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
--
Vincent Godard
CEREGE, OSU Pythéas
Aix-Marseille Université
Europôle Méditerranéen de l’Arbois - BP 80
13545 Aix-en-Provence cedex 04, France
[email protected]
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