[amsat-bb] Re: Magnetic North vs True North

[jlv]

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" <kl7uw at acsalaska.net>
To: "jlv" <jlv at 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 at 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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