JOUR.GEOL.SOC.INDIA, VOL.75, JAN. 2010 32 CEES W. PASSCHIER AND ULRIKE EXNER Digital Mapping in Structural Geology – Examples from Namibia and Greece CEES W. PASSCHIER 1 and ULRIKE EXNER 2 1 Cees Passchier, Department of Earth Sciences, University of Mainz, D 55099 Mainz, Germany 2 Ulrike Exner, Department for Geodynamics and Sedimentology, University of Vienna, Austria Email: cpasschi@uni-mainz.de Abstract: Many problems in geology, especially structural geology, can only be solved by detailed mapping. Presently, mapping is still mainly carried out on paper using techniques from the 19 th Century. However, tools are now available to carry out most mapping tasks on microcomputers in the field without any need of paper. This speeds up geological mapping and reduces the errors involved in the mapping process. Digital mapping also allows work in featureless areas and areas of great structural complexity that would not be possible using paper maps. We present two practical examples of the new technology of digital mapping using microcomputers, from Namibia and Greece. Keywords: Digital geological mapping, Differential GPS, Geospatial data, Field studies. geologically in any detail, and in most areas the mapping that has been done is outdated because of progress in the understanding of geological structures and the way they form. For this reason, geological mapping of large areas for the simple purpose of producing geological maps is continuously necessary. For geological research, whether basic research or work for the mineral and oil industry, mapping plays an important role. Because of the complexity of geological observation, it is usually insufficient to simply take samples or make isolated observations if one has to understand the larger geological context. Even if a geological map is available, it may not be up to date or not show enough detail of the feature investigated; in all such cases, some degree of mapping is necessary to create a context for the new observations. Geological maps have been paper maps since the Turin papyrus of 1150BC (Harrell and Brown, 1992) and William Smith’s 1815 map of Great Britain (cf. Winchester, 2001). Besides the fact that paper maps are unwieldy and impractical in adverse weather conditions, their main limit is the concept of scale. Once a map scale is chosen, small details closely spaced together cannot be shown, and features outside the map must be found on other sheets. Geologically relevant data such as lithology, structure, mineral parageneses, magnetics, gravity and radiometric data must be shown on separate paper maps in order to avoid clustering. Even for small areas, several maps are usually INTRODUCTION The natural sciences originated from our wish to understand the world around us, and from our curiosity as to why it is arranged the way we see it. In the course of time, most natural sciences have specialised to the extent that their questions can only be answered by carefully controlled experiments carried out in laboratories. The same happened to some branches of geology, but geology is similar to archaeology and other observational sciences in that it is hard or impossible to carry out experiments on the development of larger-scale structures; the processes involved are too large-scale in space and even more extensive in time. Therefore, geology makes progress by careful observation of features in outcrop and by elimination of a number of possible interpretations. Interpretation models are set up based on observations, which are then modified until new observations either invalidate them, or only refine them, after which a model is considered to be the most likely interpretation. Most large-scale geological processes can only be understood if sufficient data are collected in the field. Such data can include observations on lithology and mineral content of the rock, or structural observations on shape and orientation of sedimentary, igneous or deformation structures. In order to place such information in the right context and to understand their mutual relationship over a larger area, it is necessary to map their distribution in the terrain. Many areas on Earth have not yet been mapped JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.75, January 2010, pp.32-42 0016-7622/2010-75-1-32/$ 1.00 © GEOL. SOC. INDIA