| Abstract | Introduction | Methods1 | Methods2| Results1 | Results2 | Results3 | Discussion1 | Discussion2 | Discussion3 | Future| Acknowledgments |
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| Determination of Water Depth at the Deep Edge of Seagrass Meadows in Tampa Bay Using GPS Carrier Phase Processing |
| J.O.R. Johansson, K.B. Hennenfent and J.J. Pacowta. (City of Tampa, Bay Study Group) |
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| Determination of Measurement Errors
Trimble specifications for the GPS Pathfinder PRO XR system with carrier-phase post-processing report the accuracy of position determinations as approximately 5cm+5ppm with 30min of satellite tracking (see figure below).
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| Performance of the Trimble Phase Processor v.2 software with the GPS Pathfinder PRO XR system according to Trimble (1997). Figure modified from Trimble (1997). Horizontal errors are shown, however, Trimble (1997) states that vertical and horizontal errors are similar for phase processed solutions. |
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The 5ppm error is caused by the distance between the base and the rover stations (baseline) and equals 0.5cm of error for each kilometer of separation. Additionally, the vertical error for carrier-phase processing solutions is similar to the horizontal error. The accuracy of the measurements can be further improved by at least 45min of of satellite tracking and post-processing the data using the Trimble Centimeter Option software.
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| Trimble Pathfinder PRO XR instruments located on the roof of the City of Tampa Bay Study Group |
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Tests were conducted on the roof of the City of Tampa Bay Study Group (COT) laboratory to determine the vertical measurement performance of the PRO XR system both with and without using the Centimeter Option (see photograph below). Two PRO XR instruments were placed on the roof at a location with a known MTL elevation. The two antennas were located at near identical elevations and separated less than 1.0m horizontally. One instrument was used as a base station and the other as a rover station. The instruments were configured to the Trimble recommendations and the time interval between measurements was 5s.
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