Ed: That is true.
For my position
MONTEVIDEO - URUGUAY
Latitude: 34° 54' 38.2" S
Longitude: 56° 11' 35.9" W
Magnetic declination: 9° 34' WEST
Declination is NEGATIVE
Inclination: -39° 37'
Magnetic field strength: 23116.9 nT
regards
Jose Luis Vila
CX2AN
----- Original Message -----
From: "Edward R. Cole" <kl...@acsalaska.net>
To: "jlv" <j...@fing.edu.uy>
Sent: Thursday, September 08, 2011 1:12 PM
Subject: Re: [amsat-bb] Re: Magnetic North vs True North
At 07:30 AM 9/8/2011, you wrote:
True North
tip:
Look for the magnetic north with the compass, read their geographical
coordinate in the GPS,
use this webpage
http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp
and calculate the magnetic declination for their place.
You will know where this the true north using the magnetic north + / - the
degrees of magnetic declination.
Jose Luis Vila
CX2AN
CX0CFI op.
-----Mensaje original----- From: Luc Leblanc
Sent: Wednesday, September 07, 2011 10:07 AM
To: amsat-bb@amsat.org
Subject: [amsat-bb] Magnetic North vs True North
How i find my north!
At noon always using standard time i pointed the beam in the direction of
top tower pole shadow on the ground. Quite simple and accurate
enough here.
"-"
Luc Leblanc VE2DWE
Skype VE2DWE
www.qsl.net/ve2dwe
DSTAR urcall VE2DWE
WAC BASIC CW PHONE SATELLITE
thanks Jose,
very useful as declination is moving +17min/year here
17deg52min east
I have old aviation maps of the region showing 26-deg declination.
The sun shadow method works only if you know accurately what time solar
noon is. For our time zone it is 2202:52 utc (today) which corresponds to
2:02:52 pm local time. So if you used the shadow at 12:00:00 local time
you would be off considerably from true north. Of course one hour is due
to daylight savings time which advances the clock one hour in summer and
the fact that our local time was permanently advanced by one hour for
political/business reasons (so we would only be +4 hours from EST in the
USA).
This is the reason that one must know true north to orient a sundial.
Sea navigators know they either need to know time precisely to "shoot the
sun" and find their location or know true north to determine the exact
time of meridian crossing at noon.
73, Ed - KL7UW, WD2XSH/45
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