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Ordnance Survey FAQ and Excel Mapping Routines

The Ordnance Survey of Britain


Britain is covered by a series of maps produced by an organisation called the Ordnance Survey (OS).  As the name suggests, the organisation has military origins but it is now an independent company.  These maps are the natural choice for all sorts of activity from walking and motoring to land surveying.  They are so well established that OS references are given in publications describing the location of campsites, youth hostels, good pubs, and features on walks rather than longitude and latitude.  The maps are readily available in bookshops, newsagents and outdoor pursuit shops across Britain and many ‘tourist traps’ stock a few local maps.  They cover mainland England, Scotland, Wales, the Isle of Man, the Orkney and the Shetland Islands but do not cover Ireland, Northern Ireland or the Channel Islands.

The scales published include 4cm/25Km for route planning, 2cm/Km for motoring or walking and 4cm/Km for walking.  More detailed maps for surveying and land ownership matters are also available.  The OS web site is  and has lots of interesting information.

Road atlases published by the AA (Automobile Association) are also based on the Ordnance Survey grid, are widely available and can often be found at discount prices so shop around.   At one time they included the 100Km square identifying letters both in the index and on the maps but this was discontinued in the mid 1990s when the letters were totally omitted.  Most motoring atlases are based on the OS grid, but they vary in the degree of referencing information they give.

Harvey’s publish maps covering the more popular walking areas as well as many long distance paths.  They have a 1:25,000 scale (4cm/Km), conform to the OS grid and are plasticised so are waterproof.  These are produced especially for the walking public so place less stress on land ownership boundaries which do obscure the OS maps in places and are very clear as a result.   See:

You may also find Bartholomew maps for walkers.  These have essentially the same co-ordinate system as OS but a modified reference system.  They have references which omit the two letter square of the OS system but give eastings and northings in metres from the OS false origin.  See

The visitor to Britain will find that detailed paper based  maps based on longitude and latitude or on UTM or WGS84 are impossible to obtain.  Whilst longitude and latitude are shown on OS maps, they are only shown on the margins of the map and are very clumsy to use compared with the OS reference with its regular 1Km or 10Km grid lines which I would encourage the visitor to use.  They are also relative to the Ordnance Survey origin and not WGS84 now universally used by electronic systems.

Phil Brady © 2020