A Close-Range Photogrammetric Technique for Mapping Neotectonic Features in Trenches

Abstract

Close-range photogrammetric techniques and newly available computerized plotting equipment were used to map exploratory trench walls that expose Quaternary faults in the vicinity of Yucca Mountain, Nevada. Small-scale structural, lithologic, and stratigraphic features can be rapidly mapped by the photogrammetric method. This method is more accurate and significantly more rapid than conventional trench-mapping methods, and the analytical plotter is capable of producing cartographic definition of high resolution when detailed trench maps are necessary. In this method, field data in the form of contacts and structural features are recorded on pairs of stereographic photographs of the trench walls after the geologist has studied and delineated the relevant geologic and structural features. Stereophoto pairs with a minimum of four surveyed control points for each stereo model are oriented in an analytical plotter. Geographic data handling software is used to collect, edit, and plot the trench map. The major advantages of using close-range photogrammetry and digital plotting over conventional mapping procedures include: 1) greater cartographic accuracy, 2) decreased field and office time to produce a detailed trench-wall map, 3) creation of a permanent photographic record of the field data which can be reanalyzed for verification or revision and which may meet many Quality Assurance Program requirements, 4) ability to easily edit or add new data, and 5) ability to easily and rapidly change scales of the final trench map.