[GRASS-user] Re: Limit r.fillnulls to interpolate only small gaps

LeeDaniel Lee.Daniel.1986 at gmail.com
Fri Feb 18 10:34:20 EST 2011


I think William's right, the shape factor is important.

A way to combine the two so that the shapes of the large null areas is the
same as the gaps in the original raster would be to make polygons out of the
original gap areas, then use William's method with r.grow, then making
polygons that match the unfilled areas. The polygons that have the area of
the original gaps that also overlap polygons generated using the r.grow
method would then be the polygons to use as a mask. Thus the thin gaps would
be filled in.

The only problem there is that large gaps with a bottleneck somewhere would
be shut out of the analysis, although the bottleneck could theoretically be
interpolated quite well. But that would have happened with my original
suggestion too.

Or you could use r.grow and just accept the fact that even the large
interpolated areas will be interpolated on the edges. Then the bottlenecking
problem would be gone.
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