Hi, This question pops up every now and then in various forums: People have received dataset in unknown SRS and they ask which coordinate system it might be using. Most often data are shapefiles without .prj file or image files with only .tfw file or sometimes scanned paper maps as plain images.
In case of shapefiles and tfw users can always pick a Ground Control Point (GCP) having coordinates in the unknown system. With scanned maps it may be possible too because maps have often a printed grid with coordinates. On the other hand, people usually know roughly the location of data and it would be easy to capture reference coordinates in EPSG:4326 or EPSG:3857 from world wide map services. I suppose that it would be quite easy to make a python script that converts the reference coordinates to all projections which have an EPSG code in the Proj4 "epsg" file somehow similarly thn cs2cs and gdal_transform do, compute delta-X, delta-Y and Root Mean Square Error (RMSE) from the converted coordinates and GCP coordinates that the user gives as input. Finally the script would print a few best guesses ordered by ascending RMSE. Hard core developers may feel this too trivial but perhaps we have some GIS teachers reading this list and wondering what would be their next challenge for their students. -Jukka Rahkonen- _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
