This course examines current Global Navigation Satellite Systems (GNSS). The course initially explores how these systems work, and the general requirements levied on navigation systems. A range of augmentation techniques are then examined before the course delves into the linear and extended Kalman filtering techniques that are used to improve navigation performance in the face of noise and bias in several inputs. The course provides an overview of these techniques and is supported by appropriate exercises to illustrate the behaviour or application of each system or technique. Inertial navigation systems are then discussed in order to compare and contrast the systems as well as to be able to discuss combined systems. The course concludes by examining the benefits that estimation techniques provide in real world systems.