WALKING INTO THE DIGITAL WORLD: DINOSAUR TRACK MAPPING AND DATA COLLECTION

Our project recreates dinosaur trackways using close range photography. The goal was to create a virtual field site which contained correctly oriented and scaled imagery. To accomplish this, we combined differential GPS receivers, a total station surveyor and hand held snapshots of the dinosaur tracks. The final product is a virtual field location in GIS, where we can measure track direction, size, shape, and degree of preservation, as well as additional environmental data, such as ripple marks, and layer thickness and orientation. We demonstrate in this presentation how to accomplish this with relatively modest technology.

The main problem was how to georeference the photographs, since we had over a hundred tracks to measure. We chose a compass as an oriented scale object for each photograph. We measured locations on the compass to the nearest mm, and converted those to a local coordinate system aligned to north. We then aligned the compass to north on the ground next to each track. We used a reflectorless total station to shoot a known point on the compass, and the camera recorded a photograph. We converted the total station measurements into georeferenced data with a two dimensional conformal coordinate transformation, using two static differential GPS receivers as control points. We then created ground control points for each photograph from the measured coordinates on the compass by translating the local compass coordinates into the georeferenced UTM coordinate system. The compass ground control points were then read into a GIS, and then used to rectify the photos.

Given the several transformations, how did our virtual field site fare? We show several data sets derived from the virtual site, including statistics on track size, rose diagrams of track directions, and characterizations of track preservation. We also compare our maps to published maps of the tracks. An additional value added to a virtual georeferenced field site is its transportability. We will show how to share the field site with the world via Google Maps, Picasa, and Fusion Tables. Thus, we think the steps involved in creating a virtual site are more than worth the effort, as the dinosaur tracks can now be investigated by anyone with access to the internet.