On Tue, Feb 26, 2013 at 2:17 PM, José María Michia Roberts <jose.maria.mic...@gmail.com> wrote: > Hi all! > > I've found that values of transformation matrix reported by > v.transform are erroneous after using this values in ST_Affine (a > PostGIS's function). > > The values that seems to be erroneous are x_offset and y_offset. The > rotation values seems to are fine. > > The transformed elements are ok (it is, their coordinates are in the > right place). > > Values reported by v.transform: > > xoff = -139153.031250 > yoff = 8352534.450195 > > The correct values must be (aproximately): > > xoff = 5461371 > yoff = 6321181 > > The complete session's log with one test element is there (same > results with a whole layer): > > http://pastebin.com/FUtnePvb > > Local map: tmp > Transformed map: tmp_geo > > Take a look at the map region for tmp/tmp_geo (reported by v.info), > and compare these values with those of x_off / y_off (reported by > v.transform). >
Note that there are two transformation matrices, one for forward transformation, one for backward transformation. Can the PostGIS ST_Affine function print both matrices? If possible, rather use v.rectify in GRASS 7 instead of v.transform in GRASS 6. With a recent version of GDAL/OGR, you can also add GCPs to a datasource with ogr2ogr -gcp which should then automatically transform the coordinates. Markus M > Maybe I'm not interpreting this correctly. > > Thanks all! > Jose > _______________________________________________ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user