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GeoDCAT-AP [PR]: Revise text related to the default CRS of a bounding box just to say: follow GeoSPARQL

Andrea PEREGO
Published on: 22/07/2015 Discussion Archived

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Explanation

The GeoDCAT-AP WG received feedback about how the CRS of a bounding box is specified. Wrong conclusions were made, misinterpreting that it is recommended to copy the way of how a geometry can be encoded as WKT from GeoSPARQL. It was suggested to leave open options for new (improved) versions of GeoSPARQL.
 
Proposed solution. The GeoDCAT-AP specifications are going to be updated, detailing that the CRS must be encoded following GeoSPARQL when using WKT and GML.

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Documentation

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improvement
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stijngoedertier (not verified) Mon, 12/10/2015 - 14:30

Proposed solution:

  • Original text (draft 6): It is worth noting that currently there is no agreement on a preferred format to be used in RDF for the representation of geometries. Geometries can be provided in any, and possibly multiple, encodings, but at least one of the following must be made available: WKT or GML. An additional requirement concerns the coordinate reference system (CRS) used, which may vary on a country or territory basis. Following GeoSPARQL, the CRS must be always specified in the WKT endcoding when it is different from CRS84 (WGS84, with axis order longitude / latitude). Summarising:
    o    Geometries can be provided in multiple encodings, but at least one of the following must be made available: GML and WKT.
    o    The coordinate reference system used must be always specified when different from CRS84.
    o    For GML and WKT, the CRS must be specified as defined in GeoSPARQL [32].
  • Revised text (draft 7): It is worth noting that currently there is no agreement on a preferred format to be used in RDF for the representation of geometries. Geometries can be provided in any, and possibly multiple, encodings, but at least one of the following must be made available: WKT or GML. An additional requirement concerns the coordinate reference system (CRS) used, which may vary on a country or territory basis. The CRS must be specified in the GML or WKT encoding as required by GeoSPARQL. Geometries shall be interpreted using the axis order defined in the spatial reference system used. For example, for WGS84 the axis order is longitude / latitude. Summarising:

o    Geometries can be provided in multiple encodings, but at least one of the following must be made available: GML and WKT.

o    For GML and WKT, the CRS must be specified as defined in GeoSPARQL [32].

stijngoedertier (not verified) Mon, 21/12/2015 - 22:17
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