Aerial and Close-range Photogrammetric Technology: Providing Resource Documentation, Interpretation, and Preservation
Photogrammetry is the art and science of obtaining precise mathematical measurements and three-dimensional (3D) data from two or more photographs. The Bureau of Land Management has benefited from its in-house photogrammetric capabilities, support, and expertise for more than 20 years. This support includes creating unique and value-added digital datasets and serving as subject matter experts and contracting officer’s representatives to obtain aerial photography and other types of 3D data. Traditionally, most people think of photogrammetry in the context of aerial photography. Photogrammetric techniques can be applied to virtually any source of imagery, whether it comes from 35-mm digital cameras or an earth-orbiting satellite. As long as the images are captured with stereoscopic overlap, one can derive accurate 3D data at a very wide range of scales.
The rapid evolution of digital cameras and increasing capabilities of computers and analytical software has dramatically expanded the variety of situations to which photogrammetry may be applied, while simultaneously decreasing the costs of acquisition, processing, and analysis. A variety of resource specialists (such as hydrologists, soil scientists, archaeologists, paleontologists, biologists, range conservationists, and engineers) can greatly benefit from 3D products derived from modern photogrammetric techniques. This is especially true in the field of ground-based or close-range photogrammetry. This document provides a general overview of photogrammetry, with separate sections focusing on traditional aerial photogrammetry and close-range photogrammetry. The appendices contain technical information on the equipment and suggested methods for capturing stereoscopic imagery. Their purpose is to assist field resource specialists in the successful completion of the imagery collection portion of a basic, close-range photogrammetry project.