int gctpc_get_latlon(unsigned char **sec, double **lon, double **lat) {
int gdt;
unsigned char *gds;
double r_maj; /* major axis */
double r_min; /* minor axis */
double lat1; /* first standard parallel */
double lat2; /* second standard parallel */
double c_lon; /* center longitude */
double c_lat; /* center latitude */
double false_east; /* x offset in meters */
double false_north;
double dx, dy;
double x0, y0;
long int (*inv_fn)();
double *llat, *llon, rlon, rlat;
int i, nnx, nny, nres, nscan;
unsigned int nnpnts;
long long_i;
gdt = code_table_3_1(sec);
gds = sec[3];
/* only process certain grids */
if (gdt != 10 && gdt != 20 && gdt != 30 && gdt != 31) return 1;
get_nxny(sec, &nnx, &nny, &nnpnts, &nres, &nscan);
/* potentially staggered */
if (nnx < 1 || nny < 1) return 1;
llat = *lat;
llon = *lon;
if (llat != NULL) {
free(llat);
free(llon);
*lat = *lon = llat = llon = NULL;
}
inv_fn = NULL;
dx = dy = 0.0;
if (gdt == 10) { // mercator
/* get earth axis */
axes_earth(sec, &r_maj, &r_min);
dy = GDS_Mercator_dy(gds);
dx = GDS_Mercator_dx(gds);
/* central point */
c_lon = GDS_Mercator_ori_angle(gds) * (M_PI/180.0);
c_lat = GDS_Mercator_latD(gds) * (M_PI/180.0);
/* find the eastling and northing of of the 1st grid point */
false_east = false_north = 0.0;
long_i = merforint(r_maj,r_min,c_lon,c_lat,false_east,false_north);
rlon = GDS_Mercator_lon1(gds) * (M_PI/180.0);
rlat = GDS_Mercator_lat1(gds) * (M_PI/180.0);
long_i = merfor(rlon, rlat, &x0, &y0);
/* initialize for 1st grid point */
x0 = -x0;
y0 = -y0;
long_i = merinvint(r_maj,r_min,c_lon,c_lat,x0,y0);
inv_fn = &merinv;
}
else if (gdt == 20) { // polar stereographic
/* get earth axis */
axes_earth(sec, &r_maj, &r_min);
dy = GDS_Polar_dy(gds);
dx = GDS_Polar_dx(gds);
/* central point */
c_lon = GDS_Polar_lov(gds) * (M_PI/180.0);
c_lat = GDS_Polar_lad(gds) * (M_PI/180.0);
/* find the eastling and northing of of the 1st grid point */
false_east = false_north = 0.0;
long_i = psforint(r_maj,r_min,c_lon,c_lat,false_east,false_north);
rlon = GDS_Polar_lon1(gds) * (M_PI/180.0);
rlat = GDS_Polar_lat1(gds) * (M_PI/180.0);
long_i = psfor(rlon, rlat, &x0, &y0);
/* initialize for 1st grid point */
x0 = -x0;
y0 = -y0;
long_i = psinvint(r_maj,r_min,c_lon,c_lat,x0,y0);
inv_fn = &psinv;
}
else if (gdt == 30) { // lambert conformal conic
/* get earth axis */
axes_earth(sec, &r_maj, &r_min);
dy = GDS_Lambert_dy(gds);
dx = GDS_Lambert_dx(gds);
//printf(">>> gctpc dx %lf, dy %lf\n", dx, dy);
/* latitudes of tangent/intersection */
lat1 = GDS_Lambert_Latin1(gds) * (M_PI/180.0);
lat2 = GDS_Lambert_Latin2(gds) * (M_PI/180.0);
/* central point */
c_lon = GDS_Lambert_Lov(gds) * (M_PI/180.0);
c_lat = GDS_Lambert_LatD(gds) * (M_PI/180.0);
/* find the eastling and northing of of the 1st grid point */
false_east = false_north = 0.0;
long_i = lamccforint(r_maj,r_min,lat1,lat2,c_lon,c_lat,false_east,false_north);
rlon = GDS_Lambert_Lo1(gds) * (M_PI/180.0);
rlat = GDS_Lambert_La1(gds) * (M_PI/180.0);
long_i = lamccfor(rlon, rlat, &x0, &y0);
/* initialize for 1st grid point */
x0 = -x0;
y0 = -y0;
long_i = lamccinvint(r_maj,r_min,lat1,lat2,c_lon,c_lat,x0,y0);
inv_fn = &lamccinv;
}
else if (gdt == 31) { // albers equal area
/* get earth axis */
axes_earth(sec, &r_maj, &r_min);
dy = GDS_Albers_dy(gds);
dx = GDS_Albers_dx(gds);
/* latitudes of tangent/intersection */
lat1 = GDS_Albers_Latin1(gds) * (M_PI/180.0);
lat2 = GDS_Albers_Latin2(gds) * (M_PI/180.0);
/* central point */
c_lon = GDS_Albers_Lov(gds) * (M_PI/180.0);
c_lat = GDS_Albers_LatD(gds) * (M_PI/180.0);
/* find the eastling and northing of of the 1st grid point */
false_east = false_north = 0.0;
long_i = alberforint(r_maj,r_min,lat1,lat2,c_lon,c_lat,false_east,false_north);
rlon = GDS_Albers_Lo1(gds) * (M_PI/180.0);
rlat = GDS_Albers_La1(gds) * (M_PI/180.0);
long_i = alberfor(rlon, rlat, &x0, &y0);
/* initialize for 1st grid point */
x0 = -x0;
y0 = -y0;
long_i = alberinvint(r_maj,r_min,lat1,lat2,c_lon,c_lat,x0,y0);
inv_fn = &alberinv;
}
if (inv_fn == NULL) return 1;
if ((*lat = llat = (double *) malloc(nnpnts * sizeof(double))) == NULL) {
fatal_error("gctpc_get_latlon memory allocation failed","");
}
if ((*lon = llon = (double *) malloc(nnpnts * sizeof(double))) == NULL) {
fatal_error("gctpc_get_latlon memory allocation failed","");
}
/* put x[] and y[] values in lon and lat */
if (stagger(sec, nnpnts, llon, llat)) fatal_error("gctpc: stagger problem","");
printf(">> stagger gctpc x00 %lf y00 %lf\n",llon[0], llat[0]);
#pragma omp parallel for schedule(static) private(i)
for (i = 0; i < nnpnts; i++) {
inv_fn(llon[i]*dx, llat[i]*dy, llon+i, llat+i);
llat[i] *= (180.0 / M_PI);
llon[i] *= (180.0 / M_PI);
if (llon[i] < 0.0) llon[i] += 360.0;
}
return 0;
}
int mercator2ll(unsigned char **sec, double **lat, double **lon) {
double dx, dy, lat1, lat2, lon1, lon2;
double *llat, *llon;
int i, j;
unsigned int k;
double dlon, circum;
double n,s,e,w,tmp,error;
unsigned char *gds;
int nnx, nny, nres, nscan;
unsigned int nnpnts;
get_nxny(sec, &nnx, &nny, &nnpnts, &nres, &nscan);
gds = sec[3];
dy = GDS_Mercator_dy(gds);
dx = GDS_Mercator_dx(gds);
lat1 = GDS_Mercator_lat1(gds);
lat2 = GDS_Mercator_lat2(gds);
lon1 = GDS_Mercator_lon1(gds);
lon2 = GDS_Mercator_lon2(gds);
if (lon1 < 0.0 || lon2 < 0.0 || lon1 > 360.0 || lon2 > 360.0) fatal_error("BAD GDS lon","");
if (lat1 < -90.0 || lat2 < -90.0 || lat1 > 90.0 || lat2 > 90.0) fatal_error("BAD GDS lat","");
if (GDS_Mercator_ori_angle(gds) != 0.0) {
fprintf(stderr,"cannot handle non-zero mercator orientation angle %f\n",
GDS_Mercator_ori_angle(gds));
return 0;
}
if (nnx == -1 || nny == -1) {
fprintf(stderr,"Sorry geo/mercator code does not handle variable nx/ny yet\n");
return 0;
}
if ((*lat = (double *) malloc(nnpnts * sizeof(double))) == NULL) {
fatal_error("mercator2ll memory allocation failed","");
}
if ((*lon = (double *) malloc(nnpnts * sizeof(double))) == NULL) {
fatal_error("mercator2ll memory allocation failed","");
}
/* now figure out the grid coordinates mucho silly grib specification */
/* find S and N latitude */
if (GDS_Scan_y(nscan)) {
s = lat1;
n = lat2;
}
else {
s = lat2;
n = lat1;
}
if (s > n) fatal_error("Mercator grid: lat1 and lat2","");
/* find W and E longitude */
if ( ((nscan & 16) == 16) && (nny % 2 == 0) && ((nres & 32) == 0) ) {
fatal_error("grib GDS ambiguity","");
}
if ( ((nscan & 16) == 16) && (nny % 2 == 0) ) {
fatal_error("more code needed to decode GDS","");
}
if (GDS_Scan_x(nscan)) {
w = lon1;
e = lon2;
} else {
w = lon2;
e = lon1;
}
if (e <= w) e += 360.0;
llat = *lat;
llon = *lon;
dlon = (e-w) / (nnx-1);
circum = 2.0 * M_PI * radius_earth(sec) * cos(GDS_Mercator_latD(gds) * (M_PI/180.0));
dx = dx * 360.0 / circum;
// dlon should be almost == to dx
// replace dx by dlon to get end points to match
if (dx != 0.0) {
error = fabs(dx-dlon) / fabs(dx);
if (error >= 0.001) { fprintf(stderr,
"\n*** Mercator grid error: inconsistent d-longitude, radius and grid domain\n"
"*** d-longitude from grid domain %lf (used), d-longitude from dx %lf (not used)\n",
dlon, dx);
}
dx = dlon;
}
s = log(tan((45+s/2)*M_PI/180));
n = log(tan((45+n/2)*M_PI/180));
dy = (n - s) / (nny - 1);
for (j = 0; j < nny; j++) {
tmp = (atan(exp(s+j*dy))*180/M_PI-45)*2;
for (i = 0; i < nnx; i++) {
*llat++ = tmp;
}
}
for (j = 0; j < nnx; j++) {
llon[j] = w + j*dx >= 360.0 ? w + j*dx - 360.0 : w + j*dx;
}
for (k = nnx; k < nnpnts; k++) {
llon[k] = llon[k-nnx];
}
return 0;
} /* end mercator2ll() */
