In this new edition of the book, only minor changes were made to the original nine chapters but three new chapters treat topics of increasing interest to GPS users and equipment developers. One topic, improving the GPS receiver sensitivity may extend their operations into buildings, which is becoming important for emergency rescue and urban warfare. Thus, Chapters 10 and 11 are devoted to the processing of weak signals, as well as the limitations of autonomous GPS receivers. These same approaches are also applicable to GPS receivers in noisy environments and under interference conditions.