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#define PJ_LIB__
#include <stdio.h>
#include <stdlib.h>
#include "projects.h"
#include "proj_math.h"
#define MAX_ITERATIONS 10
#define TOL 1e-12
LP nad_cvt(LP in, int inverse, struct CTABLE *ct) {
LP t, tb,del, dif;
int i = MAX_ITERATIONS;
const double toltol = TOL*TOL;
if (in.lam == HUGE_VAL)
return in;
/* normalize input to ll origin */
tb = in;
tb.lam -= ct->ll.lam;
tb.phi -= ct->ll.phi;
tb.lam = adjlon (tb.lam - M_PI) + M_PI;
t = nad_intr (tb, ct);
if (t.lam == HUGE_VAL)
return t;
if (!inverse) {
in.lam -= t.lam;
in.phi += t.phi;
return in;
}
t.lam = tb.lam + t.lam;
t.phi = tb.phi - t.phi;
do {
del = nad_intr(t, ct);
/* This case used to return failure, but I have
changed it to return the first order approximation
of the inverse shift. This avoids cases where the
grid shift *into* this grid came from another grid.
While we aren't returning optimally correct results
I feel a close result in this case is better than
no result. NFW
To demonstrate use -112.5839956 49.4914451 against
the NTv2 grid shift file from Canada. */
if (del.lam == HUGE_VAL)
break;
dif.lam = t.lam - del.lam - tb.lam;
dif.phi = t.phi + del.phi - tb.phi;
t.lam -= dif.lam;
t.phi -= dif.phi;
} while (--i && (dif.lam*dif.lam + dif.phi*dif.phi > toltol)); /* prob. slightly faster than hypot() */
if (i==0) {
/* If we had access to a context, this should go through pj_log, and we should set ctx->errno */
if (getenv ("PROJ_DEBUG"))
fprintf( stderr, "Inverse grid shift iterator failed to converge.\n" );
t.lam = t.phi = HUGE_VAL;
return t;
}
/* and again: pj_log and ctx->errno */
if (del.lam==HUGE_VAL && getenv ("PROJ_DEBUG"))
fprintf (stderr, "Inverse grid shift iteration failed, presumably at grid edge.\nUsing first approximation.\n");
in.lam = adjlon (t.lam + ct->ll.lam);
in.phi = t.phi + ct->ll.phi;
return in;
}
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