NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Advancing position circles: Huxtable vs. Zevering
From: Philip Bailey
Date: 2006 Sep 20, 19:57 -0500
I was interested to see that the Journal of Navigation have published
(The Journal of Navigation (2006) 59(3), 521) George Huxtable's
comments on K. Herman Zevering's previous article in that journal, as
discussed in June on the old (Nav-L) list. The journal allowed
Zevering a rebuttal.
George has previously explained why Zevering's proposal of simply
translating a position circle given by the observation of one celestial
body, in the direction of travel, to obtain a running fix from a second
observation (possibly of another body), will not give accurate results.
This is because the initial circle would in the general case change
shape in a way apparently not accounted for by Zevering.
George's arguments in the article are clear and appear to be correct;
Zevering's reply conversely is long and opaque. To give a flavour, the
latter's conclusion is given below (meanings of his abbreviations in
brackets):
"The inherent construction principle of RFT/LSQ [running fix
technique/Yallop-Hohenkerk Least-Squares solution program] derives from
terrestrial RFT, which guarantees that the position backward-projected
from the fix will lie on the original position circle. In the
celestial case this construction principle only conforms to GD-UT
[GHA-Dec updating technique] when Zd is small. RFT therefore merely
represents a gimmick performed on the chart whereby the transferred
position line does not actually represent a mathematically correctly
transferred position circle. The properties of a transferred position
circle passing through the RFT/LSQ fixes depend on a given 2nd sight's
properties and in the due-N case it cannot account consistently for the
given run displacement at cardinal position points. The implied GP
transfer matching a particular set of RFT/LSQ fixes is in the general
celestial case contrary to the run data. There is no theoretical
explanation for this."
So what does _that_ mean?!
Philip Bailey
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From: Philip Bailey
Date: 2006 Sep 20, 19:57 -0500
I was interested to see that the Journal of Navigation have published
(The Journal of Navigation (2006) 59(3), 521) George Huxtable's
comments on K. Herman Zevering's previous article in that journal, as
discussed in June on the old (Nav-L) list. The journal allowed
Zevering a rebuttal.
George has previously explained why Zevering's proposal of simply
translating a position circle given by the observation of one celestial
body, in the direction of travel, to obtain a running fix from a second
observation (possibly of another body), will not give accurate results.
This is because the initial circle would in the general case change
shape in a way apparently not accounted for by Zevering.
George's arguments in the article are clear and appear to be correct;
Zevering's reply conversely is long and opaque. To give a flavour, the
latter's conclusion is given below (meanings of his abbreviations in
brackets):
"The inherent construction principle of RFT/LSQ [running fix
technique/Yallop-Hohenkerk Least-Squares solution program] derives from
terrestrial RFT, which guarantees that the position backward-projected
from the fix will lie on the original position circle. In the
celestial case this construction principle only conforms to GD-UT
[GHA-Dec updating technique] when Zd is small. RFT therefore merely
represents a gimmick performed on the chart whereby the transferred
position line does not actually represent a mathematically correctly
transferred position circle. The properties of a transferred position
circle passing through the RFT/LSQ fixes depend on a given 2nd sight's
properties and in the due-N case it cannot account consistently for the
given run displacement at cardinal position points. The implied GP
transfer matching a particular set of RFT/LSQ fixes is in the general
celestial case contrary to the run data. There is no theoretical
explanation for this."
So what does _that_ mean?!
Philip Bailey
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
