The previous two editions of this classic treatment on GPS played an important role in my classrooms to educate our next generation GNSS experts. This new edition is further strengthened with additional coverage on new GNSS and RNSS including GLONASS, BDS, QZSS, and NavIC as well as recent advances in navigation technologies such as precise point positioning (PPP) and hybrid positioning systems. To address the demands on growing new applications of navigation technology, the book provided a timely coverage on techniques to integrate GNSS with low cost inertial sensors and other RF signals available on mobile devices for indoor and other areas with GNSS signal blockage. I am looking forward to share these and other new materials in this new edition with my students.