6.4.19 Gazetteers
From Geostandards
6 INSPIRE
6.1 Background and Motivation
- 6.1.1 Spatial Data Infrastructures
- 6.1.2 Requirements for a European SDI
- 6.1.3 Existing foundation for a European SDI
- 6.2.1 Background and history
- 6.2.2 The five components of the Directive
- 6.2.3 Implementation, status and schedule
- 6.2.4 Groups and responsibilities within INSPIRE
- 6.2.5 INSPIRE Implementing Rules and INSPIRE Guidance Documents
- 6.2.6 European and Global initiatives in the context of INSPIRE
6.3 Technical Architecture Overview
- 6.3.1 Relationship between the different components, in particular spatial data, metadata, registers, and network services
- 6.3.2 Terminology
6.4 Interoperabilty of spatial data sets / INSPIRE data specifications
- 6.4.1 Requirements of the INSPIRE Directive
- 6.4.2 Interoperability of spatial data
- 6.4.3 INSPIRE data scope
- 6.4.4 Modelling Framework
- 6.4.5 Generic Conceptual Model
- 6.4.6 ISO 19100 series of International Standards
- 6.4.7 Rules for application schemas and feature catalogues
- 6.4.8 Identifier Management
- 6.4.9 Object referencing modelling
- 6.4.10 Coordinate referencing
- 6.4.11 Multi-lingual text and cultural adaptability
- 6.4.12 Data quality
- 6.4.13 Metadata for evaluation and use
- 6.4.14 Multiple representations
- 6.4.15 Consistency between data
- 6.4.16 Portrayal model
- 6.4.17 Conformance
- 6.4.18 Generic Network Model
- 6.4.19 Gazetteers
- 6.4.20 Encoding and data formats
- 6.4.21 INSPIRE registers
- 6.4.22 Annex I data specifications
- 6.4.23 Outlook to Annex II/III data specifications
- 6.4.24 Extensions by countries or communities
While the importance of gazetteers is recognised in general (for use in the INSPIRE geoportal or in the context of object referencing), the specific role of gazetteers in INSPIRE is unclear so far. In particular, it is unclear which spatial data will be provided using a gazetteer, if any.
Whenever used, gazetteers and spatial reference systems using geographic identifiers in INSPIRE follow ISO 19112. However, the schema from ISO 19112 is not used as-is to correct errors in that schema and allow for a better integration in INSPIRE as a spatial data infrastructure.
To be applicable for indirect spatial referencing, it is crucial that all geographic identifiers are unique.
All spatial object types may be used to define a location type of a gazetteer.
The schema contains the following changes to the ISO 19112 model based on requirements of INSPIRE and implementation experiences:
- PT_FreeText has been used as a data type instead of CharacterString for properties that may contain multilingual text. While PT_FreeText is a subtype of CharacterString and can replace that type through the usual polymorphism mechanisms, the type has been used explicitly as gazetteers in INSPIRE are assumed to be multilingual.
- In localised character strings, the locale could reference well-known locales managed in a register.
- SI_LocationType is realised by LocationType with the following non-trivial changes:
- “theme” is implemented by a reference to a definition in a registered feature catalogue;
- “identification” is implemented by a code list, the values of the code list will be identified during the process of modelling the INSPIRE application schemas.
- Multiple alternative geographic identifiers are supported (there is an inconsistency in ISO 19112: according to the UML, only one alternative geographic identifier is allowed, however, the textual description states that multiple alternative geographic identifiers can be provided).
- Since the temporal extent is specified in ISO 19112 as “the date of creation of this version of the location instance”, a more appropriate data type and attribute name are used. Also, this property has been tagged as life-cycle information.
- ISO 19112 specifies that the geographic extent shall be defined in one of the following ways: either as a collection of smaller spatial objects (for example the European Union, defined by its constituent countries) or by a bounding polygon. However, the data type EX_GeographicExtent is not appropriate for this as it does not support the first method while it supports additional methods that are not allowed (a rough bounding box or a geographic identifier). At the same time the position attribute is restricted to a point. However, in INSPIRE it is expected that the positions/extents of locations are described by either points, curves, surfaces or even solids (or aggregates of these). Therefore, the attribute “geographicExtent” is of type GM_Object and “position” has been dropped.
- The information about the location is one piece of information to be derived from a gazetteer. Another piece of information that is considered important in INSPIRE is the reference to a spatial object that is associated with the location. An association has been added to allow representing such information in an INSPIRE gazetteer.
- This also allows, in principle, that the “geographicExtent” attribute can be derived on demand. For example, the EuroGeoNames project will head in the same direction: coordinates are no longer stored (duplicated) in the gazetteer, but are referenced to and maintained in the national reference data set(s), at various scales.
- The attributes of Gazetteer (i.e. name, custodian, scope) could be represented by references to registry entries.
In location types where geographic identifiers are based on a linguistic name (vs. a structured identifier), the topic of “equally treated names” requires additional clarification and guidance. In principle, such a clarification should be part of ISO 19112, but since this is not the case, it is expected that the current OGC Standards Working Group may provide guidance about this subject. As a result, it is likely that the standardisation of a gazetteer application schema in the current OGC Standards Working Group may lead to changes of the schema discussed above.
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