ISO 19112:2003 Geographic information - Spatial referencing by geographic identifiers
|Full name||ISO 19112:2003, Geographic information - Spatial referencing by geographic identifiers|
|Published by||ISO/TC 211|
|Type of standard|| ISO International Standard |
|Application|| A spatial reference system is a system for identifying a position in the real world. There are two ways of identifying positions: using coordinates or using geographic identifiers. In a spatial reference system using geographic identifiers, positions are identified by a label or code that identifies a location. |
The standard can be applied in two ways: firstly, to describe a spatial reference system using geographic identifiers, and secondly, to describe a directory of geographic identifiers, known as a gazetteer.
|Conformance classes|| Spatial reference system |
|Fundamental geographic dataset|| Category: Administration and spatial organisation |
Data Theme: Geographic names
ISO 19112:2003 defines the conceptual schema for spatial references based on geographic identifiers. It establishes a general model for spatial referencing using geographic identifiers, defines the components of a spatial reference system and defines the essential components of a gazetteer.
Spatial referencing by coordinates is addressed in ISO 19111:2007 Geographic information - Spatial referencing by coordinates. However, a mechanism for recording complementary coordinate references is included.
ISO 19112:2003 enables producers of data to define spatial reference systems using geographic identifiers and assists users in understanding the spatial references used in datasets. It enables gazetteers to be constructed in a consistent manner and supports the development of other standards in the field of geographic information.
ISO 19112:2003 is applicable to digital geographic data, and its principles may be extended to other forms of geographic data such as maps, charts and textual documents.
Spatial reference systems assist users in understanding the spatial references used in geographic datasets, maps, charts or textual documents. Conforming to ISO 19112:2003 ensures that gazetteers and their location instances are well defined. This facilitates interoperability and exchange of gazetteers. For example, a gazetteer can be used in more than one software product or different gazetteers can be used in the same software. Well-defined gazetteers also support the maintenance (e.g. through versioning) of location instances.
A spatial reference identifies the position of a feature in the real world. The position can be identified either explicitly by using coordinates, or indirectly by using a geographic identifier, i.e. a label or code that uniquely identifies a location on, below or above the earth’s surface. In ISO 19112:3003 the location identified by the geographic identifier is regarded as a (feature and) reference for other features.
A spatial reference system using geographic identifiers is comprised of a set of one or more location types, together with their corresponding geographic identifiers. These location types may be related to each other through aggregation or disaggregation, possibly forming a hierarchy. Refer to the table above for examples of spatial reference systems.
Examples of spatial reference systems by identifier
|Spatial reference system||Location types||Geographic identifiers|
|Municipalities of South Africa|| Province
| Province name |
District municipality name or identifier
Metropolitan municipality name or identifier
Municipality name or identifier
|Human settlements in a region|| Municipality
| Municipality name or identifier |
|Road names|| Suburb
| Suburb name |
Road name or identifier
A gazetteer is a directory of geographic identifiers for location instances. A location instance is an instance of a specific location type. For example, ‘South Africa’ is a location instance of the ‘country’ location type. The gazetteer may include information about the position of each location instance, such as, a coordinate reference or any other descriptive information about the location instance. More than one gazetteer could exist for a location type. For example, for the ‘Village’ location type in the table below, there could be gazetteers for different time periods.
A spatial reference system by identifier conforming to ISO 19112:2003 meets the following requirements (see examples in table below):
- The spatial reference system comprises of a set of one or more ISO 19112:2003 conformant location types with a common theme.
- The spatial reference system is described by at least the following four attributes:
- name, which serves as identifier;
- theme, which characterises the spatial reference system;
- overall owner, i.e. the authority with overall responsibility for the spatial reference system; and
- domain of validity, i.e. the geographic area within which the reference system occurs.
- The spatial reference system is versioned as follows:
- The version information is included in the name attribute.
- A new version is created whenever a location type is added, removed or replaced by a new version of a location type.
Descriptions of spatial reference systems by identifier conforming to ISO 19112:2003
|Name||Theme||Overall owner||Domain of validity||Location types|
| Census 2001
|Census||StatsSA||South Africa|| Province |
| Enumeration area
Karoo after 1994
|Population||Department of Human Settlements||Karoo|| Municipality |
| Boreholes in the
|Hydrography||Department of Water Affairs||Kalahari desert within Botswana’s borders|| Water management |
A location type in a spatial reference system conforms to ISO 19112:2003 if it meets the following requirements (see examples in the following table):
- The location type is described by at least the following six attributes:
- theme, e.g. ‘administration’, ‘electoral’, ‘postal’;
- identification, i.e. the method of uniquely identifying location instances;
- definition, i.e. the way in which location instances are defined;
- territory of use, i.e. the geographic area within which the location type occurs; and
- owner, i.e. the name of an organisation or class of organisations with the ability to create and destroy location instances.
- The location type is versioned; a new version is created whenever one of its attributes is modified. While ISO 19112:2003 does not specify this, it is practical to include version information in the name of the location type.
- The location type is uniquely identified by means of one or more geographic identifiers.
- There is at least one gazetteer of location instances for the location type.
- The location type may be related to parent and child location types, possibly forming a hierarchy.
Example: Descriptions of location types conforming to ISO 19112:2003
|Name||Theme||Identification||Definition||Territory of use||Owner|
|Municipality||Administrative boundaries||Name assigned by the Municipal Demarcation Board||Municipal boundary demarcated by the Municipal Demarcation Board||South Africa||Municipal Demarcation Board|
|Village||Settlement patterns||Name used by the village population||A cluster of twenty or more dwellings||Karoo||Department of Human Settlements|
|Water of management area||Water resource management||Alphanumeric identifier assigned by the Department of Water Affairs||Administrative boundary for the management of water resources||Botswana||Department of Water Affairs|
|Borehole||Water resources||Alphanumeric identifier, which is a combination of the land parcel identifier and a sequence number starting with 1 for each land parcel||A narrow shaft bored into the ground for the extraction of water||Kalahari desert within Botswana’s borders||Department of Water Affairs|
A gazetteer conforming to ISO 19112:2003 meets the following requirements (see examples in following table):
- The gazetteer is described by at least the following four attributes:
- territory of use, i.e. the geographic domain covered by the gazetteer;
- custodian, i.e. the organisation responsible for maintenance of the gazetteer; and
- the location types for which instances are recorded in the gazetteer.
- Optionally, the gazetteer may also be described by the following two attributes:
- scope, i.e. description of the location types in the gazetteer; and
- coordinate reference system, i.e. name of the coordinate reference system used to describe positions of location instances in the gazetteer.
- The gazetteer is versioned; a new version is created whenever any location instance is added, removed or replaced with a new version of a location instance. The version information is included in the name attribute.
- All location instances are recorded in the gazetteer and location instances conform to ISO 19113:2002 Geographic information - Quality principles.
Example: Gazetteer descriptions conforming to ISO 19112:2003
|Name||Census 2001 geographic area hierarchy v2000-03||Karoo villages v2004||Karoo villages v2006|
|Territory of use||South Africa||Northern Cape province||Northern Cape province|
|Custodian||StatsSA||Northern Cape Premier’s Office||Northern Cape Premier’s Office|
|Scope||Hierarchical structure of geographic areas used for the Census||Villages||Villages|
|Coordinate reference system||WGS 84 (EPSG::4326)||WGS 84 (EPSG::4326)||WGS 84 (EPSG::4326)|
A location instance in a gazetteer conforms to ISO 19112:2003 if it meets the following requirements (see examples in the following table):
- The location instance is associated with a location type.
- The location instance is described by at least the following three attributes:
- geographic identifier, i.e. the unique identifier for the location instance;
- geographic extent, i.e. description of the location instance itself; and
- administrator, i.e. the organisation responsible for defining the characteristics of the location instance.
- Optionally, the location instance may also be described by the following three attributes:
- temporal extent, i.e. the date on which this location instance was created in the gazetteer;
- alternative geographic identifier (for the same location instance);
- position, i.e. coordinates of a representative point of the location instance (e.g. centroid of an administrative area). Note that positions shall be recorded if the geographic identified contains insufficient information to identify the location.
- The location instance is versioned; a new version of a location instance is created whenever any of its attributes is modified, for example, when the boundary of a municipality changes during a demarcation process. The version information is recorded in the temporal extent attribute.
- The location instance may be related to parent and child location instances.
Example: Location instances of the ‘Karoo villages v2004’ gazetteer conforming to ISO 19112:2003
|Geographic extent||<polygon boundary>||<polygon boundary>||<polygon boundary>|
|Administrator||Municipal Demarcation Board||Department of Human Settlements||Department of Human Settlements|
|Alternative geographic identifier||Hantam Local Municipality (NC 065)||-||Mountain view|
|Parent location instance||-||Hantam||Hantam|
|Child location instances|| Buitepos
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