Monday, November 7, 2011

British Aerial Photography and Photographic Interpretation on the Western Front - Pt 19

Back to Part 18

During 1915, map production and map revision time, from the start of drawing to receipt of the map ready for use, took about two weeks.  By 1916 the pressure of work at the Ordnance Survey had extended the production timescale out to four weeks (Chasseaud, Artillery’s Astrologers. p. 87.).  As a consequence by the time a map was received at the front it was already out of date.  This issue of currency was appreciated as early as the battle of Loos in 1915 when copies of aerial photographs were circulated so that staff and regimental officers could make hand written amendments to their maps (Chasseaud, Artillery’s Astrologers. p. 108.).  During Loos, Romer (First Army Maps and Printing Section 1915) had his section working through the night producing and printing special map sheets showing the new detail derived from that day’s aerial photographs; these sheets were sent by dispatch rider to the affected units (Chasseaud, Artillery’s Astrologers. p. 110.).

Aerial Photography Limitations

Aerial photography was proving central to maintaining situation awareness, although it was not a panacea but had marked limitations which included; a lack of persistence, weather dependency, and a slow (relatively) response time.  Aerial photography lacked the persistence of visual reconnaissance; it was after all ‘a snap shot in time’.  But to counter this it did provide a permanent record not prone to memory failings, in addition the ability to revisit an area of interest through a collection of photographs, the HOC, gathered over time proved invaluable for change detection.  Weather played a key role in the successful collection of aerial photography.  The poor weather at the end of Third Ypres is probably one of the reasons why II ANZAC Corps’ photograph availability was so low during the period (Figure 15).  Response time proved problematic during the war.  Much has been made of the ‘speed tests’ demonstrated during the Somme where from aircraft landing to processed prints arriving at Headquarters took as little as 30 minutes (Finnegan, Shooting the Front. p. 75.).  It should be noted that photograph processing, printing and delivery was not the whole picture.  Including tasking and flying time, plus time for interpretation and product dissemination; any response would have be extended to several hours or even longer as illustrated by the Lambert (Royal Scots Company Commander 1917) anecdote above.  In the static warfare of the Western Front this was less of an issue, which was tempered further through regular pre-planned photograph collection.  The intent, weather permitting was to photograph the German trench system up to a depth of 3,000 yards every five days, and the counter-battery area every 10 days (B.E. Sutton, ‘Some Aspects of the Work of the Royal Air Force with the B.E.F. in 1918’, RUSI Journal, 67 (1922:Feb./Nov). p. 339.).  During operations this tempo would obviously change.  At Messines in 1917, aerial photographs of the German defences were taken every day during the preliminary bombardment, and the known artillery positions every two days (Chasseaud, Artillery’s Astrologers. p. 304.).  This meant that even outside of operations a regular supply of photographs was available and distributed.

Access to Aerial Photography

As has been outlined, access to aerial photography and intelligence derived from it expanded down through the echelons of the BEF throughout the war.  Figure 9 illustrates the availability of aerial photography to the Australian forces in France from April 1916 to October 1918 based on a review of I and II ANZAC Corps and the Australian Corps daily INTSUMS over the period.  Bearing in mind that the Dominion forces were fully integrated and supported within the BEF, it is probably fair to assume that the availability illustrated is representative for all the Corps in the BEF from 1916.

Figure 9.  Aerial Photograph availability derived from I and II ANZAC Corps and the Australian Corps daily IntelligenceSummaries.

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