Mathematics of Dead Reckoning and drift compensation

Monty Hall wrote:

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

Jerry
--
Engineering is the art of making what you want from things you can get.
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On Sun, 14 Jun 2009 23:12:00 +0000, Monty Hall wrote:


(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?

--
www.wescottdesign.com

Tim Wescott wrote:

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
--
Engineering is the art of making what you want from things you can get.
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