[ptx] Projections (was Alternative fisheye projections)

[JD Smith]

On Fri, 2006-04-07 at 22:45 +0200, Pablo d'Angelo wrote:
> JD Smith wrote:
> > On Fri, 2006-04-07 at 00:22 +0200, Pablo d'Angelo wrote:
> > 
> >>Are there any other interesting projections that should be included in
> >>panotools?
> > 
> > Hi Pablo:
> > 
> > Very nice.  Here's a discussion we had on the PanoTools list about what
> > projections might be interesting to add:
> > 
> > http://thread.gmane.org/gmane.comp.graphics.panotools/22701/
> 
> I'll take a look at it.
> 
> Btw. Do you know a page or book that analyses the numerical stability of the
> transforms? the mathworld site doesn't contain such information.

I don't know of any such reference, but I did dig up a library from the
US Geological Survey, which does many types of map transformations:

http://edcftp.cr.usgs.gov/pub//software/gctpc/

The C code is easy to peruse, and includes reference links for various
transformations.  For instance, in the file lamfor.z, I find:

1.  "New Equal-Area Map Projections for Noncircular Regions", John P. Snyder,
    The American Cartographer, Vol 15, No. 4, October 1988, pp. 341-355.

2.  Snyder, John P., "Map Projections--A Working Manual", U.S. Geological
    Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
    State Government Printing Office, Washington D.C., 1987.

3.  "Software Documentation for GCTP General Cartographic Transformation
    Package", U.S. Geological Survey National Mapping Division, May 1982.

I'm not sure how much emphasis they put into numerical stability
concerns, but I do note that they convert Mercator forward differently
than you do.  

JD