Abstract: An altimetric type measurement method for use on a satellite transmits a pulse towards the surface of the sea and carries out frequency transformation on the return signal resulting from the reflection of this pulse at the surface of the sea. This produces a spectral signal of samples successively comprising:(a)--a first zone with a low amplitude level,(b)--a second zone with a sharply increasing slope ending at a peak, and(c)--a third zone of decreasing slope.Samples of the spectral signal are selected within a selection zone that corresponds to the first and second zones for a predetermined maximal level of the height of the waves at the surface of the sea and maximum likelihood processing is applied only to the selected samples.

Abstract: A method of defocusing range ambiguities in a pulse radar, in particular of the SAR type, the method comprising the following steps:radar pulses are spread on transmission by using a plurality of "chirp" rules for varying the frequency of the transmitted wave as a function of time;during transmission of successive pulses, chirp rules are alternated between chirps that rise and chirps that fall in the frequency/time plane of the pulse;received echoes are compressed by matched filtering using a correlation operation between the received echo signal and the chirp rule that was applied at the time of transmission of the pulse that gave rise to said echo signal;said method being characterized in that said plurality of rules for varying the frequency of the transmitted wave as a function of time comprise a number M of said rules, with M being an integer greater than or equal to 3.