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

[Markus Neteler]

On Wed, May 2, 2018 at 7:13 PM, Martin Landa <landa.martin at gmail.com> wrote:
> 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)

I'd suggest to look at the univariate statistics first (r.univar -e)
and compare that instead of min/max only.

markusN

> 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
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-- 
Markus Neteler, PhD
http://www.mundialis.de - free data with free software
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