DEM ANALYSIS FOR SURFICIAL MAPPING IN THE LAKES REGION, NEW HAMPSHIRE

Digital Elevation Model data can be manipulated, enhanced, and visualized by different digital computerized methods to help delineate surficial geologic and geomorphic features remotely. By way of example, six 7.5' quadrangles in the Lakes Region (Alton, Belmont, Laconia, Northfield, West Alton, and Winnisquam Lake) are analyzed and displayed. Hybrid images combining side-illuminated elevation terrane, overlain by 1- to 3-meter topographic contours, with or without elevation-ramped color shading provides clear visualization of most features. ‘Fly-throughs' and 3-D rotation visualizations of the images, further enhances their use as visualization/mapping tools. Side-illumination (shadow-enhancement) from different ‘lighting' directions helps enhance specific, trend-related features, such as eskers, drumlins and glacially-elongated hills. “Flooding” the terrane at specific elevations (as if the terrane were submerged), helps reveal paleo-lake elevations, deltaic features, etc. Specific elevations, selected by field-based observations of materials of interest, can be selected and enhanced to help ‘trace out' the possible extent a specific deposit, the identification of deposits with similar elevations, and/or the elevation of spillways related to these deposits. Slope- and change-in-slope (second derivative)-analyses can further reveal areas of geomorphic complexity, easily overlooked in the field or on standard topographic maps, to help direct field mapping efforts. ‘Draping' of aerial imagery, geologic maps, or color-enhanced satellite (multi-spectral) images can also greatly aid in the delineation of surficial geologic features.