(meteorobs) OT- Map question.

[stange]

Hi David, Thank you.

It is all coming together now with the relationships of California maps to 
longitude lines, magnetic declinations of flight maps(Commercial Pilot & 
Instructor et.al., Jeff) and magnetic declination to longitudal lines & maps 
true north rotation.

I need only to carefully plum-bob my 2 closest longitude lines on either 
side of my location to arrive at a close true north to match my camera 
scaling in degrees. Polar star error will be far less than the machined 
molding and markings of this vintage plastic map.

If I had followed Nystroms directions, San Francisco would be off of Bodega 
Bay and my fireballs would be plastering Lake Tahoe Casino's into players 
chips.

YCS.

----- Original Message ----- 
From: "David Entwistle" <David at radiometeor.plus.com>
To: "Global Meteor Observing Forum" <meteorobs at meteorobs.org>
Sent: 2008/12/31 02:36
Subject: Re: (meteorobs) OT- Map question.


> In message <000b01c96abb$fe3cb5f0$27d3d74c at NAMELESSONE>, stange
> <stange34 at sbcglobal.net> writes
>>I have a 1965 raised relief map of California I use to estimate fireball
>>explosion positions. It is a Nystrom "Lambert Conformal Conic Projection" 
>>1:
>>1,000,000.
>>
>>My question is how close are the Longitude lines in (alignment) to TRUE
>>NORTH ?
>>
>>Latitude or elevation is not an issue. Thank you.
>>
>>(I have had varying answers from Nystrom, who suggested aligning the 
>>map(?)
>>with a compass, then rotate the map CCW 16 degrees ). There are no 
>>magnetic
>>declination reference marks on this map. Just latitude and longitude.
>>
>>Larry
>>YCSentinel
>>
>
>
> Hi Larry,
>
> I think there may be some confusion here. To quote from the UK's
> Ordnance Survey web site... True North: the direction of a meridian of
> longitude which converges on the North Pole.
>
> <http://www.ordnancesurvey.co.uk/oswebsite/aboutus/reports/misc/north.htm
> l>
>
> So, lines of longitude are aligned exactly to true north.
>
> Maybe you are thinking of magnetic north and magnetic deviation, which
> does vary from place to place and from time to time?
>
> See also
>
> <http://www.ordnancesurvey.co.uk/oswebsite/gps/information/coordinatesyst
> emsinfo/guidecontents/index.html>
>
> -- 
> David Entwistle
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