[GRASSLIST:3137] blending seams in patch

GRASS GRASS user
1

I have four rasters that I would like to patch. Unfortunately there are
1 or 2 null cells along the common edges, which leave nulls in the
resulting patched map. I would like to simply average "across" the nulls
between adjoining rasters. I tried increasing the region resolution by
8x, but I still have unsightly nulls. Any suggestions?

Thanks,
Rich

--
Richard Greenwood
www.greenwoodmap.com

2

I have four rasters that I would like to patch. Unfortunately there
are 1 or 2 null cells along the common edges, which leave nulls in the
resulting patched map. I would like to simply average "across" the
nulls between adjoining rasters. I tried increasing the region
resolution by 8x, but I still have unsightly nulls. Any suggestions?

try making a map with r.neighbors and then running r.patch with the
merge map listed as the first input and the r.neighbors map as the
second input (not sure if this is null safe? [does a 3x3 mean include
the center cell in the calculation?]).

If that doesn't work you might need to use an involved r.mapcalc
command with the average of a series of neighborhood modifier references.

Hamish

3

Hamish wrote:

I have four rasters that I would like to patch. Unfortunately there
are 1 or 2 null cells along the common edges, which leave nulls in the
resulting patched map. I would like to simply average "across" the
nulls between adjoining rasters. I tried increasing the region
resolution by 8x, but I still have unsightly nulls. Any suggestions?

try making a map with r.neighbors and then running r.patch with the
merge map listed as the first input and the r.neighbors map as the
second input (not sure if this is null safe? [does a 3x3 mean include
the center cell in the calculation?]).

If that doesn't work you might need to use an involved r.mapcalc
command with the average of a series of neighborhood modifier references.

Hamish

Perfect! Thank you. Simply running "r.neighbors in=patched_map out=fixed_up_map method=average size=5" looks to have cleaned everything up quite nicely.

Best regards,
--
Richard Greenwood
www.greenwoodmap.com

4

Perfect! Thank you. Simply running "r.neighbors in=patched_map
out=fixed_up_map method=average size=5" looks to have cleaned
everything up quite nicely.

Note the resultant "fixed_up_map" will be a smoothed version of the
original!

If you need to preserve detail, run:

r.patch in=patched_map,fixed_up_map out=patched_map2

so it only fills in averaged data when it finds a null gap.

Hamish