Affiliations: Centre National d'Etudes Spatiales, 18, avenue Ed. Belin, 31401 Toulouse Cedex 9, France E-mail: norbertsuard@cnes.fr | European Space Agency, TEC-EEP, PB 299, NL-2200 AG Noordwijk, The Netherlands E-mail: bertram@tec-ee.esa.int
Abstract: This paper presents briefly the interaction between the ionosphere and the navigation signals, the ionosphere activity with its different effects and when possible a guideline on the different models that encompass the relevant effect.