Close-range photogrammetric analysis of rock surfaces

Recent advances in analytical and digital photogrammetry have led to the application of this technique to the analysis of a range of geomorphological surfaces. Close-range photogrammetry can be used to assess both relative changes in weathering forms and absolute alteration of weathered surfaces. In the case of the latter, measurements of rate of surface loss can be made and linked across a range of scales. The requirements for different forms of photogrammetric control and the limitations of close-range analysis are outlined and related to the study of rock surfaces. The potential and problems of this technique are illustrated by reference to an analysis of relative form change on artificially weathered limestone and to a study of the surface form of a stone wall. However, despite the high metrical accuracy of photogrammetric methods, the paper emphasises the vital importance of the role of the observer in interpreting the DTM output.