Ionospheric errors are the most influential source of the GPS positioning errors. In an attempt to at least partially improve the GPS positioning process, a global ionospheric correction model is introduced within the standard GPS positioning service. Referred to as the Klobuchar model after its inventor, this model appeared as a compromise between computation complexity and correction accuracy. Unfortunately, the Klobuchar model is capable of correcting up to 70% of ionospheric errors, with particularly poor performance during severe ionospheric disturbances. Wide implementations of satellite navigation systems (GPS in particular) in modern technical systems call for better corrections of the ionospheric influence. This article presents three essential approaches in modelling the GPS ionospheric errors (physical, empirical and dynamic models) and discusses their implementation in GPS-based technical systems.