[OSRS-PROJ] Pseudo X/Y values, forward and reverse

[William Hersman]

We are struggling with the following problem.  Perhaps someone could
comment.

Alaska has 10 Stateplane zones.  Let's say a point exists in zone 10 and we
want the pseudo x/y for zone 4.  On forward projection the given lat/long
returns x/y values calculated for zone 4. When one then re-inputs the x/y
values into the algorithm to get a lat/long, the inverse does not return to
the same point.  In fact, in terms of feet, it is nearly a mile off !  What
might be going wrong here, and should one expect to be able to "round-trip"
a point when junmping across zones?

Thanks,

Willy Hersman
ConocoPhillips, Alaska

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