GPS positioning, filtering, and integration

This paper explores the possibility of improving navigation solutions and easing integration requirements by using non-linear filters based on direct solutions-to the GPS equations. An alternative approach to navigation with GPS and integration of GPS with other sensor systems is discussed. This two-stage method is based on the use of statistical point estimation. After discussing the underlying concept of two-stage estimation, problems encountered in the statistics of point estimation of position and bias from GPS solutions are surveyed. This is followed by a presentation of a closed form maximum likelihood estimator for position and bias based on the assumption of Gaussian errors. To the authors´ knowledge, this MLE algorithm has not previously been published. Applications to the integration of the GPS with the INS are presented