Corrado wrote: > a very strange behaviour indeed: > > 1) location "A", one region defined TM, datum osgb36, region > s=0,w=0,e=800000,n=1300000 > > 2) location "B", one region defined lat/long, wgs84 180W,180E,60N,60S > > in location A, I use v.in.region to draw a vector called "outbox", I load it > in location B with v.proj input=outbox ouput=outbox_fromA, I set the region > in location B to the region of the box with g.region vect=outbox_fromA. > > The I go back: in location B, v.in.region to a vector called "back". In > location A I use v.proj input=back ouput=back_fromB to project it and then > set the region with g.region vect=back_fromB. > > The region I get in location A is compeltely different from the original > location ....!!!!!!!!!!! But it should not be ..... it should actually be the > same!
No it shouldn't. The current region (and hence the vector map created by v.in.region) will always be an axis-aligned rectangle. The projection step will often introduce rotation and/or other distortion, so the output of v.proj will be an arbitrary quadrilateral. Setting the current region to this map will produce the smallest rectangle which bounds the quadrilateral. Reverse-projecting the bounding region back to the original coordinate system will produce another arbitrary quadrilateral, not the original rectangle. -- Glynn Clements <[EMAIL PROTECTED]> _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
