The adjustment of SEASAT altimeter data on a global basis for geoid and sea surface height determinations
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Date
1981-12
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Ohio State University. Division of Geodetic Science
Abstract
This thesis documents the processing of SEASAT altimeter data as given on he Geophysical Data Record (GDR) produced by the Jet Propulsion Laboratory and released through the National Geodetic Survey. Special emphasis is given to the processing of this data performed at The Ohio State University with the goals of making the sea height data more suitable for geoid undulation recovery and sea surface variability studies. Before this processing, sea height values on the GDR's have a root mean squre (RMS) discrepancy of ±1.7 m at points where ground track cross (crossover points). Arcs of sea height data having common ground tracks have had relative linear trends removed and were merged by averaging at corresponding subsatellite points into master arcs. These master arcs are useful for sea surface variability studies. One global and four local crossover adjustments were performed on the sea height data in order to diminish the effects of radial orbit error. In the global adjustment, one master arc was held fixed as a minimum constraint. The results of the global adjustment were held fixed in the local adjustments (at crossover points). After adjustments, the data base bad a RMS crossover discrepancy of ±0.28 m. The crossover discrepancies were examined by arcs and were found to be large (±1.5 m) in the Hudson Bay, Mediterranean Sea, and several other areas. These areas are those in which the Schwiderski tides model, used in this study, was not valid. The adjusted sea surface heights were compared to corresponding GEOS-3 derived values. Considering 10 different areas the average difference (GEOS-3-SEASAT) was 126 cm with a standard deviation of ±66 cm. The adjusted sea surf ace heights have been put on severaly magnetic tapes for use in related studies.
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Prepared for National Oceanic and Atmospheric Administration, Rockville, Maryland: Contract No. 78-4326