well doc & dave &al
i think i have finally done it
extracted the ultimate computational truth out of
bcidwa
thanxxx also to you all
but it is still in rather long winded format
so please keep bearing with me
& maybe you can help improve it too
to begin with
cribbing from the comparatively finer but sketchier
table of geodetic constants at lower right in
http://www.convertit.com/Go?ConvertitReference/AMS55.ASP?Res=150Page=8
i have computed the length of a minute of latitude at
the 49th parallel as 1853meters plus 508mm
& borrowing directly from the coarser but busier table
in
http://home.online.no/~sigurdhu/Grid_1deg.htm
i have it as 1853meters plus 500mm
so which is truer
& how many digits are reliable in any case
but no matter
as these are only idle if still interesting questions
since both produce fully significant centisecs of
1 point 01351feet
& thats plenty significant
also
parenthetically
& only for later use
they produce fully significant millisecs of
zero point 101351 foot
but so anyway for starters
this true centisec length in 6 significant digits
rather than just a plain approximate statute foot is
the true breadth of the swath cut by the ibc centisec
coord ribbon between monuments 194 & 195
a n d
in
http://groups.yahoo.com/group/BoundaryPoint/message/14910
i was wrong to needlessly dumb down the plaque coords
to the level of the ibc coords
but by the same token i think it would also be rash to
trust the millisecs expressed on the plaque as
anything more than actual demicentisecs
since their final significant digits are
suspiciously
5 & 0 respectively
& together present a 16 to 1 probability that they are
not significant millisecs at all
but only significant demicentisecs
for these could easily prove to have been ambiguously
&or overconfidently stated on the plaque in nad83
& thus could have been overconfidently converted into
nad27 by me
with 1 full additional significant digit each
as
nlat 48d 59m 57s 357 & wlong 117d 01m 52s 848
when the likelier value ranges 5 full millsecs
between the 355th & 360th millisec actually
of the 58th second of the final minute of the 49th
degree of latitude
in the case of the datum we will need to use here
but by taking into account both the major & the minor
probability & weighting them proportionally
since neither can be dismissed out of hand
& since their relative likelihoods can also be
conveniently & precisely computed
we can indeed now improve the accuracy of the
placement of our intermonumental caus swath across the
idwa meridian no less than we have improved the
accuracy of the measurement of its width
so
recalculating the ratios in
http://groups.yahoo.com/group/BoundaryPoint/message/14912
to the limit of their actual applicability
we find that the centisec swath as stated above in
millifeet would be centered on the idwa meridian
exactly 4 point 7379807692 centisecs south of the
latitude of monument 195
which is to say
at precisely nlat 48d59m57s37262019231
on a flat earth
or comfortably down to the 373rd millisec anyway on
the geoid
& therefore
the center of the truest or at least likeliest
available bcidwa centisec swath of width 1 point 01351
feet
or 12 point 16212 inches
lies between 13 & 18 millisecs north of the 1909 disk
center
or in better words
between 1 point 317563 & 1 point 824318 feet north of
it
or in still easier words to understand
between 15 point 810756 inches north of it
& 21 point 891816 inches north of it
therefore the better of the 2 best available guesses
for true bcidwa is centered 18 point 851286 inches
north of the 1909 disk center
plus or minus 6 point 08106 inches
& the caus centisec swath therefore most
probabalistically crosses the idwa meridian between 12
point 77022 & 24 point 93234 inches north of the 1909
disk center
if however we knew the plaque coords were true
millisecs
an eventuality which is actually a 16 to 1 long shot
we could then confidently say the swath was centered
more nearly exactly 15 millisecs north of the disk
center rather than ranging so crudely 13 to 18
millisecs north of it
& in this event the truest available bcidwa would be
centered 18 point 24318 inches north of it
& thus midway between swath edges lying
12 point 16212 inches north of it
& 24 point 32424 inches north of it
so we can congratulate ourselves twice
once for nailing the major & once for the minor
premise
& for a last hurrah
combining both these premises into one
we get a slightly expanded range
extending a bit more than a full centisec now
between 12 point 16212 inches north of it
& 24 point 93234 inches north of it
but as for the best guessed single point in that range
most interestingly
by weighting & hedging the probabilities at 16 to 1
we get a las vegas betting line & final word at
18 point 81552 inches north of the 1909 disk center
thanx for your patience
& please add on or bust anything you can
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