<div dir="ltr">Hi all.<div><br></div><div>I'm analyzing some global-scale DEMs, like ETOPO1/2, SRTM30_PLUS, etc.</div><div><br></div><div>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)</div><div><br></div><div>For example, ETOPO2:</div><div><br></div><div>Using a latlong pseudo-projection (plate carré)</div><div><br></div><div><br></div><div>min:<span class="" style="white-space:pre">       </span><span style="white-space:pre">     </span>-10791<span class="" style="white-space:pre">    </span></div><div>max:<span class="" style="white-space:pre">       </span>8440</div><div>mean:<span class="" style="white-space:pre">  </span>-1888.6480792</div><div>median:<span class="" style="white-space:pre">       </span>-2457<span style="white-space:pre">        </span></div><div>stddev:<span class="" style="white-space:pre">    </span>2650.01922839<span style="white-space:pre">        </span></div><div>p25:<span class="" style="white-space:pre">       </span><span class="" style="white-space:pre">  </span>-4273</div><div>p75:<span class="" style="white-space:pre">  </span><span style="white-space:pre">     </span>216<span style="white-space:pre">  </span></div><div><br></div><div><br></div><div><div>And using equal-area cylindrical:</div><div><br></div><div>min:<span class="" style="white-space:pre"> </span><span style="white-space:pre">     </span>-10791<span class="" style="white-space:pre">    </span></div><div>max:<span class="" style="white-space:pre">       </span>8440</div><div>mean:<span class="" style="white-space:pre">  </span>-2379.78247747 </div><div>median:<span class="" style="white-space:pre">    </span>-3291      <span style="white-space:pre">  </span></div><div>stddev:<span class="" style="white-space:pre">    </span>2507.89668617 </div><div>p25:<span class="" style="white-space:pre">        </span><span class="" style="white-space:pre">  </span>-4541</div><div>p75:<span class="" style="white-space:pre">  </span><span style="white-space:pre">     </span>94<span style="white-space:pre">   </span></div><div><br></div></div><div><br></div><div><br></div><div>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). </div><div><br></div><div>thanks</div><div><br></div><div>Carlos</div><div><br></div><div><br></div><div><br></div><div><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr">Prof. Carlos Henrique Grohmann<br>Institute of Energy and Environment - Univ. of São Paulo, Brazil<div>- Digital Terrain Analysis | GIS | Remote Sensing - </div><div><br></div><div><a href="http://carlosgrohmann.com/" target="_blank">http://carlosgrohmann.com</a></div><div><a href="http://orcid.org/0000-0001-5073-5572" style="font-size:13px;color:rgb(17,85,204);font-family:arial,sans-serif;background-color:rgb(255,255,255)" target="_blank">http://orcid.org/0000-0001-5073-5572</a><br><div>________________<br>Can’t stop the signal.</div></div></div></div>
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