[geotk] Easy way to detect a horizontal 2D CRS?

[Martin Desruisseaux]

Jon Blower a écrit :
> Is there an easy way to determine, for example, that a
> CoordinateReferenceSystem object represents a 2D horizontal CRS?  I
> would guess that most of the 2D CRSs are currently horizontal, but one
> could imagine an x-z coordinate system that would not be.

In the 2D case, I use the following criterion: The CRS is considered horizontal 
if it is either an instance of GeographicCRS, or a CRS derived from 
GeographicCRS (this include the ProjectedCRS case). The 3D case is a little bit 
more difficult; for now I rely on axis directions, which is not really 
future-proof as you point out.

An easy way to make this check is to use the following convenience method:

http://www.geotoolkit.org/apidocs/org/geotoolkit/referencing/CRS.html#getHorizontalCRS%28org.opengis.referencing.crs.CoordinateReferenceSystem%29

So in the 2D case, the following idiom should evaluate to "true" if the CRS is 
horizontal:

   if (crs == CRS.getHorizontalCRS(crs)) {
       // Horizontal case
   }


	Martin