Aerial photography

Aerial photography is the taking of photographs of the ground from an elevated position. Usually the camera is not supported by a ground-based structure. Platforms for aerial photography include fixed-wing aircraft, helicopters, multirotor Unmanned Aircraft Systems (UAS), balloons, blimps and dirigibles, rockets, pigeons, kites, parachutes, stand-alone telescoping and vehicle-mounted poles. Mounted cameras may be triggered remotely or automatically; hand-held photographs may be taken by a photographer.

Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that "chase" and photograph other aircraft in flight.

History

Early history

Aerial photography was first practiced by the French photographer and balloonist Gaspard-Félix Tournachon, known as "Nadar", in 1858 over Paris, France. However, the photographs he produced no longer exist and therefore the earliest surviving aerial photograph is titled 'Boston, as the Eagle and the Wild Goose See It.' Taken by James Wallace Black and Samuel Archer King on October 13, 1860, it depicts Boston from a height of 630m.

Kite aerial photography was pioneered by British meteorologist E.D. Archibald in 1882. He used an explosive charge on a timer to take photographs from the air. Frenchman Arthur Batut began using kites for photography in 1888, and wrote a book on his methods in 1890. Samuel Franklin Cody developed his advanced 'Man-lifter War Kite' and succeeded in interesting the British War Office with its capabilities.

The first use of a motion picture camera mounted to a heavier-than-air aircraft took place on April 24, 1909 over Rome in the 3:28 silent film short, Wilbur Wright und seine Flugmaschine.

World War I

The use of aerial photography rapidly matured during the war, as reconnaissance aircraft were equipped with cameras to record enemy movements and defences. At the start of the conflict, the usefulness of aerial photography was not fully appreciated, with reconnaissance being accomplished with map sketching from the air.

Germany adopted the first aerial camera, a Görz, in 1913. The French began the war with several squadrons of Blériot observation aircraft equipped with cameras for reconnaissance. The French Army developed procedures for getting prints into the hands of field commanders in record time.

Frederick Charles Victor Laws started aerial photography experiments in 1912 with No.1 Squadron of the Royal Flying Corps (later No. 1 Squadron RAF), taking photographs from the British dirigible Beta. He discovered that vertical photos taken with 60% overlap could be used to create a stereoscopic effect when viewed in a stereoscope, thus creating a perception of depth that could aid in cartography and in intelligence derived from aerial images. The Royal Flying Corps recon pilots began to use cameras for recording their observations in 1914 and by the Battle of Neuve Chapelle in 1915, the entire system of German trenches was being photographed. In 1916 the Austro-Hungarian Monarchy made vertical camera axis aerial photos above Italy for map-making.

The first purpose-built and practical aerial camera was invented by Captain John Moore-Brabazon in 1915 with the help of the Thornton-Pickard company, greatly enhancing the efficiency of aerial photography. The camera was inserted into the floor of the aircraft and could be triggered by the pilot at intervals. Moore-Brabazon also pioneered the incorporation of stereoscopic techniques into aerial photography, allowing the height of objects on the landscape to be discerned by comparing photographs taken at different angles.

By the end of the war aerial cameras had dramatically increased in size and focal power and were used increasingly frequently as they proved their pivotal military worth; by 1918 both sides were photographing the entire front twice a day, and had taken over half a million photos since the beginning of the conflict. In January 1918, General Allenby used five Australian pilots from No. 1 Squadron AFC to photograph a 624 square miles (1,620 km²) area in Palestine as an aid to correcting and improving maps of the Turkish front. This was a pioneering use of aerial photography as an aid for cartography. Lieutenants Leonard Taplin, Allan Runciman Brown, H. L. Fraser, Edward Patrick Kenny, and L. W. Rogers photographed a block of land stretching from the Turkish front lines 32 miles (51 km) deep into their rear areas. Beginning 5 January, they flew with a fighter escort to ward off enemy fighters. Using Royal Aircraft Factory BE.12 and Martinsyde airplanes, they not only overcame enemy air attacks, but also had to contend with 65 mph (105 km/h) winds, antiaircraft fire, and malfunctioning equipment to complete their task.

Commercial aerial photography

The first commercial aerial photography company in the UK was Aerofilms Ltd, founded by World War I veterans Francis Wills and Claude Graham White in 1919. The company soon expanded into a business with major contracts in Africa and Asia as well as in the UK. Operations began from the Stag Lane Aerodrome at Edgware, using the aircraft of the London Flying School. Subsequently the Aircraft Manufacturing Company (later the De Havilland Aircraft Company), hired an Airco DH.9 along with pilot entrepreneur Alan Cobham.

From 1921, Aerofilms carried out vertical photography for survey and mapping purposes. During the 1930s, the company pioneered the science of photogrammetry (mapping from aerial photographs), with the Ordnance Survey amongst the company's clients.

Another successful pioneer of the commercial use of aerial photography was the American Sherman Fairchild who started his own aircraft firm Fairchild Aircraft to develop and build specialized aircraft for high altitude aerial survey missions. One Fairchild aerial survey aircraft in 1935 carried unit that combined two synchronized cameras, and each camera having five six inch lenses with a ten-inch lenses and took photos from 23,000 feet. Each photo covered two hundred and twenty five square miles. One of its first government contracts was an aerial survey of New Mexico to study soil erosion. A year later, Fairchild introduced a better high altitude camera with nine-lens in one unit that could take a photo of 600 square miles with each exposure from 30,000 feet.

World War II

In 1939 Sidney Cotton and Flying Officer Maurice Longbottom of the RAF were among the first to suggest that airborne reconnaissance may be a task better suited to fast, small aircraft which would use their speed and high service ceiling to avoid detection and interception. Although this seems obvious now, with modern reconnaissance tasks performed by fast, high flying aircraft, at the time it was radical thinking.

They proposed the use of Spitfires with their armament and radios removed and replaced with extra fuel and cameras. This led to the development of the Spitfire PR variants. Spitfires proved to be extremely successful in their reconnaissance role and there were many variants built specifically for that purpose. They served initially with what later became No. 1 Photographic Reconnaissance Unit (PRU). In 1928, the RAF developed an electric heating system for the aerial camera. This allowed reconnaissance aircraft to take pictures from very high altitudes without the camera parts freezing. Based at RAF Medmenham, the collection and interpretation of such photographs became a considerable enterprise.

Cotton's aerial photographs were far ahead of their time. Together with other members of the 1 PRU, he pioneered the techniques of high-altitude, high-speed stereoscopic photography that were instrumental in revealing the locations of many crucial military and intelligence targets. According to R.V. Jones, photographs were used to establish the size and the characteristic launching mechanisms for both the V-1 flying bomb and the V-2 rocket. Cotton also worked on ideas such as a prototype specialist reconnaissance aircraft and further refinements of photographic equipment. At the peak, the British flew over 100 reconnaissance flights a day, yielding 50,000 images per day to interpret. Similar efforts were taken by other countries.

Uses

Aerial photography is used in cartography (particularly in photogrammetric surveys, which are often the basis for topographic maps), land-use planning, archaeology, movie production, environmental studies, surveillance, commercial advertising, conveyancing, and artistic projects. An example of how aerial photography is used in the field of archaeology is the mapping project done at the site Angkor Borei in Cambodia from 1995-1996. Using aerial photography, archaeologists were able to identify archaeological features, including 112 water features (reservoirs, artificially constructed pools and natural ponds)within the walled site of Angkor Borei. In the United States, aerial photographs are used in many Phase I Environmental Site Assessments for property analysis.

Platforms

Aircraft

Winged aircraft, traditionally had provided the foundation for the early aerial photographers, whom also had to master the skills of pilotage, and tend to the flying while taking the photographs. In early war efforts, cameras were mounted in the aircraft with a triggering system being provided for the pilot to capture the images. Helicopters, some equipped with high power zoom and gyro stabilization emerged as the industrial standard in the early 1980s for local news casts as well as aerial photographers. Full-size, manned aircraft are prohibited from flights under 1000 feet, over congested areas and 500 feet above more sparsely populated locations. Helicopters are exempt from the restrictions on altitude, as long as the flight is conducted without hazard to humans.

Radio-controlled model aircraft

Advances in radio controlled models have made it possible for model aircraft to conduct low-altitude aerial photography. This had benefited real-estate advertising, where commercial and residential properties are the photographic subject when in 2014 the US Federal Communications Commission, issued an order banning the use of "Drones" in any commercial application related to photographs for use in real estate advertisement's. Small scale model aircraft offer increased photographic access to these previously restricted areas. Miniature vehicles do not replace full size aircraft, as full size aircraft are capable of longer flight times, higher altitudes, and greater equipment payloads. They are, however, useful in any situation in which a full-scale aircraft would be dangerous to operate. Examples would include the inspection of transformers atop power transmission lines and slow, low-level flight over agricultural fields, both of which can be accomplished by a large-scale radio controlled helicopter. Professional-grade, gyroscopically stabilized camera platforms are available for use under such a model; a large model helicopter with a 26cc gasoline engine can hoist a payload of approximately seven kilograms (15 lbs). Recent (2006) FAA regulations grounding all commercial RC model flights have been upgraded to require formal FAA certification before permission to fly at any altitude in USA.

In Australia Civil Aviation Safety Regulation 101 (CASR 101) allows for commercial use of radio control aircraft. Under these regulations radio controlled unmanned aircraft for commercial are referred to as Unmanned Aircraft Systems (UAS), where as radio controlled aircraft for recreational purposes are referred to as model aircraft. Under CASR 101, businesses/persons operating radio controlled aircraft commercially are required to hold an operator certificate, just like manned aircraft operators. Pilots of radio controlled aircraft operating commercially are also required to be licenced by the Civil Aviation Safety Authority (CASA). Whilst a small UAS and model aircraft may actually be identical, unlike model aircraft, a UAS may enter controlled airspace with approval, and operate within close proximity to an aerodrome.

Due to a number of illegal operators in Australia making false claims of being approved, CASA maintains and publishes a list of approved UAS operators

Because anything capable of being viewed from a public space is considered outside the realm of privacy in the United States, aerial photography may legally document features and occurrences on private property.

FAA-USA regulations

June 25, 2014, The FAA in ruling 14 CFR Part 91 [Docket No. FAAâ€"2014â€"0396] "Interpretation of the Special Rule for Model Aircraft" banned the commercial use of unmanned aircraft over the U.S. airspace until it develops rules for their part in the national airspace, at least, the FAA is not completely against commercial drones, it's currently working on regulations that would allow commercial drones by September 2015. On February 14, 2012, the President signed into law the FAA Modernization and Reform Act of 2012 (Pub. L. 112â€"95) (the Act), which established, in Section 336, a ‘‘special rule for model aircraft.’’ In Section 336, Congress confirmed the FAA’s long-standing position that model aircraft are aircraft. Under the terms of the Act, a model aircraft is defined as ‘‘an unmanned aircraft’’ that is ‘‘(1) capable of sustained flight in the atmosphere; (2) flown within visual line of sight of the person operating the aircraft; and (3) flown for hobby or recreational purposes.’’ Public Law 112â€"95, section 336(c). Defined as:

Hobby or recreational uses

• Flying a model aircraft at the local model aircraft club.
• Taking photographs with a model aircraft for personal use.
• Using a model aircraft to move a box from point to point without any kind of compensation.
• Viewing a field to determine whether crops need water when they are grown for personal enjoyment.

Banned use of drone in the USA

• Receiving money for demonstrating aerobatics with a model aircraft.
• A realtor using a model aircraft to photograph a property that he is trying to sell and using the photos in the property’s real estate listing.
• A person photographing a property or event and selling the photos to someone else.
• Delivering packages to people for a fee.
• Determining whether crops need to be watered that are grown as part of commercial farming operation.

The FAA can pursue enforcement action against persons operating model aircraft who endanger the safety of the national airspace system.’’ Public Law 112â€"95, section 336(b).

September 26, 2014, the FAA granted rights to use drones in a commercial applications to 6 production companies giving certain exemptions and special status specifically for the purpose of aerial filmmaking with drones. Operators hold private pilot certificates, keeping UAS within the line of sight at all times and restricting the UAV's flight operations to a "sterile area" on production set. the press release also states that an additional 40 application are currently under review.

Types

Oblique

Photographs taken at an angle are called oblique photographs. If they are taken from a low angle earth surfaceâ€"aircraft, they are called low oblique and photographs taken from a high angle are called high or steep oblique.

Vertical

Vertical photographs are taken straight down. They are mainly used in photogrammetry and image interpretation. Pictures that will be used in photogrammetry are traditionally taken with special large format cameras with calibrated and documented geometric properties.

Combinations

Aerial photographs are often combined. Depending on their purpose it can be done in several ways, of which a few are listed below.

• Panoramas can be made by stitching several photographs taken with one hand held camera.
• In pictometry five rigidly mounted cameras provide one vertical and four low oblique pictures that can be used together.
• In some digital cameras for aerial photogrammetry images from several imaging elements, sometimes with separate lenses, are geometrically corrected and combined to one image in the camera.

Orthophotos

Vertical photographs are often used to create orthophotos, alternatively known as orthophotomaps, photographs which have been geometrically "corrected" so as to be usable as a map. In other words, an orthophoto is a simulation of a photograph taken from an infinite distance, looking straight down to nadir. Perspective must obviously be removed, but variations in terrain should also be corrected for. Multiple geometric transformations are applied to the image, depending on the perspective and terrain corrections required on a particular part of the image.

Orthophotos are commonly used in geographic information systems, such as are used by mapping agencies (e.g. Ordnance Survey) to create maps. Once the images have been aligned, or "registered", with known real-world coordinates, they can be widely deployed.

Large sets of orthophotos, typically derived from multiple sources and divided into "tiles" (each typically 256 x 256 pixels in size), are widely used in online map systems such as Google Maps. OpenStreetMap offers the use of similar orthophotos for deriving new map data. Google Earth overlays orthophotos or satellite imagery onto a digital elevation model to simulate 3D landscapes.

Aerial video

With advancements in video technology, aerial video is becoming more popular. Orthogonal video is shot from aircraft mapping pipelines, crop fields, and other points of interest. Using GPS, video may be embedded with meta data and later synced with a video mapping program.

This "Spatial Multimedia" is the timely union of digital media including still photography, motion video, stereo, panoramic imagery sets, immersive media constructs, audio, and other data with location and date-time information from the GPS and other location designs.

Aerial videos are emerging Spatial Multimedia which can be used for scene understanding and object tracking. The input video is captured by low flying aerial platforms and typically consists of strong parallax from non-ground-plane structures. The integration of digital video, global positioning systems (GPS) and automated image processing will improve the accuracy and cost-effectiveness of data collection and reduction. Several different aerial platforms are under investigation for the data collection.

See also

• Aerial archaeology
• Aerial landscape art
• Aerial photographers category
• Aerofilms Ltd., the first commercial aerial photography company in the UK, founded in 1919
• Airborne Real-time Cueing Hyperspectral Enhanced Reconnaissance
• Astrocam
• Aviation photography
• Battle of Neuve Chapelle
• Douglas Douglas-Hamilton, 14th Duke of Hamilton 1932 photo flight over Mount Everest
• English Heritage Archive the public archive of English Heritage, who hold one of the largest collections of aerial photographs of England
• Fairchild K-20 A WWII era aerial camera
• Federal Aviation Regulations
• Geoinformatics
• Kite aerial photography
• Oracle model photographic rocket
• Pictometry
• Pigeon photography
• Photogrammetry
• Remote sensing
• Satellite imagery
• TopoFlight
• Unmanned aerial vehicle

References

Further reading

• Price, Alfred (2003). Targeting the Reich: Allied Photographic Reconnaissance over Europe, 1939-1945. [S.l.]: Military Book Club. N.B.: First published 2003 by Greenhill Books, London. ISBN 0-7394-3496-9

External links

• Aerial photography and remote sensing
• INTERACTIVE MAP OF Drone "Restriction Areas"
• California Coastal Records Project
• Bird's eye view of the Delaware Valley by the Dallin Aerial Survey Company (1924â€"1941)
• Historic aerial photos of Columbia, South Carolina from the University of South Carolina Library
• Historical Aerial Photographs of New York , Cornell University Library & Cornell Institute for Resource Information Sciences
• National Collection of Aerial Photography The official archive of British Government declassified aerial photography.
• History of Aerial photos by Kite - KAP
• Aerial Photographic Techniques Suitable for Children
• Graber Collection of Florida Aerial Photographs at the University of South Florida