Detailed Lithological Mapping using Airborne LiDAR Topographic Data: Application to the Troodos Ophiolite, Cyprus

摘要

Geological mapping is traditionally undertaken through field-based surveys. As detailed field mapping over vast areas is both costly and time-consuming, mapping is often conducted at small-scales, potentially resulting in a lack of accurate and detailed lithological information. Remote sensing data, such as aerial photographs and satellite imagery, is typically used to try help and overcome some of the problems associated with field mapping. However, spatial and spectral limitations of the imagery and dense forest cover may affect the ability to undertake detailed lithological mapping using such data. With the capability of acquiring accurate and high-resolution topographic data in forested terrain, airborne Light Detection And Ranging (LiDAR) provides an opportunity to overcome these problems. An algorithm is presented for the detailed lithological mapping of a 16 km~(2) section of the Troodos ophiolite, Cyprus, using airborne LiDAR topographic data. Morphometric variables (slope, curvature and surface roughness) are derived from a 4 m bare-earth digital elevation model in order to characterise topographic signatures associated with each major lithological unit. An artificial neural network is then used to produce a lithological map through pixel classification with these variables as inputs. This algorithm successfully identifies the major lithological units and the resultant map surpasses the quality and detail of the existing geological maps. The results of this study demonstrate the significant potential of airborne LiDAR topographic data to enable lithological discrimination and quickly furnish detailed geological maps over large areas of either forested or non-forested terrain.