Aerial photography


Aerial photography is the taking of photographs from an aircraft or other flying object. Platforms for aerial photography include fixed-wing aircraft, helicopters, unmanned aerial vehicles, 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.
, showing Stonebridge Road, Stamford Hill, and Seven Sisters Curve, part of the Tottenham and Hampstead Junction Railway, taken from on 29 May 1882 - the earliest extant aerial photograph taken in the British Isles.
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. The same year, Cecil Shadbolt devised a method of taking photographs from the basket of a gas balloon, including shots looking vertically downwards. One of his images, taken from over Stamford Hill, is the earliest extant aerial photograph taken in the British Isles. A print of the same image, An Instantaneous Map Photograph taken from the Car of a Balloon, 2,000 feet high, was shown at the 1882 Photographic Society exhibition.
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 defenses. 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, taking photographs from the British dirigible Beta. He discovered that vertical photos taken with a 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 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 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 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, hired an Airco DH.9 along with pilot entrepreneur Alan Cobham.
1932, aerial photograph of Fairchild Aerial Surveys Inc.
From 1921, Aerofilms carried out vertical photography for survey and mapping purposes. During the 1930s, the company pioneered the science of photogrammetry, with the Ordnance Survey amongst the company's clients. In 1920, the Australian Milton Kent started using a half-plate oblique aero camera purchased from Carl Zeiss AG in his aerial photographic business.
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 lens 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. 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

Vertical aerial photography is used in cartography, land-use planning, archaeology. Oblique aerial photography is used for movie production, environmental studies, power line inspection, surveillance, construction progress, 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 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

In the United States, except when necessary for take-off and landing, full-sized manned aircraft are prohibited from flying at altitudes under 1000 feet over congested areas and not closer than 500 feet from any person, vessel, vehicle or structure over non-congested areas. Certain exceptions are allowed for helicopters, powered parachutes and weight-shift-control aircraft.

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 Aviation Administration, issued an order banning the use of "Drones" in any commercial application related to photographs for use in real estate advertisements. The ban has been lifted and commercial aerial photography using drones of UAS is regulated under the FAA Reauthorization Act of 2018. Commercial pilots have to complete the requirements for a Part 107 license, while amateur and non-commercial use is restricted by the FAA.
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. In addition to gyroscopically stabilized footage, the use of RC copters as reliable aerial photography tools increased with the integration of FPV technology. Many radio-controlled aircraft are now capable of utilizing Wi-Fi to stream live video from the aircraft's camera back to the pilot's or pilot in command's ground station.

Regulations

Australia

In Australia Civil Aviation Safety Regulation 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, whereas 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 licensed by the Civil Aviation Safety Authority. Whilst a small UAS and model aircraft may actually be identical, unlike model aircraft, a UAS may enter controlled airspace with approval, and operate in 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. However, CASA has modified the regulations and from the 29th of September 2016 drones under 2 kg may be operated for commercial purposes.

United States

2006 FAA regulations grounding all commercial RC model flights have been upgraded to require formal FAA certification before permission is granted to fly at any altitude in the US.
June 25, 2014, The FAA, in ruling 14 CFR Part 91 "Interpretation of the Special Rule for Model Aircraft", banned the commercial use of unmanned aircraft over U.S. airspace. On September 26, 2014, the FAA began granting the right to use drones in aerial filmmaking. Operators are required to be licensed pilots and must keep the drone in view at all times. Drones cannot be used to film in areas where people might be put at risk.
The FAA Modernization and Reform Act of 2012 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 " capable of sustained flight in the atmosphere; flown within visual line of sight of the person operating the aircraft; and flown for hobby or recreational purposes."
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.
The FAA can pursue enforcement action against persons operating model aircraft who endanger the safety of the national airspace system. Public Law 112–95, section 336.
June 21, 2016, the FAA released its summary of small unmanned aircraft rules. The rules established guidelines for small UAS operators including operating only during the daytime, a 400 ft. ceiling and pilots must keep the UAS in visual range.
April 7, 2017, the FAA announced special security instructions under 14 CFR § 99.7. Effective April 14, 2017, all UAS flights within 400 feet of the lateral boundaries of U.S. military installations are prohibited unless a special permit is secured from the base and/or the FAA.

United Kingdom

Aerial photography in the UK has tight regulations as to where a drone is able to fly.
Aerial Photography on Light aircraft under 20 kg. Basic Rules for non commercial flying Of a SUA.
Article 241 Endangering safety of any person or property.
A person must not recklessly or negligently cause or permit an aircraft to endanger
any person or property.
Article 94 small unmanned aircraft
1. A person must not cause or permit any article or animal to be dropped from a small unmanned aircraft so as to endanger persons or property.
2. The person in charge of a small unmanned aircraft may only fly the aircraft if reasonably satisfied that the flight can safely be made.
3. The person in charge of a small unmanned aircraft must maintain direct, unaided visual contact with the aircraft sufficient to monitor its flight path in relation to other aircraft, persons, vehicles, vessels and structures for the purpose of avoiding collisions.
4. The person in charge of a small unmanned aircraft which has a mass of more than 7 kg excluding its fuel but including any articles or equipment installed in or attached to the aircraft at the commencement of its flight, must not fly the aircraft:
4.1 In Class A, C, D or E airspace unless the permission of the appropriate air traffic control unit has been obtained;
4.2 Within an aerodrome traffic zone during the notified hours of watch of the air traffic control unit at that aerodrome unless the permission of any such air traffic control unit has been obtained;
4.3 At a height of more than 400 feet above the surface
5. The person in charge of a small unmanned aircraft must not fly the aircraft for the purposes of commercial operations except in accordance with a permission granted by the CAA.
Article 95 small unmanned surveillance aircraft
1. You Must not fly your aircraft over or within 150 metres of any congested Area.
2. Over or within 150 metres of an organised open-air assembly of more than 1,000 persons.
3. Within 50 metres of any vessel, vehicle or structure which is not under the control of the person in charge of the aircraft.
4. Within 50 metres of any person, during take-off or landing, a small unmanned surveillance aircraft must not be flown within 30 metres of any person. This does not apply to the person in charge of the small unmanned surveillance aircraft or a person under the control of the person in charge of the aircraft.
Model aircraft with a mass of more than 20 kg are termed ‘Large Model Aircraft’ – within the UK, large model aircraft may only be flown in accordance with an exemption from the ANO, which must be issued by the CAA.

Types

Oblique

Photographs taken at an angle are called oblique photographs. If they are taken from a low angle relative to the earth's surface, 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.
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 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", 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 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.