REFLECTOR: compass rose

[Alex Balic]

"I am amazed by how you can take something so simple and turn it into a
government project."
Exactly right Larry- could not have said it better myself!!- if you left it
up to the feds, they would have a team of hundreds out there with surveying
equipment- what sort of accuracy do you want on the thing anyway that you
could not get with a magnetic compass? The pole moves about 25 miles/year -
so if you are looking for +/- 1 degree you are wasting time painting the
direction on the ground- just get it lined up with a good quality compass
(although a magnetized needle floating on a cork will point in the exact
same direction)

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Laurence Coen
Sent: Monday, March 23, 2009 6:20 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: compass rose

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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