Different cross-over analysis methods applied to altimetric data in the Mediterranean Sea

This paper deals with the cross-over adjustment method in altimetry .The structure of the observation equation is analyzed and the rank deficiency problem of the corresponding least squares solution is discussed. Three methods have been devised to solve it, and numerical tests have been carried out using altimetric GEOSAT ERM data over the Mediterranean Sea. This example is particularly significant since the application of these methods in closed seas (with short tracks) is different from that in the oceans. The results show the behaviours of the methods which, although theoretically equivalent, lead to slightly different numerical values.