src/projections/eck1.cpp


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#define PJ_LIB__
#include <math.h>

#include "proj.h"
#include "proj_internal.h"

PROJ_HEAD(eck1, "Eckert I") "\n\tPCyl, Sph";
#define FC  0.92131773192356127802
#define RP  0.31830988618379067154


static PJ_XY eck1_s_forward (PJ_LP lp, PJ *P) {           /* Spheroidal, forward */
    PJ_XY xy = {0.0,0.0};
    (void) P;

    xy.x = FC * lp.lam * (1. - RP * fabs(lp.phi));
    xy.y = FC * lp.phi;

    return xy;
}


static PJ_LP eck1_s_inverse (PJ_XY xy, PJ *P) {           /* Spheroidal, inverse */
    PJ_LP lp = {0.0,0.0};
    (void) P;

    lp.phi = xy.y / FC;
    lp.lam = xy.x / (FC * (1. - RP * fabs(lp.phi)));

    return (lp);
}


PJ *PROJECTION(eck1) {
    P->es = 0.0;
    P->inv = eck1_s_inverse;
    P->fwd = eck1_s_forward;

    return P
;
}