1 files changed, 41 insertions, 0 deletions
diff --git a/src/projections/fahey.cpp b/src/projections/fahey.cpp
new file mode 100644
index 00000000..85e0ab69
--- /dev/null
+++ b/src/projections/fahey.cpp
@@ -0,0 +1,41 @@
+#define PJ_LIB__
+
+#include <math.h>
+
+#include "projects.h"
+
+PROJ_HEAD(fahey, "Fahey") "\n\tPcyl, Sph";
+
+#define TOL 1e-6
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    (void) P;
+
+    xy.x = tan(0.5 * lp.phi);
+    xy.y = 1.819152 * xy.x;
+    xy.x = 0.819152 * lp.lam * asqrt(1 - xy.x * xy.x);
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    (void) P;
+
+    xy.y /= 1.819152;
+    lp.phi = 2. * atan(xy.y);
+    xy.y = 1. - xy.y * xy.y;
+    lp.lam = fabs(xy.y) < TOL ? 0. : xy.x / (0.819152 * sqrt(xy.y));
+    return lp;
+}
+
+
+PJ *PROJECTION(fahey) {
+    P->es = 0.;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}