As a preface, I'm pretty new to the world of GIS. I'm working on a personal project to create interactive event timelines over custom maps. Being I'd like to be able to intake a an event location (in Latitude/Longitude values) and place it at the correct point on a map, I'd need to be sure I knew how to convert those Lat/Lon values to the appropriate cartesian coordinates over map image I'm using.
Right now, I'm working with a Gnomonic projection of Europe centered on 51N, 15E, with a edge angle of 15 degrees (admittedly not sure what edge angle means, precisely).
I was originally using the formula laid out here (http://mathworld.wolfram.com/GnomonicProjection.html) to try and convert between lat,lon and x,y - but I'm realizing I have no idea how to take the output X,Y value and transform it into something I can use for this specific map (being it doesn't take into account the center being on Europe, or particular "zoom")
So, to get to the point - do you have any suggestions for programs/libraries I can use to do this conversion for a subset of a map projection? Right now I'm pretty lost as to what steps I'd need to take to get form point A to B - so even an outline of how you might approach the problem would be super enlightening.