DIGITAL GEOSPATIAL TECHNOLOGIES AND RESOURCES IN GEOLOGIC FIELD RESEARCH

Integrating new geospatial technologies into field research requires new instruments, resources and techniques that must be adapted to specific geologic mapping needs. We have developed a system of digital field mapping that involves several kinds of digital instruments from GPS-enabled PDA's and handheld data logging GPS (+/- 0.5 m) to survey grade RTK GPS (+/- 1.0 cm) and optical total stations (+/- 0.5 cm) along with hi-resolution digital aerial imagery (pixel ground distances down to 15 cm), low elevation camera-pole imagery (from elevations up to 14 m) and newly available airborne LiDAR data (for accurate DEM's); combined together in a GIS (ArcMap 9.3). All instruments record positional data in the same coordinate system as topographic maps and high resolution aerial imagery. Survey grade instruments (GPS and total station) are tied to the same field datum point determined through static GPS (post processed through NOAA's On-line Position Users Service (OPUS) web site - www.ngs.noaa.gov/OPUS); or to best fit coordinates for recognizable ground features visible in the aerial images. Single camera-pole photos are combined into mosaics using Adobe Photoshop and georeferenced in ArcMap to surveyed control points visible in each photo. Structural features visible in both the aerial and camera-pole imagery can be mapped by on-screen digitizing creating new shape files directly in ArcMap. Structural orientation measurements and positions are logged using hand-held GPS and plotted using ArcMap's symbol palette. These new digital tools and techniques are used to explore the nature of crustal deformation in a program of outcrop surface mapping that focuses on single, large, coastal exposures that reveal the most intricately complex geologic structures. With these techniques we are able to delineate meso-scale geologic features that are often overlooked in traditional quadrangle scale geologic mapping (features that are too small to map and too big to photograph) thus revealing new and never-before-seen structures and relationships. Syntectonic granite dike intrusions in coastal Maine, for example, have been studied using these digital techniques in order to determine the spatial distribution of ductile strain regimes related to regional shearing along the Late Paleozoic Norumbega fault and shear zone system.