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I have recently been struggling with an issue in GRASS. I am a new GRASS user and recently downloaded version 7.8.5 for my MacBook (macOS Catalina). I converted this sample dataset to a shapefile. I am able to load and visualize the file and set the region to be the set of points. When I run v.surf.idw, I get the following error:

Input vector map <coal_test@PERMANENT> is 2D - using categories to interpolate
WARNING: No record for point (cat = 1)
WARNING: No record for point (cat = 2)
WARNING: No record for point (cat = 3)
.
.
.
WARNING: No record for point (cat = 96)
0 points loaded
ERROR: No points found

I have tried to use v.surf.idw with different datasets as well and am still getting the same error. I've also tried re-installing GRASS GIS to no avail.

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  • can you share the command line you enter? or the values you are entering at the interface?
    – Elio Diaz
    Feb 12, 2021 at 0:38

1 Answer 1

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I have tried with your dataset as per https://lists.osgeo.org/pipermail/grass-user/2021-February/082215.html, it does work. The step which you are missing is to first set the computational region to the dataset (https://grasswiki.osgeo.org/wiki/Computational_region).

Since I agree that the current error message is unhelpful, I have proposed a modification (see here).

Steps:

# set computational region to vector map, target raster resolution to 10m and 
# -a align to rounded coordinates
g.region vector=coal_test -p res=10 -a

# interpolate vector points to raster map
v.surf.idw input=coal_test output=coal_test_tested
Input vector map <coal_test@PERMANENT> is 2D - using categories to
interpolate
81 points loaded
Interpolating raster map <coal_test_tested> (150 rows, 150 columns)...
 100%
v.surf.idw complete.

# compute univariate statistics of new raster map
r.univar -e coal_test_tested
 100%
total null and non-null cells: 22500
total null cells: 0

Of the non-null cells:
----------------------
n: 22500
minimum: 8.07871
maximum: 94.9344
range: 86.8557
mean: 49.5003
mean of absolute values: 49.5003
standard deviation: 23.965
variance: 574.319
variation coefficient: 48.4138 %
sum: 1113756.87386977
1st quartile: 27.2997
median (even number of cells): 49.6119
3rd quartile: 70.95
90th percentile: 82.4886

Result (use a different target resolution as needed or a different interpolation method): enter image description here

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