Hi, Do you need to use this data for the generation of a DEM? Would it be possible to use another source? seamless.usgs.gov is a great place to get gridded elevation data for the USA. Interpolating from contours should be a last resort.
Cheers, Dylan On Wed, Jul 8, 2009 at 6:42 PM, stephen sefick<[email protected]> wrote: > I tried this with points, lines and areas on the .e00 file > > v.in.e00 'file=/Users/sefick/Desktop/contours Folder/contours.e00' > type=area vect=georgia_contours --overwrite > > importing areas...... > > unable to open data <source cont> > an error occured. Stop. > > what now? > > I didn't have any luck with the grid data - tried and gave up. > > thanks > > Stephen Sefick > > On Wed, Jul 8, 2009 at 7:38 PM, Nikos > Alexandris<[email protected]> wrote: >> >> 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 >> >> > > > > -- > Stephen Sefick > > Let's not spend our time and resources thinking about things that are > so little or so large that all they really do for us is puff us up and > make us feel like gods. We are mammals, and have not exhausted the > annoying little problems of being mammals. > > -K. Mullis > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
