[GRASS-user] Re: DEM resolution from r.surf.contour

[LeeDaniel]

Interpolation's kind of a tough issue. The horizontal resolution shouldn't
necessarily be dependent on the contour step intervals, because those are
two unconnected parameters.

In principle, interpolation will "fill the gaps" between given values. Since
the gap filling values are always guesses - albeit educated guesses - the
resolution is kind of a matter of taste, in my opinion. I'd say that the
method chosen is much more important - e.g. r.surf.contour interpolates
linearly, whereas v.surf.rst uses spline with tension.

So... Lange Rede, kurzer Sinn, I'd have a hard time telling you what
resolution to take for an interpolated DEM. Factors I'd consider would be:
1. How closely spaced are the contour lines? a.k.a. if you were to translate
the surveying coverage of the vectors to horizontal resolution, what would
you guess - how exact is the spatial data you're dealing with as inputs?
2. What scale do you need for your analysis?

As far as the problem with limited memory goes, perhaps the thing to do
would be to split the area up into smaller tiles and then perform the
interpolation for them all recursively and stitching together again in the
end?
In that case I'd make the tiles a little bigger than necessary and let them
overlap, and then throw away the edges when I stitched everything back
together again. Interpolated values should be cropped at the edges, because
on those sides there's no data available to interpolate into so you get
unrealistic results.

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