Each time a new bone is discovered and excavated, the GPS Rover is called in and a series of points are taken across the surface of the bone. These GPS points provide accurate 3D spatial data for the position of the bone.A digital photograph of the bone is also taken at the same time. The digital photograph is cleaned up and the GPS points taken from the bone in the field are used to place the photograph in a 3D field in the computer so that it will display in its correct spatial position along with all of the other bones in that quarry. The software responsible for this mapping in three dimensions is called GIS (Geographic Information Systems) software, and the process of placing the bone photograph in its correct spatial positioning is called Georeferencing.
Here (left) Justin uses the Rover part of the GPS equipment to take measurements on the surface of the bone. These measurements are recorded in the handheld computer and transferred directly to the database in the main computer in camp. Then each night the data are uplinked via satellite to the main computers back in Texas thus assuring minimal chances for data loss.
The points are displayed here (right) as they appear in the computer. This array of points is from an Edmontosaurus femur, the large upper leg bone of a duckbilled dinosaur that is about four feet long. The points, in addition to giving us positional data also allow us to look at the vertical distribution of bones in the quarry. Because of this we were able to discover that the bones lie in a graded bed with large bones on the bottom and smaller bones at the top. The array of points also allows us to see the orientation of the bone.
Our next task after obtaining
the GPS data is to take a digital photograph of the bone (left). This photo can be processed in a photo editing program such as Paintshop Pro or Photoshop to remove the extraneous background material, so we have a photo of just the bone on a white background (right). This allows us to make the background invisible so it will not hide bones that may lie below it in the composite quarry image.
Now the cleaned image of the bone is combined with the 3D array of points taken from the bone to create a composite pseudo 3D image (a 2D photo wrapped over a 3D array of points) so that the bone photo now represents the true position in the quarry occupied by the actual bone when it was in the ground (left). This image now will be combined with other images treated the same way to recreate the array of bones that was in the area of the quarry near the femur (right).
The entire quarry can be reconstructed over a period of years using these methods so that the data for the positions of all of the bones remains intact (left). Our femur is recognizable as the largest bone in the lower left quadrant of the photo.Clicking on this image will bring up a larger version of the reconstructed quarry. Using this technique, the observer is able to see the virtual appearance of the bones just as they looked in the sedimentary layers but with the rock removed.
This kind of information is vitally important for the field of Taphonomy, the study of every detail affecting an animal or plant from the time it died (including the cause of death), until it is excavated from the ground. Taphonomists ask these questions: Why did it die? What happened to it after it died? How was it buried? What was altered and how after burial and how did it become exposed? These are very important questions that with good data and careful analysis may offer answers to questions about dinosaur behavior, the environment of the world in which the dinosaurs died, etc.
Experimental taphonomy can be really interesting! It may involve watching a dead animal over a period of days, weeks, months or years, to record changes to the carcass as they occur. These changes can be used to interpret the state of decay of fossil bones in terms of time and conditions. In criminology, taphonomic studies can yield accurate information on the time of death of a human, for example, long after decay has set in. Interesting….