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Kind of. "Tracking", here, means providing some kind of `f(time) -> space` API. Dead reckoning is a mechanism for incorporating velocity and whatnot into a pr
by hansvm 2y ago
Kind of.
"Tracking", here, means providing some kind of `f(time) -> space` API.
Dead reckoning is a mechanism for incorporating velocity and whatnot into a previously estimated position to estimate a new position (and is also one possible way to implement tracking, usually with compounding errors).
The Kalman filter example is better than just dead reckoning. For a simple example, imagine you're standing still but don't know exactly where. You have an API (like GPS) that can estimate your current position within some tolerance. If you're able to query that API repeatedly and the errors aren't correlated, you can pinpoint your location much more precisely.
Back to tracking with non-zero velocity, every new position estimate (e.g., from GPS) can be incorporated with all the information you've seen so far, adjusting your estimates of velocity, acceleration, and position and giving you a much more accurate current estimate but also better data for dead-reckoning estimates while you wait for your next external signal.
The technique (Kalman Filter) is pretty general. It's just merging all your noisy sources of information according to some ruleset (real-world physics being a common ruleset). You can tack on all sorts of other interesting information, like nearby wifi signals or whatever, and even very noisy signals can aggregate to give precise results.
Another application I threw it at once was estimating my true weight, glycogen reserves, ..., from a variety of noisy measurements. The sky's the limit. You just need multiple measurements and a rule for how they interact.
- jampekka 2y agoThis is a very educational and intuitive way of putting it, but to nitpick the Kalman filter is a very special case of this (it assumes a linear ruleset and Gaussian uncertainties in the sensor readings). What you're describing is in general the Bayesian filter (or Bayesian smoothing if you don't have to give the result immediately).
- hansvm 2y agoYep, that's right. I thought about adding that detail but decided it might detract from the main points. Hopefully anyone interested also sees your comment.