[GRASS-user] reproject srtm elevation map

[Markus Metz]

On Wed, Sep 14, 2011 at 5:24 PM, Salvatore Mellino
<salvatore.mellino at gmail.com> wrote:
> Hi,
>
> I downloaded srtm elevation map (lat long) for Campania Region (Italy), now I want to reproject the map into another location (wgs84 33N). I try with the following command
>
> r.proj input=DTM_srtm location=latlong mapset=usr1 method=cubic
>
> but as results I have different z values.
>
> How can I fix this problem?
>
Use method=nearest to have identical elevation values.

Before reprojecting a DEM, the intended use should be considered when
choosing the interpolation method. Most terrain features are best
preserved with method=cubic, but this method produces overshoots which
is sometimes ok, sometimes not, e.g. for hydrology (slope and aspect
will also be affected by overshoots). method=bilinear preserves
features not as well as method=cubic, but for a DEM, the result still
looks better than with method=nearest, which is probably only
recommended for categorical data like land cover classes.

HTH,

Markus M