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Bruce S wrote:
"But even if a shorter interval had been used, there would have been a
problem in clearing short distances. Most, if not all, of the popular methods of
clearing were what we call "approximate." That is, they calculated a set of
corrections to apply to the apparent distances. The calculations were based on some
not-exactly-true assumptions. A final correction took care of this. When the
distance got short, this final correction got a bit wild."
The erroneous, archaic expression 'approximate' for these methods refers to a
series expansion. The series expansion and the direct triangle solution are
identical to any desired degree of accuracy. It is simply not true that these
methods were based on 'not-exactly-true assumptions'. They had limits of
applicability like any other practical calculation. It was not difficult to extend
them to shorter distances, but shorter distances were avoided for other
reasons, specifically the non-linear interpolation which Bruce already mentioned but
also the greater requirements for accurate altitudes at those shorter
distances.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
