Hi I have a couple of questions about DEMs, and how they work in GRASS. My application is hydrological and hydraulic analysis, and at the moment I'm investigating using r.sim.water to generate floodlines.
Usually, for this sort of analysis, I would have 5m contours for the catchment and a detailed survey (i.e. spot heights, sometimes with triangles) for sections of river. So my first question is, what is the best way to generate a DEM from this information? I know that I can use r.surf.contour to create a DEM from the contours, and I'd assume that something like v.surf.rst would be best for the points, but I need a single DEM for the analysis. The second problem is that I don't need a highly detailed DEM for the catchment, I only need detail along the watercourses - i.e. where I have the detailed survey. If I create two DEMs at different resolutions, can I patch them without losing detail? My third question is about creating a mask. If I'm working along the coast, or if I'm creating a detailed DEM along the watercourse, I only want raster data where there is base data (i.e. contours or points). Is there a way to quickly generate a mask for this? Regards David
_______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user