide any geographic area into small units, each of which carries an identifier that
describes its type. The results can then be represented as a discrete coverage as described in ISO 19123.
Many such classification systems can be defined to address any geographic area. Different application areas
and different information communities can define their own classification systems. However, if the
classification system is defined in a compatible way, interaction between different information communities
becomes possible. In addition, in a particular application area, it is desirable that there be a few
well-established classification systems, and that these themselves be standardized within information
communities.
This part of ISO 19144 describes the common structure, while subsequent parts will allow for the
standardization of specific classification systems.
A coverage is a function that returns values from its range for any direct position within its spatial, temporal or
spatiotemporal domain. A discrete coverage is a function that returns the same feature attribute values for
every direct position within any single spatial object, temporal object or spatiotemporal object in its domain.
The domain is an area covered by the coverage function, and the discrete coverage breaks that area down
into a set of spatial, temporal or spatiotemporal objects. The geometry of the discrete coverage used to
represent the results of applying a classification system can be any type of discrete coverage — for example,
a set of polygons fitted together like a jig-saw puzzle, a set of grid cells, or a set of points or curves.
A classification system consists of a set of classifiers. These classifiers may be algorithmically defined, or
established according to a set of classification system definitions. The classifiers are
application-area-dependent and are or will be defined in the other parts of ISO 19144 or other standards or
publications. A register allows for the maintenance of a set of classifiers for a particular application area. A
spatial, temporal or spatiotemporal object defined in terms of a set of classifiers is a classified object.
There is a commonality between conventional geographic features and classified objects. A feature is defined
in ISO 19101 as an abstraction of real world phenomena. An example of a class of feature is a building, and a
particular building, e.g. the UN building in New York, is an instance of a feature class. Conventional
geographic features are atomic units that are assembled to build one type of geographic information data set.
A classification system works in the opposite manner, from the top down, by successively decomposing the
whole within a coverage area. Classified objects are features, in that they are an abstraction of a real world
phenomena, but classified objects are not atomic, because they are necessarily related to each other by the
classifiers that decompose the whole. In a simple example of a classification system, the earth as a whole can
be covered by either “land” or “water”, and two classifiers can be defined partitioning the attribute range into
ISO 19144-1:2009(E)
two, identifying objects as being either land or water. Any particular area on the earth, corresponding to a
classified object, would be of type “land” or “water”.
ISO 19135 specifies that a technical standard be required to define the item classes in any conformant
register. This part of ISO 19144 defines schemas for registers conformant to ISO 19135 and serves as the
technical standard that defines the item classes required for the registration of classifiers. It establishes a set
of rules for specifying definitions that can be used in a particular context to establish classified objects.
Registers of classifiers can serve as sources of reference for similar registers established by other geographic
information communities as part of a system of cross-referencing. Cross-referencing between respective items
in registers of classifiers might be difficult in cases where the structure of registers differs between information
communities. This part of ISO 19144 can serve as a guide for different information communities for the
development of compatible registers that can support a system of classifier cross-referencing.
The structure of a classification system together with the mechanism of defining and registering classifiers
defined in this part of ISO 19144 is general and can be applied to many different information-community-
defined classification systems, including soil, landform, vegetation, urbanization and systems for
understanding biodiversity and climate change. The use of this document will allow the relationship between
different classification systems to be described.
vi © ISO 2009 – All rights reserved
INTERNATIONAL STANDARD ISO 19144-1:2009(E)
Geographic information — Classification systems —
Part 1:
Classification system structure
1 Scope
This part of ISO 19144 establishes the structure of a geographic information classification system, together
with the mechanism for defining and registering the classifiers for such a system. It specifies the use of
discrete coverages to represent the result of applying the classification system to a particular area and defines
the technical structure of a register of classifiers in accordance with ISO 19135.
The structure can be used to develop specific classification systems that address particular application areas,
specified in other parts of ISO 19144.
2 Conformance
2.1 Classes
Three conformance classes are identified in this part of ISO 19144.
2.2 Conformance of a classification system
Any classification system for which conformance to this part of ISO 19144 is claimed shall be in accordance
with Annex A (see A.2).
2.3 Conformance of a register of classifiers
Any register of classifiers for which conformance to this part of ISO 19144 is claimed shall be in accordance
with Annex A (see A.3) and ISO 19135:2005, A.1.
2.4 Representation of classification results
Any legend of classifiers for which conformance to this part of ISO 19144 is claimed shall be in accordance
with Annex A (see A.4).
3 Normative references
The following referenced documents are indispensable for the application 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/TS 19103:2005, Geographic information — Conceptual schema language
ISO 19110:2005, Geographic information — Methodology for feature cataloguing
ISO 19115, Geographic information — Metadata
ISO 19144-1:2009(E)
ISO 19123, Geographic information — Schema for coverage geometry and functions
ISO 19135:2005, Geographic information — Procedures for item registration
4 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms, definitions and abbreviated terms apply.
4.1 Terms and definitions
4.1.1
a posteriori classification
classification (4.1.4) scheme based upon definition of classes after clustering the field samples collected
NOTE 1 Taken from FAO LCCS version 2 (see Reference [2]).
NOTE 2 See Annex B for an examination of this and a priori classification (4.1.2).
4.1.2
a priori classification
classification (4.1.4) scheme structured so that the classes are abstract conceptualizations of the types
actually occurring
NOTE 1 Taken from FAO LCCS version 2 (see Reference [2]).
NOTE 2 The approach is based upon the definition of classes before any data collection actually takes place.
NOTE 3 See Annex B for an examination of this and a posteriori classification (4.1.1).
4.1.3
classified object
spatial object, temporal object or spatiotemporal object assigned to a specific legend class (4.1.16)
4.1.4
classification
abstract representation of real world phenomena using classifiers (4.1.6)
4.1.5
classification system
system for assigning objects to classes
4.1.6
classifier
definition used to assign objects to legend classes (4.1.16)
NOTE Classifiers can be defined algorithmically or according to a set of classification system (4.1.5) specific rules.
4.1.7
coverage
feature (4.1.10) that acts as a function to return values from its range (4.1.17) for any direct position within its
spatial, temporal or spatiotemporal domain (4.1.9)
[ISO 19123:2005]
EXAMPLE Raster image, polygon overlay, digital elevation matrix.
NOTE A coverage is a feature that has multiple values for each attribute type, where each direct position within the
geometric representation of the feature has a single value for each attribute type.
2 © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
4.1.8
discrete coverage
coverage (4.1.7) that returns the same feature attribute (4.1.11) values for every direct position within any
single spatial object, temporal object, or spatiotemporal object in its domain (4.1.9)
[ISO 19123:2005]
NOTE The domain of a discrete coverage consists of a finite set of spatial, temporal, or spatiotemporal objects.
4.1.9
domain
well-defined set
[ISO/TS 19103:2005]
NOTE Domains are used to define the domain and range (4.1.17) of operators and functions.
4.1.10
feature
abstraction of real world phenomena
[ISO 19101:2002]
EXAMPLE The phenomenon “Eiffel Tower” can be classified with other similar phenomena into a feature type
“tower”.
NOTE A feature can occur as a type or an instance. In this part of ISO 19144, type is meant unless otherwise
specified.
4.1.11
feature attribute
characteristic of a feature (4.1.10)
[ISO 19101:2002]
4.1.12
feature concept dictionary
dictionary that contains definitions of, and related descriptive information about concepts that may be specified
in detail in a feature (4.1.10) catalogue
1)
[ISO 19126:— ]
4.1.13
identifier
linguistically independent sequence of characters capable of uniquely and permanently identifying that with
which it is associated
[ISO 19135:2005]
4.1.14
item class
set of items with common properties
[ISO 19135:2005]
NOTE “Class” is used in this context to refer to a set of instances, not the concept abstracted from that set of
instances.
1) To be published.
ISO 19144-1:2009(E)
4.1.15
legend
application of a classification (4.1.4) in a specific area using a defined mapping scale and specific data set
NOTE Taken from FAO LCCS version 2 (see Reference [2]).
4.1.16
legend class
class resultant from the application of a classification (4.1.4) process
NOTE The result of a classification process is termed legend class in this part of ISO 19144 in order to avoid
confusion with the term “class” as used in UML modelling.
4.1.17
range
〈coverage〉 set of feature attribute (4.1.11) values associated by a function with the elements of the
domain (4.1.9) of a coverage (4.1.7)
[ISO 19123:2005]
4.1.18
register
set of files containing identifiers (4.1.13) assigned to items with descriptions of the associated items
[ISO 19135:2005]
4.1.19
registry
information system on which a register (4.1.18) is maintained
[ISO 19135:2005]
4.1.20
technical standard
standard containing the definitions of item classes (4.1.14) requiring registration
[ISO 19135:2005]
4.1.21
vector geometry
representation of geometry through the use of constructive geometric primitives
[ISO 19107:2003]
4.2 Abbreviated terms
4.2.1 General
CRS Coordinate Reference System
LCCS Land Cover Classification System
UML Unified Modelling Language
4.2.2 Notation
The conceptual schema specified in this part of ISO 19144 is described using the Unified Modelling Language
(UML), following the guidance of ISO/TS 19103.
4 © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
Several model elements used in this schema are defined in other standards in the ISO 19100 series. By
2)
convention within this suite of International Standards, names of UML classes , with the exception of basic
data type classes, include a two-letter prefix that identifies the International Standard and the UML package in
which the class is defined.
UML classes defined in this part of ISO 19144 have the two-letter prefix “CL”.
Table 1 lists the other International Standards and the packages in which UML classes used in this part of
ISO 19144 have been defined.
Table 1 — Sources of externally defined UML classes
International
Prefix Package
Standard
CV ISO 19123 Coverage core and discrete coverages
DS ISO 19115 Metadata application information
GF ISO 19109 General feature model
GM ISO 19107 Geometry root
MD ISO 19115 Metadata entity set information
MI ISO 19115-2 Metadata entity set imagery
RE ISO 19135 Procedures for registration
SC ISO 19111 Spatial referencing by coordinates
TM ISO 19108 Temporal objects
5 Classification systems
5.1 Concept
A discrete coverage returns the same feature attribute for every direct position within any single geometric
object in its spatiotemporal domain. The spatiotemporal domain consists of a set of geometric objects that
together form the coverage.
EXAMPLE 1 The discrete coverage of postal zones within a country: each zone has a different code and it is not
possible to interpolate between these codes. Nevertheless, there could be a high level relationship between the codes.
The small country of Monaco is divided into five quartiers: “Moneghetti”, “La Condamine”, “Fontvieille”, “Monaco-Ville” and
“Monte-Carlo”. These political jurisdictions completely cover the area of the country. The area of Monaco can be
represented as a discrete coverage with five spatial objects where each object has the geometry of a polygon. The
attribute value for each spatial object is the name of the political jurisdiction. See Figure 1.
2) There is potential confusion between the use of the term “class” as used in UML, “class” as used in a classification
scheme and “item class” as used in the procedures for registration. Class as used in a classification scheme is termed
legend class in this part of ISO 19144.
ISO 19144-1:2009(E)
Moneghetti La Condamine
Monte-Carlo
Monaco
Fontvieille Monaco-Ville
Figure 1 — Example of discrete coverage with polygon geometry
The geometry of the spatial objects associated with a discrete coverage can also be grid cells within a grid
structure. Each of the grid cells may carry an attribute.
EXAMPLE 2 A discrete coverage with grid geometry of the same area as used in the previous example. See Figure 2.
The figure legend identifies the instances of the attribute values that actually exist in the data.
Monte-Carlo
Monaco
Moneghetti
Monaco-Ville
Fontvieille
La Condamine
Figure 2 — Example of discrete coverage with grid geometry
NOTE The discrete coverages illustrated by the above examples are simple because only one relatively simple
attribute has been used. However, in reality the attributes for each of the coverage spatial objects can be very complex. In
order to describe land cover it is necessary to integrate a large number of descriptive parameters related to soil, biology
and density into a comprehensive land cover classification system. Such a classification system is of course
application-area-dependent. An oceanographer will have a different classification system than that of a meteorologist.
Classification systems can vary widely in different application areas, but for similar application areas there needs to be
some commonality in order for data from different sources to be used together.
6 © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
A classification system allows one to define classifiers in order to partition the attribute range of a discrete
coverage to establish classified objects.
5.2 Classification and legend
Classification is an abstract representation of real world phenomena (i.e. the situation in the field) using
classifiers. A classification is a systematic framework with the names of the classes and the definitions used to
distinguish them, and the relation between classes. Classification thus necessarily involves definition of class
boundaries that must be clear and based upon objective criteria.
A classification system shall be
⎯ scale independent, meaning that the classes at all levels of the system shall be applicable at any scale or
level of detail, and
⎯ source independent, implying that it is independent of the means used to collect information.
NOTE 1 Scale independence and source independence exist in the general case of a classification system. When the
system is applied to real data, i.e. when a legend is created, the scale and source limitations of the data can create
restrictions on the legend.
A legend is the application of a classification in a specific area using a defined mapping scale and specific
data set. Therefore, a legend may contain only a proportion, or subset, of all possible classes of the
classification.
A legend shall be
⎯ scale dependent, and
⎯ source dependent.
EXAMPLE 1 Scale dependence: some elements might be too small to be delineated independently when collected at
a particular scale.
EXAMPLE 2 Source dependence: elements collected from different sources, such as an aerial photograph and a
satellite false colour composite image, could be different.
A legend is a selection of a set of the classifiers from all of the possible classifiers within a classification
system. A legend could correspond to the classifiers that apply to a single data set or it could be applicable to
a number of related data sets.
NOTE 2 A legend is analogous to the set of features within a feature catalogue, which is a subset of all of the possible
features within a feature concept dictionary.
EXAMPLE 3 The derivation of legend classes from a classification system: when applying the reference classification
system to a given geographic area with a specific data type, only a subset of the classes from the reference system will
occur in the real data. This set of classes is the legend with which the mapping system will be carried out. The reference
system in Figure 3 is shown as a matrix with two parameters: the height of plants, ranging from 5 m to greater than 50 m,
and the percentage crown cover, ranging from less than 10 % to 100 %. The classes are numbered with a code number
from 1 to 100. In this specific case, the legend will have only four reference classification classes, numbers 33, 47, 78 and
83.
ISO 19144-1:2009(E)
Reference Classification System
>50 m 30 m >5 m
12 3 4
100%
DEFINED
GEOGRAPHIC
47 AREA
50%
given scale and data type
97 98 99 100
10%
mapping
derived
units
legend
[2]
Figure 3 — Legend as application of classification in a particular area
5.3 Hierarchical versus non-hierarchical systems
There are two basic forms of classification system: hierarchical and non-hierarchical.
a) Hierarchical classification systems
⎯ Classifiers shall be defined so that all classes at a specific level of the hierarchy are mutually
exclusive.
⎯ Criteria used to define a classifier at one level of a hierarchical classification shall not be repeated at
another level (e.g. criteria used to define a classifier at a lower level shall not be duplicated to a
higher level of the hierarchy).
NOTE 1 Most classification systems are hierarchically structured. Such a classification offers greater consistency,
owing to its ability to accommodate different levels of information — starting with structured broad-level classes —
which allow further systematic subdivision into more detailed subclasses. At the higher levels of the classification
system, few diagnostic criteria are used; whereas at lower levels, the number of diagnostic criteria increases.
b) Non-hierarchical classification systems
Classifiers shall be defined so that all classes are mutually exclusive.
NOTE 2 Non-hierarchical classification systems apply to only a single level of information, e.g. a single scale or
type of information.
5.4 A priori and a posteriori classification systems
Two approaches are defined for establishing classification systems: a priori and a posteriori classifications.
The first is based on the establishment of a classification scheme before the collection of the data to which it is
applied, whereas the second is based on the establishment of classes based on the common properties
identified in the data collected.
8 © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
NOTE Both approaches have applications. An a posteriori approach to classification provides additional flexibility that
allows the classification scheme to more closely match the data. However, it can make it more difficult to compare data
collected and classified separately. If standardized rules are used to establish classes in an a posteriori classification
system, then these rules can be used to generate broader sets of classes that encompass multiple separate
classifications. The a priori and a posteriori classification system approaches are discussed in Annex B.
5.5 Structure of classified data
5.5.1 Systematic arrangement
Classification is the process of systematic arrangement of objects into groups on the basis of their attributes.
The set of classes established in a classification system allows one to organize the attributes of geographic
features so that the attribute value for a feature instance is the name of a class from the classification system.
The groups can be directly defined or parametric rules can be used to generate the groups. A subset of the
set of groups in a specific area becomes a legend.
NOTE The concept of classification is very general and is widely used in many scientific and other disciplines.
Most geographic attributes are distributed spatially. That is, instances of geographic attributes normally have
different values at different spatial locations. Geographic information with discrete attributes can be
represented as a discrete coverage or with vector geometry describing a boundary-defined spatial data set
(vector data). Since the same real-world phenomenon may be represented using either coverage or vector
data, the systematic arrangement of objects into groups forming the classification can be applied to both
coverage and boundary-defined spatial vector data.
5.5.2 Representation using discrete coverages
The result of classifying an area is a legend that may be represented as a type of discrete coverage, as
specified in ISO 19123. The range of a discrete coverage is a set of feature attribute values represented as a
set of records with a common schema defined by the classification system. The domain consists of a finite
collection of classified objects together with their direct positions. The geometric object and its associated
record form a geometry value pair.
The class CV_Coverage (see ISO 19123) represents a feature type in accordance with the general feature
model from ISO 19109:2005, Figure 4. Class CV_Coverage has three attributes: the domainExtent, the
rangeType and the commonPointRule. In discrete coverages, there is a direct one-to-one relationship where
each CV_GeometryValuePair links to corresponding attributes. Attribute domainExtent describes the extent of
the domain coverage. The data type EX_Extent is defined in ISO 19115. Attribute rangeType describes the
structure and composition of the attribute data record. Attribute rangeType makes use of the data type
RecordType, which is defined in ISO/TS 19103. A RecordType is a metaclass that describes the structure of a
set of records. A RecordType consists of a list of attribute name/data type pairs. A simple list is the most
common form of rangeType. Attribute commonPointRule identifies the procedure to be used for evaluating the
CV_Coverage at a position that falls either on a boundary between geometric objects or within the boundaries
of two or more overlapping geometric objects, where the geometric objects are either CV_DomainObjects or
CV_ValueObjects. The data type CV_CommonPointRule is defined ISO 19123.
Associated with a CV_Coverage is a specification of the coordinate reference system (CRS) to which the
objects in the domain are referenced. The coordinate reference system is defined in ISO 19111.
Also associated with the CV_Coverage class are the CV_Domain and the CV_AttributeValues classes. The
CV_Coverage links the set of domain objects to the set of records containing the attribute values. A
CV_DomainObject can be any spatial or temporal or spatiotemporal object. The domain objects of a
CV_DiscreteSurfaceCoverage are constrained to be instances of GM_Surface. There is one instance of
CV_AttributeValues (i.e. one data record) for each instance of CV_DomainObject (i.e. each grid cell or
polygon area).
See Figure 4.
ISO 19144-1:2009(E)
<>
GF_FeatureType
(from general feature model)
<>
<>
CV_Coverage
(from coverage core)
CoordinateReferenceSystem
+ domainExtent[1.*] : EX_Extent
0.*
+ rangeType : RecordType
+ commonPointRule : CV_CommonPointRule
+collection +collection
Range
Domain
1 +CRS 1.* +domainElement 0.* +rangeElement
<>
CV_AttributeValues
CV_DomainObject
SC_CRS (from coverage core) (from coverage core)
(from spatial referencing by coordinates)
+ values : Record
+spatialElement +temporalElement
SpatialComposition TemporalComposition
0.* 0.*
<>
TM_GeometricPrimitive
GM_Object (from temporal objects)
(from geometry root)
Figure 4 — Elements of a coverage
CV_DiscreteCoverage is the subclass that returns the same record of feature attribute values for any direct
position within a single CV_DomainObject in its domain. Each geometry value pair consists of a domain object
(e.g. a grid cell or a polygon) and a record of feature attribute values. See Figure 5. In discrete coverages
there is a direct one-to-one relationship where each CV_GeometryValuePair is composed of a
CV_DomainObject such as a GM_Object and a CV_AttributeValues value.
10 © ISO 2009 – All rights reserved
ISO 19144-1:2009(E)
<>
CV_Coverage
(from coverage core)
+ domainExtent[1.*] : EX_Extent
+ rangeType : RecordType
+ commonPointRule : CV_CommonPointRule
CV_DiscreteCoverage
(from discrete coverages)
0.* +collection
CoverageFunction
1.* +element
CV_GeometryValuePair
(from coverage core)
+ geometry : CV_DomainObject
+ value : Record
Figure 5 — Elements of a discrete coverage
The type of discrete coverage is based on the type of geometric object in the spatial domain. ISO 19123:2005,
Clause 6, identifies five types of discrete coverage with different geometries:
⎯ a discrete point coverage, consisting of a set of independent points;
⎯ a grid point coverage, consisting of a set of grid points;
⎯ a discrete curve coverage, consisting of a set of curves;
⎯ a discrete surface coverage, consisting of a set of surfaces, typically GM_Surface objects (polygons) or
congruent rectangles (grid cells) or regular hexagons, but possibly TIN objects or Thiessen Polygon
objects;
⎯ a discrete solid coverage, consisting of a set of solid volumes.
A classification system can make use of any type of geometric object in its spatial domain. It is possible to
establish classifiers to identify the range values for any type of discrete coverage. Discrete coverages that
partition an area are addressed by discrete surface coverage.
5.5.3 Discrete surface coverage
A classification system that makes use of a coverage whose range partitions an area shall make use of the
CV_Discrete surface coverage in accordance with ISO 19123:2005, 6.8. The use of GM_Surface as the
geometry element is illustrated in Figure 6.
ISO 19144-1:2009(E)
CoverageFunction CV_GeometryValuePair
CV_DiscreteCoverage (from coverage core)
+collection +element
(from discrete coverages)
0.* 1.*
+ geometry : CV_DomainObject
+ value : Record
CoverageFunction
CV_SurfaceValuePair
CV_DiscreteSurfaceCoverage
+collection +element
(from discrete coverages)
(from discrete coverages)
1.*
+ geometry : GM_Surface
Figure 6 — Discrete surface coverage
The surfaces that constitute the domain of a discrete surface coverage can be mutually exclusive and
exhaustively partition an area or can be independent sub-areas. The type of coverage geometry used often
depends upon the method by which data was collected. Natural phenomena tend to have irregular boundaries
and are often represented as a set of congruent polygons. Some phenomena, types of sensor data or the
results of calculations tend to be organized in terms of a grid tessellation where the domain is a set of
congruent rectangles. Subtypes of CV_DiscreteSurfaceCoverage that may be used in classification systems
are illustrated in Figure 7. Different grid tessellations may be used. O
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...