Photogrammetry is the science and technology of extracting quantitative information through measurements from overlapping photographs.Aerial photographs, taken with the appropriate geometric conditions and with suitable ground control pointscan be processed using photogrammetric software to create accurate orthoimages and DEM’s.We often use the results and products of aerial photogrammetry without necessarily being aware. Nearly all national mapping is, in fact, created in this way. However it is often the case that the vector-based mapping products take precedence over the other data created by the photogrammetry, that have the potential to provide ‘landscape scientists’ with a most valuable resource. In order to derive topographic mapping from vertical aerial photography the modern photogrammetric process creates detailed Digital Elevation Models (DEMs) and geometrically-corrected photographic images (orthophotos), both assets in their own right.

The development of photogrammetric applications for PC’s has replaced the previously complex optical-mechanical (analogue) instruments and has brought aerial photogrammetry into the realm of the non-specialist. It is now a realistic proposition for landscape scientists to plan and process a photogrammetric project designed to generate orthophotos and detailed DEM’s specifically for landscape analysis

Orthoimagery and the associate DEM’s have proven so successful that we would see this as an integral part of any future landscape project’s method statement. The DP alone has gathered and processed a number of project areas and we have advised and assisted a number of other projects.

The Discovery Programme has PCI Geomatica 10.0 software, which contains the Orthoengine photogrammetric processing module. This allows the processing of images stage by stage to extract the DEM and use it to create the ortho-rectified images, which are mosaiced to produce orthophoto maps.