Developments in photogrammetry; the geomorphological potential

Current emphasis in geomorphology recognizes the need for the accurate representation of topographic form, reflected in the growth of digital terrain and elevation modelling. A key requirement of such strategies is the efficient acquisition of information in an appropriate form and at an appropriate resolution to the landform under consideration. The traditional use of photographs in geomorphology has been for interpretation, but developments in photogrammetry may allow the full advantages of the photograph as a means of acquiring and storing quantitative information to be used. The photograph can provide information on all areas visible on a photograph; the information is acquired retrodictively; the photograph preserves the spatial relationship of morphological units; the collection of photographs requires minimal landform contact; the photograph records extra explanatory information; and photographs can be obtained at an appropriate temporal resolution to the landform under investigation. However, optical and mechanical limitations imposed by traditional photogrammetric approaches have prevented its rigorous and widespread application to geomorphology. Developments within photogrammetry, notably the analytical approach, now open up wider geomorphological possibilities. The analytical approach overcomes these limitations through the use of an interactive mathematical model at the stage of photographic analysis. The obtained information is in a form directly suited to the construction of digital terrain or elevation models. This technique can be used both for landform monitoring and for the analysis of archival photographs to reconstruct historical landform change.