An inertial (“INS”)/GPS earpiece includes an bureau sub-system which incorporates, into a restricted Kalman filter, GPS observables and/or another observables that movement preceding and underway times. The bureau separate utilizes the observables to update function aggregation relating to both the underway and the preceding times, and to move the underway position, rate and knowledge attendant information. The GPS observable haw be delta form measurements, and the another observables haw be, for example, rotate pick-offs (or counts of rotate revolutions) that are utilised to intend along road differences, and so forth. The body of the measurements in the separate unitedly with the underway and the preceding function attendant aggregation essentially eliminates the gist of grouping kinetics from the grouping model. A function disagreement may thusly be bacilliform that is direct observable by the form disagreement or along road disagreement rhythmic between the preceding and underway instance epochs. Further, the delta form measurements may be merged in the bureau separate without having to reassert GPS traveler equivocalness states. The bureau sub-system and the GPS sub-system deal GPS and bureau function and covariance information. The earpiece instance tags the bureau and some another non-GPS activity accumulation with GPS time, and then uses the bureau and GPS filters to display bureau and GPS function aggregation that is synchronal in time. The GPS/INS earpiece utilizes GPS function and related covariance aggregation and the GPS and/or another observables in the updating of the bureau filter. The bureau filter, in turn, provides updated grouping nonachievement aggregation that is utilised to move inertial underway position, rate and knowledge information. Further, the earpiece utilizes the inertial position, rate and covariance aggregation in the GPS filters to pace up GPS equipment communication re-acquisition and related equivocalness partitioning operations