I want to change coordinate system of a shapefile from British National Grid to WGS84 (in order to be able to convert it to KML later on). To get the best results of projecting I would like to use OSGB_1936_To_WGS_1984_NGA_7PAR transformation (or later on define different transformation depending on location in UK).
The only description of this transformation that I know comes from ArcMap and looks like this:
Coordinate Frame – dx=446,000000 dy=-99,000000 dz=54,000000 rx=-0,9450000 ry=-0,261000 rz=0,435000 s=-20,892700
.. and I have no clue how to use it with osr.CoordinateTransformation(BNG, WGS84)
Any help highly appreciated!!
Jarek
Best Answer
Since OSR is based on Proj4 you are at the mercy of whatever it can accomplish. Have a look at this related post and the proj4 FAQ on towgs84. It appears from this that proj4 is handling the datum shift, etc. I would hope this would pass through into OGR/OSR, but can't comment specifically.
Assuming the other post is correct you could project your OGR features like so: