NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
How accurate are fixes in practice?
From: Peter Fogg
Date: 2008 Jul 12, 07:46 +1000
From: Peter Fogg
Date: 2008 Jul 12, 07:46 +1000
Bill asked:
"I would appreciate any
real-world input from the list members as to the range and standard
deviation of scatter (under poor to great conditions) they experience."
Jeremy writes:
Ah, such is the luxury of having a relatively stable sea-going platform to work from, plus a generous elevation - more than 100 feet, as I recall?
From a relatively small boat that typically moves in half a dozen different directions all at once, and from an elevation only just above the waves themselves, in average conditions (between 1 and 2 metres of swell) I think a fix is good if it yields a position within 10 nautical miles of the actual position, and excellent if it gets to within 5nm. From this perspective many of the finer points so beloved of armchair navigators just fade away into total insignificance.
However, from a stable and elevated platform I would agree that less than 5nm is to be expected. Would Jeremy be able to distinguish between 1 and 2 metres of swell?
By the way Bill, you haven't answered your own question .. I've heard that Lake Michigan can work up a short nasty swell, particularly down there close to the Windy City ..?
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"I would appreciate any
real-world input from the list members as to the range and standard
deviation of scatter (under poor to great conditions) they experience."
Jeremy writes:
... my "Cutoff" is a rather arbitrary 5 nm.
Ah, such is the luxury of having a relatively stable sea-going platform to work from, plus a generous elevation - more than 100 feet, as I recall?
From a relatively small boat that typically moves in half a dozen different directions all at once, and from an elevation only just above the waves themselves, in average conditions (between 1 and 2 metres of swell) I think a fix is good if it yields a position within 10 nautical miles of the actual position, and excellent if it gets to within 5nm. From this perspective many of the finer points so beloved of armchair navigators just fade away into total insignificance.
However, from a stable and elevated platform I would agree that less than 5nm is to be expected. Would Jeremy be able to distinguish between 1 and 2 metres of swell?
By the way Bill, you haven't answered your own question .. I've heard that Lake Michigan can work up a short nasty swell, particularly down there close to the Windy City ..?
--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
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