--- In BoundaryPoint@yahoogroups.com, "Ron McConnell"
<rcmcc@e...> wrote:

>
> "aletheiak" says,
> "... true mdvawv are in nad83
> nlat 39d19m16s80205 x wlong 77d43m10s14059
>
> What are the other lat/long values?
> I didn't find them in a search of recent digests.
> (Coulda looked right over them.)

no you are right
i have never divulged them publicly before
& thanx very much indeed for your interest & experience here

in fact i am especially gratified to be telling you now that my other
great circle arc terminus was
nlat 39d19m16s17539 x wlong 77d43m10s75219
in equally reliable equally official nad83
because i think you may be uniquely well qualified to most
faithfully evaluate these data in every possible way

& i should also hasten to add that the officially derived horizontal
length of my arc is
79 feet & 6 inches point 7695
to as many decimal places as can be similarly trusted

> Your instinct not to trust them is well justified.
> There are calculators that output
> 12 or more decimal points for lat/long/distance
> of which maybe only the first 4 or 5 are valid.

good thanx
& even that would have been telling in this case
to account for most of the maybe 557742 millionths of an inch of
potential discrepancy
but all of it is cast into great doubt now

i really trust the surveyor guy implicitly all the way to the last digit

> You are obviously using a much better than average
> great circle calculator. The most common, modern
> cosine spherical algorithm chokes long before
> you get as close as 79' 6".
> The ancient haversine spherical formula works fine
> for very close points. There are at least
> two ellipsoidal algorithms, one by Thaddeus Vincenty
> and one by Emmanuel Sodano, that also work,
> supposedly down to millimeters.
> For such very short distances, ordinary plane
> geometry works fine, too. In any case
> one must be very careful with the computer arithmetic
> and the earth radius chosen
> (there are many choices)
> to preserve whatever accuracy one has
> with the latitude and longitude input values.
> Even with WAAS-capable GPS, getting that
> 0.1 second or last few feet are a challenge.
>
> Which great circle calculator(s) do you use?

hah
i wish i could find it again this morning

it is a usda web tool i browsed right up to last night
which gives an atrocious number of decimal places
& i have used it many times in the past too
but it is evidently elusive in daylight or just now

yet no matter since clearly it is you who have the right stuff

> I have my own freeware great circle/geodesic
> calculators on my web site (below)
> with Vincenty, Sodano and spherical
> (great circle and rhumb lines) algorithms.
> I have limited the output distances
> to 3 decimal places (km, miles, nmi)
> since more than that is rarely justified
> by the input latitude and longitude accuracy.
> That is enough to compare results
> among the different calculation methods
> and datum choices for my own curiosity.
>
> The GCGC program also has the Vincenty direct/forward
> algorithm where one can enter
>
> lat1 & long1, azimuth 1-2 and distance 1-2
>
> and get out
>
> lat2 & long2 and azimuth 2-1
>
> GCGC also calculates magnetic/compass bearings
> from true azimuths using the magnetic declination/variation
> offsets from World Magnetic Model
> for the given lat1/long1 and lat2/long2.
>
> It would an easy and quick matter to output
> more decimals, and units in feet, inches, chains, ...
> for comparing such things as official marker locations
> versus actual boundary points
> if anyone is interested.

yes i wish you would do as complete an analysis as you can or
wish
at least on these particular data
since it is quite exciting to see how far we can take this

we appear to be on the leading edge of corroborative technique
here
& this point & many others could benefit from such precision
findings

& i hope you will join us when we actually go to try to find true
mdvawv again too
as it sounds like you must have or know all the right stuff we will
need

remember
we were still at the retractable tape measure level of high tech
at least with regard to mdvawv
before you chimed in
so this is really quite something to hope to so pinpoint our visit

> Cheers, 73,
>
> Ron McC.
> w2iol@a...
>
> Ronald C. McConnell, PhD
>
> WGS-84: N 40º 46' 57.6" +/-0.1"
> W 74º 41' 22.1" +/-0.1"
> FN20ps.77GU31 +/-
> V +5058.3438 H +1504.2531
>
> http://home.earthlink.net/~rcmcc
>
> If a GPS receiver is misplaced,
> but it is turned on and has a lock
> on four or more satellites,
> is it lost?