/Proj4/pj_deriv.c

http://github.com/route-me/route-me · C · 36 lines · 34 code · 1 blank · 1 comment · 10 complexity · f621de6882d1b00b0f3928c4e4f7e71e MD5 · raw file 

    

  1. /* dervative of (*P->fwd) projection */
    2. 

  2. #ifndef lint
    3. 

  3. static const char SCCSID[]="@(#)pj_deriv.c	4.4	93/06/12	GIE	REL";
    4. 

  4. #endif
    5. 

  5. #define PJ_LIB__
    6. 

  6. #include "projects.h"
    7. 

  7. 	int
    8. 

  8. pj_deriv(LP lp, double h, PJ *P, struct DERIVS *der) {
    9. 

  9. 	XY t;
    10. 

  10. 

  11. 	lp.lam += h;
    12. 

  12. 	lp.phi += h;
    13. 

  13. 	if (fabs(lp.phi) > HALFPI) return 1;
    14. 

  14. 	h += h;
    15. 

  15. 	t = (*P->fwd)(lp, P);
    16. 

  16. 	if (t.x == HUGE_VAL) return 1;
    17. 

  17. 	der->x_l = t.x; der->y_p = t.y; der->x_p = -t.x; der->y_l = -t.y;
    18. 

  18. 	lp.phi -= h;
    19. 

  19. 	if (fabs(lp.phi) > HALFPI) return 1;
    20. 

  20. 	t = (*P->fwd)(lp, P);
    21. 

  21. 	if (t.x == HUGE_VAL) return 1;
    22. 

  22. 	der->x_l += t.x; der->y_p -= t.y; der->x_p += t.x; der->y_l -= t.y;
    23. 

  23. 	lp.lam -= h;
    24. 

  24. 	t = (*P->fwd)(lp, P);
    25. 

  25. 	if (t.x == HUGE_VAL) return 1;
    26. 

  26. 	der->x_l -= t.x; der->y_p -= t.y; der->x_p += t.x; der->y_l += t.y;
    27. 

  27. 	lp.phi += h;
    28. 

  28. 	t = (*P->fwd)(lp, P);
    29. 

  29. 	if (t.x == HUGE_VAL) return 1;
    30. 

  30. 	der->x_l -= t.x; der->y_p += t.y; der->x_p -= t.x; der->y_l += t.y;
    31. 

  31. 	der->x_l /= (h += h);
    32. 

  32. 	der->y_p /= h;
    33. 

  33. 	der->x_p /= h;
    34. 

  34. 	der->y_l /= h;
    35. 

  35. 	return 0;
    36. 

  36. }
    37.