GNSS positioning performance may degrade due to its vulnerability to signal jamming and the limitations in positioning geometry when the sky view is obstructed. Even when an inertial navigation system (INS)/GNSS integration positioning is used, performance gaps may still persist. Pseudolite, as a complement to GPS operations, is integrated with an INS to provide accurate navigation without dependence on GNSS signals. However, the system’s performance indoors remains inferior to its outdoor performance due to the more significant multipath effects in indoor environments. This chapter focuses on precise indoor and outdoor positioning and attitude determination using pseudolite. An “on-the-fly” pseudolite positioning algorithm, which leverages geometric changes through an extended Kalman filter, is introduced. Then, a new navigation algorithm, Position and Attitude Modelling System (PAMS), is presented for processing carrier phase and azimuth measurements using an unscented Kalman filter. Based on this, a “loosely coupled” pseudolite/INS integration architecture is proposed. Finally, experimental results and analysis are provided.