1 files changed, 44 insertions, 0 deletions
diff --git a/src/projections/PJ_gall.cpp b/src/projections/PJ_gall.cpp
new file mode 100644
index 00000000..a8697482
--- /dev/null
+++ b/src/projections/PJ_gall.cpp
@@ -0,0 +1,44 @@
+#define PJ_LIB__
+
+#include <math.h>
+
+#include "projects.h"
+
+PROJ_HEAD(gall, "Gall (Gall Stereographic)") "\n\tCyl, Sph";
+
+#define YF  1.70710678118654752440
+#define XF  0.70710678118654752440
+#define RYF 0.58578643762690495119
+#define RXF 1.41421356237309504880
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    (void) P;
+
+    xy.x = XF * lp.lam;
+    xy.y = YF * tan(.5 * lp.phi);
+
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    (void) P;
+
+    lp.lam = RXF * xy.x;
+    lp.phi = 2. * atan(xy.y * RYF);
+
+    return lp;
+}
+
+
+PJ *PROJECTION(gall) {
+    P->es = 0.0;
+
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}