ORIGINAL ARTICLE The ionosphere: effects, GPS modeling and the benefits for space geodetic techniques

Abstract The main goal of this paper is to provide a sum-mary of our current knowledge of the ionosphere as it relates to space geodetic techniques, especially the most informa-tive technology, global navigation satellite systems (GNSS), specifically the fully deployed and operational global posi-tioning system (GPS). As such, the main relevant modeling points are discussed, and the corresponding results of ion-ospheric monitoring are related, which were mostly com-puted using GPS data and based on the direct experience of the authors. We address various phenomena such as horizon-tal and vertical ionospheric morphology in quiet conditions, traveling ionospheric disturbances, solar flares, ionospheric storms and scintillation. Finally, we also tackle the question of how improved knowledge of ionospheric conditions, espe-cially in terms of an accurate understanding of the distribu-tion of free electrons, can improve space geodetic techniques at different levels, such as higher-order ionospheric effects