1 files changed, 57 insertions, 0 deletions
diff --git a/src/projections/mbt_fps.cpp b/src/projections/mbt_fps.cpp
new file mode 100644
index 00000000..66ed9458
--- /dev/null
+++ b/src/projections/mbt_fps.cpp
@@ -0,0 +1,57 @@
+#define PJ_LIB__
+
+#include <math.h>
+
+#include "projects.h"
+
+PROJ_HEAD(mbt_fps, "McBryde-Thomas Flat-Pole Sine (No. 2)") "\n\tCyl, Sph";
+
+#define MAX_ITER    10
+#define LOOP_TOL    1e-7
+#define C1 0.45503
+#define C2 1.36509
+#define C3 1.41546
+#define C_x 0.22248
+#define C_y 1.44492
+#define C1_2 0.33333333333333333333333333
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    double k, V, t;
+    int i;
+    (void) P;
+
+    k = C3 * sin(lp.phi);
+    for (i = MAX_ITER; i ; --i) {
+        t = lp.phi / C2;
+        lp.phi -= V = (C1 * sin(t) + sin(lp.phi) - k) /
+            (C1_2 * cos(t) + cos(lp.phi));
+        if (fabs(V) < LOOP_TOL)
+            break;
+    }
+    t = lp.phi / C2;
+    xy.x = C_x * lp.lam * (1. + 3. * cos(lp.phi)/cos(t) );
+    xy.y = C_y * sin(t);
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    double t;
+
+    lp.phi = C2 * (t = aasin(P->ctx,xy.y / C_y));
+    lp.lam = xy.x / (C_x * (1. + 3. * cos(lp.phi)/cos(t)));
+    lp.phi = aasin(P->ctx,(C1 * sin(t) + sin(lp.phi)) / C3);
+    return (lp);
+}
+
+
+PJ *PROJECTION(mbt_fps) {
+
+    P->es = 0;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}