Comments: This is an example of an interferogram. The imaged area is again the volcano Mount Etna. The difference in the amount of fringes between a 12m and a 60m baseline is shown in the both images. It has to be noted, that a larger baseline is not necessarily better for a good height resolution. First of all, with too much fringes the "counting" of the fringes later on might get a very hard task. Secondly, a certain limit for the baseline is existing, the called "critical baseline". Above this length, no interferometry is possible because spectral decorrelation effects (not part of this presentation).