Pull request #117 proposes the addition of a GTModelTypeGeoKey value for geocentric CRS associated to a two-dimensional spherical coordinate system. This pull request proposes to add an engineering CRS, but also associated to a two-dimensional spherical coordinate system. The definition would be similar to #117 except for the datum:
For a user-defined engineering CRS (spherical 2D) the user is expected to provide:
coordinate reference system name (through the EngineeringCitationGeoKey);
engineering datum through the EngineeringDatumGeoKey:
user-defined engineering datum name and other defining information:
the geodetic datum name (through the EngineeringCitationGeoKey);
axis unit through the GeogAngularUnitsGeoKey, either:
angle unit code (if available through standard EPSG code), or
user-defined angle unit name (through the EngineeringCitationGeoKey) and scaling from SI base unit of radian (through the GeogAngularUnitSizeGeoKey).
Note:GeogAngularUnitsGeoKey is not an appropriate name. Maybe this key should be renamed only AngularUnitGeoKey. Such renaming would not be a compatibility break if the numerical value does not change.
New GeoKeys
EngineeringCitationGeoKey
EngineeringDatumGeoKey
Open questions
Should we support a spherical 3D case?
Should we support a Cartesian 3D case? That one seems hard to implement because GeoTIFF images are 2D. For the shperical case, we can said that the third-dimension (the radius) is the pixel value. For the Cartesian case there is no obvious axis to use as pixel values.
Pull request #117 proposes the addition of a
GTModelTypeGeoKey
value for geocentric CRS associated to a two-dimensional spherical coordinate system. This pull request proposes to add an engineering CRS, but also associated to a two-dimensional spherical coordinate system. The definition would be similar to #117 except for the datum:Section to edit
User-defined Model Coordinate Reference Systems with the addition of the following sub-section:
For a user-defined engineering CRS (spherical 2D) the user is expected to provide:
EngineeringCitationGeoKey
);EngineeringDatumGeoKey
:EngineeringCitationGeoKey
);GeogAngularUnitsGeoKey
, either:EngineeringCitationGeoKey
) and scaling from SI base unit of radian (through theGeogAngularUnitSizeGeoKey
).Note:
GeogAngularUnitsGeoKey
is not an appropriate name. Maybe this key should be renamed onlyAngularUnitGeoKey
. Such renaming would not be a compatibility break if the numerical value does not change.New GeoKeys
EngineeringCitationGeoKey
EngineeringDatumGeoKey
Open questions