# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Re: Cocked hats, again.**

**From:**Dave Walden

**Date:**2007 Mar 16, 06:07 -0700

An attemp to summarize and establish consensus. Assertions, for equally spaced observations with a common bias and normally distributed uncertainties with the same standard deviation in altitude: 1. The most likely location is the center of the cocked hat. 2. The probability of being within the cocked hat is 25%. 3. The magnitude of the common bias has no effect on the location of the most likely location. 4. Small cocked hats exist that do not contain the true location. 5. Large cocked hats exist that do not contain the true location. Notes: 1. Doesn't say it's there, doesn't say how likely it is to be there (although given the right data, it can be calculated), just says there is no more likely location. (The size of any single cocked hat, a random result, does not provide enough information to establish the standard deviation of the uncertainty in altitude.) 2. I believe this has been conclusively demonstrated in this group probabilistically, statistically, heuristically, by experience and by Monte Carlo. (The somewhat confusing case of the eight is the one where the point lies on the outside of all three lines. It turns out, after some thought, that the most likely location is the center of the cocked hat.) 3. The great advantage of an equally spaced round of sights! A changing common bias opens or closes the hat, but doesn't move its center. 4. and 5. Some examples from a Monte Carlo simulation were given in an earlier post. As was pointed out in a recent post, it is easier for many to conceptualize if you consider all possible cocked hats, rather than try to generalize from one or a few special cases. Or, trying to say it another way, we may be better off to start by not thinking about where the true location is for a given cocked hat, but where the cocked hats are for a given true location. Then, after some thought, we can say some useful things about the first case. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To unsubscribe, send email to NavList-unsubscribe@fer3.com -~----------~----~----~----~------~----~------~--~---