SABRE Maps/25k First Series coverage project

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SABRE Maps Co-ordinate Finder • Sheetfinder Online Grid Calibrator Adding maps in depth Map layer names • Georeferencing

Early 1:25k First Series revision codes are located under the key, 20047 in this example

Most 1:25k First Series sheets have this style of revision code that appear under the sheet number, A in this example

The 100km OSGB National Grid squares

Later 1:25k First Series revision codes are located immediately underneath the map sheet, B///* in this example

This SABRE Maps Coverage Project is to provide online coverage of the Ordnance Survey 1:25,000 First Series.

This Coverage Project covers maps labelled as the Provisional Edition, the Regular Edition, and the First Series, all of which are generally considered a single map series, each sheet of which covered a single 10km grid square.

Due to the small sheet size, 2,027 individually numbered sheets were produced. This is despite the fact that the mapping did not cover the whole of Great Britain, as no mapping was produced across large parts of the Highlands, the Western Isles, Orkney or Shetland.

Slightly confusingly, this Coverage Project also includes the Second Series Provisional Edition, which only had a single sheet published. This is actually to assist with a potential point of confusion because it holds the sheet number of 856, but is completely unrelated to and in a different part of the world from. the later Pathfinder / Second Series sheet 856. It is tracked as part of 10km National Grid square SS.

Which projection type are these maps?

See Also: SABRE Maps/Calibrating

The OS 1:25000 First Series uses the OSGB National Grid and should be georeferenced accordingly.

How do I find out the date of the map?

See Also: SABRE Maps/OS Copyright

The OS didn't actually put the exact date of the map on each map. The date that appears on the map (either with the words Crown Copyright or Made and published by the Director General of the Ordnance Survey) often is not the correct date of the map, but the date of the last full revision. Roads are updated every minor revision, so there is every chance that a map may actually be from quite a number of years away from the copyright date.

Revision codes on 1:25k First Series sheets can generally been found at the bottom left of the map sheet, with three primary locations in that area: under the map key for early sheets; under the sheet number for most sheets; or immediately under the map itelf for later sheets. Early sheets have the revision codes italicised, whilst later sheets do not.

Revision codes both date the actual sheet and appear in the heading within SABRE Maps, and so this information is extremely valuable to capture.

It also should be noted that the official copyright requirement of Ordnance Survey is that the critical date for copyright purposes is the Crown Copyright date rather than the actual date of the map. This means that some maps less than 50 years old can still appear on SABRE Maps, and not be in breach of copyright.

Progress by every sheet ever printed

As there are simply too many individual sheets to be able to track in a single table, the progress chart has been split into 100km lettered grid squares, each containing up to 100 individual map sheets.

Sheets are numbered according to the 10km grid square they covered, though early sheets are numbered after the original numbered 100km grid squares, whilst later sheets are numbered according to the more familiar lettered squares. For example, 31/44 is the same map as ST44, just in the earlier format.

Where an individual map also took in part of a different grid square (which are mostly coastal sheets), then their primary square is that used within the tables, and the secondary area is not shown.

Sheetnames only appeared starting from 1964, and never appeared on the maps themselves, only on the covers. Some titles only appeared on Ordnance Survey catalogues rather than on the relevant covers, and some appear to have never been formally allocated, or at least that allocation has not been recorded. In this last case, those "missing" sheetnames are given those that have been created by the Charles Close Society for their reference, and are as given in their publication A guide to the Ordnance Survey 1:25,000 First Series, which is available to purchase from the CCS.