One of the developed methods, designated GNSS-derived Path Delay (GPD), determines the tropospheric delay due to the wet component of the troposphere in points that have an invalid MWR correction, using a com-bination of three types of data: MWR measurements at valid points, wet path delays determined at coastal GNSS stations and data provided by a meteorological model such as the one provided by ECMWF. Details about the method can be found in Fernandes et al. (2010) and in Obligis et al.(2011).InFernandes et al. (2010), the application of the method to a region of the SW Europe is presented. Since then, several studies have been conducted to improve some of the adopted procedures and allow a global implementa-tion of the methodology. One of the innovations of this method is the use of tropospheric delays determined by GNSS techniques. Since the atmosphere is a non-dispersive medium at frequencies below 20 GHz (Thayer, 1974), the zenith total delays which affect the GNSS measurements (frequencies in the L band, 1-2 GHz) are also valid for radar altimetry measurements (Ku-band frequencies,