Mathematics of Dead Reckoning and drift compensation

Nathaniel Bowditch: /The American Practical Navigator/. Any edition your library has.

Jerry

(Thanks to Jerry for reminding me of the existence of this rather terse posting).

What are you trying to _do_? Pure "dead reckoning", from my understanding of the term, would indicate that you're making an entirely open-loop estimate of your position from various measurements -- i.e. it's a cloudy day (or week), you forgot the batteries for your GPS receiver, and your watch is busted. If so, then the accuracy of your result is entirely dependent on the size of your aggregate measurement errors.

"Drift compensation" implies that you're making some sorts of measurements some time (your watch started working, perhaps?) and you're trying to estimate your past measurement errors for the purposes of making better measurements in the future. True?

Dead reckoning at sea might estimate distance traveled from a count of propeller turns, accounting for different slip at different RPMs. Drift compensation often involves known currents (gulf stream, etc) and wind if on the surface. Sailors who know the waters they navigate sometimes put tallow in the hollow of the sounding lead (that's why the hollow is there!) and examine and smell the bit of bottom it brings up. Depth also informs.

Jerry