r.surf.idw won't make interpolation

[kuszinger]

However r.surf.idw won't make the interpolation for my dataset, I tested on NC sample dataset where it was ok. ??

I was not able to reproduce it with any other dataset but mine. I've created a cut of my data and accessible in the next comment.

Projection: UTM 48N / WGS84 (on the area of Cambodia)

+proj=utm +no_defs +zone=48 +a=6378137 +rf=298.257223563 +towgs84=0.000,0.000,0.000 +to_meter=1

Symptom:

r.surf.idw runs for the whole coverage. No error message displayed. When finished, the target raster map is the very same as the input was.

Command run: r.surf.idw --overwrite input=debugfrom@lidar output=debugto npoints=7 Purpose: generate a continuous surface from a very sparse set of points on the map.

[kuszinger]

Test data is accessible here: ​http://www.giscom.hu/debugfrom.pack. 4.4 MB and I tested r.surf.idw against it with the command above. Output was the same as input.

[annakrat]

Replying to kuszinger:

Test data is accessible here: ​http://www.giscom.hu/debugfrom.pack. 4.4 MB and I tested r.surf.idw against it with the command above. Output was the same as input.

Confirmed. Does it work in 6.4? What example did you use with NC dataset? I was not able to make it work.

[kuszinger]

NC: used elevation, the whole, set g.region res=5 so the target dataset is bigger, it ran well with good results. Anyway, the source dataset is not sparse. I rerun on the NC elevation and making it sparse with random nulls, ok?

6.4: yes, worked like charm, less than 2GB memory usage (same machine same everything). One more extra: while the above debug region is:

projection: 1 (UTM)
zone:       48
datum:      wgs84
ellipsoid:  wgs84
north:      1529314.78008
south:      1528778.59005
west:       448590.883652
east:       449308.347889
nsres:      0.19999628
ewres:      0.20001791
rows:       2681
cols:       3587
cells:      9616747

the whole map which was successfully interpolated in 6.4 was:

projection: 1 (UTM)
zone:       48
datum:      wgs84
ellipsoid:  wgs84
north:      1525100
south:      1522400
west:       449885
east:       453027
nsres:      0.2
ewres:      0.2
rows:       13500
cols:       15710
cells:      212085000

so, my packed sample is only a cut of which was successfully processed in 6.4

Anyway, I try NC with its modified eleveation and coome back with the results...

thanks

[kuszinger]

Got it!

• Go to NC in Grass7.1
• g.region raster=elevation@PERMANENT
• r.random -z --overwrite input=elevation@PERMANENT npoints=100000 raster=elev_sparse
• r.surf.idw --overwrite input=elev_sparse@user1 output=elev_sparse_idw npoints=7

Result is not interpolated.

Also tested in the same mapset with Grass6.4

• r.surf.idw --overwrite input=elev_sparse@user1 output=elev_sparse_idw_64 npoints=7

Result is ok in 6.4

[annakrat]

I think I fixed it in r65214. Null values were not identified correctly. I still don't understand why 64 version actually works.

By the way, r.surf.idw works only with integer rasters. But this is for a different ticket.

[neteler]

The indicated test is now performed as follows:

# GRASS 7.1.svn (nc_spm_08_grass7)
g.region raster=elevation@PERMANENT -p
r.random -z --overwrite input=elevation@PERMANENT npoints=100000 raster=elev_sparse
r.surf.idw --overwrite input=elev_sparse output=elev_sparse_idw npoints=7
ERROR: This module currently only works for integer (CELL) maps

So, no result should be expected unless #2672 is solved.

Replying to annakrat:

I think I fixed it in r65214. Null values were not identified correctly. I still don't understand why 64 version actually works.

Backported in r65261.

By the way, r.surf.idw works only with integer rasters. But this is for a different ticket.

Closing here, continuing in ticket #2672

[neteler]

Milestone renamed