diff options
Diffstat (limited to 'src/pj_deriv.c')
| -rw-r--r-- | src/pj_deriv.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/src/pj_deriv.c b/src/pj_deriv.c new file mode 100644 index 00000000..f6477b08 --- /dev/null +++ b/src/pj_deriv.c @@ -0,0 +1,36 @@ +/* dervative of (*P->fwd) projection */ +#ifndef lint +static const char SCCSID[]="@(#)pj_deriv.c 4.4 93/06/12 GIE REL"; +#endif +#define PJ_LIB__ +#include "projects.h" + int +pj_deriv(LP lp, double h, PJ *P, struct DERIVS *der) { + XY t; + + lp.lam += h; + lp.phi += h; + if (fabs(lp.phi) > HALFPI) return 1; + h += h; + t = (*P->fwd)(lp, P); + if (t.x == HUGE_VAL) return 1; + der->x_l = t.x; der->y_p = t.y; der->x_p = -t.x; der->y_l = -t.y; + lp.phi -= h; + if (fabs(lp.phi) > HALFPI) return 1; + t = (*P->fwd)(lp, P); + if (t.x == HUGE_VAL) return 1; + der->x_l += t.x; der->y_p -= t.y; der->x_p += t.x; der->y_l -= t.y; + lp.lam -= h; + t = (*P->fwd)(lp, P); + if (t.x == HUGE_VAL) return 1; + der->x_l -= t.x; der->y_p -= t.y; der->x_p += t.x; der->y_l += t.y; + lp.phi += h; + t = (*P->fwd)(lp, P); + if (t.x == HUGE_VAL) return 1; + der->x_l -= t.x; der->y_p += t.y; der->x_p -= t.x; der->y_l += t.y; + der->x_l /= (h += h); + der->y_p /= h; + der->x_p /= h; + der->y_l /= h; + return 0; +} |