Assessment of Systematic Errors in the Computation of Gravity Gradients from Satellite Altimeter Data
With satellite radar altimetry, the oceanic geoid can be determined with high precision and resolution. Double differentiation of these data along satellite altimeter ground tracks yields along-track gravity gradients that can be used to compute vertical gravity gradients at ground
track crossovers. One way to counteract the noise amplification due to the differentiation is to smooth the data using smoothing splines. Although the effect of satellite altimeter data noise has been investigated to some extent, the associated systematic errors have not been assessed so far.
Here we show that some of the systematic errors cannot be neglected. In particular, we found that the negligence of the dynamic ocean topography (DOT) may introduce errors that are greater than the measurement noise induced errors. If the gravity gradients are to be used for GOCE validation,
then also in this case the DOT may not be neglected as the signal at GOCE altitude of 260 km may be above the GOCE requirements. In addition, we show that the altimetry derived gravity gradients cannot be compared one-to-one with those in a local Cartesian frame. The differences are small
compared with the total signal, but they may be larger than the satellite altimetry induced stochastic errors and may be above the GOCE requirements. The cubic splines second derivative truncation error requires the use of 10 Hz altimeter data for the computation of gravity gradients at the
Earth's surface, while 1 Hz data are sufficient for validation at GOCE altitude.
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Document Type: Research Article
Deutsches Geodatisches Forschungsinstitut (DGFI), Munich, Germany
Deutsches Geodatisches Forschungsinstitut (DGFI), Munich, Germany,Faculty of Civil Engineering, Department of Advanced Geodesy, Czech Technical University in Prague, Prague, Czech Republic,Academy of Sciences of the Czech Republic, Astronomical
Institute, Prague, Czech Republic
April 1, 2011
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