1 files changed, 97 insertions, 0 deletions
diff --git a/src/projections/putp6.cpp b/src/projections/putp6.cpp
new file mode 100644
index 00000000..1186b18b
--- /dev/null
+++ b/src/projections/putp6.cpp
@@ -0,0 +1,97 @@
+#define PJ_LIB__
+
+#include <errno.h>
+#include <math.h>
+
+#include "projects.h"
+
+namespace { // anonymous namespace
+struct pj_opaque {
+    double C_x, C_y, A, B, D;
+};
+} // anonymous namespace
+
+PROJ_HEAD(putp6, "Putnins P6") "\n\tPCyl, Sph";
+PROJ_HEAD(putp6p, "Putnins P6'") "\n\tPCyl, Sph";
+
+#define EPS      1e-10
+#define NITER    10
+#define CON_POLE 1.732050807568877
+
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double p, r, V;
+    int i;
+
+    p = Q->B * sin(lp.phi);
+    lp.phi *=  1.10265779;
+    for (i = NITER; i ; --i) {
+        r = sqrt(1. + lp.phi * lp.phi);
+        lp.phi -= V = ( (Q->A - r) * lp.phi - log(lp.phi + r) - p ) /
+            (Q->A - 2. * r);
+        if (fabs(V) < EPS)
+            break;
+    }
+    if (!i)
+        lp.phi = p < 0. ? -CON_POLE : CON_POLE;
+    xy.x = Q->C_x * lp.lam * (Q->D - sqrt(1. + lp.phi * lp.phi));
+    xy.y = Q->C_y * lp.phi;
+
+    return xy;
+}
+
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double r;
+
+    lp.phi = xy.y / Q->C_y;
+    r = sqrt(1. + lp.phi * lp.phi);
+    lp.lam = xy.x / (Q->C_x * (Q->D - r));
+    lp.phi = aasin( P->ctx, ( (Q->A - r) * lp.phi - log(lp.phi + r) ) / Q->B);
+
+    return lp;
+}
+
+
+PJ *PROJECTION(putp6) {
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
+    if (nullptr==Q)
+        return pj_default_destructor(P, ENOMEM);
+    P->opaque = Q;
+
+    Q->C_x = 1.01346;
+    Q->C_y = 0.91910;
+    Q->A   = 4.;
+    Q->B   = 2.1471437182129378784;
+    Q->D   = 2.;
+
+    P->es = 0.;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}
+
+
+PJ *PROJECTION(putp6p) {
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
+    if (nullptr==Q)
+        return pj_default_destructor(P, ENOMEM);
+    P->opaque = Q;
+
+    Q->C_x = 0.44329;
+    Q->C_y = 0.80404;
+    Q->A   = 6.;
+    Q->B   = 5.61125;
+    Q->D   = 3.;
+
+    P->es = 0.;
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+
+    return P;
+}