[GRASS-user] flow accumulation (GRASS and Esri ArcGIS)

[Martin Landa]

Hi,

one of my colleague is dealing with flow accumulation calculation in
GRASS, and comparing results with Esri ArcGIS (builtin Flow
Accumulation [1]). Tool in ArcGIS to me knowledge uses D8, so we run
r.watershed with -s flag and also -a flag to avoid negative values.
Resultant values are very different.

* Esri ArcGIS (range: 0 - 20741)
* r.watershed -s (range: -34068 - 5697)
* r.watershed -sa (1 - 34068)

Do you have idea why results are so different? Thanks for any pointers
in advance! Martin

[1] http://desktop.arcgis.com/en/arcmap/10.5/tools/spatial-analyst-toolbox/flow-accumulation.htm

-- 
Martin Landa
http://geo.fsv.cvut.cz/gwiki/Landa
http://gismentors.cz/mentors/landa