GeoTIFF currently allows a CRS to be specified either by an authority code, or by user-supplied definition. When an authority code is used, then it shall be an EPSG code. The GeoTIFF specification does not allow other authorities. However we will probably need to support IAU codes in the future such as the ones listed in OGC registry. So some way to use other authorities is desired.
Proposal
Standard Model Coordinate Reference Systems said
"standard CRSs are identified through reference to an EPSG CRS code." It can be replaced by
"standard CRSs are identified through a CRS code from EPSG registry or other authority."
Requirements Class GeodeticCRSGeoKey allow a short integer values. If that integer is in the range 1024 … 32766 inclusive, it is an EPSG code. If the value is 32767, it is a user-supplied code. We propose to add a new reserved code: if the integer value is 1, then the TextDefGeoKey shall be an identifier as a character string in the form AUTHORITY:CODE. For example "IAU:1085". If the integer value is 2, then TextDefGeoKey is a WKT string.
GeoTIFF currently allows a CRS to be specified either by an authority code, or by user-supplied definition. When an authority code is used, then it shall be an EPSG code. The GeoTIFF specification does not allow other authorities. However we will probably need to support IAU codes in the future such as the ones listed in OGC registry. So some way to use other authorities is desired.
Proposal
TextDefGeoKeyshall be an identifier as a character string in the formAUTHORITY:CODE. For example"IAU:1085". If the integer value is 2, thenTextDefGeoKeyis a WKT string.