Image Capture (Archaeology)
The capture and analysis of image data is an integral part of the archaeological process and digital applications and techniques have revolutionised methods of data gathering, no more so than with aerial and satellite photography. Software applications have enabled new processing and analysis techniques for these types of images and problems such as the abutting of oblique angled photographs of undulating terrain can be carried out using, for example, the rectification component of the Bonn Archaeological Software Package (BASP), a collaboratively developed suite of tools in development since 1973 which also includes functions for seriation, clustering, correspondence analysis, and mapping. Airphoto is a low cost orthophoto programme which allows the user to correct a distorted aerial view and represent terrain as a relief model, combining the geometric accuracy of a map with the detail of a photograph. The use of multiple photographs to determine accurate measurements and to produce digital terrain models (DTM’s) is a highly technical process known as photogrammetry, for which a range of software is available. (http://www.gisvisionmag.com/vision.php?article=200202%2Frevi...)
English Heritage are responsible for the National Library of Air Photographs which consists of 2 million vertical, and 680,000 oblique photographs providing near-complete coverage for the whole of England (similar holdings are available for Scotland and Wales). This largely black and white collection is an enormously valuable resource and represents, for many thousands of archaeological sites, the sole evidence of their existence, ranging from isolated simple ring-ditches to very complex multi-featured landscapes showing human interventions onto the landscape from a range of historical periods. Image manipulation packages such as Adobe Photoshop or Gimp can be used on digitized versions of these images to enhance areas that are obscure and bring out features in the landscape that might indicate the presence of sub-surface archaeology.