stephen sefick wrote: > I am trying to make a DEM from contour lines downloaded from here > http://csat.er.usgs.gov/statewide/layers/contours.html > I converted this to a shape file
You don't need to convert it to Shapefile. You can import vector .e00 files directly in GRASS using v.in.e00. Note that you need to have to programs installed: "avce00" and "e00compr". > reprojected it, why? from what to what CRS? Did you not create a location based on the coordinate reference system in which the data are referenced? Did you have any success with the "GRID" data, if of course you tried? > and then v.to.rast use=value and got out a raster with a range of 1 > to 1. That is so because the v.to.rast module expects from the user to define the "value" incase you use the "use=value" parameter. If the user does not define the "value" then "value=1" is taken as default. Please read the respective manual(s) [1]. I suppose that "v.to.rast use=val value=SomeValue" is not what you want. Giving a fixed value to all of the vector features that will be rasterized wont be useful if you want to play further with the data (e.g. create a DEM as you mention above). > How do I do this? --%<---code--%<--- # I downloaed the data you mention and did the following: v.in.e00 contours.e00 vect=contours type=line # check attribute table v.info -c contours v.info -c contours Displaying column types/names for database connection of layer 1: INTEGER|cat INTEGER|UserId INTEGER|FNODE_ INTEGER|TNODE_ INTEGER|LPOLY_ INTEGER|RPOLY_ DOUBLE PRECISION|LENGTH INTEGER|CONTOURS_ INTEGER|CONTOURS_I INTEGER|ELEV # match region ## I am unsure about the resolution (=look at the original data resolution from which the contours derived) g.region vect=contours res=SomeResolutionValue -pa # the last column is probably of your interest, so v.to.rast use=val value=attr col=ELEV --%<---code--%<--- Perhaps you do not even need to rasterise. Have a look at v.surf.rst [2]. Of course I am no expert with DEM's, v.surf.rst might not be what you need. Kind regards, Nikos --- [1] http://grass.osgeo.org/grass64/manuals/html64_user/v.to.rast.html [2] http://grass.osgeo.org/grass64/manuals/html64_user/v.surf.rst.html _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
