1 files changed, 87 insertions, 0 deletions
diff --git a/src/projections/oea.cpp b/src/projections/oea.cpp
new file mode 100644
index 00000000..0c401b2f
--- /dev/null
+++ b/src/projections/oea.cpp
@@ -0,0 +1,87 @@
+#define PJ_LIB__
+#include <errno.h>
+#include "proj.h"
+#include "projects.h"
+#include "proj_math.h"
+
+PROJ_HEAD(oea, "Oblated Equal Area") "\n\tMisc Sph\n\tn= m= theta=";
+
+namespace { // anonymous namespace
+struct pj_opaque {
+    double  theta;
+    double  m, n;
+    double  two_r_m, two_r_n, rm, rn, hm, hn;
+    double  cp0, sp0;
+};
+} // anonymous namespace
+
+
+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 Az, M, N, cp, sp, cl, shz;
+
+    cp = cos(lp.phi);
+    sp = sin(lp.phi);
+    cl = cos(lp.lam);
+    Az = aatan2(cp * sin(lp.lam), Q->cp0 * sp - Q->sp0 * cp * cl) + Q->theta;
+    shz = sin(0.5 * aacos(P->ctx, Q->sp0 * sp + Q->cp0 * cp * cl));
+    M = aasin(P->ctx, shz * sin(Az));
+    N = aasin(P->ctx, shz * cos(Az) * cos(M) / cos(M * Q->two_r_m));
+    xy.y = Q->n * sin(N * Q->two_r_n);
+    xy.x = Q->m * sin(M * Q->two_r_m) * cos(N) / cos(N * Q->two_r_n);
+
+    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 N, M, xp, yp, z, Az, cz, sz, cAz;
+
+    N = Q->hn * aasin(P->ctx,xy.y * Q->rn);
+    M = Q->hm * aasin(P->ctx,xy.x * Q->rm * cos(N * Q->two_r_n) / cos(N));
+    xp = 2. * sin(M);
+    yp = 2. * sin(N) * cos(M * Q->two_r_m) / cos(M);
+    cAz = cos(Az = aatan2(xp, yp) - Q->theta);
+    z = 2. * aasin(P->ctx, 0.5 * hypot(xp, yp));
+    sz = sin(z);
+    cz = cos(z);
+    lp.phi = aasin(P->ctx, Q->sp0 * cz + Q->cp0 * sz * cAz);
+    lp.lam = aatan2(sz * sin(Az),
+        Q->cp0 * cz - Q->sp0 * sz * cAz);
+
+    return lp;
+}
+
+
+
+
+PJ *PROJECTION(oea) {
+    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;
+
+    if (((Q->n = pj_param(P->ctx, P->params, "dn").f) <= 0.) ||
+        ((Q->m = pj_param(P->ctx, P->params, "dm").f) <= 0.)) {
+            return pj_default_destructor(P, PJD_ERR_INVALID_M_OR_N);
+    } else {
+        Q->theta = pj_param(P->ctx, P->params, "rtheta").f;
+        Q->sp0 = sin(P->phi0);
+        Q->cp0 = cos(P->phi0);
+        Q->rn = 1./ Q->n;
+        Q->rm = 1./ Q->m;
+        Q->two_r_n = 2. * Q->rn;
+        Q->two_r_m = 2. * Q->rm;
+        Q->hm = 0.5 * Q->m;
+        Q->hn = 0.5 * Q->n;
+        P->fwd = s_forward;
+        P->inv = s_inverse;
+        P->es = 0.;
+    }
+
+    return P;
+}
+