Inertial Navigation on Earth... and Beyond


It's all a matter of keeping track of gravity so the system can subtract the buoyant force that accelerometers measure to get the acceleration relative to what we really care about - the surface of the Earth. The direction and magnitude of gravity (and therefore of the buoyant force) changes for predictable reasons - the ship's motion along the earth's surface and towards or away from the center of the earth. If the predictions are accurate, the outputs of the system are accurate, but if the predictions are wrong, errors result - and the characteristics of the errors depend on which predictions are wrong.

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