The use of altitude constraints within mining navigation

Many navigation problems involve constraints. For example, motor vehicle travel tends to be constrained by road and building boundaries. We consider filtering problems where censuring functions can be used to constrain the measurements. It is established that the ensuing filtered estimates are unbiased, provided that the underlying probability density functions are even and the censuring functions are odd. A loosely-coupled GPS and inertial navigation system (INS) application is discussed in which an integrated solution exhibits improved performance during GPS outages when a priori information is used to constrain the altitude measurements.