NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Deviation Card with GPS
From: Frank Reed CT
Date: 2006 Jul 23, 17:55 -0500
George H, you wrote:
"So what's to be gained by invoking GPS, I ask? Certainly, you are
likely to get into trouble if you compare compass heading with the
course shown by a GPS receiver, under way. What you need, for the
deviation, is to know the heading of the bow. If there's any leeway,
your course through the water will differ from that. If there's any
current, your course over the ground will differ, again, from that,
and that's what the GPS will tell you."
Unless I have misunderstood, they're not talking about using the GPS
receiver's calculation of course based on motion. Instead, you use its built-in
ability to calculate bearings of known objects from your current position. You
enter those known objects as way-points, by sailing up to them and pressing a
button, as Lu Abel suggested, or by keying in the coordinates taken from a
chart. Then wherever you happen to be floating when you decide to check compass
deviation, the GPS will give an extremely accurate true bearing to any of
those way-point objects. It's very simple. And note that your boat can be moving
with a current and it won't do any harm since the bearings are updated
continuously based on present true position.
This whole question, of course, raises the issue of what it means to
navigate by traditional means. Am I cheating the game if I adjust a magnetic compass
using a GPS? Or a sextant with a laser? For some of us, the answer would be
no. For others, yes. I have the sense that the majority of people who enjoy
the sport of traditional navigation have no problem using the latest and
greatest technological tools for adjusting and testing their traditional tools,
but the high-tech is supposed to be left behind while the game is underway.
(apologies in advance if this message turns up twice)
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
From: Frank Reed CT
Date: 2006 Jul 23, 17:55 -0500
George H, you wrote:
"So what's to be gained by invoking GPS, I ask? Certainly, you are
likely to get into trouble if you compare compass heading with the
course shown by a GPS receiver, under way. What you need, for the
deviation, is to know the heading of the bow. If there's any leeway,
your course through the water will differ from that. If there's any
current, your course over the ground will differ, again, from that,
and that's what the GPS will tell you."
Unless I have misunderstood, they're not talking about using the GPS
receiver's calculation of course based on motion. Instead, you use its built-in
ability to calculate bearings of known objects from your current position. You
enter those known objects as way-points, by sailing up to them and pressing a
button, as Lu Abel suggested, or by keying in the coordinates taken from a
chart. Then wherever you happen to be floating when you decide to check compass
deviation, the GPS will give an extremely accurate true bearing to any of
those way-point objects. It's very simple. And note that your boat can be moving
with a current and it won't do any harm since the bearings are updated
continuously based on present true position.
This whole question, of course, raises the issue of what it means to
navigate by traditional means. Am I cheating the game if I adjust a magnetic compass
using a GPS? Or a sextant with a laser? For some of us, the answer would be
no. For others, yes. I have the sense that the majority of people who enjoy
the sport of traditional navigation have no problem using the latest and
greatest technological tools for adjusting and testing their traditional tools,
but the high-tech is supposed to be left behind while the game is underway.
(apologies in advance if this message turns up twice)
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
