Techniques for GPS navigation used to determine the position and velocity of a moving object. Pseudorange (PR) measurements and accumulated delta range (ADR) measurements are made at the object from received GPS signals. Differences are computed between ADR measurements that are separated by a time interval that is greater than a time interval between consecutive ADR measurements. Navigational parameters (e.g., position, velocity and clock) are estimated from the PR measurements and the ADR differences. The ADR measurement equations set for herein are formulated in a much more accurate way so that the time interval between the ADR measurements used to compute an ADR difference can be much larger than that used for current ADR differencing techniques in GPS navigation applications. Consequently, the ADR differences are more accurate, which translates into a much more accurate navigation solution. In addition, the ADR differencing technique contributes to shorten convergence times of the Kalman filter processing, and thereby improve the accuracy of spacecraft navigation. Techniques are also provided to extend these highly accurate ADR processing algorithms to integrated GPS/IMU navigation applications, where IMU data is used as an accurate propagation model to propagate the state vector.