[GRASS-user] nulls left by r.surf.nnbathy

[Maciej Sieczka]

Nick Cahill wrote:
> I'm trying to create a dem from digitized contour lines with
> r.surf.nnbathy. I've started with vector contour lines, converted them
> to a raster with v.to.rast, then interpolate these using r.surf.nnbathy.
> The output looks good, except that it is speckled with random-looking
> null cells, as in the enclosed screen shot (white are nulls)
> 
> I can't figure out what is causing these: some are on a contour line,
> some are between contours; I don't see an obvious pattern. Is this a
> known issue with r.surf.nnbathy, and if so, is there a workaround?

Hi Nick,

Glad to see somebody using it!

I haven't had such an issue on my Linux box. Any chances you have a
mask set?

> On a related note, when I've tried to fill the nulls with r.fillnulls,
> the program crashes gis.m with a segmentation fault, leaving a couple
> temporary rasters and a mask.

Try reproducing this in spearfish and please report a bug if confirmed.

> I'm running GRASS 6.3, on Mac OS X 10.4.8, using William Kyngesburye's
> excellent binaries (dated 9/29/06, maybe not the most recent build). I
> built the binary for nnbathy myself; perhaps this is the problem. How
> would I test that?

Dunno. What nnbathy version? Last I tried was 1.66 and it works as good
as few previous versions. Can you reproduce the error on Linux?

Can you reproduce the error with plain nnbathy on your Mac? (look for
supiciously located 'NaN's in it's output; there shouldn't be any
within the convex hull) If so, please contact Pavel Sakov, the author,
and let us now the status.

Maciek