TURNER, Lawrence E, Math/Physical Science Department, firstname.lastname@example.org, CHADWICK, Arthur V, Geology Department, Southwestern Adventist University, Keene, TX 76059, and SPENCER, Lee, EHRC, 30 Panorama Rd., Running Springs, CA 92382.
The Global Positioning System (GPS) has become a standard method of locating one’s position on the earth. The modern paleontologist who hopes not to become extinct must be familiar with this technology. While it is not necessary to be a GPS expert, it is useful to understand how GPS works and how current paleontological research can be enhanced by utilizing this increasing indispensable tool.
The handheld GPS units are quite inexpensive and serve to determine locations to within 5 m. While this is satisfactory for recording a general location, it cannot be used for the precise determinations needed in a fossil quarry. Fortunately, standard high-precision surveying GPS equipment is available that has a precision of less than 1 cm. To achieve the spectacular results that GPS is capable requires the application of modern technology and physics. The simple handheld units use Einstein’s General Theory of Relativity!
The GPS utilizes a constellation of satellites in half-sidereal day orbits transmitting information on two frequencies. The data is encoded in such a way that the distance to each satellite can be computed using a simple passive multi-channel receiver with an inexpensive clock. The detection and capture of four satellites permits the computation of the clock error and the location of the unit in three-dimensions.
The use of two frequencies permits correcting for the major effects of the variable propagation delay of the signals as they pass through the ionosphere. Utilizing a base station with a known location that receives the satellite information and transmits corrections to a rover unit that is simultaneously receiving information from the same set of satellites provides a more precise location of the rover. Applying phase information of the carrier frequencies finally permits the desired sub-centimeter precision.
While this equipment has been designed for high-precision surveying problems and is typically used for obtaining surface topology, the precision achieved allows the measurement of individual fossils. The location data is recorded and saved in a digital format that permits direct input into GIS software for analysis and display.
Accepted for the GIS Symposium SVP 2004 meeting, Denver, CO, Nov 2004—subsequently changed to a poster presentation due to scheduling conflicts.