Support for gml:CompoundCRS

[Piero Campalani]

Currently Petascope builds compound CRSs by concatenating URIs of single CRSs. Single CRSs can be temporal, projected, geodetic, index etc.

Since compound definitions are officially defined too, Petascope should support compounds of either single or compound definitions.

For instance, ​EPSG:7405 is the official compound CRS which concatenates the single horizontal ​EPSG:27700 and the vertical ​EPSG:5101.

Workaround: While waiting for this feature, URIs of CRSs should simply reference single definitions, so in the example above instead of referencing ​EPSG:7405 one should explicitly concatenate ​EPSG:27700 and ​EPSG:5101.

[Dimitar Misev]

Compounding is only possible over single CRS according to the specification. Nesting compound CRS should be an error, see #150

[Piero Campalani]

Ok, thanks for the link.
Ideally then one should be able to use a gml:CompoundCRS alone, with a guard check to avoid further compositions (in Petascope).