NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Round-off
From: John Karl
Date: 2009 May 14, 19:17 -0700
From: John Karl
Date: 2009 May 14, 19:17 -0700
> Frank wrote: > > That's right except for one little detail. Round-off error is a random number taken from a uniform sample distribution. What you want for the step size if not the maximum size of the round-off error, but the standard deviation of that. You'll find that this amounts to 1/sqrt(12) times the width of the round-off band. So if you have a dozen numbers added up where you've dropped the tenths, your expected error is only ONE tenth. > This question is more a matter of navigational philosophy. I subscribe to the old adage that it's most important to know where you are not, i.e., DEFINITELY where you are not. And that's not a matter of statistics. I'm not satisfied to miss reefs only a percentage of the time. So I look at the maximum round off error. Rounding every one of 12 numbers to the nearest whole minute could lead to a maximum error of about 0.4'x12 = 4.8'. Why introduce this possible error when it's completely unnecessary? JK --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---