On Fri, May 13, 2016 at 9:42 AM, Eric Patton <thepatton...@gmail.com> wrote: > Hi list, > > What is the best approach to take when georectifying a scanned, projected > map (but the projection is unknown)? Is it necessary to georectify the map > first into a lat-long location and *then* r.proj the map into a target > projection? This is the method I used, using 20 GCPs (reading lat-long > graticule intersections from the map) and a cubic rectification, but there > is still a lot of error (see attached; I overlaid the GSHHG coastline for > comparison). > > I'm not sure if I am going about this the correct way.
I don't have too much experience with this, but I think it's a good approach. But you also need to know the ellipsoid, not sure if that could cause the misalignment. Anna > > > Thanks for any thoughts, > > -- > Eric Patton <thepatton...@gmail.com> > > _______________________________________________ > 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
