--- In
BoundaryPoint@yahoogroups.com, "Lowell G. McManus"
<mcmanus71496@m...> wrote:
> I seem to have misconstrued the original quest as pertaining
to tripoints.
>
> If it pertained to [just] points, then I think that the two points
farthest
> apart diametetrically would be the two equatorial or very nearly
equatorial
> antipodes with the greatest combined elevation above sea
level. The bulging
> equatorial diameter would easily overcome any elevational
advantages of
> non-equatorial points. I would nominate some Ecuadorian
peak and its Sumatran
> antipode.
good thinking
i also realized the diametric maximum would fall within the
famous equatorial bulge
just as the diametric minimum would fall within the equally
famous area of polar compression
but have no idea how broad or how locally steep this bulge & this
compression are
like
are they very nearly as linear & perpendicular as the equator &
axis themselves are
being confined to say only a very few degrees of spheroidal arc
or
do they perhaps spread out much more broadly & blend much
more gradually with their surrounding regions until finally
disappearing somewhere around the 45th parallel
if the former
then you must be right on with ecuador & sumatra
& we might proceed to narrow the possibilities further
& if the latter
then we might have to consider peaks of the entire equatorial
region
conceivably even as far afield as the tropics
still guessing wildly here of course
in other words
i do realize lowness of latitude will generally trump height of
altitude
but dont know yet at what latitude this advantage begins to taper
off
so can you think of any way to evaluate these parameters
or to at least bridge the apparent data gap
because i think this additional understanding could be essential
before proceeding further
more below
> The two most circumferentially distant antipodes present an
entirely different
> question. The polar flattening causes the shortest
circumferential routes
> between any two antipodes to be along a great circle through
the poles.
ok but thats the shortest & we want the longest
& does your next statement follow from this
you seem to follow now by saying there are none shorter than
any others
which seems a contradiction of the above
or do both of these propositions make sense independently
On a
> smooth oblate spheroid (an earth without relief), any pair of
antipodes would be
> equally interdistant one from the other. This is because any
imaginable great
> circle connecting them would make two crossings of the
bulging equatorial region
> and two of the flattened polar regions. On the real world, only
the matter of
> elevational relief crossed in the process would differentiate the
distances
> between any pair of antipodes. You would want to pick the
diametrically
> opposite pair of west and east longitudes that cross the
maximum amount of
> continental relief during their circuit of the earth, then choose
any two
> antipodes on that circuit--perhaps something like 70° W and
110° E.
interesting too
tho i am not sure i understand
are you saying here that all circumferential differences are
levelled except for those presented by relief
but in that case it seems to me we face the difficulty of having to
measure in detail the actual terrain crossed by every possible
great circle in the world
or rather not just the difficulty but the ultimate imponderability &
practical impossibility of it
so maybe the supposed answerability of this question actually
evaporates under the heat of scrutiny
but i am sure i dont fully understand this yet
so please clarify further if you can
thanx
end insertions
>
> Lowell G. McManus
> Leesville, Louisiana, USA
>
>
> ----- Original Message -----
> From: "acroorca2002" <orc@o...>
> To: <BoundaryPoint@yahoogroups.com>
> Sent: Wednesday, March 10, 2004 12:41 PM
> Subject: [BoundaryPoint] Re: How far is it?
>
>
> > in bp terms
> > you have improved as well as redeemed what was only a try
> > pointing quest by turning it into an actual tripointing quest
> >
> > moreover your upgraded version is interesting in its own right
> >
> > & it holds forth some promise of being ultimately answerable
too
> >
> >
> > so have a leading pair of candidates suggested themselves
yet
> >
> >
> >
> > & having tried a few things too
> > i can report that the original quest
> > namely
> > which points on earth are farthest apart
> > & exactly how far apart are they
> > remains as hard to make any real headway with as it is hard
to
> > improve upon in curiosity value & elegance
> >
> >
> > --- In BoundaryPoint@yahoogroups.com, "Lowell G.
McManus"
> > <mcmanus71496@m...> wrote:
> > > If one wanted to determine the two tripoints that are farthest
> > apart, one should
> > > first determine which few pairs are the most likely
candidates
> > based on their
> > > relative antipodality from each other. This would take some
> > trial and error.
> > > However, since the antipodes of most continents are
oceanic,
> > there shouldn't be
> > > an abundance of likely candidates.
> > >
> > > Next, the few candidates might have to be evaluated for the
> > effects of the
> > > spheroidicity of the earth and for elevation. The earth is an
> > oblate spheroid,
> > > bulging at the Equator and flattened at the poles. However,
the
> > difference
> > > between sea level diameters pole-to-pole and Equator to
> > Equator is typically
> > > stated in the range of 40 to 43 km. The supposedly most
> > precise model pegs the
> > > figure at 42,952 meters, which is less than 27 miles. On
top of
> > this distance,
> > > elevation could add a few more miles if one found a pair of
> > relatively antipodal
> > > tripoints both in high mountains. Elevation would most
affect
> > diametric
> > > distance and would be much less significant
circumferentially.
> > >
> > > Considering the relative paucity of land-land antipodes and
the
> > relative paucity
> > > of tripoints near the poles, the variations due to
spheriodicity
> > and elevation
> > > above sea level would probably be inconsequential in
> > determining the two most
> > > interdistant tripoints.
> > >
> > > At http://williams.best.vwh.net/gccalc.htm , you will find yet
> > another
> > > great-circle distance calculator into which one can enter the
> > coordinates of any
> > > two points and get their circumferential distance apart.
This
> > calculator
> > > differs from the others in that you can chose from various
> > mathematical models
> > > of the shape of the earth, from perfectly spherical through a
> > number of
> > > spheroidal models. Among these last, the one currently
> > accepted is
> > > WGS84/NAD83/GRS80.
> > >
> > > Lowell G. McManus
> > > Leesville, Louisiana, USA
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: "acroorca2002" <orc@o...>
> > > To: <BoundaryPoint@yahoogroups.com>
> > > Sent: Wednesday, March 10, 2004 8:31 AM
> > > Subject: [BoundaryPoint] Re: How far is it?
> > >
> > >
> > > > really
> > > > i dont remember that
> > > >
> > > > & it is an interesting question
> > > > as well as a challenging try pointing quest
> > > >
> > > > perhaps even 2 of each
> > > > since the farthest pair of points measured
circumferentially
> > > > might not be the same points as the diametrically farthest
> > pair
> > > >
> > > >
> > > > yet exactly how to solve for either set
> > > >
> > > >
> > > >
> > > > alternatively
> > > > someone may already have solved & posted answers for
> > them
> > > >
> > > > so perhaps a prior question is
> > > > exactly how to search for any such ready made answers
> > > >
> > > >
> > > > &or
> > > > failing that
> > > > there must be some data on the geoid already developed
&
> > > > available somewhere that might be useful toward these
> > ends
> > > > if we knew what to look for
> > > >
> > > > like
> > > > greatest circumference & diameter figures might be a
good
> > > > place to start
> > > > since these are likely to have been worked out to some
> > degree
> > > > of specificity & accuracy
> > > >
> > > > but where & how to find them
> > > >
> > > > & could we in fact approach the correct answers via these
> > data
> > > >
> > > > & if so
> > > > by exactly what means could we get there from here
> > > >
> > > >
> > > >
> > > > but can anyone solve or advance this
> > > >
> > > > or even clearly see the right way to go
> > > >
> > > >
> > > > --- In BoundaryPoint@yahoogroups.com, "L. A. Nadybal"
> > > > <lnadybal@c...> wrote:
> > > > > We discussed some time back the maximum distance
that
> > any
> > > > two places
> > > > > on earth could be from one another.
> > > > >
> > > > > This site claims to deliver the distances between two
> > selected
> > > > points:
> > > > >
> > > > > www.indo.com/distance/
> > > > >
> > > > > LN
> > > >
> > > >
> > > >
> > > >
> > > > Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >