Global Positioning System
My Research Project
The Global Positioning System (GPS) is a collection of over 24 satellites that oribt around the earth and allow receivers on earth to triangulate positions based off the Space Vehicles (SV's) position. The GPS was originally designed by the Department of Defense (DOD) to allow more precise navigation in the battle field and all over the world. The shipping industry realized the importance of GPS in designing automatic navigation. A GPS receiver on a large ore boat will locate the boat on the earth and then automatic navigation software can steer the boat to its programmed location because the software can "see" where the boat currently is and where the boat needs to go.

The DOD designed the GPS program so that the accuracy of the triangulation can vary from within 50 meters to within 5000 miles. This creates a safety buffer in time of war. There is a way to correct for this problem though. By traingulating the data from the satellites and then differentially correcting it with data sent from a land based radio tower, the buffer is removed and the accuracy of the triangulation is usually within 10 meters.
Figure 1 to the left shows how a receiver can triangulate its position based on the position of satellites.
Figure 2 to the right shows the orbital patterns for the 24 NAVSTAR satellites.
Collecting GPS Data:

The project that I took on involved the collection of GPS data. As of today, most GPS users collect GPS data on hand-held data units in the field. One then returns to the main base, downloads the data, converts it to a Global Information Systems (GIS) database format, and then begins to design a finalized GIS project.

With the purchase of a Fujitsu Pen-Top computer and software called Field Notes, it is possible to directly connect the GPS receiver to a computer and build a finalized GIS project on the fly.

Figure 3 to the left shows a beautiful example of collecting GPS data with a Trimble PRO XR GPS receiver and the Fujitsu Stylistic 1200 Pen Top computer. I was mapping a dune. It was over 1/2 a kilometer long, 1/4 kilometer wide and about 25 meters in maximum height. The temperature was about 80 degrees Farenheit.
Figure 4: (Above) All done for the day.
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