In this doctoral thesis, the land vehicle low cost GPS/IMU integrated navigation system has been studied. This integrated navigation system consists of MEMS-based inertial measurement unit (IMU), consumer GPS receiver and sensors data processing unit. The IMU comprises three magnetometers, three MEMS automotive grade accelerometers, and three MEMS automotive grade gyroscopes. MEMS technologies are offering lightweight, small size and low-cost sensors. The new MEMS-based inertial navigation is a challenging trend of the developing navigation systems. The integration of a GPS receiver, MEMS inertial sensors and magnetometers together with the use of efficient algorithm of sensors data processing allows obtaining low cost integrated navigation system with better performance. The focus in this research was devoted to the investigation and analysis of the automotive grade inertial sensors data processing algorithms for the aim of improving its performance and achieving tactical grade performance of such GPS/MEMS IMU integrated navigation systems. The design and analysis of such systems is a challenging task that required extensive research and adaptation of data processing algorithms. This thesis contains 197 pages, 219 figures, 37 tables and a reference list of 100 sources. The doctoral thesis consists of an introduction, 8 chapters, a conclusion and references.