Hi, On 07/14/10 11:54, Paul Meems wrote: > > I'm using this proj4 string for the OSM tiles: > +proj=merc +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +a=6378137 +b=6378137 > +units=m +no_defs > This one is not correct if you want to do a datum transformation : the +towgs84 parameter is missing. Jean-Claude