The Prospect: News from CNDLS



Jayant GandhiThe Stereoscope and WWII IMINTHow an Old Invention Added New Depth to Allied Intelligence GatheringAerial imagery intelligence has been around well over a hundred years; dating as far back as the American Civil War. In its infancy it consisted of photographs taken from hot air balloons used to gain a bird’s eye view of an enemy’s movements. With the introduction of aircrafts into the theatre of war aerial imagery intelligence took on a new life. Not only was its range extended, but it could now be better directed and controlled so that the information gathered could prove more useful. This greater flexibility not only increased the importance of aerial intelligence gathering, but also opened it up to new options. During WWII, allied intelligence combined the newfound mobility of aerial imagery with the old technology of stereoscopy in order to create three-dimensional landscapes of occupied Europe that would play a huge role in diminishing the effectiveness of Germany’s V-weapons. This technology, while incredibly labour intensive, would prove itself invaluable and pave the way for the future of imagery intelligence.The stereoscope dates back to the Victorian Era when it was originally invented by English scientist Sir Charles Wheatstone in 1838 to demonstrate how the human eye creates the sensation of depth. It works by presenting a slightly different image to each eye, which the brain then interprets as depth in the image. Most stereoscopes utilize two superimposed images on translucent film and special lenses that divide the images between the eyes so that the three-dimensional effect can be achieved. This technology immediately found a home as a popular parlor trick and led to the creation of popular items like the View-Master. It would not be until the Second World War that the benefit of having a 3D image for intelligence purposes would be truly realized. Stereoscopy was briefly used during the First World War, but the high demands placed on the image interpreters combined with the limited capabilities of aerial image gathering techniques made it impractical and time consuming. In 1940, the Royal Air Force (RAF) created the Photographic Reconnaissance Unit and refitted the Spitfire fighter-plane with five state of the art cameras. The Spitfire, which had already proven itself in the Battle of Britain as a reliable aircraft, was a relatively fast and agile plane making it an excellent choice to take the precision photographs required for stereographic analysis. These aircrafts were sent across occupied Europe to take pictures of the German war machine so that the Allies could remain informed as to what was happening in mainland Europe. Stereoscopic images proved incredibly useful at revealing German camouflage by displaying the landscape in greater detail than a 2D image and it served a vital function in the campaign to destroy German dams. The ability to measure the height of objects in the stereoscopic images allowed the Allies to know exactly when the water level was at the precise level to launch their bombing campaign against German dams. However, the biggest triumph of stereoscopy would be how it led to the discovery and crippling of the German V-weapons program. In 1942, a Spitfire pilot noticed what looked like an airfield near the remote German village of Peenemünde in North-Eastern Germany. The pilot proceeded to photograph the site multiple times to ensure that the stereographic process could be used. The site included three circular concrete and earth structures that were very different from any other structures seen in German controlled territories. At the time, though, the photographs were shelved as the photographic interpreters (PIs) did not think they were of any significance.The photos remained unanalyzed until a year later a bugged conversation between two German officers being held in London after being captured in North Africa revealed the existence of the V-weapons program. Information had been relayed in December of 1942 by an Allied agent operating in Berlin that the Germans were testing some form of rocket weapon near the Baltic, but it was deemed by British officials to be too fantastic a story. However, the combination of the bugged conversation and this report by an agent aroused suspicion and resulted in a large scale aerial reconnaissance mission along with the reevaluation of images already taken.A second look at the photos taken at Peenemünde revealed a cylindrical object that looked like a rocket. The rocket was very difficult to spot since it looks like a pole when in the upright position, but the stereoscopic effect helped the PIs notice the peculiar shape and calculate its height by using its shadow. Without the illusion of depth provided by stereoscopy the rocket would have been nothing more than a tiny dot and would have most likely gone unnoticed.This was the V-2 rocket. Capable of traveling at 3500 mph and delivering a 1 ton warhead up to 200 miles away, it was an incredibly terrifying weapon for the time. The other weapon revealed by the mass reconnaissance mission was the V-1 flying bomb. Both of these weapons would be launched at Britain (and later targets in Belgium and France) causing thousands of casualties, most of which were civilians, with the intent to inflict mass terror.Finally convinced of the German rocket threat, the Allies launched a night-time precision bombing run on Peenemünde to eliminate the threat on August 17th and 18th, 1943. Unfortunately, by this time, Nazi production of V-1 and V-2 weapons was firmly established. It, therefore, became necessary to locate and eliminate as many launch sites as possible. While V-2 launch sites were fairly noticeable because of the huge dome structures used to house the weapons, V-1s were launched from ramps that could be easily concealed in wooded areas.Stereoscopic images were able to reveal the hidden V-1 launch ramps since the illusion of depth allowed PIs to distinguish between the sloped ramps and the surrounding landscape. Operation ‘Crossbow’, as it was called, revealed and resulted in the destruction of over 96 V-1 launch sites in Northern France. These discoveries came at a crucial time for the Allies as they were planning to launch the D-Day invasion. If the V-1s were left operational they could have caused severe damage to the invading troops.Despite its primary function as a simple parlor trick, the stereoscope proved that when used in tandem with aerial reconnaissance it could provide vital information. By adding depth to otherwise flat 2D images it brought the images to life in a way that enabled the PIs to accomplish things they otherwise could not. A 1940s reconnaissance manual describes the epiphany that would occur once a PI had mastered the ability to view images in 3D: “When coincidence of the photographs is secured, as above, the relief should seem to come right up and hit you.”When working with stereoscopic images, PIs not only had a clearer image to work with, but also had a more tangible image that impressed the urgency of their work upon them. All images only had a limited life-span for usefulness so being able to inspire PIs to work with a greater sense of immediacy was incredibly important. A former PI at the RAF Medmenham house, Constance Babington-Smith, described the sensation of successfully viewing one’s first stereoscopic image: It might have taken a little time, and you felt convinced that something was wrong with your eyes, and you strained your muscles and tried squinting and then magic! Shapes in plan were transformed into real-life ships or churches or bridges. You begged for more prints, and like the child with its new plaything, you spent a half-hour in a wonderland of discovery.Three-dimensional imagery’s primary benefit, however, was the increased detail of the photos added by the inclusion of depth. This had very practical effects on increasing the efficiency of planning bombing runs. Operation Chastise, the military action that resulted in the destruction of several German dams in May of 1943, relied upon extremely precise measurements of the height of the dams and water levels. The stereoscope allowed PIs to make the three dimensional calculations from the aerial reconnaissance of the area.The true advantage of stereoscopic imagery revealed itself when this increased level of detail was combined with the eagerness it instilled in the PIs assigned to analyze the images. It aided intelligence officers in identifying anomalies by making the rest of the image seem more natural. The added dimension also exposed objects that would have otherwise been unseen, such as the upright V-2 rocket or the V-1 launch ramps hidden in the woodlands of Northern France.It was critical that the Allies were able to see the V-2 standing upright and a V-1 on its launch ramp at Peenemünde because otherwise the launch methods of the weapons would have been left up to conjecture. The stereoscopic images allowed the Allied PIs to deduct the methods of launch of each weapon and then use that knowledge to locate the launch sites within range of Great Britain. There were, however, several key drawbacks to the effectiveness of stereoscopic imagery that restricted its usefulness. In order to achieve the stereographic effect several passes would have to be made over a target by the reconnaissance plane. There was no doubt that the Spitfires could obtain the level of accuracy need to superimpose the images (stereoscopy requires an exact overlap of 60% to work correctly), but it was no safe job flying around German airspace in an unarmed aircraft. Because of the weight of the cameras that the Spitfires were outfitted with, there was no room for weaponry, leaving the pilot completely vulnerable to enemy defenses. Additionally, the cameras were positioned in such a way that it required the pilot to maintain a level flight path while the images were being collected. This restricted a pilot’s ability to maneuver evasively.Stereoscopic image analysis also required PIs to develop a sense of hyperstereopsis; a more intense sensation than that achieved by a regular person looking through a stereoscope. This often required anywhere between 15-20 hours of practice with stereoscopic photographs and, even once hyperstereopsis was achieved, analysis of the images required extreme patience as you sifted through all the details the images brought to life. This meant that important information could get overlooked as happened with the initial photographs of Peenemünde.The largest weakness of stereographic imaging, however, is its reliance on other disciplines of intelligence gathering. By themselves, the images can only tell an intelligence officer so much. The sheer quantity of information stored in the 3D image can overwhelm an analyst if he or she does not know what to look for. Intelligence gathered by Allied agents in Germany (HUMINT) and bugged conversations between Nazi officers (COMINT) were what sparked the effort to locate and eliminate the V-weapon threat. If these pieces of information did not surface it is probable that the V-weapons at Peenemünde would have gone unnoticed until they had already inflicted serious damage on Great Britain.The use of stereoscopy in WWII was crucial in thwarting Nazi plans to pummel Great Britain into submission by use of terror inducing weapons. Its simplicity allowed its application in many situations even if it asked more of the PIs than traditional photography. 3D imagery technology has come a long way since then as satellites and computer modeling enable us to create virtual worlds, but the principle is still the same: create a more tangible and detailed view of your enemy’s actions.Overall, it proved itself to be an effect way to analyze aerial intelligence and demonstrates what the goal of the IMINT discipline should be. The world is not a two dimensional object and so much can be lost when the third dimension is omitted. The success of stereoscopy in preventing the Nazi V-weapons program from succeeding proves that the benefits of this technology outweighed the drawbacks. This success is also what paved the way for the current 3D imaging. If stereoscopes had proven themselves to be ineffective, then the development of 3D imaging technology would not have occurred at anywhere near the same rate. The stereoscope was not only vital in saving the lives of thousands, but also in opening up a whole new branch of the IMINT discipline.Bibliography:On some remarkable, and hitherto unobserved, Phenomena of Binocular Vision; by Wheatstone, Charles; June 21, 1838; King’s College, London.“Modernist reconnaissance”; Saint-Amour, Paul; April 2003; Johns Hopkins University Press; pp. 349-380.3D Spies of WWII; NOVA; PBS; Original Air Date: January 18, 2012.“Operation Crossbow: How 3D Glasses Helped Defeat Hitler”; Kelly, Jon; 12 May, 2011; BBC News Magazine.The Secret War: Episode 3 “Terror Weapons”; The Secret War; BBC; Presented by William Woollard; Original Air date: 1977.“V-Weapons (Crossbow) Campaign”; ................
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