It's All about Context Remapping mammoth bone bed with ArcGIS By Donald Anton Esker, the Mammoth Site of Hot Springs, South Dakota Scientists at a South Dakota research center are remapping the location of bones of Ice Age mammoths with GIS to preserve the context of the find and allow for the automation of quantitative analyses. The Mammoth Site of Hot Springs, South Dakota, is an indoor, in situ Pleistocene bone bed that contains the remains of at least 56 mammoths and numerous other Ice Age animals. Approximately 26,000 years ago, the bone bed was the site of a steep-sided warm-water sinkhole pond. The warm water and year-round vegetation along the edges attracted mammoths, but once in the pond, the steep sides prevented their escape. Although entrapment was probably a rare event, the sinkhole was active as a trap for 300 to 700 years, which accounts for the large number of remains. Early Mapping Methods Initially, the Mammoth Site used a string grid to map the bone bed, and the cartography was entirely hand drawn. However, finding bones using one of these maps was like a treasure hunt. Most important, any quantitative analysis of a hand-drawn map also had to be done by hand. Early efforts to computerize the mapping process using CAD software and a Nikon laser transit met with mixed success. The software was not well suited to mapping, and the Nikon transit proved difficult to use in the bone bed. The resulting map permitted automated cataloging of the bone bed but was less accurate and less detailed than the old stringgrid system. Enter ArcGIS The Mammoth Site recently embarked on a project to completely remap the bone bed using the latest technology. The center upgraded the GIS software to ArcGIS 9.2, bought a Trimble robotic transit, and improved site photography. These upgrades vastly improved map quality and opened the doors to hitherto impossible research. The Mammoth Site employs a complex photographic mapping process that starts with anchor points. These are actually four or more metal washers that are placed around a bone before it is mapped. Larger bones require more washers. The washers appear in each photograph, and the Trimble transit is used to shoot in the precise coordinates of each washer. Photos for Mapping and Documentation While researchers use photographs to document the bones, photographs are also integral to the mapping process. Because the outline of the bone becomes part of the map, the photograph of the bone should be taken from directly above the bone on a level plane to avoid distortion. Good photographs of smaller bones can be made with a bubble level on the camera, but mammoth bones, such as a femur or skull, cannot be fit in a single picture taken from The Trimble 5600 robotic transit being mounted to its tripod The site was discovered in 1974 during excavation for a housing development. Three mammoths were found during the first season. From the beginning, site mapping was a high priority. Mapping shows the location of each bone and records information about where it was found. By studying the bone bed's taphonomy [i.e., studying what happened to an organism between the time of its death and the time it was excavated], researchers can determine the environment of deposition and gain a clearer insight into the world of the mammoths. 24 ArcUser Spring 2009 The bone bed at the Mammoth Site is 150 feet long by 75 feet wide and 67 feet deep. ground level. Photo-stitching software helps but invariably introduces distortion because of the changes in camera perspective. The best solution is to take the picture from well above ground level. Fortunately, the building enclosing the bone bed contains a remote-controlled crane that is used for bone and sediment removal and also serves as a mobile high-altitude digital camera mount. It is remotely controlled from a Panasonic CF-30 Toughbook laptop via a USB connection. www.esri.com