[GRASS-user] unstable results with r.param.scale ?

[Vincent Bain]

Hello Vincent,

in case it could be related to my recent issue with r.param.scale:

https://lists.osgeo.org/pipermail/grass-user/2020-October/081788.html

In my case there was most probably something wrong with my OpenMP
configuration.

HTH,
Vincent.

Le mercredi 09 décembre 2020 à 13:59 +0100, Vincent Godard a écrit :
> Dear Grass users,
> 
> I've been using r.param.scale to compute various type of curvatures
> over 
> a 1 m LiDAR DEM (FCELL) (from opentopography.org) :
> 
> r.param.scale --o -c input=dem output=curvature size=15 method=profc
> r.info -r curvature
> 
> I usually get reasonable results like (checked with independent 
> calculations) :
> 
> min=-0.203124601340989
> max=0.0685868278408049
> 
> But when running this command repeatedly, I randomly (usually every
> 3rd 
> or 4th time) get very different results like :
> 
> min=-127112309.998249
> max=131128979.492382
> 
> I am running GRASS 7.8.4 on Ubuntu 20.04. The problem is also
> present 
> when running r.param.scale from QGIS or rgrass7 (in a R session).
> 
> I have replicated the problem with another high resolution DEM of 
> different source (still FCELL), and also with a 30 m SRTM DEM
> (CELL), 
> but in this case the occurrence of these odd results is less
> frequent 
> and they are not contrasting as much with the expected outcome
> ("only" 
> by a 1 or 2 order of magnitude). The problem is present with or
> without 
> the -c option, and seems only to affect the computation of
> curvatures 
> (profc,planc,longc,crosc,minic,maxic).
> 
> Has anyone encountered something like that, or have any idea about
> what 
> might be going on?
> 
> Thanks in advance,
> 
> Vincent
>