1 files changed, 56 insertions, 0 deletions
diff --git a/src/projections/eck2.cpp b/src/projections/eck2.cpp
new file mode 100644
index 00000000..f76ab4ec
--- /dev/null
+++ b/src/projections/eck2.cpp
@@ -0,0 +1,56 @@
+#define PJ_LIB__
+
+#include <math.h>
+
+#include "proj.h"
+#include "projects.h"
+
+PROJ_HEAD(eck2, "Eckert II") "\n\tPCyl, Sph";
+
+#define FXC     0.46065886596178063902
+#define FYC     1.44720250911653531871
+#define C13     0.33333333333333333333
+#define ONEEPS  1.0000001
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    (void) P;
+
+    xy.x = FXC * lp.lam * (xy.y = sqrt(4. - 3. * sin(fabs(lp.phi))));
+    xy.y = FYC * (2. - xy.y);
+    if ( lp.phi < 0.) xy.y = -xy.y;
+
+    return (xy);
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    (void) P;
+
+    lp.lam = xy.x / (FXC * ( lp.phi = 2. - fabs(xy.y) / FYC) );
+    lp.phi = (4. - lp.phi * lp.phi) * C13;
+    if (fabs(lp.phi) >= 1.) {
+        if (fabs(lp.phi) > ONEEPS) {
+            proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+            return lp;
+        } else {
+            lp.phi = lp.phi < 0. ? -M_HALFPI : M_HALFPI;
+        }
+    } else
+        lp.phi = asin(lp.phi);
+    if (xy.y < 0)
+        lp.phi = -lp.phi;
+    return (lp);
+}
+
+
+
+PJ *PROJECTION(eck2) {
+    P->es = 0.;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}