/Proj4/PJ_boggs.c

http://github.com/route-me/route-me · C · 35 lines · 34 code · 1 blank · 0 comment · 5 complexity · 28f799b7d226ce44f46aec18807f1565 MD5 · raw file 

    

  1. #ifndef lint
    2. 

  2. static const char SCCSID[]="@(#)PJ_boggs.c	4.1 94/02/15     GIE     REL";
    3. 

  3. #endif
    4. 

  4. #define PJ_LIB__
    5. 

  5. # include	"projects.h"
    6. 

  6. PROJ_HEAD(boggs, "Boggs Eumorphic") "\n\tPCyl., no inv., Sph.";
    7. 

  7. # define NITER	20
    8. 

  8. # define EPS	1e-7
    9. 

  9. # define ONETOL 1.000001
    10. 

  10. # define FXC	2.00276
    11. 

  11. # define FXC2	1.11072
    12. 

  12. # define FYC	0.49931
    13. 

  13. # define FYC2	1.41421356237309504880
    14. 

  14. FORWARD(s_forward); /* spheroid */
    15. 

  15. 	double theta, th1, c;
    16. 

  16. 	int i;
    17. 

  17. 

  18. 	theta = lp.phi;
    19. 

  19. 	if (fabs(fabs(lp.phi) - HALFPI) < EPS)
    20. 

  20. 		xy.x = 0.;
    21. 

  21. 	else {
    22. 

  22. 		c = sin(theta) * PI;
    23. 

  23. 		for (i = NITER; i; --i) {
    24. 

  24. 			theta -= th1 = (theta + sin(theta) - c) /
    25. 

  25. 				(1. + cos(theta));
    26. 

  26. 			if (fabs(th1) < EPS) break;
    27. 

  27. 		}
    28. 

  28. 		theta *= 0.5;
    29. 

  29. 		xy.x = FXC * lp.lam / (1. / cos(lp.phi) + FXC2 / cos(theta));
    30. 

  30. 	}
    31. 

  31. 	xy.y = FYC * (lp.phi + FYC2 * sin(theta));
    32. 

  32. 	return (xy);
    33. 

  33. }
    34. 

  34. FREEUP; if (P) pj_dalloc(P); }
    35. 

  35. ENTRY0(boggs) P->es = 0.; P->fwd = s_forward; ENDENTRY(P)
    36.