On 13/09/13 14:28, OpenStreetmap HADW wrote:
How does one find that out for the tiles served by os.openstreetmap.org, and if they are not using the high accuracy conversions, why not? (OS' own online viewer also uses WGS84 coordinates to label their tiles - suggesting that they should be using the high quality WGS-84 calibration.)
They are produced using mapserv from a gdal vrt with the source projection defined by:
PROJCS["OSGB 1936 / British National Grid", GEOGCS["OSGB 1936", DATUM["OSGB_1936", SPHEROID["Airy 1830",6377563.396,299.3249646000044, AUTHORITY["EPSG","7001"]], TOWGS84[375,-111,431,0,0,0,0], AUTHORITY["EPSG","6277"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4277"]], PROJECTION["Transverse_Mercator"], PARAMETER["latitude_of_origin",49], PARAMETER["central_meridian",-2], PARAMETER["scale_factor",0.9996012717], PARAMETER["false_easting",400000], PARAMETER["false_northing",-100000], UNIT["metre",1, AUTHORITY["EPSG","9001"]], AUTHORITY["EPSG","27700"]] Tom -- Tom Hughes (t...@compton.nu) http://compton.nu/ _______________________________________________ Talk-GB mailing list Talk-GB@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-gb