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/Proj4/PJ_nell_h.c

http://github.com/route-me/route-me
C | 33 lines | 32 code | 1 blank | 0 comment | 4 complexity | 0635d053547b2a6de4a674553605e31d MD5 | raw file
    

  1. #ifndef lint
    2. 

  2. static const char SCCSID[]="@(#)PJ_nell_h.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(nell_h, "Nell-Hammer") "\n\tPCyl., Sph.";
    7. 

  7. #define NITER 9
    8. 

  8. #define EPS 1e-7
    9. 

  9. FORWARD(s_forward); /* spheroid */
    10. 

  10. 	xy.x = 0.5 * lp.lam * (1. + cos(lp.phi));
    11. 

  11. 	xy.y = 2.0 * (lp.phi - tan(0.5 *lp.phi));
    12. 

  12. 	return (xy);
    13. 

  13. }
    14. 

  14. INVERSE(s_inverse); /* spheroid */
    15. 

  15. 	double V, c, p;
    16. 

  16. 	int i;
    17. 

  17. 

  18. 	p = 0.5 * xy.y;
    19. 

  19. 	for (i = NITER; i ; --i) {
    20. 

  20. 		c = cos(0.5 * lp.phi);
    21. 

  21. 		lp.phi -= V = (lp.phi - tan(lp.phi/2) - p)/(1. - 0.5/(c*c));
    22. 

  22. 		if (fabs(V) < EPS)
    23. 

  23. 			break;
    24. 

  24. 	}
    25. 

  25. 	if (!i) {
    26. 

  26. 		lp.phi = p < 0. ? -HALFPI : HALFPI;
    27. 

  27. 		lp.lam = 2. * xy.x;
    28. 

  28. 	} else
    29. 

  29. 		lp.lam = 2. * xy.x / (1. + cos(lp.phi));
    30. 

  30. 	return (lp);
    31. 

  31. }
    32. 

  32. FREEUP; if (P) pj_dalloc(P); }
    33. 

  33. ENTRY0(nell_h) P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P)
    34. 

  34.