[Proj] NAD 27 v 83 Distances

strebe strebe at aol.com
Fri Oct 1 19:16:53 EST 2010

Makes sense. Thanks.

To confirm, WGS84 isn’t necessarily an improvement over any given regional datum; it just happens to be in this case because the Clarke 1866/NAD27 was extended far beyond its original survey. Correct?

A distance is a distance regardless of bureaucratic fiat. A real distance may not hold up in court… but it might make a gravity wave detector work better. The original inquiry came without context.

— daan Strebe

On Oct 1, 2010, at 3:49:34 PM, "Clifford J Mugnier" <cjmce at lsu.edu> wrote:

There were next to no classical triangulation arcs in California as of 1860.  Therefore, the "fit" by COL Clark was really only to the East coast and west to the Lower Mississippi Valley, at best.  The NAVD88 is off only by a couple of centimeters according to the latest geoid models in Louisiana for NAD83/GRS80.  The  best geoid computed on the Clarke 1866 was an astrogeodetic geoid model computed by Dr. Irene Fisher of Army Map Service in the middle 1960s.  Besides which, the NAD27 was off (internal accuracy) by METERS in California - that's why the National Academy of Science recommended we go to a "new" horizontal datum.
In regard to "legal," if it's not recognized as a "legal" reference, ... what good is it?

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