f Advances in Virtual Outcrop Geology

Virtual Outcrops, in which geological exposures are digital captured in a workstation, provide a new and rapidly emerging tool for the collection and analysis of field data. The advantages of virtual outcrop are primarily twofold; the rapid collection of accurate, spatially constrained measurements of geological features and, the improved visualization of outcrops which allows better correlation and mapping coupled with an ability to illustrate and communicate field observations to a wider audience. Virtual Outcrop geology is a rapidly expanding field of study which has grown over the last 10 years from photogrammetrry and basic digital mapping to the advanced data collection and visualization methods utilized today. This presentation addresses two recent developments: the collection and utilization of very large datasets and the integration of hyperspectral imagery to allow the remote mapping of lithology and mineralogy. To date the majority of photo-realistic virtual outcrops are generated from ground based lidar systems. While producing excellent results, these systems are limited by mobility and range, especially when studying very large outcrops. A solution to this problem is to mount the lidar system in a helicopter and scan the outcrop obliquely. This allows the rapid collection of very large volumes of data and has the added advantage of optimizing the angle at which both the scan and associated photos are taken, reducing the occurrence of scan-shadows. Very large virtual outcrops that cover 10s of km can be collected in hours. Despite the speed of acquisition, heli-based data presents a new set of challenges, not least the creation of very large datasets which cannot be visualized using conventional software. The acquisition, processing and utilization of these data will be illustrated with examples from fluvial and shallow marine systems from Utah. Airborne hyper-spectral imagery is an established method for remote sensing which utilizes the absorption characteristics of light outside the visible range (near infer-red) to identify mineralogy and other surface features (vegetation, land use etc). Mounting a similar camera on a tripod and obliquely scanning geological outcrops allows the remote mapping of lithology and mineralogy. The acquisition of oblique data from surfaces with significant topography has presented challenges for the processing of such data. Integration with the detailed terrain mapping provided by the lidar has allowed the spectral absorption response to be modelled and meaningful virtual outcrops, textured with quantitative mineralogical information to be produced. The results is a virtual outcrop which is textured with false coloured images that record mineralogy and can be accurately and rapidly investigated for quantitative information. <br>