Hi Frank and friends,
Just to wrap this one up - we actually ended up receiving a geocoded
image and I used gdal_translate to assign EPSG:27700 (the image was
missing the coord sys declaration - this seems to be the case with a
few image providers I've noticed):
gdal_translate -a_srs EPSG:27700 ...
Anyhow all good. Thanks for the help.
Cheers,
-C
On 16/08/2008, at 7:54 PM, Christopher Hunt wrote:
Thanks for your reply Frank.
On 16/08/2008, at 2:05 PM, Frank Warmerdam wrote:
I believe EPSG:27700 is British National Grid which is a projected
coordinate system based on the OSGB 1936 datum. So you should
ensure the provider means the dataset is actually in BNG, in addition
to being based on OSGB 1936.
OK, will do.
If you can get BNG coordinates then that is great.
I've asked so fingers crossed.
If you can only
get WGS84 or OSGB1936 lat/long coordinates then you can
convert these to BNG using a program like cs2cs though that is
a bit tricky.
Understood.
Hopefully one last question on this though: the a_ullr parameters -
given the a_srs spec of EPSG:27700, are the a_ullr parameters
expected to be in BNG coordinates i.e. eastings and northings
values? Asking this another way, what actually dictates the
coordinate system used for the a_ullr parameters?
Cheers,
-C
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