1 files changed, 72 insertions, 0 deletions
diff --git a/src/projections/fouc_s.cpp b/src/projections/fouc_s.cpp
new file mode 100644
index 00000000..c5e711de
--- /dev/null
+++ b/src/projections/fouc_s.cpp
@@ -0,0 +1,72 @@
+#define PJ_LIB__
+
+#include <errno.h>
+#include <math.h>
+
+#include "proj.h"
+#include "projects.h"
+
+PROJ_HEAD(fouc_s, "Foucaut Sinusoidal") "\n\tPCyl, Sph";
+
+#define MAX_ITER    10
+#define LOOP_TOL    1e-7
+
+namespace { // anonymous namespace
+struct pj_opaque {
+    double n, n1;
+};
+} // anonymous namespace
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double t;
+
+    t = cos(lp.phi);
+    xy.x = lp.lam * t / (Q->n + Q->n1 * t);
+    xy.y = Q->n * lp.phi + Q->n1 * sin(lp.phi);
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double V;
+    int i;
+
+    if (Q->n != 0.0) {
+        lp.phi = xy.y;
+        for (i = MAX_ITER; i ; --i) {
+            lp.phi -= V = (Q->n * lp.phi + Q->n1 * sin(lp.phi) - xy.y ) /
+                (Q->n + Q->n1 * cos(lp.phi));
+            if (fabs(V) < LOOP_TOL)
+                break;
+        }
+        if (!i)
+            lp.phi = xy.y < 0. ? -M_HALFPI : M_HALFPI;
+    } else
+        lp.phi = aasin(P->ctx,xy.y);
+    V = cos(lp.phi);
+    lp.lam = xy.x * (Q->n + Q->n1 * V) / V;
+    return lp;
+}
+
+
+PJ *PROJECTION(fouc_s) {
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
+    if (nullptr==Q)
+        return pj_default_destructor (P, ENOMEM);
+    P->opaque = Q;
+
+    Q->n = pj_param(P->ctx, P->params, "dn").f;
+    if (Q->n < 0. || Q->n > 1.)
+        return pj_default_destructor (P, PJD_ERR_N_OUT_OF_RANGE);
+
+    Q->n1 = 1. - Q->n;
+    P->es = 0;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+    return P;
+}