Abstract: A method and apparatus for processing data from a positioning or navigation system, such as global positioning system (GPS) navigation system data. In preferred embodiments, the invention is a method and apparatus for estimating position based on GPS measurements and optionally, measurements from other types of navigation sensors combined with GPS navigation system data. The apparatus of the invention includes a point position estimator (which preferably approximates a maximum likelihood estimator) for processing data from a positioning or navigation system to generate point position estimate data, and a smoothing filter for smoothing the point position estimate data. The smoothing filter can be a linear Kalman filter.