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#define PJ_LIB__
#include <errno.h>
#include "proj.h"
#include <math.h>
#include "proj_internal.h"
PROJ_HEAD(tpeqd, "Two Point Equidistant")
"\n\tMisc Sph\n\tlat_1= lon_1= lat_2= lon_2=";
namespace { // anonymous namespace
struct pj_opaque {
double cp1, sp1, cp2, sp2, ccs, cs, sc, r2z0, z02, dlam2;
double hz0, thz0, rhshz0, ca, sa, lp, lamc;
};
} // anonymous namespace
static PJ_XY tpeqd_s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
PJ_XY xy = {0.0, 0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double t, z1, z2, dl1, dl2, sp, cp;
sp = sin(lp.phi);
cp = cos(lp.phi);
z1 = aacos(P->ctx, Q->sp1 * sp + Q->cp1 * cp * cos (dl1 = lp.lam + Q->dlam2));
z2 = aacos(P->ctx, Q->sp2 * sp + Q->cp2 * cp * cos (dl2 = lp.lam - Q->dlam2));
z1 *= z1;
z2 *= z2;
t = z1 - z2;
xy.x = Q->r2z0 * t;
t = Q->z02 - t;
xy.y = Q->r2z0 * asqrt (4. * Q->z02 * z2 - t * t);
if ((Q->ccs * sp - cp * (Q->cs * sin(dl1) - Q->sc * sin(dl2))) < 0.)
xy.y = -xy.y;
return xy;
}
static PJ_LP tpeqd_s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
PJ_LP lp = {0.0,0.0};
struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
double cz1, cz2, s, d, cp, sp;
cz1 = cos (hypot(xy.y, xy.x + Q->hz0));
cz2 = cos (hypot(xy.y, xy.x - Q->hz0));
s = cz1 + cz2;
d = cz1 - cz2;
lp.lam = - atan2(d, (s * Q->thz0));
lp.phi = aacos(P->ctx, hypot (Q->thz0 * s, d) * Q->rhshz0);
if ( xy.y < 0. )
lp.phi = - lp.phi;
/* lam--phi now in system relative to P1--P2 base equator */
sp = sin (lp.phi);
cp = cos (lp.phi);
lp.lam -= Q->lp;
s = cos(lp.lam);
lp.phi = aasin (P->ctx, Q->sa * sp + Q->ca * cp * s);
lp.lam = atan2 (cp * sin(lp.lam), Q->sa * cp * s - Q->ca * sp) + Q->lamc;
return lp;
}
PJ *PROJECTION(tpeqd) {
double lam_1, lam_2, phi_1, phi_2, A12;
struct pj_opaque *Q = static_cast<struct pj_opaque*>(calloc (1, sizeof (struct pj_opaque)));
if (nullptr==Q)
return pj_default_destructor(P, ENOMEM);
P->opaque = Q;
/* get control point locations */
phi_1 = pj_param(P->ctx, P->params, "rlat_1").f;
lam_1 = pj_param(P->ctx, P->params, "rlon_1").f;
phi_2 = pj_param(P->ctx, P->params, "rlat_2").f;
lam_2 = pj_param(P->ctx, P->params, "rlon_2").f;
if (phi_1 == phi_2 && lam_1 == lam_2)
return pj_default_destructor(P, PJD_ERR_CONTROL_POINT_NO_DIST);
P->lam0 = adjlon (0.5 * (lam_1 + lam_2));
Q->dlam2 = adjlon (lam_2 - lam_1);
Q->cp1 = cos (phi_1);
Q->cp2 = cos (phi_2);
Q->sp1 = sin (phi_1);
Q->sp2 = sin (phi_2);
Q->cs = Q->cp1 * Q->sp2;
Q->sc = Q->sp1 * Q->cp2;
Q->ccs = Q->cp1 * Q->cp2 * sin(Q->dlam2);
Q->z02 = aacos(P->ctx, Q->sp1 * Q->sp2 + Q->cp1 * Q->cp2 * cos (Q->dlam2));
if( Q->z02 == 0.0 ) {
// Actually happens when both lat_1 = lat_2 and |lat_1| = 90
return pj_default_destructor(P, PJD_ERR_LAT_1_OR_2_ZERO_OR_90);
}
Q->hz0 = .5 * Q->z02;
A12 = atan2(Q->cp2 * sin (Q->dlam2),
Q->cp1 * Q->sp2 - Q->sp1 * Q->cp2 * cos (Q->dlam2));
const double pp = aasin(P->ctx, Q->cp1 * sin(A12));
Q->ca = cos(pp);
Q->sa = sin(pp);
Q->lp = adjlon ( atan2 (Q->cp1 * cos(A12), Q->sp1) - Q->hz0);
Q->dlam2 *= .5;
Q->lamc = M_HALFPI - atan2(sin(A12) * Q->sp1, cos(A12)) - Q->dlam2;
Q->thz0 = tan (Q->hz0);
Q->rhshz0 = .5 / sin (Q->hz0);
Q->r2z0 = 0.5 / Q->z02;
Q->z02 *= Q->z02;
P->inv = tpeqd_s_inverse;
P->fwd = tpeqd_s_forward;
P->es = 0.;
return P;
}
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