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Robinson: fix wrong values for forward path for latitudes >= 87.5 (fixes #1172), and fix inaccurace inverse method #1292

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Merged
kbevers merged 1 commit into from
Feb 24, 2019
+29 −7
Merged

Robinson: fix wrong values for forward path for latitudes >= 87.5 (fixes #1172), and fix inaccurace inverse method #1292

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10 changes: 4 additions & 6 deletions src/projections/robin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
PROJ_HEAD(robin, "Robinson") "\n\tPCyl, Sph";

#define V(C,z) (C.c0 + z * (C.c1 + z * (C.c2 + z * C.c3)))
#define DV(C,z) (C.c1 + z * (C.c2 + C.c2 + z * 3. * C.c3))
#define DV(C,z) (C.c1 + 2 * z * C.c2 + z * z * 3. * C.c3)

/*
note: following terms based upon 5 deg. intervals in degrees.
Expand Down Expand Up @@ -74,7 +74,7 @@ static const struct COEFS Y[] = {
#define RC1 0.08726646259971647884
#define NODES 18
#define ONEEPS 1.000001
#define EPS 1e-8
#define EPS 1e-10
/* Not sure at all of the appropriate number for MAX_ITER... */
#define MAX_ITER 100

Expand All @@ -90,7 +90,7 @@ static PJ_XY s_forward (PJ_LP lp, PJ *P) { /* Spheroidal, forward */
proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
return xy;
}
if (i >= NODES) i = NODES - 1;
if (i >= NODES) i = NODES;
dphi = RAD_TO_DEG * (dphi - RC1 * i);
xy.x = V(X[i], dphi) * FXC * lp.lam;
xy.y = V(Y[i], dphi) * FYC;
Expand Down Expand Up @@ -133,10 +133,8 @@ static PJ_LP s_inverse (PJ_XY xy, PJ *P) { /* Spheroidal, inverse */
T = Y[i];
/* first guess, linear interp */
t = 5. * (lp.phi - T.c0)/(Y[i+1].c0 - T.c0);
/* make into root */
T.c0 = (float)(T.c0 - lp.phi);
for (iters = MAX_ITER; iters ; --iters) { /* Newton-Raphson */
t -= t1 = V(T,t) / DV(T,t);
t -= t1 = (V(T,t) - lp.phi) / DV(T,t);
if (fabs(t1) < EPS)
break;
}
Expand Down
26 changes: 25 additions & 1 deletion test/gie/builtins.gie
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Original file line number Diff line number Diff line change
Expand Up @@ -4438,7 +4438,7 @@ Robinson
===============================================================================

-------------------------------------------------------------------------------
operation +proj=robin +a=6400000 +lat_1=0.5 +lat_2=2
operation +proj=robin +a=6400000
-------------------------------------------------------------------------------
tolerance 0.1 mm
accept 2 1
Expand All @@ -4450,6 +4450,18 @@ expect -189588.423282508 107318.530350703
accept -2 -1
expect -189588.423282508 -107318.530350703

accept 0 89.5
expect 0.000000000000 8639799.718722090125

accept 0 90
expect 0.000000000000 8654720.000000000000

accept 0 -89.5
expect 0.000000000000 -8639799.718722090125

accept 0 -90
expect 0.000000000000 -8654720.000000000000

direction inverse
accept 200 100
expect 0.002109689 0.000931806
Expand All @@ -4460,6 +4472,18 @@ expect -0.002109689 0.000931806
accept -200 -100
expect -0.002109689 -0.000931806

accept 0.000000000000 8639799.718722090125
expect 0 89.5

accept 0.000000000000 8654720.000000000000
expect 0 90

accept 0.000000000000 -8639799.718722090125
expect 0 -89.5

accept 0.000000000000 -8654720.000000000000
expect 0 -90


===============================================================================
Roussilhe Stereographic
Expand Down