[gdal-dev] resampling techniques in GDAL

[Markus Neteler]

On Wed, Jun 17, 2009 at 12:52 AM, Gregory,
Matthew<matt.gregory at oregonstate.edu> wrote:
> Hi all,
>
> A recent post got me thinking about resampling techniques.  I've posted
> a graphic to help illustrate my question.
>
>  http://www.fsl.orst.edu/lemma/sandbox/resample.png
>
> In the graphic, assume the input image is the 3x3 grid with black
> outlines and blue and yellow dot centers.  Assume the red outlined
> pixels represent three different output resolutions of a single pixel
> each having its center at the black dot.
>
> Using bilinear interpolation, each of these three output resolutions get
> the same value (tested using gdalwarp) based on the four yellow cell
> centers.  I understand why this is happening and realize this is the
> expected behavior.
>
> My question, however, is whether or not there is a resampling technique
> (inside or outside GDAL) that uses the proportional weights and values
> of *all* input pixels touched by the output pixel.

This would be a great addition (especially for gdalwarp). I have to
reproject population maps (LatLong, people/pixel) and a weighted
approach should gain more precision, right?

In GRASS, we have
http://grass.itc.it/grass64/manuals/html64_user/r.resamp.stats.html
-w: Weight according to area (slower)

but that's not for reprojecting...

Markus