/Proj4/PJ_eck2.c

http://github.com/route-me/route-me · C · 31 lines · 31 code · 0 blank · 0 comment · 5 complexity · 94bd3e0bb9e2fcd1ba69100bb04aa537 MD5 · raw file

  1. #ifndef lint
  2. static const char SCCSID[]="@(#)PJ_eck2.c 4.1 94/02/15 GIE REL";
  3. #endif
  4. #define PJ_LIB__
  5. # include "projects.h"
  6. PROJ_HEAD(eck2, "Eckert II") "\n\tPCyl. Sph.";
  7. #define FXC 0.46065886596178063902
  8. #define FYC 1.44720250911653531871
  9. #define C13 0.33333333333333333333
  10. #define ONEEPS 1.0000001
  11. FORWARD(s_forward); /* spheroid */
  12. xy.x = FXC * lp.lam * (xy.y = sqrt(4. - 3. * sin(fabs(lp.phi))));
  13. xy.y = FYC * (2. - xy.y);
  14. if ( lp.phi < 0.) xy.y = -xy.y;
  15. return (xy);
  16. }
  17. INVERSE(s_inverse); /* spheroid */
  18. lp.lam = xy.x / (FXC * ( lp.phi = 2. - fabs(xy.y) / FYC) );
  19. lp.phi = (4. - lp.phi * lp.phi) * C13;
  20. if (fabs(lp.phi) >= 1.) {
  21. if (fabs(lp.phi) > ONEEPS) I_ERROR
  22. else
  23. lp.phi = lp.phi < 0. ? -HALFPI : HALFPI;
  24. } else
  25. lp.phi = asin(lp.phi);
  26. if (xy.y < 0)
  27. lp.phi = -lp.phi;
  28. return (lp);
  29. }
  30. FREEUP; if (P) pj_dalloc(P); }
  31. ENTRY0(eck2); P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P)