The contribution of the atmosphere in SAR interferometry is not completely known. Therefore, the goal of the project is to characterise the atmosphere, i.e., to study the way it relates to interferograms. The analysis of the atmospheric parameters that have an inuence on interferometry will cause a better understanding of the atmosphere. One of the objectives is to determine the relationship between interferograms and the refractivity calculated on the Earth's surface, to evaluate whether variations or changes of refractivity involve a change in the interferograms. This work also deals with the analysis of the atmospheric distance of correlation. This distance indicates the maximum separation between two correlated points of the atmosphere. SAR di erential interferometry uses this parameter to extract the component of phase due to the atmosphere, so the calculation of velocities of deformation of the land is better.