[GRASS5] [bug #859] (grass) raster data at lower resolution: no resampling...

Michel Wurtz mw at teledetection.fr
Tue Nov 27 09:56:59 EST 2001

Helena wrote:

> If raster represents a continuous field, one has to
> reinterpolate,
> if it is an area or line map with categories (what GRASS originally was
> designed for) the resampling was acceptable.

Well, for continuous field, it depends what you are doing and what
represent your values : you may prefer to resample... 

For categories, the right answer is probably to take the most
represented value...

BTW, Are the values representing an average on the pixel's surface,
or a sampled value somewhere inside the pixel (generaly the center
or the top left corner).
In Grass, where is the point representing the pixel ?

the second solution is very interesting when you resample by
an integer factor : you have just to take one line of n and in
each line one point of n, beginning first row, first column.

In the other case, a factor of 2 puts just the resampling point
at the corners of 4 pixels, unless you move the region for the
new raster a half pixel NW, in order to use the same algorithm
as above..

Michel WURTZ - DIG - Maison de la télédétection
               500, rue J.F. Breton
               34093 MONTPELLIER Cedex 5

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