In the scope of the project COASTALT (Development of Radar Altimetry Data Processing in the Oceanic Coastal Zone), funded by the European Space Agency (ESA), methods have been developed by the authors, at University of Porto (U.Porto), for the determination of the path delay caused by the water vapour content in the atmosphere, on satellite altimetry measurements in coastal zones. In these areas, the wet tropospheric correction determined from measurements of microwave radiometers (MWR) on board altimeter satellites, ceases to be valid in a strip of about 50 km wide around the coast, due to the large footprint of the radiometer (circle with 30–50 km in diameter, depending on the MWR frequency).