proj.js

function fx(x, y) {
// Cassini projection
// just a transverse equirectangular projection
// implemented from wikipedia description
d2r = Math.PI / 180;
return Math.asin(Math.sin(x * d2r) * Math.cos(y * d2r));}
function fy(x, y) {
return Math.atan2(Math.sin(y * d2r),
Math.cos(y * d2r) * Math.cos(x * d2r));}