On Thu, Feb 6, 2014 at 5:57 PM, Markus Neteler <[email protected]> wrote: > On Thu, Feb 6, 2014 at 1:14 PM, Blumentrath, Stefan > <[email protected]> wrote: >> Dear all, >> >> I am testing, trying, learning GRASS 7`s hydrology moduls at the moment. And >> I am very, very satisfied with the available tools. r.watershed managed to >> process a really big elevation model (150,000 x 120,000 pixels), which is >> amazing. > > Wow! Please consider to add a note to > http://grasswiki.osgeo.org/wiki/GRASS_GIS_Performance#Large_raster_data_processing > > (or in a blog entry or the like) > >> However, when I use r.hydrodem addon on the same big grid with 150,000 x >> 120,000 pixels (with the memory option) I get the following warning (and >> finally error) message: >> >> r.hydrodem input=dem_10m memory=10000 output=dem_10m _hydro > ... >> WARNING: segment_format(fd,1,-221837149,1,262144,16): illegal value(s) > > This is an integer overflow of ncols etc: > > [neteler@pgis_north r.hydrodem]$ grep nrows seg.c > seg_open(SSEG *sseg, int nrows, int ncols, int row_in_seg, int col_in_seg, > > In r.watershed it is defined differently: > > [neteler@pgis_north r.watershed]$ grep nrows seg/sseg_open.c > seg_open(SSEG * sseg, GW_LARGE_INT nrows, GW_LARGE_INT ncols, int > row_in_seg, int col_in_seg, > if (0 > (errflag = segment_format(fd, nrows, ncols, > > I suppose that this is an "easy" fix given the experience of r.watershed. > To not interfere, I'll leave the change to the module author.
The fix would be relatively easy, I will do it as soon as time permits... Note that r.hydrodem and r.watershed use the same mechanism, therefore r.hydrodem can not improve a DEM for r.watershed. The r.hydrodem module is meant to perform hydrological conditioning (sink removal) of a DEM when the DEM is used with other modules or other software. However, to my knowledge no other software exists that is able to perform surface flow accumulation on such a large raster. Two examples for sophisticated hydrological modelling packages are TauDEM and WhiteBox (formerly TAS). The last time I checked, both were not able to process DEMs with more than 2 billion grid cells. Even r.terraflow, designed for massive grids, can not process a 150,000 x 120,000 DEM. Markus M _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
