Hi Rich, I'm no expert in projection or Grass for that matter but this is what I understand about the way Grass projects rasters and vectors. Hope not to be making things worse :)
In order to project a raster you have to "bring it in" your current location from another location that has a different projection. That is done using r.proj. The trick is that, when you bring your new raster into the current location, it will respect you current region settings, that is, limits and resolution. So, let's say you want to project an Oregon map but you current region is set to Florida. This will not work and your raster will not be projected. So, in order to know where you projected raster will fall, you can use the v.in.region trick. The command will create a bounding box in your map and you can project the vector (using v.proj), and not wory about the current region. Then you set your region to the recently projected vector (g.region vect=box) and fix your resolution. Now you are ready to project your raster and you know the current region matches the region where your raster is coming from. This is better explained in the r.proj manual page, in the notes section http://www.ces.iisc.ernet.in/grass/grass62/manuals/html62_user/r.proj.html Cheers Daniel On Tue, Dec 22, 2009 at 2:54 PM, Rich Shepard <rshep...@appl-ecosys.com> wrote: > On Tue, 22 Dec 2009, Hamish wrote: > >> tip: v.proj'ing over a v.in.region box can help there. Then I usually try >> to set the resolution to be a tiny bit better than the source rows x cols. >> If there will bit a lot of rotation I try to set it even finer. > > Hamish, > > I'm missing something important which is probably obvious to you and > others. The project location contains vector maps. My reading of the > v.in.region man page tells me its function is to "Create a new vector from > the current region." That suggests that the resulting output map is the same > as the displayed vector map but with a new name. > > If I then run v.proj on the display of the new map what have I changed? > More importantly, how does that help resolve my inability to run r.proj on a > DEM map and reproject it to the project's location? > > A clue stick would help. > > Thanks, > > Rich > _______________________________________________ > 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