REFLECTOR: compass rose

[Laurence Coen]

I am amazed by how you can take something so simple and turn it into a 
government project.  If you want to find magnetic north, use a magnetic 
compass.  That is what they are for.  You can get a good quality sighting 
compass for about $25.  That, two plumb bobs, chalk and some string and 
you're fully equipped to do the job.

Larry Coen
N136LC

--------------------------------------------------
From: "Sid Knox" <sbjknox at earthlink.net>
Sent: Monday, March 23, 2009 10:22 AM
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Subject: Re: REFLECTOR: compass rose

> ----- Original Message ----- 
> From: "Tom" <tomcat05 at comcast.net>
> To: <reflector at tvbf.org>
> Sent: Sunday, March 22, 2009 6:51 PM
> Subject: Re: REFLECTOR: compass rose
>
>
>> You can't beat GPS accuracy. Why not walk a portable instead of trying to 
>> taxi---you can walk it as many times as you'd like for verification. Lay 
>> down some tape for a straight line to walk on and try not to drink 
>> beforehand.
>
>
> That is essentially what I did a couple years ago when my son painted a 
> Rose at our local airport (KTQH Tahlequah OK) for his Eagle Scout project.
>
> 1)  First we did a calibration run or sanity-check by measuring the runway 
> as follows:
> Pick a spot on one end, let the GPS sit there for 15 or 20 minutes to get 
> a good solid fix.  This is point A.  Walk the GPS down the runway about a 
> quarter-mile and let it get a fix there as Point B.  Make sure the GPS is 
> in the Magnetic mode, not True mode.
> Using the published runway heading, confirm that the line from points A 
> and B agrees.  This verifies your technique.
>
> 2)  From the center of the Rose, let the GPS find Point C.  Move the GPS 
> in some convenient direction about a quarter-mile away and let it get a 
> fix there as Point D.  This point must be visable rom the Rose.
>
> 3)  Stand at the far side (relative to point D) of the Rose.  Have another 
> person stand at the center of the Rose.  Have a third person stand at the 
> opposite side of the Rose (between you and Point D).  Move left or right 
> as nesessary such that  the center person is directly in-line with the 
> marker at Point D.
> Using hand gestures, have the person at the opposite side move left or 
> right as nesessary to be on the same line.  Now, with all three of you in 
> line with the C-D line, you have established a reasonably accurate bearing 
> line thru the center of your Rose.  From there, it is just simple trig and 
> careful measurements with a long tape-measure to obtain the remaining Rose 
> points.  Mark your points with tape, chalk or paint spots.
>
> Don't get too hung-up with accuracy... remember the annual drift of the 
> Magnetic Variation.
>
> Sid Knox
> Oklahoma
>
> Velocity  173 RG  N199RS
> Starduster  N666SK
> KR2         N24TC
> W7QJQ
>
>
>
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