[GRASS-user] r.param.scale issue

[Markus Neteler]

Hi Vincent

On Sun, Oct 11, 2020 at 8:08 PM Vincent Bain <bain at toraval.fr> wrote:
>
> Dear Grass users,
> has anyone ever experienced such issue with r.param.scale?
>
> Here's the point:
> I use to invoke r.param.scale instead of r.slope.aspect to calculate
> topographical slopes in various situations. I especially appreciate to
> have a hand on the size of processing window. I rencently had trouble
> with the result of the following command:
>
> g.region rast=topo
> r.param.scale input=topo output=slope_test size=5 method=slope --o
>
> It seems to run fine, but when I inspect the result it /sometimes/
> turns out to be really buggy (see attached .gif).
> As I said above it's a very strange behaviour; the command run on the
> same input file (same region settings) fails , let's say, in 10 %
> cases.

Weird indeed.

I tried locally (btw: which GRASS GIS version do you use?):

GRASS nc_spm_08_grass7/user1:~ > g.region raster=elev_lid792_1m
for i in $(seq 1 12) ; do r.param.scale input=elev_lid792_1m
output=slope_test size=5 method=slope --o ; r.univar -eg slope_test >
slope_test.$i ; done
 100%
 100%
 100%
 100%
 100%
 100%
 100%
 100%
 100%
 100%
 100%
 100%
GRASS nc_spm_08_grass7/user1:~ > md5sum slope_test.*
b74294ec45c02ca6a86ac81380af5a73  slope_test.1
b74294ec45c02ca6a86ac81380af5a73  slope_test.10
b74294ec45c02ca6a86ac81380af5a73  slope_test.11
b74294ec45c02ca6a86ac81380af5a73  slope_test.12
b74294ec45c02ca6a86ac81380af5a73  slope_test.2
b74294ec45c02ca6a86ac81380af5a73  slope_test.3
b74294ec45c02ca6a86ac81380af5a73  slope_test.4
b74294ec45c02ca6a86ac81380af5a73  slope_test.5
b74294ec45c02ca6a86ac81380af5a73  slope_test.6
b74294ec45c02ca6a86ac81380af5a73  slope_test.7
b74294ec45c02ca6a86ac81380af5a73  slope_test.8
b74294ec45c02ca6a86ac81380af5a73  slope_test.9

Even more tests:

GRASS nc_spm_08_grass7/user1:~ > for i in $(seq 1 111) ; do
r.param.scale input=elev_lid792_1m output=slope_test size=5
method=slope --o ; r.univar -eg slope_test > slope_test.$i ; done
 100%
 100%
 100%
...

GRASS nc_spm_08_grass7/user1:~ > md5sum slope_test.*
b74294ec45c02ca6a86ac81380af5a73  slope_test.1
b74294ec45c02ca6a86ac81380af5a73  slope_test.10
b74294ec45c02ca6a86ac81380af5a73  slope_test.100
b74294ec45c02ca6a86ac81380af5a73  slope_test.101
...
b74294ec45c02ca6a86ac81380af5a73  slope_test.98
b74294ec45c02ca6a86ac81380af5a73  slope_test.99

Looks all fine...

Maybe check if the computer disk is still ok?

Best,
Markus

-- 
Markus Neteler, PhD
https://www.mundialis.de - free data with free software
https://grass.osgeo.org
https://courses.neteler.org/blog