A major new collection of 137,859 Ordnance Survey maps of England and Wales dating from the 1940s to the 1970s has gone online.
The maps were published on the National Library of Scotland maps website, which offers free access to old maps of Britain.
The maps are the most detailed maps published by Ordnance Survey of England and Wales after the Second World War. All urban areas with more than about 20,000 inhabitants were mapped at 1:1,250 scale, and all other inhabited areas and cultivated land were mapped at 1:2,500. At 1:1,250 scale, most detached features covering 1 square metre or larger are usually shown, including individual houses and even garden sheds.
Chris Fleet, Map Curator at the National Library of Scotland, said: “These are the most detailed Ordnance Survey maps which cover all areas of England and Wales after the Second World War, and they provide an unrivalled insight into towns and settlements in the mid-20th century. The National Library of Scotland is very keen to share our map collections with the widest possible audiences, and we hope these new online maps will be of great interest for a wide range of research purposes.”
The maps are the earliest Ordnance Survey maps to comprehensively show house numbers. They are a good resource for tracing house history, particularly the history of houses which were only built in the 20th century.
Unlike the earlier OS County Series with specific dates of survey and updating based on counties, these OS National Grid maps were placed under continuous revision from their inception in the 1940s. What this means is that new editions of each map were published when there had been sufficient change on the ground to warrant a new edition for that sheet. For many urban areas undergoing more change, there are therefore successive editions of the same sheet over time, which are extremely useful for documenting changes on the ground over the decades.
To determine when a new edition would be made, Ordnance Survey quantified change through ‘house units’. The addition of a complete, independent building to the map counted as a 'house unit'. The following equivalents for house unit purposes were in use in the 1960s and 1970s:
- Demolition of a house without the addition of new features as 0.5 unit
- Large buildings as 15-20 units per hectare
- Motorways, dual-carriageways and major public roads; standard gauge railways as 5-10 units per 100 metres
- Minor public roads and private roads as 2-5 units per 100 metres
- Tracks and narrow guage railways as 2 units per 100 metres
- Power lines as 2 units per 100 metres
- Reservoirs as 2 units per hectare
- Altered high or low water marks: 1 unit per 100 metres
- Altered house numbers or names as 1 unit per 10
- Altered names of roads or buildings as 1 unit
- Altered administrative, physical and district names as 2 units
The maps can be used to trace the changes as cities were rebuilt after the Blitz.
As with all the other NLS maps, it is possible to search using a map interface. In the Map Finder - with Outlines viewer, you can search by placename, National Grid Reference, county and parish, by your geolocation, or just by zooming in on the map on your place of interest, and then when you then click on the map, all the OS National Grid maps are returned covering the place you have clicked on.
The maps are also georeferenced so that you can view them as a continuous layer, overlaid on modern map or satellite image layers. Once georeferenced, you can also easily measure real-world distances and areas, view the height of any place, view its Grid Reference and view it in related viewers, including the 3D map viewer, or the Side by Side viewer. It is also easy to obtain customised images or printouts of sections of the map at a range of sizes and orientations.
The Side by Side viewer also allows you to easily compare the new 1940-1970s mapping with the present day, or with earlier editions of mapping, so that change over time can be easily seen.
