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GEOLOGIC MAPPING IN GOOGLE EARTH: TOOLS AND CHALLENGES
We developed a tool for making fully-featured geological maps in Google Earth. The desktop application lacks the capacity for ornamenting lines and polygons. We created a web interface for post processing field data as 3D symbology and including standard geologic symbology on polylines. Data gathered in the field are imported into the API from a CSV file. The user can draw and annotate contacts. Various annotations and line ornamentations distinguish contacts, faults, fold axes, etc. Polygonal regions are defined using contact borders, and a KMZ file is exported to the Google Earth application. This tool goes beyond Google Maps Engine in supporting geological mapping.
We have also developed a Structural Geology Mapping Challenge. The exercise begins with outlining bedding traces and measuring strike and dip variations to determine folds. Students start by measuring strike and dip at preset locations. Their answers are compared with instructor’s stored values by a vector cross-product calculation and auto-scored with game-style gold, silver, bronze, or wooden medallions. Once the preset locations are measured, students determine a fold axis by fitting a great circle to the bedding poles on the inset stereographic net. The axial plane is also fitted. Once the training section is completed, students can continue adding dip and strike measurements to better constrain the fold profile to their outcrops. In an advanced stage of the exercise, students estimate principal curvatures of doubly-plunging folds.
Results from the students’ mapping are submitted to instructors for further analysis. By stacking strike and dip measurements, weighted by accuracy scores, from many students, instructors can improve mapping quality, identify regions of high difficulty, and scaffold their students’ learning experience. We envisage applications pre- and post- live field excursions and in distance education classes.