NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Annual Increase of Variation
From: Rodney Myrvaagnes
Date: 2002 Feb 12, 09:13 -0500
From: Rodney Myrvaagnes
Date: 2002 Feb 12, 09:13 -0500
As one data point for an answer, I laid hands on an expired US chart 12364 publ. July 23, 1994. It is actually a flio or strip chart with several pages between New Haven and Port Jefferson to the East and Throgs Neck (Bronx) to the west. All roses bear the date 1992 for the variation. Both the variation and its rate of change are different for different roses.
Chart 18652-- SF Bay to Antioch, December 1988, has roses dated 1987.
13299 of 1991 has roses dated 1989.
All of these roses show resurvey since the previous edition. I suspect that NOAA vessels or maybe CG cutters plot variation vs position continuously, so the info is available to the HO whenever needed.
On Tue, 12 Feb 2002 14:11:14 +0100, Steven Wepster wrote:
--Original Message Text---
I don't know the policy of the hydrographic
office: whether they update the compass rose only at new editions of a
chart or also at reprints. If the former applies, and no new edition has
occured in 20 years, then you don't see a change in variation on the chart.
Rodney Myrvaagnes J36 Gjo/a
"Religious wisdom is to wisdom as military music is to music."
"What contemptible scoundrel stole the cork from my lunch?" -- W. C Fields
Chart 18652-- SF Bay to Antioch, December 1988, has roses dated 1987.
13299 of 1991 has roses dated 1989.
All of these roses show resurvey since the previous edition. I suspect that NOAA vessels or maybe CG cutters plot variation vs position continuously, so the info is available to the HO whenever needed.
On Tue, 12 Feb 2002 14:11:14 +0100, Steven Wepster wrote:
--Original Message Text---
I don't know the policy of the hydrographic
office: whether they update the compass rose only at new editions of a
chart or also at reprints. If the former applies, and no new edition has
occured in 20 years, then you don't see a change in variation on the chart.
"Religious wisdom is to wisdom as military music is to music."
"What contemptible scoundrel stole the cork from my lunch?" -- W. C Fields
