Sea Surface Height Determination in the Mediterranean Sea by Local Adjustment of GEOSAT Altimeter Data
The pre-processing and the crossover adjustment of GEOSAT altimeter data are carried out in order to obtain a precise approximation of the gravity field in the Mediterranean sea. Altimeter data from the U.S. National Oceanographic Data Center (NODC) have been used covering a time period of about one year. With the rejection of outliers and sub-satellite points whose standard deviation (s.d.) exceeds ±0.09 m, the s.d. of the crossover differences was ±3.5 m. After applying a fit and crossover adjustment model, the s.d. of the crossover differences decreased to ±0.16 m. In order to test the efficiency of the sea surface heights performed, a number of predictions was carried out using as data: (a) adjusted satellite altimetry and (b) sea-gravimetry. Least squares collocation was then used to predict subsets of the data types (a) and (b) from subsets of the same data types. The results given here are in terms of s.d. of observed minus predicted values. Using adjusted altimeter data for gravity prediction a s.d. of ±9.36 mgal was found. When gravity values spaced 10′ apart were used to predict, (1) gravity values in a grid with the same mesh width shifted 5′ and (2) altimeter observations, a s.d. of ±5.08 mgal and ±0.18m, respectively, were found. A combination of gravity and altimeter data made the first s.d. of ±5.08 mgal decrease to ±4.34 mgal showing the impact of combining the two data types. In all the above prediction computations the use of topographic-isostatic effects has been taken into account.
KeywordsGravity Field Gravity Anomaly Altimeter Data Geoidal Height Geoid Undulation
Unable to display preview. Download preview PDF.
- Arabelos D. and I.N. Tziavos (1989). Sea Surface Heights in the Mediterranean Sea from GEOSAT Altimeter Data. Submitted for publication J. Geophys Res Google Scholar
- Cheney, R.E., B.C. Douglas, R.W. Agreen, L. Miller, D.L. Porter, M.S. Doyle (1987). Geosat altimeter geophysical data record user handbook. NOM technical memorandum NOS NGS-46.Google Scholar
- Cruz, J.Y., and R.H. Rapp (1982). Sea surface heights in the Mediterranean area from Seasat altimeter data. Boll Geof Thor. Appì XXIV, (95),167–174.Google Scholar
- Dermanis A. (1987). Adjustment of observations and estimation theory. In Greek.Google Scholar
- Fukuda, Y., J. Segawa, H. Watanabe, and A. iwasita (1988). Geosat altimeter data processing. Journal of the Geodetic Society of Japan, 34, (2), 97–108.Google Scholar
- Knudsen, P. (1987). Adjustment of satellite altimeter data from crossover differences using covariance relations for the time varying components represented by Gaussian functions. In Proceedings of the /AG Symposia, X/X General Assembly, Vancouver, Canada, Aug. 10–22, Vol. II, 617–628.Google Scholar
- Rapp, R. H. (1977). Mean gravity anomalies and sea surface heights derived from Geos3 altimeter data.Dept. of Good Set. Surv. Rep. 325, Ohio State Univ., Columbus.Google Scholar
- Rapp, R. H. (1981). The earth’s gravity field to degree and order 180 using Seasat altimeter data, terrestrial gravity data, and other data.Dept. of Geod. Sc1 Sun! Rep. 322, Ohio State Univ., Columbus.Google Scholar
- Rowlands, D. (1981). The adjustment of Seasat altimeter data on a global basis for geoid and sea surface height determinations.Dept. of Good. ScI Sun Rep. 325, Ohio State Univ., Columbus.Google Scholar
- Tscherning, C.C. (1975). Covariance expressions for second and lower order derivatives of the anomalous potential.Dept. of Good Sci Surv. Rep. 225, Ohio State Univ., Columbus.Google Scholar
- Vermeer, M. (1983). A new Seasat altimeter geoid for the Baltic. FinniSh Geodetic Institute, Rep. 83, (4), 1–10.Google Scholar