Ordnance Survey Minor Control Point Albums 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). 1950 - c. 1955 with updates up to the 1980s