Tuesday, August 16, 2011

British Aerial Photography and Photographic Interpretation on the Western Front - Pt 3

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British Balloon Capabilities

Despite the evidence British moves towards balloon acceptance still stuttered.  Two officers, Beaumont, and Captain G. E. Grover tried unsuccessfully in 1863 to persuade the British military to recognize the military value of balloons.  They failed for two reasons, cost and the operational limitations of not being able to produce hydrogen in the field.  However, in 1878, following a change of personnel at the War Office, Captains J. L. B. Templer and H. P. Lee were appointed to the Woolwich Arsenal with the task of constructing and trialing balloons for military use.  By 1879 there were five balloons in British military service (Eaton, APIS Soldiers with Stereo. p. 1.).

In 1883, Major H. Elsdale, RE, whilst serving in Canada, made an experimental attempt at balloon aerial photography.  Elsdale took photographs of the fortress at Halifax, Nova Scotia using a clockwork-operated plate camera that when an exposure had been taken triggered a mechanism that ripped the balloon fabric and brought the camera back to earth.  In 1885 balloons were deployed with the British expedition to Bechuanaland and although Elsdale was present no mention is made of his aerial cameras.  Figure 1 is a vertical aerial photograph taken by Elsdale in 1886 of the Balloon School camp at Lydd in Kent.

Figure 1.  Balloon School Camp at Lydd in Kent 1886.

[A number of systems have been used to classify photographs.  The most common system is the one that separates photographs into terrestrial and aerial.  Terrestrial photos are taken on the ground and are usually oblique or horizontal, while aerial photos are taken from a platform in the air and may be either oblique or vertical.  Oblique aerial photos are photographs purposely taken with an angle between 3 and 90 degrees from the vertical.  They can be low oblique, if the horizon is not visible, or high oblique, if the horizon is visible.  Vertical photographs can be truly vertical, or slightly tilted, less than 3 degrees from the vertical.  In reality most aerial photos are tilted to some degree.  One of the limitations of the vertical aerial photograph is the lack of apparent relief.  This limitation can be overcome through the taking of a photographic stereo pair, two photographs of a single object from two slightly different positions.  A stereo pair when viewed through a stereoscopic viewer, invented by Sir Charles Wheatstone in 1838, presents the scene three-dimensionally.  Vertical and oblique aerial photographs each have unique advantages and disadvantages.  The vertical photograph is generally uniform in scale and has no vertical obstructions (terrain or man made objects) making it suitable for scaling measuring and map making.  On the down side it presents an unfamiliar view to the uninitiated user.  Additionally from the perspective of collection the target to be photographed has to be over flown which in the military context alerts the enemy to the collectors interest in that point.  Conversely oblique photographs present a more natural view and are therefore more easily used by the untrained eye.  In addition the oblique offers a standoff capability that can allow objects to be seen that have been concealed along tree lines or under camouflage without alerting an adversary.  On the down side the oblique photograph may contain vertical obstructions (terrain or man made objects) that obscure critical areas within the photograph.]

A School of Ballooning was formally established at Chatham in 1888, and was moved to Stanhope Lines, Aldershot in 1890 when a balloon section and depot were formed as permanent units of the RE establishment.  The Boer war (1899-1902) saw an expansion in British military ballooning with a further four sections, including a photographic reconnaissance section, being authorised and employed in South Africa.  The primary roles for the balloon sections was observing enemy troop movements and directing artillery fire.  Some of their most important but less published roles was to improve the very poor maps the British had at the outbreak of war, to sketch Boer camps and battle dispositions and take the earliest aerial photographs.  Figure 2 is an oblique photograph taken from a British balloon at 1,000 feet.  The white patches on the image are smoke from exploding shells.

Figure 2.  Boer War - British Camp Balloon Base (date unknown).

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