[Antennas] Using GeoClock To Find True North

Tue, 19 Feb 2002 06:15:13 -0600

As the azimuth and elevation of the sun increase from sunrise to noon
and decrease from noon to sunset a plot of the shadow will describe a
straight segment from west to east of which the perpendicular bisector
will be north/south. Try it!
To do what you describe the sun would have to be at the same elevation
all day and then you would be at the North Pole in summer or South Pole
in winter. 

Jim, N5QL 

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Don Havlicek
Sent: Monday, February 18, 2002 5:41 PM
To: Jim Clark; [email protected]
Subject: Re: [Antennas] Using GeoClock To Find True North

As the sun rises, the tip of the shadow will move from near West to a
point approaching North .. then, after Noon, it will approach East.
Therefore, the segment from 0900 'tip' to 1000 'tip' will be somewhere
along a SW/NE line.  Sooooo .. the permendicular bisector of that
segment will be close to NW/SE !
Don
N8DE

Jim Clark wrote:
> 
> Just a thought
> As the sun "rises" between 9 and 10, the 10 o'clock shadow will be
lower
> and back in the E/W plane, maybe?
> 
> Jim, N5QL
> 
> -----Original Message-----
> From: Don Havlicek [mailto:[email protected]]
> Sent: Monday, February 18, 2002 5:17 PM
> To: Jim Clark
> Cc: [email protected]
> Subject: Re: [Antennas] Using GeoClock To Find True North
> 
> No, no, no .... if the two marks were made at 0900 and 1000, then N/S
> line would be somewhere close to NW/SE !!!!!
> 
> Better to do this:
> 1.  Drive the stick into the ground and mark the end of its shadow at
> some time in the early morning, recording the clocktime.
> 2.  Mark the the end of its shadow again at a time which is the SAME
> AMOUNT AFTER noon that the first mark is BEFORE noon.
> 3.  Now do what you suggest:  the perpendicular bisector of the
segment
> between the two points is APPROXIMATELY the N/S line.
> 4.  Better way:  Use the North Star as someone previously mentioned.
> 5.  Best way:  Use a compass and apply the correct declination
> correction.
> Don
> N8DE
> 
> Jim Clark wrote:
> >
> > This sounds like a job for Indiana Jones or Laura Croft. (I'll take
> > Laura!)
> >
> > Egyptian compass:
> >
> > Pick a nice sunny day.
> > Drive a stick several feet long into the ground straight up.
> > Mark the end of its shadow with a small stick.
> >
> > About an hour or so later mark the shadow's position again.
> > Draw a line between these two points.
> > A line perpendicular to that line is north / south.
> >
> > Jim, N5QL
> >
> >
> >
> > - - -
> >
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> 
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