[GRASS-user] Unable to perform resampling

[Veronica Andreo]

Hello Bharath,

I think your problem is that you are working in a latlong location and
trying to set a resolution of 8000 degrees, which is not possible. If your
desired final resolution is ~8 km, you will need to set the region
resolution to its equivalent in degrees (the unit of latlong CRS).
Otherwise, work with projected CRS like UTM for example (recommended).

Furthermore, if you want to go from high res to lower res (upscaling),
r.resamp.stats is your friend, so the second approach would be fine. The
problem lays in the resolution you are setting.

HTH,
Vero


El lun, 23 nov 2020 a las 22:20, BHARATH RAM (<br11 at iitbbs.ac.in>) escribió:

> Hello everyone,
>
>     I am interested in performing resampling of a fine resolution DEM
> Model (which is imported as a GTiff file in grass GIS). I tried the
> following 2 approaches and neither of them was successful. Can you help me
> figure out where I went wrong? Thanks in Advance.
>
> *Details about originally imported DEM model:*
> *projection: 3 (Latitude-Longitude)*
>
>
>
>
>
>
>
>
>
>
>
> *zone:       0datum:      wgs84ellipsoid:  wgs84north:      29Nsouth:
>  28:06Nwest:       72Eeast:       77:24Ensres:      0:00:01.08ewres:
>  0:00:01.08rows:       3000cols:       18000cells:      54000000*
>
> *MY AIM:* To convert a fine grid DEM (30 m resolution) to coarse grid DEM
> (8km)
>
> *APPROACH 1: Using r.resample.rst*
>
> *g.region raster=test5_r1*
>
> *r.resamp.rst input=test5_r1 ew_res=8000 ns_res=8000   *
>   In this second command's execution, I get error (log attached below):
> *                Processing all selected output files will require **4
> bytes of disk space for temp files.*
>
>
>
> *                Temporarily changing the region to desired resolution
> ...                Changing back to the original region ...
> Percent complete:                ERROR: Unable to seek: Invalid argument*
>
> *APPROACH 2: Using r.resample.stats*
> *g.region raster=test5_r1*
> *g.region nsres=8000 ewres=8000 *// problematic part
> *r.resamp.stats -w input=test5_r1 output=test5_r1_8km*
>    In this second command's execution the entire map seems to get clubbed
> into a single large pixel. I have attached results of *g.region -ap*
>  below:
> *                projection: 3 (Latitude-Longitude)*
>
>
>
>
>
>
>
>
>
>
>
> *                 zone:       0                 datum:      wgs84
>         ellipsoid:  wgs84                 north:      29N
> south:      28:06N                 west:       72E                 east:
>     77:24E                 nsres:      0:54                 ewres:
>  5:24                 rows:       1                 cols:       1
>       cells:      1*
>
>
> Also, can you tell me which method will be more suitable for my final goal?
>
> Thanks & Regards,
> Bharath
>
>
>
>
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