[Proj] Projection gs48 error?

Frank Willett fyw at wwwtools.com
Sat Sep 10 08:36:42 PDT 2011


In the routine PJ_mod_ster.c which handles the gs48 projection
the code is:

ENTRY0(gs48)
	static COMPLEX /* 48 United States */
AB[] = {
	{0.98879,	0.},
	{0.,		0.},
	{-0.050909,	0.},
	{0.,		0.},
        {0.075528,	0.}
};

	P->n = 4;
	P->lam0 = DEG_TO_RAD * -96.;
	P->phi0 = DEG_TO_RAD * -39.;
	P->zcoeff = AB;
	P->es = 0.;
	P->a = 6370997.;
ENDENTRY(setup(P))

I believe that phi0 should be +39 instead of -39.

After I made this change and recompiled/linked I ran the
following tests:

$proj +proj=gs48
-96 39
-0.00	-20670.77
$proj -I +proj=gs48
0 -20670.77	
96dW	39d0'0.759"N
$proj -I +proj=gs48
0 0	
168dE	39dN

I would expect the lon/lat at -96,39 to be 0,0 in x/y, and 0,0 x/y
to be at -96,39.

Any help would be greatly appreciated :-)

fyw



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