[APG Public List] Regarding GPS

John Yates john at jytangledweb.org
Mon Nov 1 18:24:45 MDT 2010


On 11/1/2010 2:39 PM, linda at fpr.com wrote:
> Jay replied to a question I had asked John about one of his (John's)
> posts:
>
>>
>> A few items were mentioned in the last several postings regarding GPS.
>>
> [Linda asked John]
>>> How exactly would one associate a GPS coordinate set with a place name,
>>> so that it complies with your [John's] 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 [John] wrote "the GPS
>>> coordinates of it will never change,"  what is the "it" ?
>>
> [Jay answered]
>> "It" would be the point on the earth of  particular coordinates.

Correct.

>>
>
> Jay, when I read John's statement I thought he meant the "it" referred
> to "place."   Restated in my own words, I read his statement to mean
> that while the place names might change [for a variety of reasons] the
> coordinates [for a place] wouldn't, ever.
>
> This does not make any sense to me.  So I asked John questions so that I
> might improve my understanding of what he wrote, including different
> scenarios of name changes, boundary changes, and overlapping boundaries.
>
>
> Your reading of "it" is clearly different than mine.   Only John can
> give further explanation of what he meant when he wrote his statement.

See above.

In a chosen coordinate system, the coordinates of a precise place won't
change. If they do, it exposes a flaw in defining the coordinate system.
Are there flaws in latitude longitude? Yes. One is continental drift.
Sizable over millennia. Not so much in a lifetime. Catastrophic events
like bomb blasts, earthquakes, etc. Possible, but rare.

If we change coordinate systems, there will be a one time, one to one
mapping of the old coordinate pairs to the new coordinates. The place
hasn't moved, just how we describe it.

I pretty much depend on the fact that my house will be at the same
digital location when I come home again. And if I invite someone over
for dinner, all I need to give them is a day, a time, and a pair of
numbers. No other information is required. No city, state, continent,
etc. And yet anyone in the world could find my door. Elegant!

John

> Linda
> ____________
> Linda Gardner
> Massachusetts
>
>


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