<div dir="ltr"><div>Hello Cesar</div><div><br></div><div>That was weird, so I tested it again. The number of cells is the same for both projections, but the values differ. This must be related to reprojecting.</div><div><br></div><div>To me, they shouldn't de different, since a nearest neighbor should preserve the original values. I'm not really comfortable with this, as I'm not sure I can trust the stats after projecting. </div><div><br></div><div>best</div><div><br></div><div>Carlos</div><div><br></div><div><br></div><div>GRASS 7.1.svn (latlong):~ > g.region raster=gdem_etopo1_ice -pa</div><div>projection: 3 (Latitude-Longitude)</div><div>zone: 0</div><div>datum: wgs84</div><div>ellipsoid: wgs84</div><div>north: 90N</div><div>south: 90S</div><div>west: 180W</div><div>east: 180E</div><div>nsres: 0:01</div><div>ewres: 0:01</div><div>rows: 10800</div><div>cols: 21600</div><div>cells: 233280000</div><div>GRASS 7.1.svn (latlong):~ > r.univar map=gdem_etopo1_ice -ge percentile=100</div><div>n=233280000</div><div>null_cells=0</div><div>cells=233280000</div><div>min=-10803</div><div>max=8333</div><div>range=19136</div><div>mean=-1892.40422534294</div><div>mean_of_abs=2644.91906490912</div><div>stddev=2649.98339302808</div><div>variance=7022411.98332463</div><div>coeff_var=-140.032629262802</div><div>sum=-441460057688</div><div>first_quartile=-4286</div><div>median=-2457</div><div>third_quartile=214</div><div>percentile_100=8333</div><div><br></div><div><br></div><div><br></div><div><br></div><div><div>GRASS 7.1.svn (eqarea):~ > g.region -p</div><div>projection: 99 (Equal Area Cylindrical)</div><div>zone: 0</div><div>datum: wgs84</div><div>ellipsoid: wgs84</div><div>north: 6363885.33192604</div><div>south: -6363885.33192604</div><div>west: -20037508.34278924</div><div>east: 20037508.34278924</div><div>nsres: 1178.49728369</div><div>ewres: 1855.32484655</div><div>rows: 10800</div><div>cols: 21600</div><div>cells: 233280000</div><div>GRASS 7.1.svn (eqarea):~ > r.univar map=gdem_etopo1_ice -ge percentile=100 </div><div>n=233280000</div><div>null_cells=0</div><div>cells=233280000</div><div>min=-10803</div><div>max=8333</div><div>range=19136</div><div>mean=-2382.28934158093</div><div>mean_of_abs=2845.10169015775</div><div>stddev=2508.93105538271</div><div>variance=6294735.0406638</div><div>coeff_var=-105.315966939504</div><div>sum=-555740457604</div><div>first_quartile=-4544</div><div>median=-3285</div><div>third_quartile=93</div><div>percentile_100=8333</div></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Nov 16, 2015 at 7:43 PM, César Augusto Ramírez Franco <span dir="ltr"><<a href="mailto:caesarivs@gmail.com" target="_blank">caesarivs@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="color:rgb(39,78,19)">Carlos,</div><div class="gmail_extra"><br><div class="gmail_quote"><span class="">2015-11-16 14:47 GMT-05:00 Carlos Grohmann <span dir="ltr"><<a href="mailto:carlos.grohmann@gmail.com" target="_blank">carlos.grohmann@gmail.com</a>></span>:<br></span><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><span class=""><div>GRASS 7.1.svn (base_maps):~ > g.region -p raster=gdem_etopo1_ice</div></span><div>cells: 233280000<br></div><div></div></div><div><br></div><div><span class=""><div>GRASS 7.1.svn (base_maps):~ > r.univar map=gdem_etopo1_ice -ge percentile=100</div></span><div>cells=58320000</div><div><br></div></div><div><span class=""><div>GRASS 7.1.svn (eqarea):~ > r.univar map=gdem_etopo1_ice -ge percentile=100</div></span><div>cells=233280000</div></div></div></blockquote><div><br></div></div><div class="gmail_default" style="color:rgb(39,78,19)">Notice how the number of pixels differs, that's the reason the statistics are not the same, I don't get why the region has a different number of pixels than the raster itself in the original latlong projection... I think that's the root of the issue</div><span class="HOEnZb"><font color="#888888"><div><br></div>-- <br><div><div dir="ltr"><div><b>César Augusto Ramírez Franco</b><br>Laboratorio de Sistemas Complejos Naturales<br>Escuela de Geociencias - Facultad de Ciencias<br>Universidad Nacional de Colombia - Sede Medellín<br>Teléfono: (57-4) 430 9369 - 300 459 6085<br></div><a href="http://labscn-unalmed.github.io/" target="_blank">http://labscn-unalmed.github.io/</a><br></div></div>
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</blockquote></div><br><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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