Hi again, On Tue, Jun 2, 2015 at 11:58 AM, Markus Neteler <[email protected]> wrote: ... >> I am just trying again with this dataset: >> https://dl.dropboxusercontent.com/u/24062833/ES2003_1m_mb_contour.zip
Ok, I went through this example. Indeed, it only takes minutes even on my small laptop when reducing the area of computation to where the data actually are (there is no point in interpolation from contours where no contour lines are - this will also be MUCH faster). This is done by setting a raster MASK. On order to do so, I modified the example posted earlier: # Generate new location, for the lazy via command line: grass70 -c ES2003_1m_mb_contour.shp ~/grassdata/ES2003 # verify projection g.proj -w # import v.in.ogr ES2003_1m_mb_contour.shp output=ES2003_1m_mb_contour # set computational region and get extent of vector map g.region vector=ES2003_1m_mb_contour -e north-south extent: 5405.637436 east-west extent: 3945.019961 # generate points (point distance at e.g. circa 1% of extent) v.to.points input=ES2003_1m_mb_contour output=ES2003_1m_mb_contour_points dmax=50 # get alpha shape extension, see http://grass.osgeo.org/grass70/manuals/addons/v.concave.hull.html g.extension v.concave.hull v.concave.hull input=ES2003_1m_mb_contour_points output=riverbed threshold=5 # note: we do not need to be perfect here since we buffer the area later on d.vect ES2003_1m_mb_contour_points d.vect riverbed color=red type=boundary # generate buffer in order to get a slightly larger bathymetry v.buffer input=riverbed output=riverbed_50m distance=50 # reset computational region to area of interest g.region vector=riverbed_50m res=1 -ap projection: 1 (UTM) zone: 10 datum: wgs84 ellipsoid: wgs84 north: 4079844 south: 4074337 west: 608294 east: 612340 nsres: 1 ewres: 1 rows: 5507 cols: 4046 cells: 22281322 # restrict computation to where the data are r.mask vector=riverbed_50m # rasterize points v.to.rast input=ES2003_1m_mb_contour use=attr output=contours_rast attribute_column=CONTOUR # interpolate DEM from contour lines (rather fast) r.surf.contour input=contours_rast output=dmt_rast # remove MASK r.mask -r # check the result r.colors dmt_rast color=byr d.rast dmt_rast d.grid 1000 Screenshot of the result attached. Hope this helps, Markus -- http://consulting.neteler.org http://courses.neteler.org/blog <http://courses.neteler.org/blog> http://gis.cri.fmach.it/neteler/
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