1 files changed, 161 insertions, 0 deletions
diff --git a/src/projections/robin.cpp b/src/projections/robin.cpp
new file mode 100644
index 00000000..987977ae
--- /dev/null
+++ b/src/projections/robin.cpp
@@ -0,0 +1,161 @@
+#define PJ_LIB__
+#include "proj_math.h"
+#include "proj_internal.h"
+#include "proj.h"
+#include "projects.h"
+
+PROJ_HEAD(robin, "Robinson") "\n\tPCyl, Sph";
+
+#define V(C,z) (C.c0 + z * (C.c1 + z * (C.c2 + z * C.c3)))
+#define DV(C,z) (C.c1 + z * (C.c2 + C.c2 + z * 3. * C.c3))
+
+/*
+note: following terms based upon 5 deg. intervals in degrees.
+
+Some background on these coefficients is available at:
+
+http://article.gmane.org/gmane.comp.gis.proj-4.devel/6039
+http://trac.osgeo.org/proj/ticket/113
+*/
+
+namespace { // anonymous namespace
+struct COEFS {
+    float c0, c1, c2, c3;
+};
+} // anonymous namespace
+
+static const struct COEFS X[] = {
+    {1.0f, 2.2199e-17f, -7.15515e-05f, 3.1103e-06f},
+    {0.9986f, -0.000482243f, -2.4897e-05f, -1.3309e-06f},
+    {0.9954f, -0.00083103f, -4.48605e-05f, -9.86701e-07f},
+    {0.99f, -0.00135364f, -5.9661e-05f, 3.6777e-06f},
+    {0.9822f, -0.00167442f, -4.49547e-06f, -5.72411e-06f},
+    {0.973f, -0.00214868f, -9.03571e-05f, 1.8736e-08f},
+    {0.96f, -0.00305085f, -9.00761e-05f, 1.64917e-06f},
+    {0.9427f, -0.00382792f, -6.53386e-05f, -2.6154e-06f},
+    {0.9216f, -0.00467746f, -0.00010457f, 4.81243e-06f},
+    {0.8962f, -0.00536223f, -3.23831e-05f, -5.43432e-06f},
+    {0.8679f, -0.00609363f, -0.000113898f, 3.32484e-06f},
+    {0.835f, -0.00698325f, -6.40253e-05f, 9.34959e-07f},
+    {0.7986f, -0.00755338f, -5.00009e-05f, 9.35324e-07f},
+    {0.7597f, -0.00798324f, -3.5971e-05f, -2.27626e-06f},
+    {0.7186f, -0.00851367f, -7.01149e-05f, -8.6303e-06f},
+    {0.6732f, -0.00986209f, -0.000199569f, 1.91974e-05f},
+    {0.6213f, -0.010418f, 8.83923e-05f, 6.24051e-06f},
+    {0.5722f, -0.00906601f, 0.000182f, 6.24051e-06f},
+    {0.5322f, -0.00677797f, 0.000275608f, 6.24051e-06f}
+};
+
+static const struct COEFS Y[] = {
+    {-5.20417e-18f, 0.0124f, 1.21431e-18f, -8.45284e-11f},
+    {0.062f, 0.0124f, -1.26793e-09f, 4.22642e-10f},
+    {0.124f, 0.0124f, 5.07171e-09f, -1.60604e-09f},
+    {0.186f, 0.0123999f, -1.90189e-08f, 6.00152e-09f},
+    {0.248f, 0.0124002f, 7.10039e-08f, -2.24e-08f},
+    {0.31f, 0.0123992f, -2.64997e-07f, 8.35986e-08f},
+    {0.372f, 0.0124029f, 9.88983e-07f, -3.11994e-07f},
+    {0.434f, 0.0123893f, -3.69093e-06f, -4.35621e-07f},
+    {0.4958f, 0.0123198f, -1.02252e-05f, -3.45523e-07f},
+    {0.5571f, 0.0121916f, -1.54081e-05f, -5.82288e-07f},
+    {0.6176f, 0.0119938f, -2.41424e-05f, -5.25327e-07f},
+    {0.6769f, 0.011713f, -3.20223e-05f, -5.16405e-07f},
+    {0.7346f, 0.0113541f, -3.97684e-05f, -6.09052e-07f},
+    {0.7903f, 0.0109107f, -4.89042e-05f, -1.04739e-06f},
+    {0.8435f, 0.0103431f, -6.4615e-05f, -1.40374e-09f},
+    {0.8936f, 0.00969686f, -6.4636e-05f, -8.547e-06f},
+    {0.9394f, 0.00840947f, -0.000192841f, -4.2106e-06f},
+    {0.9761f, 0.00616527f, -0.000256f, -4.2106e-06f},
+    {1.0f, 0.00328947f, -0.000319159f, -4.2106e-06f}
+};
+
+#define FXC 0.8487
+#define FYC 1.3523
+#define C1  11.45915590261646417544
+#define RC1 0.08726646259971647884
+#define NODES   18
+#define ONEEPS  1.000001
+#define EPS 1e-8
+/* 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};
+    long i;
+    double dphi;
+    (void) P;
+
+    dphi = fabs(lp.phi);
+    i = isnan(lp.phi) ? -1 : lround(floor(dphi * C1));
+    if( i < 0 ){
+        proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+        return xy;
+    }
+    if (i >= NODES) i = NODES - 1;
+    dphi = RAD_TO_DEG * (dphi - RC1 * i);
+    xy.x = V(X[i], dphi) * FXC * lp.lam;
+    xy.y = V(Y[i], dphi) * FYC;
+    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};
+    long i;
+    double t, t1;
+    struct COEFS T;
+    int iters;
+
+    lp.lam = xy.x / FXC;
+    lp.phi = fabs(xy.y / FYC);
+    if (lp.phi >= 1.) { /* simple pathologic cases */
+        if (lp.phi > ONEEPS) {
+            proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+            return lp;
+        }
+        else {
+            lp.phi = xy.y < 0. ? -M_HALFPI : M_HALFPI;
+            lp.lam /= X[NODES].c0;
+        }
+    } else { /* general problem */
+        /* in Y space, reduce to table interval */
+        i = isnan(lp.phi) ? -1 : lround(floor(lp.phi * NODES));
+        if( i < 0 || i >= NODES ) {
+            proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+            return lp;
+        }
+        for (;;) {
+            if (Y[i].c0 > lp.phi) --i;
+            else if (Y[i+1].c0 <= lp.phi) ++i;
+            else break;
+        }
+        T = Y[i];
+        /* first guess, linear interp */
+        t = 5. * (lp.phi - T.c0)/(Y[i+1].c0 - T.c0);
+        /* make into root */
+        T.c0 = (float)(T.c0 - lp.phi);
+        for (iters = MAX_ITER; iters ; --iters) { /* Newton-Raphson */
+            t -= t1 = V(T,t) / DV(T,t);
+            if (fabs(t1) < EPS)
+                break;
+        }
+        if( iters == 0 )
+            pj_ctx_set_errno( P->ctx, PJD_ERR_NON_CONVERGENT );
+        lp.phi = (5 * i + t) * DEG_TO_RAD;
+        if (xy.y < 0.) lp.phi = -lp.phi;
+        lp.lam /= V(X[i], t);
+    }
+    return lp;
+}
+
+
+PJ *PROJECTION(robin) {
+    P->es = 0.;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}
+
+