Several approaches have been made in the context of data assimilation in order to improve the estimates of electron density. The key point is to combine different types of data that offer complementary information, thus allowing to obtain a three dimensional description of the electronic content of the ionosphere. In this paper a data assimilation scheme will be proposed in which the complementarity of information will be given by the ground GPS data (horizontal variation) and vertical profiles derived from ionosonde data (vertical variation). The results of this assimilation scheme will be verified by an external source of data, the GPS data gathered from receiver onboard GPSMET, a low earth orbiter at 750km. This comparison will show the feasability of this assimilation scheme. Moreover it will be shown how this method is able to provide with valuable information about the topside ionosphere by means of comparison with the vertical profiles retrieved from Radio Occultations using Abel inversion. To do this the approach of Abel inversion based on a separability hypothesis will be explained, and it will be compared with the classical approach that assumes spherical symmetry.