Winter 2000

A Bird's Eye View

Article by Daniel Wrench

Aerial photography is used almost every day by managers along the Sefton Coast. Modern aerial photography is an accurate method for capturing an enormous amount of information and with computer processing it can be made to overlay the Ordnance Survey base maps. It can even be draped over three dimensional survey information to produce realistic bird's eye views of the coast from every angle.

The Sefton Coast was one of the centres of pioneering aviation in the early twentieth century. No aerial photographs have been found from this date but some wonderful photographs have survived from the 1920s showing the Ainsdale and Birkdale sandhills as a very open landscape. Taking photographs from the cockpit of an aeroplane gives oblique (angled) views which, although they have great value, cannot be easily converted to a map base.

In the second world war both the Luftwaffe and the RAF developed reconnaissance aerial photography where a large format camera was mounted in the hull of the aeroplane and vertical pictures were taken. These could be related to maps and could be taken at different scales (e.g. 1:10,000) depending on the height of the aircraft. If successive prints overlap it is possible to view the images in 3D with a stereoscope. After the war the RAF put its new technology into use to undertake the first complete aerial survey of the British Isles. Early photography was black and white; later both colour and false-colour (infra-red) became common forms. Nowadays most photography is colour and current technology is moving towards digital photography, video and the use of radar.

Aerial photography is used as a base for many studies. Vegetation maps of the coast are initially drawn on aerial photographs and then checked in the field. Land use change can be recorded from one survey to the next, while the condition of the dunes as a sea defence can be monitored and the impacts of recreation pressure assessed.

Costs of acquiring aerial photography are usually shared between several partners and the copyright is held by the funders. An added value of aerial photography is that, once it has been used for its primary purpose, it remains an unique archive to be used time and again in assessing landscape change. The coastal resource centre has some aerial photography dating back to the first RAF survey of 1945 and a fairly complete set from 1961. Researchers are welcome to visit the centre to make use of the information.