MAPPING REPRODUCIBLE LINEAMENTS USING DIGITAL ELEVATION MODELS

This study explored the utility of mapping lineaments on shaded relief images created with ENVI image analysis software and a USGS, 7.5 minute DEM (digital elevation model) of Arcola, Virginia. Lighting directions at 15 degree increments between 0 and 180 degrees were used with an illumination height of 20 degrees. One lineament mapping trial was conducted on each shaded relief image (12 trails). A total of 4,911 DEM-lineaments were drawn; these were reduced to 377 through reproducibility analysis. Key trends are 4°, 23°, 90°, 116°, and 144°. Reproducible DEM-lineaments were then compared to reproducible lineaments drawn on 1:12,000 and 1:24,000 topographical contour maps, published geologic maps, and fracture-fabric data. There are several advantages to using DEMs for lineament mapping: DEM-lineaments do not have to be recognized through the obscuring effects of cultural features and vegetation, as do those lineaments mapped on aerial and topographic maps; DEMs allow for the adjustment illumination height and direction for the maximum enhancement of selected lineament trends. Results show that DEM-lineaments oriented to the direction of illumination were significantly subdued. A strong correlation exists between DEM lineaments and topographic lineaments, even though some clearly identifiable DEM-lineaments were not distinguishable on topographic maps. Topographic lineaments, photolineaments, and DEM-lineaments can be used in conjunction for the identification of reproducible lineaments, greatly reducing the occurrence of missed features. The strong spatial and trend correlation of DEM-lineaments with geology, faults, and fractures suggests DEMs can be an important component in geologic mapping.