Subject: Re: but why suppose an eglysd datum has ever been stated or even can be synthesized
Date: Jan 11, 2006 @ 18:44
Author: aletheiak ("aletheiak" <aletheiak@...>)
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--- In BoundaryPoint@yahoogroups.com, "aletheiak" <aletheiak@y...> wrote:
>
> thank you
> thank hugh
> huge thanxx & hugs
>
> & a few intertwingles follow
>
> --- In BoundaryPoint@yahoogroups.com, "Hugh Wallis" <hugh@o...> wrote:
> >
> > >>because the far greater component of any datum shift
> > displacement
> > both potentially & typically i believe
> > is in the longitude rather than the latitude
> > <<
> >
> > At http://www.colorado.edu/geography/gcraft/notes/datum/edlist.html (a.k.a.
> > http://tinyurl.com/8sexy - a fortunate coincidence - easy to remember at any
> > rate - hope it makes it through eveyone's spam filter) you can see the datum
> > shift from Local to WGS84 for many datums for long and lat in the dx and dy
> > columns (in metres). While the above assertion is true in some cases, if we
> > look at the datums that have typically been used for Egypt (European 1950
> > giving dx = -130 and dy = -117, Old Egyptian 1907 giving dx = -130 and dy =
> > 110), the lat and long displacements are not really "far greater" although
> > they are greater. If we look at those typically used for Sudan (Adindan
> > gving either dx = -166 and dy = -15 or dx = -161 and dy = -14) then they
> > are, however. Libya does not appear in the table.
> >
> > In some parts of the word the shift difference is the other way around -
> > e.g. Indonesia and much of South East Asia, some users of the European 1950
> > datum such as Spain and Portugal, and various remote islands, almost all
> > users of NAD27 i.e., Canada, USA, Central America, much of Eastern Europe
> > using S-42.
> >
> > It seems as though a general statement cannot be made therefore and that
> > every datum comparison needs to be done independently.
>
> you are right
> a general statement cant be made if you drag the exceedingly anomalous & inapplicable
> east indies into this african desert once again
>
> & at the same time you are right on again in having very much corrobrated for us the
full
> extent of practically all the anomalies or variables that are actually applicable here
> for which i am exceedingly grateful
> & which does amply sustain my general statement & approach in this particular case
>
> so i should add to your excerpted swatch above
> & thanx to your attention
> if not far far greater
> as seems far likeliest
> then still unquestionably greater in any case
>
> & therefore
> we can now fully expect eglysd to be noticeably closer
> to the 22nd parallel than the eglys rock is to the 25th meridian
> in any known local datum including most particularly wgs84
>
> even if not absolutely necessarily much closer
> or very much closer
>
>
> & thats the point here
> specifically
> to get as close as possible to eglysd with what we actually do have to go by
> & where anything indonesian etc is almost definitely again a pure mirage
>
> unless you were trying to make a different point that i missed
>
> & one more insert below
>
> > On Brownlie - if anyone has access to a copy, some relevant references are
> > found at http://arabworld.nitle.org/texts.php?module_id=3
> > <http://arabworld.nitle.org/texts.php?module_id=3&reading_id=119&sequence=6>
> > &reading_id=119&sequence=6 (a.k.a. http://tinyurl.com/b89pu ) summarised
> > therin thus: "Libya's eastern borders result from agreements between Egypt
> > and Italy in 1925 and 1926, which superceded (sic) an earlier arrangement
> > between the Ottoman empire and Egypt in 1841, and from agreements in 1934
> > between Britain and Egypt (as the condiminium powers in Sudan) on the one
> > hand and Italy on the other. The latter agreement transferred the Sarra
> > triangle to Libya - the territory allocated to Sudan under the 1899
> > convention and lying to the south of the 22N parallel (Brownlie 1979;
> > 102-109, 133-140).". This secondary (or is it tertiary) source is quite
> > likely accurate, but, of course, may not be complete (which is what you are
> > hoping I guess).
>
> thank you
> this is again very much to the point
> & tho nothing new beyond what we have seen in ibs 10 & 18 & 61
> the fact that you promise 15 more pages gives reason to pursue this anyway
> along with the fact that it is a good decade or 2 more recent than the ibs studies
>
> end inserts
>
> >
> >
> > _____
> >
> > From: BoundaryPoint@yahoogroups.com [mailto:BoundaryPoint@yahoogroups.com]
> > On Behalf Of aletheia kallos
> > Sent: Wednesday, January 11, 2006 11:06 AM
> > To: boundaryPoint@yahoogroups.com
> > Subject: Re: [BoundaryPoint] Re: but why suppose an eglysd datum has ever
> > been stated or even can be synthesized
> >
> >
> > thanxx
> > i appreciate the question no less than the critical
> > review behind it
> > but first
> > with regard to the egsd signs
> > all indications thus far are that they date from the
> > militarily tense early to mid 1990s period
> > so their accuracy was very likely limited by selective
> > availability in any case
> >
> > & regarding egly
> > yes indeed i could & probably should ask this just to
> > rule it out with greater certainty
> > tho i have already given my reasons for doubting there
> > is a bilaterally official datum even there
> > in my previous post
> > to which i should now add that the elusiveness or
> > formlessness of all those so hopefully lovely egly
> > border arcs
> > which arent at all discernible as arcs on any maps i
> > have yet seen
> > is just one more indication of the crudeness & hence
> > datumlessness of the 1927 egly demarcation survey
> >
> > & yikes reason even to doubt that the commissioners
> > would have been proud enough of their handiwork in the
> > wilderness to even plat it out
> > or worry about it in any other way much beyond
> > degmindec or degmindodec
> > let alone degminsec etc
> >
> >
> > but in the meantime i also realized that tho my
> > proposed 487 mile extrapolation from the nearest egly
> > rock would nail the longitude of eglysd with as much
> > precision as that rock itself had already been nailed
> > with
> > it still wouldnt at all necessarily nail the latitude
> > of eglysd any better than we already have it
> >
> > 22nd parallel
> >
> > hahahahaha
> >
> > ahhh
> >
> >
> > nevertheless i believe this will prove to be a smaller
> > shortcoming than one might initially think
> > because the far greater component of any datum shift
> > displacement
> > both potentially & typically i believe
> > is in the longitude rather than the latitude
> > since latitude is first a sidereal fact while
> > longitude is only a terrestrial & far more subjective
> > one
> >
> > meaning all possible versions of the 22nd or any other
> > parallel will bunch up much closer together generally
> > than will all possible versions of the 25th or any
> > other meridian
> >
> >
> > for example the example i think we may have begun with
> >
> > azconmut shifting between nad27 & nad83
> > has 59 meter longitudinal displacement & only 2 meter
> > latitudinal
> > which btw per pythagoras means more than 99point94
> > percent of the distance of any shift there is
> > contributed by the longitudal portion of the shift
> > alone
> >
> > so our range of possible latitude values here at
> > eglysd should be a correspondingly small fraction of
> > the distance from the 25th meridian of the
> > southernmost egly rock
> > in whatever datum it is bagged & or expressed
> >
> > which means
> > using say pilotage gps on the southernmost egly rock
> > we would get the correct submeter wide ribbon of
> > longitude for eglysd in any datum
> > & but only the correct say meter or at most several
> > meter broad ribbon of latitude for it
> >
> > & thus using commercial gps any datum shift in the
> > latitude would most likely be imperceptible
> >
> >
> > & tho i thought of this saving grace shortly before
> > falling asleep last night
> > the confirmation of it came to me in a dream
> > from which i awoke laughing out loud
> >
> > in the dream i had just reached eglysd by car & found
> > a border guard there with his young son who was
> > operating a walkie talkie
> >
> > of course the guard asked me to open my trunk
> > which i did
> > & inside it
> > much to my surprise
> > was his other son
> > an identical twin for all i could tell
> > talking back to them on another walkie talkie
> >
> > hahahahaha
> >
> > & smiling & shaking my head in amazement ever since
> >
> > can you dig it
> >
> >
> > but anyway
> > where do i think we are now
> >
> > i think
> > we are beginning to think mohamed wont answer perhaps
> > because he doesnt know
> > & we are looking for brownlie just to check as much as
> > we can of our guesswork to date
> > as well as to get a better fix on any potential source
> > docs
> >
> > but actually
> > it just occurs to me too
> > since this southernmost egly rock
> > which we are trying to hang our hat on
> > is so beguilingly close to the 29x25 project
> > intersection point
> > why dont we just sponsor a fellowship for some
> > deserving confluencer to bag it for us
> >
> > --- "Lowell G. McManus" <lgm@w...> wrote:
> >
> > > While you're corresponding with them, couldn't you
> > > just ask if there is an
> > > official datum for the delimited but undemarcated
> > > portions of the EGLY boundary
> > > and what datum they used when erecting the
> > > (presumably) unilateral signs on
> > > EGSD? Wouldn't that beat trying to extrapolate from
> > > afar?
> > >
> > > Lowell G. McManus
> > > Leesville, Louisiana, USA
> > >
> > >
> > > ----- Original Message -----
> > > From: "aletheiak" <aletheiak@y...>
> > > To: <BoundaryPoint@yahoogroups.com>
> > > Sent: Tuesday, January 10, 2006 9:36 PM
> > > Subject: [BoundaryPoint] Re: but why suppose an
> > > eglysd datum has ever been
> > > stated or even can be synthesized
> > >
> > >
> > > > aha & far better
> > > > we just ask the egypt border force if it happens
> > > to have gps era survey data
> > > > on this
> > > > southernmost egly marker at any level of
> > > exactitude
> > > > & extrapolate eglysd from it
> > > > aha
> > > > of course
>