NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Deviation Card with GPS
From: hellos
Date: 2006 Jul 30, 18:28 -0500
George-
It would seem like the answer lies in a few short sentences in this article:
> Bill mentioned Richard Langley's article, referred to in [894] as-
>
> ""Getting Your Bearings: The Magnetic Compass and GPS":
> <http://gauss.gge.unb.ca/papers.pdf/gpsworld.september03.pdf>
To the effect that the two sensors will each present the same data stream to the
computer, but 90d out of phase. Therefore when the computer compares the two
data streams it can count phase crossings to "count" a full circle. And the rest
apparently has to do with a 4-dimensional equation in which the datastreams
should produce a defined ellipse, with any difference from the predicted shape
being mathematically reolvable (to those four varables) to produce the deviation
error.
In simple words, the fluxgate compass is reaeding and comparing two data streams
and can calculate the deviation from them, with no time base needed, and in fact
only a 90d turn needed for a minimal solution. I assume the 720 slow rate turns
suggested in the instructions that I have seen are there because that gives the
computer better detail to work with, producing a more reliable correction.
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
From: hellos
Date: 2006 Jul 30, 18:28 -0500
George-
It would seem like the answer lies in a few short sentences in this article:
> Bill mentioned Richard Langley's article, referred to in [894] as-
>
> ""Getting Your Bearings: The Magnetic Compass and GPS":
> <http://gauss.gge.unb.ca/papers.pdf/gpsworld.september03.pdf>
To the effect that the two sensors will each present the same data stream to the
computer, but 90d out of phase. Therefore when the computer compares the two
data streams it can count phase crossings to "count" a full circle. And the rest
apparently has to do with a 4-dimensional equation in which the datastreams
should produce a defined ellipse, with any difference from the predicted shape
being mathematically reolvable (to those four varables) to produce the deviation
error.
In simple words, the fluxgate compass is reaeding and comparing two data streams
and can calculate the deviation from them, with no time base needed, and in fact
only a 90d turn needed for a minimal solution. I assume the 720 slow rate turns
suggested in the instructions that I have seen are there because that gives the
computer better detail to work with, producing a more reliable correction.
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
