Historical map and survey archives

There are two sets of air photographs. One is held at the National Collection of Aerial Photography (NCAP) in Scotland, and the second has been entrusted to Oxford University to support global climate change research.

The collection holds approximately 1.5 million monochrome, vertical aerial photographs. Each one is survey-standard and suitable for viewing stereoscopically in 3D. Most are at nominal scale 1:30 000 – 1:60 000 and in 230 mm by 230 mm format. Mostly panchromatic, though there are infrared, monochrome prints, off-colour, infra-red negatives, and a few colour prints.

Nearly all the photography was taken for topographic or land use mapping purposes. Sources and scales varied over the years; dating back to flights taken by United States Army Air Force and the US Navy over Caribbean and Pacific islands during the Second World War.

Almost all photography of Africa, Aden, Malaya, and Borneo flown between 1946 and 1953 was taken with Fairchild® K17 cameras, and from 1951 with Williamson F49 cameras, both using the same focal length of 152 mm. These were carried in aircraft (mainly Lancasters) of RAF photographic reconnaissance squadrons. The planned scale of photography was 1:30 000, selected as a compromise that would provide specialist departments (geology, forestry, agriculture) with photography that both enabled interpretation of thematic information, and suited topographic mapping.

In specific cases, photography was needed at a scale larger than 1:30 000. For example, the Volta River delta and dam site was taken at 1:5000 scale in 1946. Gee-H radar was used in Africa and Aden to navigate a series of concentric flight lines around a ground radar station. Visual, straight-line navigation was used occasionally in Africa, for large-scale photography of the Freetown Peninsula, Sierra Leone, and in British Somaliland for some 1:30 000 scale cover.

Contract photography was first taken in 1949 and predominates from 1953 onwards, flown by British commercial air survey firms using visual navigation methods. Over 200 contracts were let by DOS. Each usually covered the area of a proposed mapping or land use project, sometimes extending over several countries such as in the Caribbean, and at several different scales. In 1954 the scale of photography for 1:50 000 scale changed to 1:40 000. From the 1960s, with increasing use of super-wide-angle (89 mm) lenses, photo scales were often smaller, 1:50 000 or 1:60 000. Large-scale mapping areas still required larger scales, such as 1:12 500 photography for 1:2500 scale mapping blocks. Photography was sometimes flown at scales larger than 1:40 000 for specialist interpretation, such as 1:25 000 for forestry interpretation.

In addition to contract photography, the collection occasionally holds cover obtained by the national survey departments, and other aid agencies such as the Canadian International Development Agency.

RAF photography at varying scales is held, along with Royal Navy photography. Additional records exist for more than one set of cover at various dates and is available for environmental research, geomorphology, vegetation, communications, and settlement, across a 40–50-year time span.

Most of the photography used by DOS for mapping, including the RAF and contract cover, is indexed on record reference cover diagrams, generally at 1:500 000 scale. The written catalogue is a Roneodex card index, with one card per film recording:

• Camera, lens type and number
• Calibrated principal distance
• Film type
• Flying heights
• Dates of photography

A small-scale guide to this photography is included in the DOS Annual Reports from 1951 to 1984, to be held by The National Archives (TNA). Other photography in the collection is shown on non-DOS cover diagrams or sortie plots produced by the originator of the photography. Summary diagrams for each country illustrate the location of all photography. The principal points of photos used in the mapping are shown and numbered on almost all DOS 1:50 000–1:125 000 scale topographic maps and provide accurate indications of the location of individual photos. Air photo mosaics and print laydowns (uncontrolled mosaics produced as map substitutes on standard sheetlines in advance of the regular mapping) are archived at the National Collection of Aerial Photography.

Technical records include camera calibration certificates, film reports with dates and times of photography, and contract documents. The film negatives of RAF and RN photography are held by the RAF; those of contract and other cover are held by the national mapping agency concerned, except in the case of British Antarctic Territory, for which the films are held by the British Antarctic Survey, Cambridge. Some satellite imagery, Landsat and SPOT is also held.

This collection is predominately held by the Royal Geographic Society with the Institute of British Geographers (RGS-IBG), with additional records held by The National Archives.

Royal Geographic Society with the Institute of British Geographers

The RGS-IBG collection contains all series produced by the Directorate of Colonial Services (DCS) and its subsequent successors between 1946 and 1999. This includes:

• Superseded Directorate of Overseas Surveys (DOS) editions
• Other agencies’ editions in series produced jointly by DOS, national mapping agencies and British Military Survey
• Series – mainly geological – printed by DOS for third parties

Although most of the maps are topographic, there are significant holdings of geological and land use mapping. Other thematic maps include climate, soils, and population.

A basic scale used on former British territories was 1:50 000. Smaller scales were used in arid lands such as British Somaliland (1:125 000) and parts of Botswana (1:125 000, later 1:100 000). Larger scales (1:25 000) in Mediterranean and Caribbean islands. "Selected" areas, and sometimes whole islands (Malta, Gozo, Bermuda), were mapped at 1:2500 scale (occasionally 1:5000, 1:2400, 1:1200) and, rarely, at 1:500 scale (Male, Stanley).

A guide to the areas mapped by DOS is included in the DOS Annual Reports from 1951 to 1984; later maps (1967 onwards) indicate areas where there is both pre- and post-1960 mapping. Sheet indices exist for most series.

DOS topographic mapping is supplemented by a range of print laydowns (PLDs), which are uncontrolled mosaics of air photographs, usually at 1:125 000 scale. They were often produced as map substitutes, on standard sheet lines, in advance of the regular mapping, mainly using 1940s–1960s aerial photography. They provide a synoptic view of relief and vegetation patterns in more detail than the maps and more conveniently than using original contact prints. This set of PLDs is unique in its completeness as it was not formally published or supplied to Copyright Libraries.

The DOS maps from the collection have been re-located to RGS-IBG, which now holds a complete set designated as The Ordnance Survey International Collection (OSIC) Map Archive.

The National Archives

International boundary maps and associated DOS files are preserved at The National Archives, Kew.

The DOS map library catalogue and finding aids were originally catalogued in Kalamazoo® binders providing access at series level. All individual sheets (covering less than the whole country) are marked up in scale order on graphic composite indices, to provide quick access to the mapping that is available for any particular part of a country. The original Kalamazoo binders, the unique DOS series number books (two vols), and post‑1960 master graphic catalogue are all held at The National Archives.

The following survey records are all held by The National Archives (TNA). 

Between 1946 and the late 1980s, Directorate of Overseas Surveys (DOS) field parties worked towards establishing ground control (planimetric and height) for mapping, observing national primary and secondary survey frameworks, and assisting with tertiary and cadastral control and levelling. The collection includes results of control surveys by other organisations, some connected to DOS schemes and most used by DOS in its mapping programmes.

Records of field work by the Falkland Islands Dependencies Survey and the British Antarctic Survey, formerly held by the DOS Survey Data Library, are now held by the British Antarctic Survey, Cambridge.

The information contained in the survey data files is summarised in master trig diagrams (MTDs), master control diagrams (MCDs) and master control cards (MCCs). These are designed to allow quick retrieval of coordinates for all plan control known to DOS in any specified area.

30th Meridian triangulation in Africa

The records of the Arc of the 30th Meridian triangulation in Africa, are mainly those of the 1930s observations by Major Hotine (later i/c Retriangulation of Great Britain, Director of Military Survey and Director of Colonial Surveys) and others in East Africa. The records include work dating back to 1903 and up to Directorate of Overseas Surveys (DOS) Tellurometer® scale checks of 1963. The 30th Arc records include correspondence, observations, diagrams, computations and results.

They're filed under code AD rather than by individual country.

Directorate of Overseas Surveys survey data catalogue

 The Directorate of Overseas Surveys (DOS) survey data catalogue is stored in 49 Kalamazoo binders. The master control diagrams (MCDs), generally at 1:500 000 scale, show the position and classification of every astronomical, trigonometrical or Doppler station for which coordinates suitable for 1:50 000 scale mapping are held. Master trig diagrams (MTDs) on the same sheetlines and scale show the observed rays used to fix the trig stations.

The MCCs, organised by 1:100 000 scale map sheet numbers (½˚ squares – technically not ‘square,’ but normally referred to as such), give current and superseded coordinates for every point that is plotted on the MCDs. This includes heights (ground level and station mark) and references to the files that contain its coordinates, station descriptions and photo identifications.

Primary triangulation and traverse areas

A guide to main areas of primary triangulation and traverse, and secondary and minor control established by Directorate of Overseas Surveys (DOS), is provided in the DOS Annual Reports from 1959 to 1984.

Individual trig stations and occasional bench marks are plotted, with heights, on DOS 1:125 000 and larger-scale mapping.

International boundary survey data

International boundary survey data, maps, correspondence, and files are held by The National Archives. It was Directorate of Overseas Surveys (DOS) practice to show international boundaries on the medium-scale mapping wherever well-defined, and there was enough information to be drawn without significant error. Portrayal of boundaries was agreed with countries concerned, and correspondence with national survey departments provided additional data.

In difficult cases DOS would study the evolution of the boundary over many decades, then write a critique explaining how the boundary alignment was transferred from official documents to the DOS map. One example would be the former Yemen Arab Republic-People’s Democratic Republic of Yemen boundary.

Directorate of Overseas Surveys map production example set

Four maps have been permanently preserved at The National Archives as typical examples of Directorate of Overseas Surveys (DOS) map production between 1946 and 1999:

• Series DCS 22, Tanganyika 1:50,000 Sheet 207/111, Preliminary Plot, First Edition 1953
• Series DOS 419, Sierra Leone 1:50,000 sheet 76, Second Edition–DOS 1967
• Series DOS 4499P, Belize 1:50,000 Sheet 7 Ambergris Cay, Edition 3–DOS 1980
• Series YAR 50, Yemen Arab Republic 1:50,000 Sheet 1544C1, Editions 1-DOS 1980 and 2-OSD 1987

The example map sheets are held with full supporting records.

Directorate of Overseas Surveys staff lists

The Directorate of Overseas Surveys (DOS) staff lists, field party address lists and photographic albums (of map production and field survey processes) are held at The National Archives.

Directorate of Overseas Surveys book collection

The Directorate of Overseas Surveys (DOS) book collection was merged with the Ordnance Survey Library’s collection in 1987. It has since been withdrawn from the library and has relocated to other institutions under the direction of the National Archives.

Some of the major holdings were:

• Survey Department Annual Reports
• Land and survey legislation of the Commonwealth
• Projection tables
• Gazetteers
• DOS publications.
• Conference proceedings
• The Dowson and Sheppard Collection of Cadastral Survey and Land Registration Records, now held by Cambridge University Library
• 8mm cine films

Three films showing DOS activities were transferred to the British Film Institute's National Film and TV Archive. DVD copies of one of these films, a DOS training film, was supplied to all main repositories holding parts of the Ordnance Survey International Collection.

Non-Directorate of Overseas Surveys mapping

Non-Directorate of Overseas Surveys (DOS) series were mainly produced by national survey departments and held in the original OS International Library. They don't form part of the Ordnance Survey International Collection (OSIC) map archive at the Royal Geographic Society with the Institute of British Geographers (RGS-IBG). The series has been offered to academic institutions throughout the British Isles.

Directorate of Overseas Surveys progress folders

Directorate of Overseas Surveys (DOS) progress folders are not in the OSIC map archive either, but do relate to map production. Dating back to the early 1950s, the progress folders contain the technical notes and minutes relating to each project or block of mapping. Contents include:

• Full details of the plan control and aerial photography used
• Technical correspondence and internal minutes on the progress and accuracy of the mapping
• Techniques used in construction of the maps
• Maps used as source material

These records are kept in the Charles Close Society Archive, located in the Cambridge University Map Library.