Glynn: > > there are many places where PROJECTION_UTM causes > > cellhd.zone to become relevant.
ah, right (eg r.info). so UTM must be a special case. (at least for gr6) Michael: > I don't know how this works in the underlying C code, include/gis.h defines five fundamental projection types: #define PROJECTION_XY 0 #define PROJECTION_UTM 1 #define PROJECTION_SP 2 #define PROJECTION_LL 3 #define PROJECTION_OTHER 99 (these can be seen in the top line of `g.region -p`) C programs are written to behave in different ways depending on which class of projection it is. > this all can be handled in a single method that parses > proj-parms.table except for State Plane. I can see why you > call latlon a pseudo projection, but not UTM. AFAICT, it is > a legitimate projection like the others. Like state plane, UTM is a collection of (for want of a better term) epsg codes. The State Plane or UTM code/zone says which epsg-like set of parameters to use/expand. A pure projection is a mathematical formula specifying how geographic space bends. SP and UTM are a table of contents for which EPSG code to use. hope that's clearer, Hamish _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev