Calibration of satellite altimetry

The development of satellite technology has revealed an increased need for tide gauge data. Radar altimeters on board satellites currently reach near-centimetre accuracy for measuring sea level. However, the satellite measurement must be linked to a measurement from a tide gauge located vertical to the orbit due to the sampling method and the poor knowledge of the near-shore geoid. In this case, and for the study of long-term changes in sea level, the geodetic positioning of tide gauges is an absolute necessity.

 

Timbre - poste aérienne TAAF - 1992. Lancement du satellite Topex Poseidon

 

How satellite altimetry works

 

Satellite altimetry is based on the principle of radar: a transmitter and a receiver on a satellite measure round trip travel time, along the vertical path, of electromagnetic pulses reflected from the surface of the sea. The time can be translated into distance based on propagation speed, providing the height of the satellite above the surface with accuracy of a few centimetres. If we know the position of the satellite, we can deduce the position of the surface.

However, there are a number of inherent problems in using the technology and the data provided.

 

Precise positioning of the satellite

 

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