Date:         Wed, 1 Mar 2000 08:34:48 -0800
Reply-To:     Davidson <wdavidson@THEGRID.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Davidson <wdavidson@THEGRID.NET>
Subject:      Re: Precision Navigation compass
Comments: To: Greg <yeff@EARTHLINK.NET>
Content-Type: text/plain; charset="iso-8859-1"

I doubt it will really matter much if you set it to true north or magnetic
north...
1.    There appears to be no sighting device integral to the compass.
2.    In most cases you won't be able to drive a bearing since roads will
not cooperate.
3.    And there is the question of alignment of the compass with the forward
direction of the van.
Sure, it's nice to know which one you're using, but with the above factors,
the accuracy of actual in the field use is probably +or- maybe 10 or 15
percent at best.... Even with a handheld compass with a good sighting device
and lots of experience walking a bearing you will likely have an accuracy of
+ or - 5 degrees.
Bill
-----Original Message-----
From: Greg <yeff@EARTHLINK.NET>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Tuesday, February 29, 2000 11:53 PM
Subject: Re: Precision Navigation compass


>Thanks for all the info,
>I Take it I should Set it to True North.
>
>Enjoy,
>Greg
>86 Westy
>
>----- Original Message -----
>From: John Rodgers <inua@HIWAAY.NET>
>To: <vanagon@GERRY.VANAGON.COM>
>Sent: Tuesday, February 29, 2000 8:36 PM
>Subject: Re: Precision Navigation compass
>
>
>> Aeronautical maps are oriented to True North, with degrees of Magnetic
>Variation
>> printed on the chart as either easterly or westerly.. This allows the
>navigator
>> to make compass/navigation corrections.  Alabama is pretty close to the
>"Zero"
>> or"0" degrees magnetic variation line, whereas Alaska ----if memory
>serves.. is
>> something on the order of 15 degrees west.
>>
>> Pilots navigate by flying a course related to true notrh,  and a compass
>heading
>> which is adjusted for magnetic variation in the earth and magnetic
>deviation
>> (compass displacement due to ferrous metals and induced electrical fields
>with
>> in the airplane.).
>>
>> If a pilot flies a true course and a true heading of 360 degrees, with a
>15
>> degree westerly variation and a 5 degree easterly deviation , he must
>first turn
>> his airplane so the compass reads 15 degrees west of  true north or 345
>degrees,
>> then add back 5 degrees of easterly deviation, at which time his compass
>heading
>> will read 350 degrees. That will keep him on a true course of 360
degrees.
>Now
>> if you want to add in the angular vector of the wind......and the
airspeed
>of
>> the airplane and the calculated ground speed of the
>airplane..........!!!!!!
>> Well that's another story.
>>
>> I think most other navigational maps are oriented to true north as well.
>If I
>> recall correctly the true north pole points at the North Star. I can't
>remember
>> if the earths axis is around True north or around the magnetic North. I
do
>> remember they are not in the same place. As a matter of fact the magnetic
>pole
>> moves a bit each year tracing the perimeter of a circle at the top of the
>world.
>>
>> John Rodgers
>> "88GL Driver
>>
>> Greg wrote:
>>
>> > Do you Know if maps use magnetic North or true North?
>> >
>> > ----- Original Message -----
>> > From: Mark McCulley <transporter99@HOTMAIL.COM>
>> > To: <vanagon@GERRY.VANAGON.COM>
>> > Sent: Tuesday, February 29, 2000 1:39 PM
>> > Subject: Re: Precision Navigation compass
>> >
>> > > Not sure exactly what you mean by "adjust compass deviation". You
>first
>> > > calibrate the compass by putting it in CAL mode and driving in two
>> > complete
>> > > circles. You can then set the declination according to your location
>and
>> > > display true north (as opposed to magnetic north). I don't know any
>> > accuracy
>> > > specs but I'm sure this instrument works better than your typical
auto
>> > > compass. The compass can detect when it's off (because of an adjacent
>> > metal
>> > > semi, bridge superstructure, etc.) and displays the word
"Distortion".
>The
>> > > display shows degrees as well as direction (N, ENE, NE, etc.). The
>> > altimeter
>> > > shows only elevation, not barometric pressure. For accuracy you must
>> > > calibrate it at a known elevation (like all altimeters except GPS).
>> > >
>> > > MM
>> > >
>> > >
>> > > >From: David Beierl <dbeierl@IBM.NET>
>> > > >Looks pretty cool -- how do you adjust the compass deviation and how
>> > close
>> > > >can you get it (to my mind, +/- 15 degrees is not too bad for an
>> > automotive
>> > > >compass, but +/- 5 would be really nice)?  How sensitive is the
>> > > >altimeter?  How do you set it?  Will it show barometric pressure as
>well?
>> > > >
>> > > >david
>> > > >David Beierl - Providence, RI
>> > > >  http://pws.prserv.net/synergy/Vanagon/
>> > > >'84 Westy "Dutiful Passage"
>> > > >'85 GL "Poor Relation"
>> > >
>> > > ______________________________________________________
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>> > >
>>
>