[Proj] Problems with Pittman geodesic??

[Gerald I. Evenden]

On Sunday 18 January 2009 11:00:36 pm Hamish wrote:
> Gerald wrote:
> > While checking out the accuracy of Vincenty vs. Pittman
> > I was fairly consistently getting agreement to micron or
> > better.
> >
> > BUT not always!!!
> >
> > I would appreciate anyone who has a Pittman geodesic routine
> > to test the following inverse (WGS84 ellipsoid):
> >
> > point 1 at 0 lat, 0 lon and point 2 at 45N 90E.
> >
> > With my version of Pittman I get a distance of 9993541.5348708
> > AND I get the same distance while changing the longitude of the
> > second point from about 89.6 to a hair over 90.
> >
> > At 0,0/45,89.5:
> > Pittman: 9970963.0100082
> > Vincenty:9970963.01000801
> >
> > At 0,0/45,89.6
> > Pittman: 9993541.5348708
> > Vincenty:9978847.65947167
> >
> > Pittman remained constant in this longitude interval
> >
> > At 0,0/45,90
> > Pittman:  9993541.5348708
> > Vincenty:10010386.3610382
> >
> > Between 90.0000001 and 90.000001 Pittman finally came back
> > into near agreement with Vincenty.
> >
> > Note: I did nothing to the Pittman FORTRAN loaned from Mugnier
> > other than compile it with gfortran and link to a C driver.
>
> I would guess that some internal variable is defined as a REAL (float)
> instead of a DOUBLE PRECISION (double), and so the effect you are seeing
> is quantization due to variable precision.

Both replies, so far seemed to think I was trying to debug the Pittman 
procedures.

I am not interested in fixing the Pittman procedures.  I am asking for anyone 
with the Pittman routines to check if their version has the same problem mine 
has.  My only interest in Pittman is as a comparison to the Vincenty 
procedures because Pittman has been touted as the standard for geodesic 
calculations.

Thank-you.

-- 
The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist