[gdal-dev] Why is the nearest neighbour resampling method the "worst interpolation"?

[Maciej Sieczka]

Matt Wilkie pisze:
>> Would people on this list have some knowledge or maybe hints to
>> documents on what downsampling/interpolation method would be best for
>> elevation data, for example when downsampling from 90 to 250 or 500
>> meters pixel size, keeping in mind that the result will be used to
>> calculate slope/aspect from?

> In my experience with elevation data Bilinear interpolation is the best 
> to use when downsampling. Nearest Neighbor will often produce distinct 
> box like artifacts or streaking, while Cubic Spline gives a kind of ripple.
> 
> With elevation it is important to keep the numbers to the right of the 
> decimal for calculating slope/aspect (meaning: don't convert to integer) 
> even when grossly downsampling. I can't locate the paper where I learned 
> this at the moment, but it was in connection with ANUDEM, Mike 
> Hutchinson and the Australia National Elevation Model.

Vincent

I suppose you might be interested in GRASS 6.3 r.resamp.stats module 
[1], which can be of use when seeking for an optimal aggregation method.

[1]http://grass.osgeo.org/grass63/manuals/html63_user/r.resamp.stats.html

Maciek