What do you use ordnance survey maps?

so they can see the most likely routes (e.g. public foot paths) to avoid contact

Ordnance survey maps are maps that show altitude in relation to a 'known' ordnance datum. An ordnance datum is a point of particular altitude. In the UK, that ordnance datum for ordnance survey maps...

During the English civil war Oliver Cromwell, leader of the Parliamentarian side discovered that he had great difficulty hitting anything with his artillery.He realised that the root of the problem...

An OD (Ordnance Survey) map are maps that were originally used for the military. It was produced by following a series of surveys. Hope this helps. :)

it means ......The Ordnance Survey National Grid reference system is a system of geographic grid references used in Great Britain, different from using latitude and longitude.