1 files changed, 40 insertions, 0 deletions
diff --git a/src/projections/crast.cpp b/src/projections/crast.cpp
new file mode 100644
index 00000000..4e4dee8b
--- /dev/null
+++ b/src/projections/crast.cpp
@@ -0,0 +1,40 @@
+#define PJ_LIB__
+#include <math.h>
+
+#include "projects.h"
+
+PROJ_HEAD(crast, "Craster Parabolic (Putnins P4)") "\n\tPCyl, Sph";
+
+#define XM  0.97720502380583984317
+#define RXM 1.02332670794648848847
+#define YM  3.06998012383946546542
+#define RYM 0.32573500793527994772
+#define THIRD   0.333333333333333333
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    (void) P;
+    lp.phi *= THIRD;
+    xy.x = XM * lp.lam * (2. * cos(lp.phi + lp.phi) - 1.);
+    xy.y = YM * sin(lp.phi);
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    (void) P;
+    lp.phi = 3. * asin(xy.y * RYM);
+    lp.lam = xy.x * RXM / (2. * cos((lp.phi + lp.phi) * THIRD) - 1);
+    return lp;
+}
+
+
+PJ *PROJECTION(crast) {
+    P->es = 0.0;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}