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

Clifford J Mugnier cjmce at lsu.edu
Wed Jan 29 22:15:37 EST 2003

```Zone 10 is Lambert Conformal Conic (Aleutian Islands) and should return to
the same starting coordinates when going great distances from the central
meridian of zone 10.  Such is NOT the case for Transverse Mercator which is
zones 2-9.

Cliff Mugnier
LOUISIANA STATE UNIVERSITY
------------------------------------
Input    -175.1234589    59.7654305  DD
Return   -4054878.4814   2990301.082 ASP 4 FEET
Input    -4054878.4814   2990301.082 ASP 4 FEET
Return   -175.1487387    59.7638269  DD

"Ed McNierney" <ed at topozone.com>
Sent by: owner-osrs-proj at remotesensing.org

01/29/2003 03:13 PM
Any replies will be addressed to: osrs-proj

To:   <osrs-proj at remotesensing.org>
cc:
Subject:    RE: [OSRS-PROJ] Pseudo X/Y values, forward and reverse

Willy -

Can you provide us with the numbers you're using in your sample?

Are you correctly interpreting and re-entering the lat/lon values?  It
sounds like you could be getting (for example) output lat/lon in degrees
and decimal minutes which is being input as degrees/minutes/seconds.

- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: (978) 251-4242   Fax: (978) 251-1396
ed at topozone.com

-----Original Message-----
From: William Hersman [mailto:Willy.Hersman at conocophillips.com]
Sent: Wednesday, January 29, 2003 6:07 PM
To: osrs-proj at remotesensing.org
Subject: [OSRS-PROJ] Pseudo X/Y values, forward and reverse

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

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