Thursday, 21 November 2013

Five Things You Never Knew About Aerial Photography

Aerial photography has been around since Gaspard-Felix Tournachon started taking snaps from the basket of his hot air balloon in 1858. Since then, the technology has been refined to deliver complex images of land masses, settlements and military installations. Have a look through these five fascinating facts about the technology – its history, its application and its equipment – to get a handle on the most advance form of photography on (and above) the earth!

World War I was fought with aerial maps
During the First World War, aerial photography was used to create or correct maps of enemy territory. The first protracted use of aerial photography for military uses was conducted by General Allenby and a Royal Australian Air Force squadron based in the UK. His five photographers flew over enemy lines in Turkish airspace, escorted by fighter planes, to carry out a photographic survey that enabled Allenby to correct vital tactical maps.

Robot helicopters take aerial snaps
One of the most common machines used for surveying and aerial photography is the Coptercam, or Octocopter. The Octocopter is a flying robot with a camera system mounted in its belly, powered and steered by eight rotary blades (hence the name). It is used to survey land from Australian airspace, and has recently been put into service surveying the damage done by extreme weather systems.

In the US, it’s legal to spy on people using aerial photography
In America, airspace is technically public. In US law, if you can see something from a public space then you are not spying. Because of this, it is perfectly legal to use aerial cameras to capture people doing things that cannot be seen from the ground. This includes the documentation of things that are happening in the boundaries of private property – which may not be documented from the streets.

Aerial cameras have been taking giant pictures for decades
In the 1930s, Sherman Fairchild perfected his design for an aircraft mounted camera system capable of taking a single image that accurately showed 225 square miles of land. Before the end of the decade, Fairchild had increased the accuracy of his cameras to 600 square miles per exposure. The advancement of the technology started by Fairchild is the basis for modern photographic mapping.

Aerial photography forms the basis for modern maps
Photogrammetry (the process by which geometrical relationships are deduced from aerial photographs) forms the basis of much modern mapping. Highly detailed aerial photographs are taken, which are then “translated” into cartographs (maps) using the principles of projective geometry. In its simplest form, projective geometry involves measuring the distance between two points on the map, then factoring in the known geographic coordinates of those points to get the proper cartographic representation.

Photogrammetry requires range data to work properly. This is often obtained through LiDAR (Light Detection and Ranging) – a relative of RaDAR (Radio Detection and Ranging) in which light pulses are measured to determine the distances between objects. For more information about aerial mapping, LiDAR and photogrammetry, follow the link.
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