New

git-svn-id: http://svn.osgeo.org/metacrs/proj/trunk@776 4e78687f-474d-0410-85f9-8d5e500ac6b2

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;
+}