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

Carlos Grohmann carlos.grohmann at gmail.com
Mon Nov 16 08:34:26 PST 2015

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).



Prof. Carlos Henrique Grohmann
Institute of Energy and Environment - Univ. of São Paulo, Brazil
- Digital Terrain Analysis | GIS | Remote Sensing -

Can’t stop the signal.
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