On 8/16/12, Janet Choate <[email protected]> wrote: > Hi all, > i have a raster that i simply want to split in two along a line designated > by me, thereby creating two separate rasters. i have attempted to digitize > using v.digit, displaying the raster and drawing a line around the area of > interest. i go through the motions of what i think is closing the line, > then save and exit. but v.info shows no data attached to this new vector, > and when i try to display, nothing shows up. > > can anyone tell me how to make 2 rasters out of my 1 along a user specified > line, or how to successfully digitize this? > thank you, > Janet >
Hi Janet, I don't know of a command that just splits a raster (maybe there is one??) But one way to do it is to use r.digit and create a file named MASK for each of the separate rasters. Then use r.mapcalc to create new rasters. Example: # remove any old MASK file g.remove MASK # set the region to the raster you want to split up g.region rast=old # display the raster you want to work on (i.e. d.mon start=x0 select=x0) d.rast old # run r.digit on the current raster (old) r.digit output=MASK ## use mouse keys to define new raster named MASK ## save with X # use r.mapcalc (not g.copy) to create a raster called 'new1' # that automatically applies the MASK you selected r.mapcalc new1=old # clean up and view results d.erase g.remove MASK # view the original raster (old) d.rast old # view the new raster d.rast new1 repeat steps for the other half of the raster (new2, etc...) note: Use v.extract and then v.to.rast if you want to create a MASK for features base on queries (instead of a mouse based MASK). hth L. Prevett _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
