| Description | Photograph albums recording the positions of minor control points used in a now obsolete method of mapping built-up areas. The photographs are grouped into albums by National Grid Reference, a system of geographic grid references used by the Ordnance Survey distinct from longitude and latitude (see https://maps.nls.uk/geo/records/ to see the areas covered by each grid reference). The grid references in our albums refer to a kilometre square area, with the reference made up of the grid letter NJ (a 500 km by 500 km square covering the north east of Scotland) then two digits for the eastings and northings from the south west corner of the square.
Photographs were only taken for areas of 1:1250 mapping, but sketches and photographs were taken of Traverse Stations at the edges of the OS "diagram" (worked area): control was needed for reference to nearby albums. These albums have been catalogued in a sub-series DD638/X.
The albums are mainly of Aberdeen City, but capture the rural areas surrounding Aberdeen before, or in the process of, being subsumed into the City's suburbs. There are also a small number of albums for areas of Moray (these do not include photographs). |
| Administrative History | "OS surveyors took revision point (RP) photos across Britain to provide a network of surveyed locations. These known spots could then be used to "control"’ the position of detail on a large scale map. RPs were often on corners of buildings and other immovable features, and were fixed to centimetre accuracy. Finding the RPs for future map updates was an issue, and photography quickly became the best visual reference."
From the Ordnance Survey blog (https://www.ordnancesurvey.co.uk/blog/2018/03/see-historic-photos-ordnance-survey-timepix/)
The ordnance survey produced a number of photograph albums in this process: O.S. 94A are the original Minor Control Point Album, and our collection also includes O.S. 428a which are title "Revision Point Descriptions". O.S. 480 record amendments to minor control points. There were several versions of the albums:
1. The CR (or Continuous Revision) albums used by the surveyors - likely to show more wear and have lots of forms plus any survey diagrams to show how the points tied in with the next level up of survey control (minor being the lowest).
2. MS stands for Manuscript Store. This was at HQ and would be the backup copy and used at HQ if required for reference.
3. SALES copy/Revision Point Description albums. These are beautifully pristine and have no diagrams, just a list of points and the photos.
4. Some OS 480s make reference to other copies like D.O for District Office.
Some of our collection are Revision Point Description albums: some of which are marked "Sales" (3), others have stamps indicating that they are the Manuscript store copy (2).
Source of information: Timepix & Elaine Owen, formerly of the OS. |