Using Rocket Science
to Study Rock Science


Lawrence E. Turner, Arthur V. Chadwick, Lee Spencer
Southwestern Adventist University and Earth History Research Center



Abstract

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.


Problem

In a taphonomic fossil quarry it is important to measure the location and orientation of all fossils:
  • in 3-dimensional space
  • accurately
  • efficiently
Once these data are determined, they need to be recorded without error.

A complete determination and recording permits:
  • reconstructing the distribution of the fossils
  • analyzing the positions and orientations for trends and relationships


fossil quarry
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