Hi Janet, if you choose "use=attr" then the value of the attribute you set with "column=xxx" is used as the value for the raster pixel. You can check your attribute table to find out which attribute values are assign to each road section.
If you just want a "fix value" for each raster pixel of the road, you have to set "use=val" and then provide a value you want (value=xxx). So it depends what you're looking for. Which values do you want to be assigned to you road-pixel in the raster format? best regards, Johannes Am 14.03.2012 um 07:29 schrieb Janet Choate: > Hi users, > i've read the help and other posts regarding v.to.rast, but i'm still not > piecing it all together and would appreciate some help. > i have a vector map of roads that i want to convert to a raster, so it is > lines. v.support - fine, but i can not figure out what i need to do with > v.digit (and if v.digit is necessary), don't know how to use. after running > v.support, if i just run v.to.rast as: > > v.to.rast input=roads output=roads > ERROR: Column parameter missing (or use value parameter) > > but if i run as: > v.to.rast input=roads output=roads5 use=attr column=ROADNR > (or column=CODE, etc..) > > then i get a raster. values of the raster differ based on what column i > choose. so my question is, how do i choose the column, and how do i know > what to set use= to (attr,cat,val,z,dir) > > running db.describe on the road vector, i get the following info: > db.describe -c table=roads > ncols: 14 > nrows: 383 > Column 1: cat:INTEGER:11 > Column 2: UserId:INTEGER:11 > Column 3: FNODE_:INTEGER:11 > Column 4: TNODE_:INTEGER:11 > Column 5: LPOLY_:INTEGER:11 > Column 6: RPOLY_:INTEGER:11 > Column 7: LENGTH:DOUBLE PRECISION:20 > Column 8: GI00701_:INTEGER:11 > Column 9: GI00701_ID:INTEGER:11 > Column 10: YEAR:INTEGER:11 > Column 11: ROADDEC:INTEGER:11 > Column 12: CODE:INTEGER:11 > Column 13: STAT:CHARACTER:1 > Column 14: ROADNR:INTEGER:11 > > if anyone can please advise the process of turning a vector into a raster, > i.e. what commands are necessary first and how to apply them, i would really > appreciate it. > thank you, > Janet > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user
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