Validation of TOPEX/POSEIDON Measurements in the Southern Baltic Sea
In the present investigation altimetric sea-level heights from TOPEX/POSEIDON are compared with measurements of 8 coastal tide gauges in the southern Baltic Sea. The zero points of the tide gauges were determined by GPS measurements and by precise spirit levellings. Therefore, the instantaneous sea level above the ellipsoid and above an equipotential surface of the earth gravity field can be estimated only by means of tide gauge measurements.
Because tide gauge and altimeter measurements refer not to the same location it is necessary to know the differences of the ellipsoidal sea-level heights. For this purpose
different geoid models, which were fitted to the GPS-levelling points, were used;
the instantaneous sea-level height above the geoid was extrapolated to the altimeter footprints by empirical functions.
The comparison includes data from more than 5 years (Cycle 1, September 1992 to Cycle 188, October 1997). The method described here can in principle be used for the calibration of altimeter measurements. Special attention is paid to the different error sources concerning the sea-level height determination by altimetry respectively tide gauge measurements.
KeywordsTide Gauge Geoid Model Space Technique Tide Gauge Station Recent Crustal Movement
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