USING SCANNING AND PHOTOGRAMMETRY TO DEVELOP OBJECTIVE GEOMETRIC MEASURES AND EDUCATIONAL RESOURCES FOR A EUBRONTES TRACKSITE, DINOSAUR STATE PARK, CT

Laser scanning and close range photogrammetry (CRP) have increasingly been used to model and measure dinosaur ichnofossils. We used both to: 1) survey/scan, image/map and digitize/analyze a well-known Eubrontes tracksite at Dinosaur State Park (DSP) in Rocky Hill CT; 2) develop/apply new “objective” geometric measures to the tracksite, and 3) develop associated educational products. A Trimble VX spatial station was used to define survey space, scan the tracksite, and locate ground control points for rectifying image-maps and CRP data. Dim overhead-lighting and intense track-level spotlights complicated imaging. We used >100 sub-vertical overlapping RAW images captured with a Nikon D600 full-frame camera mounted on a ≈7.5 m monopod. To minimize motion-blur and maintain depth of focus, images were captured with rapid shutter speeds (<1/250 s), intermediate apertures, but elevated ISO settings (3200). While suitable for an image-map, ISO digital noise limits the quality of monopod CRP models. Consequently ≈500 additional oblique images were captured from 11 sites at ground-level using a tripod, low ISO (100), and portable studio lighting. Image-derived CRP data were used to model/measure tracks to a) compare digital metrics with similar caliper-based measures made previously by us, and b) apply and evaluate new geometrically objective measures for the DSP tracks. Initial comparisons indicate that CRP-derived footprint lengths differ from caliper measures by 2.6±3.5 cm (≈7% of length, n=9) and stride lengths differ by 2.2±3.9 cm (1.0%, n=5) which nearly triples replicate caliper measurements (foot length: 0.9±1.5 cm, 2.5%, n=39). We suspect much of this difference reflects subjectivity in selecting measurement positions in the CRP models. Analyses thus far suggest that while new geometric normalization procedures are objective, subjective choices persist when leveling models, and in choosing track outlines and digit axial positions. This supports use of both subjective and objective techniques for characterizing the DSP site. Educational outcomes include an image-map of the entire tracksite with surrounding images and notes describing stitching, mosaicking, and CRP techniques. Our images have/are also used for large-format displays and 3D print files in support of educational programming.