[APG Public List] Regarding GPS

Jay at 1familytree.com wilpolthistory at aol.com
Sun Oct 31 13:51:06 MDT 2010


A few items were mentioned in the last several postings regarding GPS.

> How exactly would one associate a GPS coordinate set with a place name,
> so that it complies with your statement that while "the name of the
> place is changed by changing, evolving, or revisionist history, the GPS
> coordinates of it will never change."   When you wrote "the GPS
> coordinates of it will never change,"  what is the "it" ?

"It" would be the point on the earth of  particular coordinates.

Maybe the cemetery is on the edge of a town today, but next year, the land
and cemetery become part of the neighboring town.....
The coordinates stay the same, the place name changes......how you
personally want to track that is your own decision.

> John responded:
> > I don't mean to harp on this, but it is important to remember, current
> > GPS devices (that I own, anyway) only have an accuracy of +/-15 feet,
> > at best. That isn't quite as accurate as your 10'x10'. :-)
> >


The device has the accuracy, it just doesn't report to you the number of
trailing decimal points in order to show you.

Actually, the various forms of accuracy and monitoring of the various Global
Positioning Satellites create an accuracy of LESS than 12 inches and in some
cases LESS than 4 inches.

(See Wikipedia for more info) ...including
"The phase difference error in the normal GPS amounts to 2–3 metres (6.6–9.8
ft) of ambiguity. CPGPS working to within 1% of perfect transition reduces
this error to 3 centimeters (1.2 in) of ambiguity. By eliminating this error
source, CPGPS coupled with DGPS normally realizes between 20–30 centimetres
*(7.9–12 in*) of absolute accuracy.*Relative Kinematic Positioning* (RKP) is
a third alternative for a precise GPS-based positioning system. In this
approach, determination of range signal can be resolved to a precision of
less than 10 centimeters* (3.9 in).*


To me the intellectual appeal of latitude/longitude or GPS is the
tantalizing thought that perhaps there's an useful universal reference
system for all locations, so one can easily model spatial relationships.
 Numbers are so appealing!   I do love them.   LOL   So, even if GPS
descriptors in this case are less precise, their appeal would lie in the
ease of use and communication to others, compared to my more elaborate
explanation of where my Grandma Nancy's grave is located.   Of course, I
do not have a GPS so it's a moot point, but if I did I think I would
have taken a reading and recorded the info.   just in case.   GPS
references require the user to also have a GPS, which may be an issue at
this point in time, but less of an issue for future researchers.  For
those with a GPS device, it certainly seems to be a useful "finding
aid."   LOL   except in this situation where there *is no physical
marker* just getting to the approximate location is not particularly
useful because there's nothing to see directly representing the grave,
one still would need the info about the reference grave, and the
relative location to that reference.


Every Smart Phone has GPS .... pretty soon every phone will........

times change faster that most of us prepare for.

Who would have imagined that when flying in an airplane you can no longer
buy a drink with CASH......only debit/credit cards allowed!

Use your GPS wherever you can and trust the set(s) of numbers being given to
you.  You will be glad you did not too far down the road.

Best To all,

Jay
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