<div dir="ltr"><br><div>On Wed, Jun 28, 2017 at 4:02 PM, preiaen <<a href="mailto:nils.hempel@gmx.de">nils.hempel@gmx.de</a>> wrote:<br>><br>> Dear Markus,<br>><br>> thank you for your answer. I did as you suggested and below are the results.<br>> As far as I can understand it, it looks fine, however the error remains.<br>><br>> *For the shapefile: *<br>><br>> *g.proj -g:*<br>><br>> -PROJ_INFO-------------------------------------------------<br>> name : WGS 84 / Pseudo-Mercator<br>> datum : wgs84<br>> ellps : wgs84<br>> proj : merc<br>> lat_ts : 0.0<br>> lon_0 : 0.0<br>> x_0 : 0.0<br>> y_0 : 0<br>> k : 1.0<br>> wktext : defined<br>> no_defs : defined<br>> -PROJ_EPSG-------------------------------------------------<br>> epsg : 3857<br>> -PROJ_UNITS------------------------------------------------<br>> unit : meter<br>> units : meters<br>> meters : 1<br>><br>> *ogrinfo:*<br>><br>> PROJCS["WGS 84 / Pseudo-Mercator",<br>> GEOGCS["WGS 84",<br>> DATUM["WGS_1984",<br>> SPHEROID["WGS 84",6378137,298.257223563,<br>> AUTHORITY["EPSG","7030"]],<br>> AUTHORITY["EPSG","6326"]],<br>> PRIMEM["Greenwich",0,<br>> AUTHORITY["EPSG","8901"]],<br>> UNIT["degree",0.0174532925199433,<br>> AUTHORITY["EPSG","9122"]],<br>> AUTHORITY["EPSG","4326"]],<br>> PROJECTION["Mercator_1SP"],<br>> PARAMETER["central_meridian",0],<br>> PARAMETER["scale_factor",1],<br>> PARAMETER["false_easting",0],<br>> PARAMETER["false_northing",0],<br>> UNIT["metre",1,<br>> AUTHORITY["EPSG","9001"]],<br>> AXIS["X",EAST],<br>> AXIS["Y",NORTH],<br><br>So far, all looks fine, but<br><br>> EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0<br>> +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext<br>> +no_defs"],<br><br></div><div>a (equatorial radius) and b (polar radius) are the same, i.e. this is a sphere, not an ellipsoid like wgs84. This can make a difference. You can try to use the proj4 term<br>+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs</div><div><br></div><div>to create a new location, then force import the shapefile with v.in.ogr -o, then reproject and check if it is the geolocation is correct.<br></div><div><br>> AUTHORITY["EPSG","3857"]]<br><br></div><div>See<br><a href="http://epsg.io/3857">http://epsg.io/3857</a><br><br><span class="gmail-caption">"Remarks: </span>Uses spherical development of
ellipsoidal coordinates. Relative to WGS 84 / World Mercator (CRS code
3395) errors of 0.7 percent in scale and differences in northing of up
to 43km in the map (equivalent to 21km on the ground) may arise."
</div><div><br></div><div>Markus M<br><br></div><div>><br>> *For the DEM:*<br>><br>> g.proj -p<br>> -PROJ_INFO-------------------------------------------------<br>> name : WGS 84<br>> datum : wgs84<br>> ellps : wgs84<br>> proj : ll<br>> no_defs : defined<br>> -PROJ_UNITS------------------------------------------------<br>> unit : degree<br>> units : degrees<br>> meters : 1.0<br>><br>> *gdalinfo:*<br>><br>> GEOGCS["WGS 84",<br>> DATUM["WGS_1984",<br>> SPHEROID["WGS 84",6378137,298.257223563,<br>> AUTHORITY["EPSG","7030"]],<br>> AUTHORITY["EPSG","6326"]],<br>> PRIMEM["Greenwich",0],<br>> UNIT["degree",0.0174532925199433],<br>> AUTHORITY["EPSG","4326"]]<br>><br>><br>> Nils<br>><br>><br>><br>> --<br>> View this message in context: <a href="http://osgeo-org.1560.x6.nabble.com/Projection-errors-with-Aster-GDEM-and-SHP-Files-tp5324655p5325865.html">http://osgeo-org.1560.x6.nabble.com/Projection-errors-with-Aster-GDEM-and-SHP-Files-tp5324655p5325865.html</a><br>> Sent from the Grass - Users mailing list archive at Nabble.com.<br>> _______________________________________________<br>> grass-user mailing list<br>> <a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a><br>> <a href="https://lists.osgeo.org/mailman/listinfo/grass-user">https://lists.osgeo.org/mailman/listinfo/grass-user</a><br><br></div></div>