Re: Separate PK in Jxn Tbl?

-CELKO- <jcelko212_at_earthlink.net> wrote:

>Let's take an example that is a very strong natural key -- (longitude,
>latitude). Established for centuries. Well-defined operations, etc.
>Validation can be done by GPS or a few million maps. Can you explain
>how this immutable key gets changed more often that some "synthetic
>key" for locations?

Datums - NAD27, NAD83, and WGS84.all have slightly different meanings for the same latitude and longitude for North America. http://en.wikipedia.org/wiki/Geodetic_datum

And there are different latitudes http://en.wikipedia.org/wiki/Latitude

Tony

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