[Proj] Errors in mod_ster

OvV_HN ovv at hetnet.nl
Sun Sep 11 05:03:10 EST 2011

In reply to:

[Proj] Projection gs48 error?
Frank Willett fyw at wwwtools.com
Sat Sep 10 10:36:42 EST 2011


[Proj] Problem with alsk projection
Frank Willett fyw at wwwtools.com
Fri Sep 9 11:17:03 EST 2011

Indeed, there are errors in several sections of PROJs and libprojs mod_ster.
See my posting dated Feb 17, 2008; 9:31am,
subject:  Small errors in modified stereographic

The phi0 in GS48 should be 39.0 instead of -39.0
The value of A3 in Lee should be -0.00881625 (not -0.0088162).
Reference: J. P. Snyder: Map projections, a working manual, PP 1395, Ch. 26, 
p. 209.

Nobody was interested at that time and the errors remained.
I will not "file a ticket" or whatever the bug reporting procedure is 

Why ALSK gives an incorrect answer in some cases, I don't know.
My own mod_ster function is derived from GCTP and its mod_ster function just 
works better.

Oscar van Vlijmen

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