2010/6/4, Micha Silver <mi...@arava.co.il>: > On 06/04/2010 04:20 PM, Hanlie Pretorius wrote: >> Hi, >> >> I've been following the procedure at >> http://grass.osgeo.org/wiki/Import_XYZ to import DEMs into GRASS. >> >> It has worked for two DEMS, but I have a problem with the third one at >> the step where one "verifies that the number of rows in the ASCII file >> corresponds to the number of cells in the enlarged region". >> >> At this point, g.region reports 1146474 cells in the region, while I >> have 1146370 lines of coordinates in my file. >> >> > Assuming you already did the "r.in.xyz -s ..." step to get and set your > region to match the input data. > So it looks like there are about 100 coordinates missing from the ASCII > file. Maybe "holes" in the data? > One way to work around this might be to import the point data as a 3D > vector, then run the usual v.surf.rst interpolation. > v.in.xyz -z in=ascii.txt out=elev_pts z=3 fs=, > then > g.region vect=elev_pts res=<choose appropriate resolution> > v.surf.rst elev_pts elev=dem layer=0
Thanks for the suggestion, Micha. I've tried the interpolation route before and found that the difference between the resulting interpolated surface and the original DEM was up to 7m. I want to use the DEMs for a flood application, so they need to be as accurate as possible. I was thinking perhaps importing the points as vectors, converting them to raster and then doing a nearest neighbour or IDW interpolation to fill the gaps. At least then I'll be able to see where the gaps are and limit the interpolated pixels using a mask? > >> The output of g.region is: >> ----- >> projection: 99 (Transverse Mercator) >> zone: 0 >> datum: ** unknown (default: WGS84) ** >> ellipsoid: wgs84 >> north: -49312.49 >> south: -74587.5 >> west: -3015862.5 >> east: -2987512.5 >> nsres: 25.00000989 >> ewres: 25 >> rows: 1011 >> cols: 1134 >> cells: 1146474 >> ----- >> >> The first three and last three coordinates in my text file are: >> ----- >> -74575.000000,-3015850.000000,1548.830000 >> -74575.000000,-3015825.000000,1548.330000 >> -74575.000000,-3015800.000000,1547.500000 >> . >> . >> . >> -49324.990000,-2987575.010000,1510.980000 >> -49324.990000,-2987550.010000,1511.240000 >> -49324.990000,-2987525.010000,1511.470000 >> ----- >> >> Can someone help me to figure out what's going on? >> >> Thanks >> Hanlie >> _______________________________________________ >> grass-user mailing list >> grass-user@lists.osgeo.org >> http://lists.osgeo.org/mailman/listinfo/grass-user >> >> This mail was received via Mail-SeCure System. >> >> >> > > > -- > Micha Silver > Arava Development Co. +972-52-3665918 > http://www.surfaces.co.il > > > _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user