Relative comparisons of satellite altimeter observations and sea level registrations at tide gauges have been particularly important to evaluate the long-term stability of satellite altimetry. Here, absolute comparisons between both time series are used to estimate the displacement between the geoid and the conventional height system, initially defined without any knowledge about the sea surface topography. The method is applied to the La Guaira tide gauge used to define the origin of the height system of Venezuela. The absolute comparison includes the determination of a local high resolution gravimetric geoid, the processing of the tide gauge time series with hourly sampling rate, the extrapolation of multi-mission altimeter data towards the tide gauge location and the geocentric positioning of the tide gauge bench mark by GPS. For the period 1992-2000, the altimetric time series and the tide gauge time series show a correlation of 0.85, a mean absolute offset of 3 cm and differences with ± 5 cm RMS. Taking into account the secular rate of mean sea level change, the Venezuelan height system is estimated to be -10 cm below the local geoid. This value agrees with the -8 cm displacement between the geoid and the national vertical datum referred to the geocentric system by GPS and leveling measurements. The investigations are a step towards the unification of national height systems in South America.
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- Absolute Comparison of Satellite Altimetry and Tide Gauge Registrations in Venezuela
- Springer Berlin Heidelberg
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