diff options
Diffstat (limited to 'src/projections/robin.cpp')
| -rw-r--r-- | src/projections/robin.cpp | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/src/projections/robin.cpp b/src/projections/robin.cpp index 8f142aad..9f7908f6 100644 --- a/src/projections/robin.cpp +++ b/src/projections/robin.cpp @@ -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. @@ -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 @@ -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; @@ -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; } |