The OS data is correct. I have checked a few points in polygons in the shp file in the OS projection and they are the same as a paper map, so somehow the transformation from OS to OSM is translating the result.
As an example a point on the transformed shp file is 53.76098, -0.48939 should be 53.76129, -0.49106. As a bodge I'll add the translation to the OSM output and then test a few more places to see if the translation is consistent across the country.
Have you allowed for the difference between the OS spheroid and WGS84?
ReplyDeleteThanks for your comment Andrew. I have applied a transform from the projection Ordnance Survey use to the WGS84 projection that OSM use. If you think there is another step or something else I need to do I would be very keen to know.
ReplyDeleteMaybe the difference between OSGB36 and OSTN02? Although I think that difference is sub-metre.
ReplyDeleteIf the difference is about 100m to the east in London then may well be due to the difference between the datums used by OSGB36 and WGS84.fe