Tidal Datum Determination and VDatum Evaluation with a GNSS Buoy

B. Hocker, N. Wardwell

Abstract:	Under a charting contract with the National Oceanic and Atmospheric Administration (NOAA), David Evans and Associates, Inc. (DEA) was tasked to evaluate the VDatum model in addition to mapping large portions of Chesapeake Bay. The VDatum software was developed by NOAA to vertically transform geospatial data among a variety of tidal, orthometric and ellipsoidal vertical datums. The goal of the evaluation was the Mean Lower Low Water (MLLW) datum model as applied to convert GNSS determined ellipsoid heights to chart datum. Using a buoy outfitted with GNSS and a tilt sensor, tidal datums were computed at three locations bounding the project area in 2009 and work continues in 2010. Data was collected at each location for a minimum of 30-days to maximize the accuracy of the datum computation. Post- Processed Kinematic (PPK) methodologies were used to process the GNSS data from the buoy and compute timetagged antenna heights. These heights were then corrected by the antenna offset to the water line and the buoy's tilt sensor data was analyzed. Corrected ellipsoid water levels were filtered and the datums were computed using the Tide-by-Tide method of simultaneous comparisons using a control station. Final results were compared with existing shore-based tide stations, GNSS water levels computed on two survey vessels and the VDatum model.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2076 - 2086
Cite this article:	Hocker, B., Wardwell, N., "Tidal Datum Determination and VDatum Evaluation with a GNSS Buoy," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 2076-2086.
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