[Proj] Unknown projection?

[Paul B. Anderson]

- Gerald,

I agree with your comments.

In regard to my comment on Dr. Schmunk -- he mentioned his research to me
during conversations he and I had when discussing various formulas and
reference material I have for use with his 'G.Projector' software. If he is
still monitoring 'Proj' he may respond to our discussion, or you could ask
him via an e-mail about this.

- Paul
On Sat, Sep 13, 2008 at 1:40 PM, Gerald I. Evenden <
geraldi.evenden at gmail.com> wrote:

>  On Saturday 13 September 2008 12:26:58 pm Paul B. Anderson wrote:
> > - Janne,
> >
> > The difficulty comes about because the Tripel is actually composed of 2
> map
> > projections -- the Aitoff (pronounced 'I-toff') projection averaged with
> > the Equirectangular projection (which provides the Special Parallel
> input).
> > Yes, there are inverse formulas out there for the Tripel, but the values
> > produced are approximations.
> >
> > One person who has researched the inverse Winkel Tripel formulas issue is
> > Dr. Robert Schmunk http://www.giss.nasa.gov/staff/rschmunk.html
> >
> > BTW, a reference for this map projection is Snyder's 'Flattening the
> > Earth'.
> >
> > Paul B. Anderson FCCS (USN, Retired)
> > Kingsport, TN native living in Norfolk, VA
> > My Map Projection web site:
> > http://www.csiss.org/map-projections/index.html
> >
> > ----- Original Message -----
> > From: <support.mn at elisanet.fi>
> > To: "PROJ.4 and general Projections Discussions" <
> proj at lists.maptools.org>;
> > <geraldi.evenden at gmail.com>
> > Sent: Saturday, September 13, 2008 11:42 AM
> > Subject: Re: [Proj] Unknown projection?
> >
> > > "Gerald I. Evenden" <geraldi.evenden at gmail.com> kirjoitti:
> > >> On Saturday 13 September 2008 10:59:24 am Paul B. Anderson wrote:
> > >> > - Janne,
> > >> >
> > >> > Your map graphic appears to be in the Winkel Tripel map projection.
> I
> > >> > would
> > >> > also suggest that it is using Oswald Winkel's original selection of
> > >> > 50.46667 degrees as the Special Parallel.
> > >> >
> > >> > Note that by the 1950s John Bartholomew was using a special parallel
> > >> > of 40
> > >> > degrees for his version of the Tripel, giving his graphic a more
> > >> > flattened
> > >> > appearance in the Y direction.
> > >>
> > >> This is exactly why I include the projection math in the manual.  The
> > >> factor Anderson is discussing is +lat_1 option for the +proj=wintri
> > >> projection.  Select your own option value and name a new projection.
> > >> ;-)
> > >
> > > Ok, now the problem seems to be that "wintri" does not have any inverse
> > > projection
> > > available. What is the reason not to have inverse projections for all
> > > routines
> > > in the library... math is too hard?
> > >
> > > Janne.
>
> I can't find any reference on his website to research on Winkel Tripel so I
> suspect he has not published it.
>
> I take back my comment on ease of solution but it would seem to be
> invertible
> using iterative techniques---but slow.  Accuracy should only be dependent
> upon how many cpu ticks you want to give it.
>
> --
> 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
> _______________________________________________
>  Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.maptools.org/pipermail/proj/attachments/20080913/c78d18d4/attachment-0001.html