Re: [GRASS-user] Re: how to get raster region corresponding to vector polygon region?
Hi Hamish, I like your r.reclass solution. Just wondering, you say it is a "virtual" map, and easy to remove. How is it virtual? When I use it I get a new map in my raster list that doesn't seem to go away so it seems permanent to me. Although I don't understand the underlying storage structure so maybe it is still virtual in that sense? Thanks, Ken On 06/17/2010 07:52 PM, Hamish wrote: Marcello wrote: There is probably a better way to do that (and I would like to "hear" it very much, specially if there is a single command to do this), but for now, I think the code below does the job: g.region vect=your_vector v.extract input=your_vector output=selected_polygon type=area where="cat=desired_cat" v.to.rast input=selected_polygon output=polygon_rasterized use=val type=area r.mask input=polygon_rasterized another way (probably there are many), v.to.rast then a loop using r.reclass to make a temporary MASK map of each category, then g.region rast=rasterized_vect g.region zoom=rasterized_vect r.reclass are tiny virtual maps (ie very quick to create+remove), g.region zoom= starts at the current region and shrinks inward until it hits a non-NULL cell. Hamish ___ 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
Re: [GRASS-user] Re: how to get raster region corresponding to vector polygon region?
Hi Marcello, Thanks for this response! After my post I also figured out exactly this method for doing it as well, although as you say would be great to have a one-liner. I will probably just write a little script that performs all these steps and takes in the relevant vector, cat, and raster values. thanks! ken On 06/17/2010 04:17 PM, Marcello Gorini wrote: Kwas wrote: Hello, I have a raster map (dem) and I want to select a region of the raster corresponding to a polygon that is in a vector map.nbsp; What is the best way to do this?nbsp; It looks like r.in.poly might be along the lines of what I need but in that case I think I would need to generate the ascii poly file first but I'm wondering if there is a better way?nbsp; Seems like there should be a single command to do this. My vector map has 45 polygons with cat values 1..45,nbsp; so I would like to get a section from my raster map corresponding to one of the polygons specified by cat value. appreciate any help! thanks, ken ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user Hello Ken, I am also new to GRASS, but I have been doing what you want quite a lot these days. There is probably a better way to do that (and I would like to "hear" it very much, specially if there is a single command to do this), but for now, I think the code below does the job: g.region vect=your_vector v.extract input=your_vector output=selected_polygon type=area where="cat=desired_cat" v.to.rast input=selected_polygon output=polygon_rasterized use=val type=area r.mask input=polygon_rasterized Now, any processing that you do will be applied only in the region corresponding to the selected polygon. If you want to create a raster corresponding to the selected polygon, just do: r.mapcalc "new_raster=any_old_raster" To take out the mask, just type: r.mask -r Hope this helps, Marcello. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] Re: how to get raster region corresponding to vector polygon region?
Kwas wrote: Hello, I have a raster map (dem) and I want to select a region of the raster corresponding to a polygon that is in a vector map.nbsp; What is the best way to do this?nbsp; It looks like r.in.poly might be along the lines of what I need but in that case I think I would need to generate the ascii poly file first but I'm wondering if there is a better way?nbsp; Seems like there should be a single command to do this. My vector map has 45 polygons with cat values 1..45,nbsp; so I would like to get a section from my raster map corresponding to one of the polygons specified by cat value. appreciate any help! thanks, ken ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user Hello Ken, I am also new to GRASS, but I have been doing what you want quite a lot these days. There is probably a better way to do that (and I would like to hear it very much, specially if there is a single command to do this), but for now, I think the code below does the job: g.region vect=your_vector v.extract input=your_vector output=selected_polygon type=area where=cat=desired_cat v.to.rast input=selected_polygon output=polygon_rasterized use=val type=area r.mask input=polygon_rasterized Now, any processing that you do will be applied only in the region corresponding to the selected polygon. If you want to create a raster corresponding to the selected polygon, just do: r.mapcalc new_raster=any_old_raster To take out the mask, just type: r.mask -r Hope this helps, Marcello. -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/how-to-get-raster-region-corresponding-to-vector-polygon-region-tp5192862p5193386.html Sent from the Grass - Users mailing list archive at Nabble.com. ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] Re: how to get raster region corresponding to vector polygon region?
Marcello wrote: There is probably a better way to do that (and I would like to hear it very much, specially if there is a single command to do this), but for now, I think the code below does the job: g.region vect=your_vector v.extract input=your_vector output=selected_polygon type=area where=cat=desired_cat v.to.rast input=selected_polygon output=polygon_rasterized use=val type=area r.mask input=polygon_rasterized another way (probably there are many), v.to.rast then a loop using r.reclass to make a temporary MASK map of each category, then g.region rast=rasterized_vect g.region zoom=rasterized_vect r.reclass are tiny virtual maps (ie very quick to create+remove), g.region zoom= starts at the current region and shrinks inward until it hits a non-NULL cell. Hamish ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
