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/
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