I've just tested the 2 definitions with GDAL trunk and proj 4.8.0 and both definitions give identical results :
$ gdaltransform -s_srs EPSG:4326 -t_srs "+proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs +wktext" 2 49 222638.981586547 5454655.04887041 0 $ gdaltransform -s_srs EPSG:4326 -t_srs "+proj=eqc +lat_ts=0 +lat_0=0 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs +wktext" 2 49 222638.981586547 5454655.04887041 0 But Antti guess seems right. Instead of +ellps=WGS84 (or +datum=WGS84), if you play with the a (semi-major axis) and b (semi-minor axis) parameters, you can see that only +a has an influence, so latest proj version seems to use a spherical version of eqc. Reviewing the history of pj_eqc.c ( http://trac.osgeo.org/proj/log/trunk/proj/src/PJ_eqc.c ) I don't see where a change of behaviour would have happened, but that might be somewhere else in proj codebase. > Hi, > > Sorry for cross posting. This seems like a proj4 issue but might be gdal > related. > > I've run into a problem that I think is related to a change in the EPSG > definition for EPSG:32662 > > The symptom is that the image after gdalwarp reprojection is about 20km > south of where it should be. > > old system is correctly aligned: > > GDAL 1.4.2.0, released 2007/06/27 > proj Rel. 4.5.0, 22 Oct 2006 > > # WGS 84 / Plate Carree > <32662> +proj=eqc +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 > +datum=WGS84 +units=m +no_defs <> > > new system is shifted about 20km south: > > GDAL 1.9.2, released 2012/10/08 > proj Rel. 4.8.0, 6 March 2012 > > # WGS 84 / Plate Carree (deprecated) > <32662> +proj=eqc +lat_ts=0 +lat_0=0 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 > +units=m +no_defs <> > > > http://spatialreference.org/ref/epsg/32662/ > This indicates that the definition in proj 4.8.0 is wrong. Would the > +ellps=WGS84 account for this shift? > > Any thoughts on this? > > Thanks, > -Steve > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Geospatial professional services http://even.rouault.free.fr/services.html _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
