On Fri, Jan 15, 2010 at 4:39 PM, Simone Cortesi <sim...@cortesi.com> wrote: > On Fri, Jan 15, 2010 at 17:27, Andy Allan <gravityst...@gmail.com> wrote: > >> The imagery isn't rectified using ground control points obtained via >> GPS units, if that's what you're asking, so no, it's not going to be >> 100% accurate. I'm not certain what was used to rectify it, but I >> suspect either Yahoo imagery or OSM data itself. >> >> If you find an area where all the OSM data is off by a fixed amount, >> then don't worry about moving the data, move the imagery instead. And >> don't worry about it overly much, since anyone on the ground with a >> GPS unit will be able to cope with a 5-10m displacement. > > have a look here: > http://www.openstreetmap.org/edit?lat=18.542645&lon=-72.337311&zoom=18&tileurl=http://maps.nypl.org/tilecache/1/haiti/!/!/!.png > (the 2 circles in the center of the image) > > or here: > http://www.openstreetmap.org/edit?lat=18.546683&lon=-72.349488&zoom=18 > (coastline)
Right, so the imagery and the OSM data are out of alignment by a few metres. I'm not sure what answer you want? Either the imagery is a few metres out, or the data is a few metres out. I don't know any more than you do. The only way to fix it is for someone there, with multiple GPSes, to go up and down the roads (and up and down the hills, too) until we have sufficient GPS traces to tell which is correct. Or, we do the best with what we've got. Cheers, Andy _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
