CAPTURING DIGITAL FIELD DATA TO CREATE 3D PHOTOREALISTIC OUTCROP MODELS OF THE STRUCTURE IN THE LOWER JURASSIC INTERBEDDED PELAGIC LIMESTONES AND MARLS OF THE LIAS FORMATION NEAR KILVE, SOMERSET, ENGLAND

The sea cliff and foreshore on the south coast of the Bristol Channel provide outstanding exposures of Lower Jurassic interbedded pelagic limestones and marls of the Lias Formation. This highly studied section of coastline exhibits several phases of deformation resulting in a set of faults, folds, and joint patterns that are exposed on the cliffs and foreshore. Numerous studies have been conducted to map the stratigraphy, determine fault offsets and to study the effects of varying stress fields on joint patterns. These structures are of particular interest as a guide to deformation patterns in the petroleum reservoirs of the North Sea. Such highly visited and studied localities provide an excellent opportunity to illustrate outcrop capture techniques that are capable of producing 3D photorealistic models.

Capturing geology digitally is the fieldwork of the future. The ability to bring outcrops home not only allows geologists to have the visualization of the outcrop at their fingertips, but also allows for the later measurement of data from the model for accurate quantitative analysis. In addition the models can be used for educational purposes, either prior to or to replace a visit to the outcrops. By combining the technologies of global positioning satellites (GPS), ground laser scanners, close range oblique high resolution digital photography, and appropriate software, such models can be created and utilized.

Data was collected in the summer of 2004, on a 3 km section of sea cliff near the village of Kilve, Somerset. GPS data, point clouds from laser scanning and outcrop photography were collected over a two week period. High resolution aerial digital photography had been acquired earlier and was calibrated and integrated with the data acquired on the ground. Oblique aerial photography was obtained of the cliff faces and foreshore using low altitude helicopter flights. After processing and data integration, the point data is used to produce 3D models of the outcrop, and the digital photography is used to drape photographic detail onto the models using a technique that minimizes distortion, thus retaining the realism and accuracy of the actual outcrop. The resulting model can then be viewed and interpreted on a variety of platforms, from PCs to GeoWall systems, to large visualization facilities, such as CAVEs.