int cyclic(unsigned char **sec) { int grid_template, nx, ny, res, scan, flag_3_3, no_dx, basic_ang, sub_ang; unsigned int npnts; unsigned char *gds; double dlon, units, lon1, lon2; get_nxny(sec, &nx, &ny, &npnts, &res, &scan); if (GDS_Scan_staggered(scan)) return 0; if (nx <= 1 || ny <= 0) return 0; grid_template = code_table_3_1(sec); gds = sec[3]; flag_3_3 = flag_table_3_3(sec); no_dx = 0; if (flag_3_3 != -1) { if ((flag_3_3 & 0x20) == 0) no_dx = 1; } if (no_dx) return 0; if (grid_template == 0) { basic_ang = GDS_LatLon_basic_ang(gds); sub_ang = GDS_LatLon_sub_ang(gds); units = basic_ang == 0 ? 0.000001 : (double) basic_ang / (double) sub_ang; /* dlon has to be defined */ dlon = units * GDS_LatLon_dlon(gds); return (fabs(nx*dlon-360.0) < ERROR); } if (grid_template == 10) { if (output_order != wesn) return 0; // only works with we:sn order lon1 = GDS_Mercator_lon1(gds); lon2 = GDS_Mercator_lon2(gds); if (lon2 < lon1) lon2 += 360.0; dlon = (lon2-lon1)*nx/(nx-1.0); return (fabs(dlon-360.0) < ERROR); } if (grid_template == 40) { basic_ang = GDS_Gaussian_basic_ang(gds); sub_ang = GDS_Gaussian_sub_ang(gds); units = basic_ang == 0 ? 0.000001 : (double) basic_ang / (double) sub_ang; /* dlon has to be defined */ dlon = units * GDS_Gaussian_dlon(gds); return (fabs(nx*dlon-360.0) < ERROR); } 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() */