by cftbq » Tue May 22, 2007 12:10 pm
Lane--don't apologize; detailed discussion is appropriate here!
Now, as I understand it, in addition to the redefinition of the geoid, there were also more accurate measurements. They are doppler radar figures generated by satellites. The old figures are all, ultimately, derived from land-based trigonometric survey values from a survey which was completed in 1929. Aircraft with stereoscopic cameras were used after that to refine intermediate values, but even those refinements still depend on the land-based benchmark figures. The radar measurements are at least capable of a higher degree of precision and, theoretically, this is built in to the results of the National Geodetic Survey (I think that's what it's called). It was actually completed in 1988, but discussions like this are only taking place now mainly because it is such a daunting project to re-do all those maps!
If it turns out that some soft/hard rankings change, then I say so be it. I doubt very seriously that theorder of elevations will change.
Also, as I understand it, while altitude values came up in Colorado, that was an accident due to our placement relative to the redefined geoid, and there may be other places where the new figures are lower than the old ones.
"from mountains high, I gained strength for my soul" --Dave Cousins