support spatial extent as description

[pvgenuchten]

In iso19139 there are 2 options to indicate spatial extent, either spatial (box or geometry) or as label

See for example

<extent> 
  <EX_Extent> 
    <geographicElement>
      <EX_GeographicDescription>
        <geographicIdentifier>
          <MD_Identifier>
            <code>
              <CharaterString>Ameland<CharaterString>
            <code>
          <MD_Identifier>
        <geographicIdentifier>
      <EX_GeographicDescription>
    <geographicElement>   
  <EX_Extent>
<extent>

Suggestion would be to support this secnario also in pygeometa, instead of

 extents:
        spatial:
            - bbox: [-141,42,-52,84]
              crs: 4326

also support

 extents:
        spatial:
            - description: Ameland

see also: http://www.datypic.com/sc/niem21/e-gmd_EX_GeographicDescription.html

[tomkralidis]

@pvgenuchten the pygeometa MCF schema makes identification.extents.spatial.bbox a required property.

To make sure, do you have use cases that only contain a spatial description, or is the spatial description in addition to spatial bbox for example (a missing / optional bbox would warrant the metadata difficult to apply spatial predicates to, unless a catalogue has a geocoding engine as part of a spatial search (which seems a bit esoteric?).

To summarize, is the spatial description in support of a query predicate or documentation/presentation? We could add description as an optional spatial property, which would be a low barrier change, but not sure if that helps your use case(s).

[pvgenuchten]

The spatial description as string or uri is quite common in dcat and datacite, and also allowed in iso19115.

Indeed the catalogue engine would need to have a geolocation api to capture the extent of the geolocation to be able to facilitate coordinate queries.

Unfortunately I haven't found online examples, however I face the challenge quite a lot when creating mcf's from excel sheets providing a limited subset of metadata properties, in that scenario providing a location by name is more easy then providing a bbox. However I could also implement the geolocation lookup as part of the mcf generation.

[tomkralidis]

@pvgenuchten see PR in #214

[tomkralidis]

Implemented in #214