The ellipsoid, geodetic datum, or spatial reference system (SRS) upon which the geometry given in footprintWKT is based.

`epsg:4326`, `GEOGCS["GCS_WGS_1984", DATUM["D_WGS_1984", SPHEROID["WGS_1984",6378137,298.257223563]], PRIMEM["Greenwich",0], UNIT["Degree",0.0174532925199433]]` (WKT for the standard WGS84 Spatial Reference System EPSG:4326)

Recommended best practice is to use the EPSG code of the SRS, if known. Otherwise use a controlled vocabulary for the name or code of the geodetic datum, if known. Otherwise use a controlled vocabulary for the name or code of the ellipsoid, if known. If none of these is known, use the value `unknown`. It is also permitted to provide the SRS in Well-Known-Text, especially if no EPSG code provides the necessary values for the attributes of the SRS. Do not use this term to describe the SRS of the decimalLatitude and decimalLongitude, nor of any verbatim coordinates - use the geodeticDatum and verbatimSRS instead.

Footprint SRS