Whenever there is a need for continuous navigation, radio-technical systems are usually integrated with inertial navigation systems (INS) or dead-reckoning systems (DR). Due to large dimensions and power consumption, as well as high prices, INS systems have been traditionally applied in high-end or military applications. Recently an unprecedented decrease of all the above mentioned factors have been witnessed, making inertial navigation suitable for a wider set of applications. However, the dead-reckoning method is still the preferred choice in low-cost land navigation systems.