Image Collection Allied Central Interpretation Unit
A black and white aerial photo of about a dozen ships pulled up on a beach. The land beyond the beach has been divided up into a grid, and the scene is slightly obscured by clouds or smoke.

Landing craft from the first waves of the D-Day landings grounded on SWORD Beach
Collection: ACIU, Sortie: US7/1750, Frame: 2072 (06 June 1944)

Allied Central Interpretation Unit

The Allied Central Interpretation Unit (ACIU) Collection at the National Collection of Aerial Photography is home to 5.5 million surviving images taken for photographic reconnaissance during the Second World War. During this time, ACIU – based at Royal Air Force (RAF) Medmenham, Buckinghamshire – was the Allied headquarters of photographic intelligence. Using stereoscopic techniques, ACIU staff analysed millions of aerial photographs taken over the European Theatre. Their work had far-reaching implications for the conduct of the war and ACIU was involved in the planning stages of practically every operation and aspect of intelligence.

History

Although the importance of aerial photography to military intelligence had been apparent to some since the First World War, it was largely neglected between the wars. In 1938, the aviator and entrepreneur Sidney Cotton was recruited by British intelligence to take clandestine photographs of German preparations for war.

A black and white aerial photo of a 4-sided woodland surrounded by fields with a road running along the bottom edge. Buildings are visible within and to the right of the wood. The area has been bombed and craters are visible in the fields and wood.
A Bois Carré V1 flying bomb launch site, identifiable from the 3 'ski' buildings; Collection: ACIU, Sortie: MU/0276, Frame: 5005 (13 April 1944)

To assist with the interpretation of the photos taken by his unit, known as No. 2 Camouflage Unit and then Special Flight, Cotton enlisted the help of Major Harold Hemming, Managing Director of the Aircraft Operating Company Ltd, an aerial survey firm based at Wembley, Middlesex.

A black and white aerial photo of factory buildings amongst trees and fields. The area has been extensively bombed and craters are visible in the fields and throughout the buildings.
The V1 and V2 weapons were developed at the Peenemunde research facility; Collection: ACIU, Sortie: WTN/1409/7712-7770, Frame: 7727 (24 August 1944)

In 1940, the Aircraft Operating Company was officially contracted to the Air Ministry as the Photographic Development Unit – Interpretation and Intelligence (PDUI). Interpretation continued at the Aircraft Operating Company’s Wembley base until expansion and bombing raids forced its move to Danesfield House at Medmenham in April 1941. At the same time, it was renamed the Central Interpretation Unit (CIU).

A black and white aerial photo of the bombed city of Cologne, with a wide river running along the right edge. The outlines of streets are visible but almost all the buildings have been destroyed. Cologne cathedral remains standing just above centre.
Cologne was one of the most heavily bombed German cities during the war; Collection: ACIU, Sortie: US7/LOC/0037D/LIB, Frame: 7178 (18 June 1945)

The initial core group of photographic interpreters at the CIU was drawn from the staff of the Aircraft Operating Company. The unit expanded during 1942 and 1943 and was involved in the exploitation of imagery taken by the Photographic Reconnaissance Unit (as Special Flight became known), to assist in the planning of wartime operations and the assessment of Allied bombing raids. The involvement of United States personnel from 1942 was recognised in 1944 when the title of the unit was changed to the Allied Central Interpretation Unit.

Acquisition

In 1961, the decision was eventually made to transfer a large portion of the ACIU Collection to the University College of North Staffordshire (now Keele University) as an official Place of Deposit under the Public Records Act. In 2006, discussions began between Keele University and The National Archives on the future of the Collection, which had grown with the acquisition of further collections. In 2008 the full extent of aerial imagery held at Keele was transferred to the Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS, now Historic Environment Scotland) and became part of the new National Collection of Aerial Photography (NCAP).

A black and white aerial photo of the city of Dunkirk, with the coast just visible in the distance. Thick clouds of black and white smoke are billowing up from the city, being driven by the wind from left to right.
The burning Saint Pol oil refinery during the Allied evacuation of Dunkirk; Collection: ACIU, Sortie: HNA/0024, Frame: 0023 (27 May 1940)

Scope

Between 1939 and 1945, tens of million of aerial reconnaissance images recording locations across the world had been accumulated at Medmenham. This vast archive of photographs, taken by British (RAF), American (USAAF), Canadian (RCAF) and South African (SAAF) units, contained a visual record of the world at war. This subset of the vast record which was held at Medmenham covers 34 countries and territories across Europe.

Geographical coverage
Albania Guernsey Norway
Austria Hungary Poland
Belgium Iceland Romania
Bosnia & Herzegovina Italy San Marino
Bulgaria Jersey Serbia
Croatia Liechtenstein Slovakia
Czechia Luxembourg Slovenia
Denmark Macedonia Sweden
Finland Moldova Switzerland
France Monaco Vatican City
Germany (except former German Democratic Republic) Montenegro
Greece Netherlands

Collection Contents

The Collection is made up of:

  • c.5.5 million aerial photographic prints
  • c.35,000 paper sortie plots. 
  • 7,500 rolls of 35mm microfilm.

Air Photo Finder

A small amount of this Collection has been digitised and is available to view on the Air Photo Finder. 

Subscriptions

Finding aids are available for this Collection and can be examined with a subscription. 

ArchivesSpace

The entirety of the Collection is accessible in the Search Room. Visit ArchivesSpace to learn about the Collection hierarchy. 

Air Photo Finder  Subscriptions  ArchivesSpace - external  

Related reading

IN THIS SECTION

A colour aerial photo of the Wimbledon area in London. Streets of houses are visible at the right and left edges. A golf course with bunkers and trees occupies the middle. To the left of centre are about 20 tennis courts and a tennis stadium.

British Aerial Survey Firms

NCAP has extensive holdings of photography taken by several important British aerial survey companies over a period of 50 years.

A black and white aerial photo of a city on the edge of the sea. There are buildings and an industrial area in the centre and fields to the right. The photo has been marked with purple pencil highlighting blocks of buildings.

Defence Geographic Centre

The DGC Collection contains aerial photographs of locations around the world, originally used to create maps for issue to British and Commonwealth forces.

A black and white aerial photo of a city. The streets are arranged in a grid. There is a coastline to the right with an area of dark sea at the right-hand edge. To the left are two meandering watercourses and an area of undeveloped wetland.

Directorate of Overseas Surveys

The DOS Collection provides a unique historical perspective, recording the changing landscapes of much of the Commonwealth throughout the 20th century.

A black and white aerial photo of coastal wetlands. The image has the appearance of abstract swirls and patterns in shades of black, white and grey. There seem to be a few trees in the centre and an area of water to the left.

Environment Agency

The EA Collection is a valuable record of the quickly changing coastal landscapes of the south-east of England, from Bournemouth round to Gravesend.

A black and white aerial photomap of a town surrounded by an irregular grid of black and white fields. The photomap is annotated with place names – including Stargard, the name of the town – and is overlaid with numbered map grid squares.

German Air Force

The GX Collection contains photos taken by the Luftwaffe during the Second World War, which were then used for intelligence purposes during the Cold War.

An oblique black and white aerial photo of a city with a coastline. The sea is at the bottom left corner. A small number of ships are on the water. The city is made up of what appears to be low-rise apartment blocks. There is a park in the centre.

Joint Air Reconnaissance Intelligence Centre

The JARIC Collection holds millions of Cold War reconnaissance images and forms unique record of British interests and activities.

A black and white aerial photo of 17 planes at an airfield. The planes are all situated in bays off two tracks running vertically through the image – one light-coloured and one dark. The planes and tracks are surrounded by featureless fields.

Mediterranean Allied Photo Reconnaissance Wing

The MAPRW Collection contains c.150,000 aerial photographs taken during WWII by Allied units operating from North Africa and Italy.

A colour aerial photo with a park containing trees and red paths at the left, and Buckingham Palace in the bottom left corner. The River Thames is to the right with the London Eye lying flat over it. The shadow of Big Ben is to the right of centre.

Millennium Mapping

NCAP is home to the Getmapping and UK Perspectives Collections, two parallel projects to create a visual record of the UK at the turn of the millennium.

A black and white oblique aerial photo of an airborne plane from side-on. The plane has one propellor and a see-through cockpit with the pilot visible. There is a rear-facing gun turret, and the fuselage is marked with an American star and ‘312’.

National Archives and Records Administration

The NARA Collection contains worldwide imagery digitised as part of a partnership with the United States National Archives and Records Administration.

A colour aerial photo of the sea, very dark blue to the left and white from the glare of the sun on the right. In the middle a thin peninsula covered in brown grass extends into the sea. It has white cliffs and ends in a series of individual stacks.

Natural Environment Research Council

The NERC Collection contains over 27,300 aerial photographs taken around Europe for research purposes on behalf of the British Geological Survey.

A colour aerial photo of islands surrounded by a deep blue sea. There is one big island left of centre and a small one to the right. The islands have green grass and a mix of rocky and sandy shores. The sea is light blue over the sand.

Scottish Office Air Photographs Unit

The Scottish Office APU Collection provides a remarkable, 100-year record of Scotland’s changing landscapes from 1.5 million aerial photos of Scotland.