Heading alignment with summarized inertial pose constraints

A discontinuity seems to exist in present aided inertial navigation systems - the operational availability of high cost inertial navigation currently depends on the availability of a valid GPS lock. In general GPS solutions can be two or more orders cheaper than their inertial sensors counterparts. This paper addresses the north alignment by gyrocompassing in the context of more modern smoothing techniques. Incremental smoothing is becoming a serious contender for in-situ state estimation. The work here presents a probabilistic model for north alignment with an analysis towards the achievable accuracy of such a system. A pose graph formulation is used to estimate inertial sensor calibration terms over a long spanning trajectory, from which a true north alignment can be extracted. The preintegral method is used to condense high rate inertial data, but allow for post integration bias correction. Results show that the proposed alignment scheme is feasible, and would for gyrocompassing alignment relaxed sensor performance constraints.