>
>You mean that along loxodromes the magnetic north is in exactly the
>same direction, or do you mean true north? I thought it was true
>north, actually, but I'm not sure now.
me too but me too
>
>And do you know whether a great circle is measured along the earths
>surface being a perfect sphere? I remember vaguely there is also an
>approximated "earth surface", not the actual one with mountains on
>it, but rather one that takes into account the fact that the earth is
>not a perfect sphere but more "pear-shaped". I can't think of the
>name now though.
would that be the oblate ellipsoid thingie
might affect great circle measurements on the order of 1 percent
or maybe 1 tenth of a percent
wild guessing as usual of course
m
>
>(And I remember vaguely (lots of vague memories)
>that there is an earths surface based on a level of equal gravity.
>But that would have to take into account the different matter inside
>the earth. This is probably beside the point here.)
>
>Peter S.
>
>--- In BoundaryPoint@y..., David Mark <dmark@g...> wrote:
>>
>> The CA-US border (Lake of the Woods to Point Robers) consists of a
>number
>> of "straight" segments between boundary markers, it is sometimes as
>far as
>> 1/4 mile north or south of the 49th parallel.
>>
>> I put "straight" in quotes because of the issue of what constitutes
>a
>> straight line on the earth's surface. The usual definition of the
>> equivalent of a straight line is a great circle. But great circles
>other
>> than meridians and the equator have costantly changing bearings
>(compass
>> directions). Lines of constant compass bearing, known as
>loxodromes, are
>> not shortest paths unless they run north-south or are along the
>equator.
>>
>> David
>>
>> On Thu, 3 May 2001, michael donner wrote:
>>
>> > actually brian has filed the ultimate dissertation on this topic
>> > but it would take a search or a chase goose to get us back to it
>> >
>> > i think one basic point of his tho was that the lines between
>each pair of
>> > monuments are unique great circles
>> > & thus actually none of them ever aligns perfectly with any other
>> >
>> > & this is apart from the slight local irregularities that
>necessarily occur
>> > everywhere a monument is placed
>> >
>> > whether there are more egregious zigzags or offsets than these i
>dont know
>> >
>> > m
>> >
>> >
>> > >
>> > >Interesting about Iraq-Jordan.
>> > >
>> > >My newest atlas show a straight line, but expedia.com shows a
>zig zag.
>> > >
>> > >Is the caus border between Point Roberts and Lake Wood 100%
>straight, or
>> > >are the local irregularities?
>> > >
>> > >Jesper
>> > >----- Original Message -----
>> > >From: "michael donner" <m@...>
>> > >To: <BoundaryPoint@y...>
>> > >Sent: Thursday, May 03, 2001 12:38 AM
>> > >Subject: Re: [BoundaryPoint] Re: Fiat boundaries
>> > >
>> > >
>> > >> peter mentioned
>> > >>
>> > >> >
>> > >> >--- In BoundaryPoint@y..., michael donner <m@d...> wrote:
>> > >> >> & jesper
>> > >> >> of these 5 or 3 singular fiat boundaries we have found
>> > >> >> your chad nigeria line is probably the truest & purest in
>the world
>> > >> >> by virtue of being totally wet as well as probably unmarked
>> > >> >> & therefore almost certainly absolutely undeflected by so
>much as a
>> > >> >single
>> > >> >> subatomic particle
>> > >> >>
>> > >> >> m
>> > >> >
>> > >> >Not deflected, but Lake Chad being a very salty one with
>fluctuating
>> > >> >amounts of water (+salt) in it, there are possibly (also
>fluctuating)
>> > >> >amounts of land that are cut by the boundary.
>> > >>
>> > >> actually it is now a completely dry line
>> > >> as recent photos clearly show in
>> > >>
><<http://www.afrol.com/Categories/Environment/env062_lake_chad.htm>
>http://www.afrol.com/Categories/Environment/env062_lake_chad.htm>
>> > >><http://www.afrol.com/Categories/Environment/env062_lake_chad.htm>
>>http://www.afrol.com/Categories/Environment/env062_lake_chad.htm
>> > >> if you can mentally supply where the border is
>> > >>
>> > >> still being legal but indefinite it remains the most
>pristine of all the
>> > >> singular fiats
>> > >>
>> > >>
>> > >> btw i also just noticed that the iraq jordan boundary
>> > >> 1 of the 2 other best claimants of singular fiathood
>> > >> has recently lapsed into a rather messy de facto zigzag
>> > >> vaguely suggestive of the egypt sudan administrative line
>> > >>
>> > >> so it may well have bitten the dust for any playful purposes
>> > >> & we could now be looking at a world class set with only 2
>members
>> > >> both dry
>> > >> one marked
>> > >>
>> > >> >>
>> > >> >> still cresting on my brendan waves
>> > >> >> & so wishing for the perfect moment point of happy landing
>> > >> >>
>> > >> >
>> > >> >Yes I know what you mean. The viscosity of these waves is
>huge, I
>> > >> >think. What substance is this? No salt water...
>> > >>
>> > >> i think it must be aurora australis concentrate
>> > >>
>> > >> responds shimmeringly to your every thought
>> > >>
>> > >> still dancing across the empyrian on it here too
>> > >>
>> > >> excelsior
>> > >> m
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
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>> > >>
>> > >>
>> > >
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