1 files changed, 94 insertions, 0 deletions
diff --git a/src/projections/somerc.cpp b/src/projections/somerc.cpp
new file mode 100644
index 00000000..15d2e765
--- /dev/null
+++ b/src/projections/somerc.cpp
@@ -0,0 +1,94 @@
+#define PJ_LIB__
+
+#include <errno.h>
+#include <math.h>
+
+#include "proj.h"
+#include "projects.h"
+
+PROJ_HEAD(somerc, "Swiss. Obl. Mercator") "\n\tCyl, Ell\n\tFor CH1903";
+
+namespace { // anonymous namespace
+struct pj_opaque {
+    double K, c, hlf_e, kR, cosp0, sinp0;
+};
+} // anonymous namespace
+
+#define EPS 1.e-10
+#define NITER 6
+
+
+static XY e_forward (LP lp, PJ *P) {          /* Ellipsoidal, forward */
+    XY xy = {0.0, 0.0};
+    double phip, lamp, phipp, lampp, sp, cp;
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+
+    sp = P->e * sin (lp.phi);
+    phip = 2.* atan ( exp ( Q->c * (
+        log (tan (M_FORTPI + 0.5 * lp.phi)) - Q->hlf_e * log ((1. + sp)/(1. - sp)))
+        + Q->K)) - M_HALFPI;
+    lamp = Q->c * lp.lam;
+    cp = cos(phip);
+    phipp = aasin (P->ctx, Q->cosp0 * sin (phip) - Q->sinp0 * cp * cos (lamp));
+    lampp = aasin (P->ctx, cp * sin (lamp) / cos (phipp));
+    xy.x = Q->kR * lampp;
+    xy.y = Q->kR * log (tan (M_FORTPI + 0.5 * phipp));
+    return xy;
+}
+
+
+static LP e_inverse (XY xy, PJ *P) {          /* Ellipsoidal, inverse */
+    LP lp = {0.0,0.0};
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+    double phip, lamp, phipp, lampp, cp, esp, con, delp;
+    int i;
+
+    phipp = 2. * (atan (exp (xy.y / Q->kR)) - M_FORTPI);
+    lampp = xy.x / Q->kR;
+    cp = cos (phipp);
+    phip = aasin (P->ctx, Q->cosp0 * sin (phipp) + Q->sinp0 * cp * cos (lampp));
+    lamp = aasin (P->ctx, cp * sin (lampp) / cos (phip));
+    con = (Q->K - log (tan (M_FORTPI + 0.5 * phip)))/Q->c;
+    for (i = NITER; i ; --i) {
+        esp = P->e * sin(phip);
+        delp = (con + log(tan(M_FORTPI + 0.5 * phip)) - Q->hlf_e *
+            log((1. + esp)/(1. - esp)) ) *
+            (1. - esp * esp) * cos(phip) * P->rone_es;
+        phip -= delp;
+        if (fabs(delp) < EPS)
+            break;
+    }
+    if (i) {
+        lp.phi = phip;
+        lp.lam = lamp / Q->c;
+    } else {
+        proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+        return lp;
+    }
+    return (lp);
+}
+
+
+PJ *PROJECTION(somerc) {
+    double cp, phip0, sp;
+    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->hlf_e = 0.5 * P->e;
+    cp = cos (P->phi0);
+    cp *= cp;
+    Q->c = sqrt (1 + P->es * cp * cp * P->rone_es);
+    sp = sin (P->phi0);
+    Q->cosp0 = cos( phip0 = aasin (P->ctx, Q->sinp0 = sp / Q->c) );
+    sp *= P->e;
+    Q->K = log (tan (M_FORTPI + 0.5 * phip0)) - Q->c * (
+        log (tan (M_FORTPI + 0.5 * P->phi0)) - Q->hlf_e *
+        log ((1. + sp) / (1. - sp)));
+    Q->kR = P->k0 * sqrt(P->one_es) / (1. - sp * sp);
+    P->inv = e_inverse;
+    P->fwd = e_forward;
+    return P;
+}