A system and method for generating a navigation solution in high interference and dynamic environments using Global Positioning System (GPS) and inertial measurement unit (IMU) data is described. The system includes an Advanced Tightly Coupled (ATC) tracking processor for a multi-satellite tracking system. The ATC accepts early, late, and on-time I and Q data from the GPS signal tracker and outputs vehicle-to-satellite range and range rate residual measurements to a navigation Kalman filter. The ATC includes nonlinear discriminators which transform I and Q data into linear residual measurements corrupted by unbiased, additive, and white noise. It also includes an amplitude estimator configured to operate in rapidly changing, high power noise; a measurement noise variance estimator; and a linear residual smoothing filter for input to the navigation filter.