[GRASS-user] r.univar: different results with different projections?

[César Augusto Ramírez Franco]

Hello Carlos,

Maybe it has something to do with the pixel resolution? I would certainly
expect the same results, but with a very similar region (i.e. same number
of rows and columns, or at least very close and a similar number of pixels)

Maybe when projecting the raster, the length of the array is varying but I
wouldn't expect to vary very much, are you getting the same results in a
previous version of GRASS? (7.0 or even 6.4?)

Greetings
El nov. 16, 2015 11:35 AM, "Carlos Grohmann" <carlos.grohmann at gmail.com>
escribió:

> Hi all.
>
> I'm analyzing some global-scale DEMs, like ETOPO1/2, SRTM30_PLUS, etc.
>
> I'm getting the statistics for the whole dataset with r.univar, but today
> I noticed that the results differ if I use different projections. (GRASS
> 7.1)
>
> For example, ETOPO2:
>
> Using a latlong pseudo-projection (plate carré)
>
>
> min: -10791
> max: 8440
> mean: -1888.6480792
> median: -2457
> stddev: 2650.01922839
> p25: -4273
> p75: 216
>
>
> And using equal-area cylindrical:
>
> min: -10791
> max: 8440
> mean: -2379.78247747
> median: -3291
> stddev: 2507.89668617
> p25: -4541
> p75: 94
>
>
>
> Are these differences expected? I would think that they should be the
> same, regardless of projection (I'm thinking on the elevation values as an
> array of values).
>
> thanks
>
> Carlos
>
>
>
>
>
> --
> Prof. Carlos Henrique Grohmann
> Institute of Energy and Environment - Univ. of São Paulo, Brazil
> - Digital Terrain Analysis | GIS | Remote Sensing -
>
> http://carlosgrohmann.com
> http://orcid.org/0000-0001-5073-5572
> ________________
> Can’t stop the signal.
>
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