[OSRS-PROJ] Significant digits in parameters

[Paul Ramsey]

In reading up on the stateplane definitions, I noticed that some states
defined their units in statute as metres, some defined them as the
american foot, and others as the international foot. The proj4 list uses
the same to_meter in all cases of metres->feet definitions, so it is
possible that we have some misdefinitions here and there in the
stateplane cases. An internation foot is 0.3048 metres precisely. An
american foot is 0.3048006096 metres more-or-less. Only a difference of
6 inches every million units, but it is still a human-scale difference
in alot of parameterizations.

Clifford J Mugnier wrote:
 
> This is not bean-counting, it's Applied Geodesy.  Applied Geodesy is what
> countries use in their legal coordinate systems for defining their
> international boundaries, their private property boundaries, their
> national-provincial boundaries, etc.  It is used everywhere, it's not just
> theory, and it's damned difficult to research.  But it's there, it exists,
> and it ain't theory.
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