1 files changed, 97 insertions, 0 deletions
diff --git a/src/projections/natearth2.cpp b/src/projections/natearth2.cpp
new file mode 100644
index 00000000..f6aba671
--- /dev/null
+++ b/src/projections/natearth2.cpp
@@ -0,0 +1,97 @@
+/*
+The Natural Earth II projection was designed by Tom Patterson, US National
+Park Service, in 2012, using Flex Projector. The polynomial equation was
+developed by Bojan Savric and Bernhard Jenny, College of Earth, Ocean,
+and Atmospheric Sciences, Oregon State University.
+Port to PROJ.4 by Bojan Savric, 4 April 2016
+*/
+#define PJ_LIB__
+
+#include <math.h>
+
+#include "projects.h"
+
+PROJ_HEAD(natearth2, "Natural Earth 2") "\n\tPCyl, Sph";
+
+#define A0 0.84719
+#define A1 -0.13063
+#define A2 -0.04515
+#define A3 0.05494
+#define A4 -0.02326
+#define A5 0.00331
+#define B0 1.01183
+#define B1 -0.02625
+#define B2 0.01926
+#define B3 -0.00396
+#define C0 B0
+#define C1 (9 * B1)
+#define C2 (11 * B2)
+#define C3 (13 * B3)
+#define EPS 1e-11
+#define MAX_Y (0.84719 * 0.535117535153096 * M_PI)
+/* Not sure at all of the appropriate number for MAX_ITER... */
+#define MAX_ITER 100
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    double phi2, phi4, phi6;
+    (void) P;
+
+    phi2 = lp.phi * lp.phi;
+    phi4 = phi2 * phi2;
+    phi6 = phi2 * phi4;
+
+    xy.x = lp.lam * (A0 + A1 * phi2 + phi6 * phi6 * (A2 + A3 * phi2 + A4 * phi4 + A5 * phi6));
+    xy.y = lp.phi * (B0 + phi4 * phi4 * (B1 + B2 * phi2 + B3 * phi4));
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    double yc, tol, y2, y4, y6, f, fder;
+    int i;
+    (void) P;
+
+    /* make sure y is inside valid range */
+    if (xy.y > MAX_Y) {
+        xy.y = MAX_Y;
+    } else if (xy.y < -MAX_Y) {
+        xy.y = -MAX_Y;
+    }
+
+    /* latitude */
+    yc = xy.y;
+    for (i = MAX_ITER; i ; --i) { /* Newton-Raphson */
+        y2 = yc * yc;
+        y4 = y2 * y2;
+        f = (yc * (B0 + y4 * y4 * (B1 + B2 * y2 + B3 * y4))) - xy.y;
+        fder = C0 + y4 * y4 * (C1 + C2 * y2 + C3 * y4);
+        yc -= tol = f / fder;
+        if (fabs(tol) < EPS) {
+            break;
+        }
+    }
+    if( i == 0 )
+        pj_ctx_set_errno( P->ctx, PJD_ERR_NON_CONVERGENT );
+    lp.phi = yc;
+
+    /* longitude */
+    y2 = yc * yc;
+    y4 = y2 * y2;
+    y6 = y2 * y4;
+
+    lp.lam = xy.x / (A0 + A1 * y2 + y6 * y6 * (A2 + A3 * y2 + A4 * y4 + A5 * y6));
+
+    return lp;
+}
+
+
+PJ *PROJECTION(natearth2) {
+    P->es = 0;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}