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  1. Spatial Information Systems
  2. SIS-536

Infer default datum from ellipsoid

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Details

    • Improvement
    • Status: Open
    • Major
    • Resolution: Unresolved
    • 0.8, 1.0, 1.1, 1.2, 1.3, 1.4
    • None
    • Referencing, Storage
    • None

    Description

      When reading a GeoTIFF file (but could also happen with other sources), the datum name is sometime unspecified. The problem is that the datum name is important for determining if two datum should be considered equal. As an alternative, we could use one of the EPSG codes for unspecified datum. There is currently 40 such datum:

      SELECT datum_code, datum_name FROM "EPSG"."Datum" WHERE datum_name LIKE 'Not specified%' AND deprecated=FALSE
      
      Code Name
      6019 Not specified (based on GRS 1980 ellipsoid)
      6013 Not specified (based on Clarke 1880 (Arc) ellipsoid)
      6014 Not specified (based on Clarke 1880 (SGA 1922) ellipsoid)
      6015 Not specified (based on Everest 1830 (1937 Adjustment) ellipsoid)
      6016 Not specified (based on Everest 1830 (1967 Definition) ellipsoid)
      6018 Not specified (based on Everest 1830 Modified ellipsoid)
      6001 Not specified (based on Airy 1830 ellipsoid)
      6002 Not specified (based on Airy Modified 1849 ellipsoid)
      6003 Not specified (based on Australian National Spheroid)
      6004 Not specified (based on Bessel 1841 ellipsoid)
      6005 Not specified (based on Bessel Modified ellipsoid)
      6006 Not specified (based on Bessel Namibia ellipsoid)
      6007 Not specified (based on Clarke 1858 ellipsoid)
      6008 Not specified (based on Clarke 1866 ellipsoid)
      6010 Not specified (based on Clarke 1880 (Benoit) ellipsoid)
      6011 Not specified (based on Clarke 1880 (IGN) ellipsoid)
      6012 Not specified (based on Clarke 1880 (RGS) ellipsoid)
      6020 Not specified (based on Helmert 1906 ellipsoid)
      6021 Not specified (based on Indonesian National Spheroid)
      6022 Not specified (based on International 1924 ellipsoid)
      6024 Not specified (based on Krassowsky 1940 ellipsoid)
      6025 Not specified (based on NWL 9D ellipsoid)
      6027 Not specified (based on Plessis 1817 ellipsoid)
      6028 Not specified (based on Struve 1860 ellipsoid)
      6029 Not specified (based on War Office ellipsoid)
      6030 Not specified (based on WGS 84 ellipsoid)
      6031 Not specified (based on GEM 10C ellipsoid)
      6032 Not specified (based on OSU86F ellipsoid)
      6033 Not specified (based on OSU91A ellipsoid)
      6034 Not specified (based on Clarke 1880 ellipsoid)
      6036 Not specified (based on GRS 1967 ellipsoid)
      6041 Not specified (based on Average Terrestrial System 1977 ellipsoid)
      6042 Not specified (based on Everest (1830 Definition) ellipsoid)
      6043 Not specified (based on WGS 72 ellipsoid)
      6044 Not specified (based on Everest 1830 (1962 Definition) ellipsoid)
      6045 Not specified (based on Everest 1830 (1975 Definition) ellipsoid)
      6047 Not specified (based on GRS 1980 Authalic Sphere)
      6052 Not specified (based on Clarke 1866 Authalic Sphere)
      6053 Not specified (based on International 1924 Authalic Sphere)
      6054 Not specified (based on Hughes 1980 ellipsoid)

      We should fallback on one of those datum when the only information are axis lengths. It should be okay since the name makes clear that the datum is actually unknown.

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              Unassigned Unassigned
              desruisseaux Martin Desruisseaux
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              Dates

                Created:
                Updated: