Quote Originally Posted by mapomatic View Post
Oh. Thanks for the quick reply. Proj4 does sound good, but is there any solution that doesn't require re-compiling a computer program every time I change something, such as a program that can open a definitions file and apply it? I see that Proj4 can use .prj definition files which is a step in the right direction, but it seems that these cannot define the fundamental projection mathematics.

Thank you
I'm not aware of any GIS software that has an integrated CAS type functionality to define projections. I expect such an on the fly custom projection definition would be significantly slower. As it is, defining even a coordinate system based on existing projections is a fairly unusual thing in GIS. That's why it tends to involve writing a Proj4 config string or WKT by hand rather than a discoverable UI with dynamic projection view with Tissots indicatrix or a distortion colour map.