Making an accelerometer precise enough to be useful for dead reckoning on a time frame more than a few hours looks like a big challenge. On a ship another way i

Making an accelerometer precise enough to be useful for dead reckoning on a time frame more than a few hours looks like a big challenge. On a ship another way is available - speed of a ship relative ocean bottom can be measured using Doppler effect (which can be used for dead reckoning). And it likely is more accurate.