[Talk-GB] OS grid positions

[Richard Bullock]

When I last looked some time ago, the OS recommended using Grid In-quest

http://www.qgsl.com/?product=gridinquest

Which they say can be downloaded free, and with no restrictions on use.

They also claimed that the calculations should be accurate to ~ 10cm.

It can convert OSGB36 -> ETRS89 - which is essentially WGS84 adjusted to 
remove movements of the European Tectonic Plate - which should be less than 
50cm difference.

Most OSBG -> WGS84 web algorithms I've seen seem to suggest that the 
calculation should be good to around 3-7m