I'm building a set of 'tiles' that actually just contain dem data to drive a 3d geograpic tool on android (using opengl es2.0)
primarily for the uk (cos that's where I am) but hopefully in a way that works anywhere. I've picked up the srtm data and used gdal translate and gdawarp as described in the http://wiki.openstreetmap.org/wiki/HikingBikingMaps openstreetmao wiki here , and used these to add height colouring and contour lines to mapnik generated tiles and this all works well and appears to be OK. To get the 'height' tiles I'm using the same giant tiff that I use as input to hill shade and colour-relief to a little home brew app that uses the gdal library to fetch out a tilesworth of data and then scales it and writes a tile file (using the same tile naming scheme as mapnik / tms. But the tiles I generate appear to be out about 1/4 degree too far north (look OK east west) over the whole area. (the mapnik generated tiles, using background from hill shade + colour-relief and data from openstreetmap in a postgis database are all fine and match exactly the position of tiles from the openstreetmap server. I am linearly scaling the raster info using the geo info from the giant tiff and the http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames code here to translate between tile numbers and lon/lat. Is linear scaling the wrong way to do this? (but if so I would expect the error to change as I move north - south). I am considering using gdal2tiles to generate out the tiles, (I think I can easily tweak the settings to generate 16bit tiffs, and then reprocess these to fix the filenames and reformat the data ready for the android device), but this is a rather long way around to get there. Anyone know why this all goes awry? -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/Using-a-gdal-generated-tiff-to-generate-DEM-tiles-losing-registration-tp6946188p6946188.html Sent from the GDAL - Dev mailing list archive at Nabble.com. _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev