Dear all, after several tests and a bit of inverse-engineering, Longzhu and I have understood the reason of such as a small difference in the delineation of the polygons basins.
All the process beyond r.watershed are computed in 3x3 moving window (e.g. slope, flow accumulation, etc.), therefore if we change the extent of study area we change the starting point of the mowing window and of course the values of the flow accumulation change a bit. These changes in the flow accumulation cause variation on the delineations of the basin borders, of adjacent tiles. The reason, it is a bit obvious but did not come into my mind, immediately. Now I'm trying to figure out a clever way to merge these flow accumulations that come from different tiles and that are slightly different. Ciao Giuseppe On Fri, 5 Jun 2020 at 02:21, Markus Neteler <nete...@osgeo.org> wrote: > Hi Giuseppe, > > On Wed, May 13, 2020 at 2:16 AM Giuseppe Amatulli > <giuseppe.amatu...@gmail.com> wrote: > > > > Hi Markus, > > > > I use GRASS 7.6.0 > > under a HPC running > > Distributor ID: RedHatEnterpriseServer > > Description: Red Hat Enterprise Linux Server release 7.7 (Maipo) > > Release: 7.7 > > Codename: Maipo > > > > The compression is: > > > > GRASS 7.6.0 (nc_spm_08_grass7):~ > r.compress -p map=flow > > <flow> is compressed (method 5: ZSTD). Data type: DCELL > > <flow> has a compressed NULL file > > [Raster MASK present]. > > > > My option in selecting r.watershed with out the -m is manly due to be > able to use the -b option and also be able to run the tile-computation in 6 > hours vs several days (probably weeks) of the full globe (or continents) > run in segmentation mode - made quit hard to do debugging and re-running. > > > > Do you have any suggestions for the mismatching of the borders? > > I have no idea but it is recommended to update to GRASS GIS 7.8.3. > > Best, > markusN > -- Giuseppe Amatulli, Ph.D. Research scientist at School of Forestry & Environmental Studies Center for Research Computing Yale University New Haven, CT, USA 06511 Teaching: http://spatial-ecology.net Work: https://environment.yale.edu/profile/giuseppe-amatulli/
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