Regional and global geoid models have been constructed over many years using results from satellite orbit analysis, together with ground-based gravity measurements. An accurate ocean geoid is vital for a range of applications, and the addition of satellite altimeter data over the oceans has greatly enhanced the detail of these models. The National Remote Sensing Centre Limited (NRSC) has developed a geoid product specifically tailored for maximum spatial resolution over local scales, geared primarily for the requirements of the oil industry. This geoid is currently being produced from ERS-1 35 day data, using the Sea Surface Topography processing sequence on the input Waveform Product data to retrack individual ocean waveforms, yielding sea-surface height information of unrivalled accuracy for ERS-1 data. The 168 day repeat cycle of ERS-1 will enable production of very detailed geoid information due to the closer track spacing. This paper presents results from the 35 day geoid product. It includes an evaluation of both the input Waveform Product Data and the improvement in altimeter data quality achieved by the Sea Surface Topography processing sequence.
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