geographical accuracy

[Dirk Koopman]

Jonathan Peterson wrote:
>> digits for northing, 6 digits for easting. I'm using 
>> Geography::NationalGrid::GB to convert these to lat/long pairs. The 
>> results are all approximately correct, but generally about 20 metres or 
> 
> Try Geo::Coordinates::OSGB ?
> 

Or I have an implementation in C that will do it. But you should use the 
correct transformation, which is (to an extent) iterative with the 
correct ellipsoid (OSGB80 [there is an OSGB36]). Also you need to 
convert to the correct ellipsoid for the lat/lang system you are using. 
The chances are that the lat/long datum is WGS84, but it may not be.

Dirk