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Ocean Color Science Software

ocssw V2022
sterinv.c
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1 /*******************************************************************************
2 NAME STEREOGRAPHIC
3 
4 PURPOSE: Transforms input Easting and Northing to longitude and
5  latitude for the Stereographic projection. The
6  Easting and Northing must be in meters. The longitude
7  and latitude values will be returned in radians.
8 
9 ALGORITHM REFERENCES
10 
11 1. Snyder, John P., "Map Projections--A Working Manual", U.S. Geological
12  Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
13  State Government Printing Office, Washington D.C., 1987.
14 
15 2. Snyder, John P. and Voxland, Philip M., "An Album of Map Projections",
16  U.S. Geological Survey Professional Paper 1453 , United State Government
17  Printing Office, Washington D.C., 1989.
18 *******************************************************************************/
19 #include "oli_cproj.h"
20 #include "oli_local.h"
21 
22 /* Variables common to all subroutines in this code file
23  -----------------------------------------------------*/
24 static double r_major; /* major axis */
25 static double lon_center; /* Center longitude (projection center) */
26 static double lat_origin; /* center latitude */
27 static double false_northing; /* y offset in meters */
28 static double false_easting; /* x offset in meters */
29 static double sin_p10; /* sin of center latitude */
30 static double cos_p10; /* cos of center latitude */
31 
32 /* Initialize the Stereographic projection
33  --------------------------------------*/
34 long sterinvint
35 (
36  double r_maj, /* major axis */
37  double center_lon, /* center longitude */
38  double center_lat, /* center latitude */
39  double false_east, /* x offset in meters */
40  double false_north /* y offset in meters */
41 )
42 {
43 /* Place parameters in static storage for common use
44  -------------------------------------------------*/
45 r_major = r_maj;
46 lon_center = center_lon;
47 lat_origin = center_lat;
48 false_northing = false_north;
49 false_easting = false_east;
50 
51 sincos(center_lat,&sin_p10,&cos_p10);
52 
53 /* Report parameters to the user
54  -----------------------------*/
55 gctp_print_title("STEREOGRAPHIC");
56 gctp_print_radius(r_major);
57 gctp_print_cenlonmer(lon_center);
58 gctp_print_origin(lat_origin);
59 gctp_print_offsetp(false_easting,false_northing);
60 return(OK);
61 }
62 
63 
64 /* Stereographic inverse equations--mapping x,y to lat/long
65  -------------------------------------------------------*/
66 long sterinv
67 (
68  double x, /* (O) X projection coordinate */
69  double y, /* (O) Y projection coordinate */
70  double *lon, /* (I) Longitude */
71  double *lat /* (I) Latitude */
72 )
73 {
74 double rh; /* height above ellipsoid */
75 double z; /* angle */
76 double sinz,cosz; /* sin of z and cos of z */
77 double con;
78 
79 /* Inverse equations
80  -----------------*/
81 x -= false_easting;
82 y -= false_northing;
83 rh = sqrt(x * x + y * y);
84 z = 2.0 * atan(rh / (2.0 * r_major));
85 sincos(z,&sinz,&cosz);
86 *lon = lon_center;
87 if (fabs(rh) <= EPSLN)
88  {
89  *lat = lat_origin;
90  return(OK);
91  }
92 else
93  {
94  *lat = asin(cosz * sin_p10 + (y * sinz * cos_p10) / rh);
95  con = fabs(lat_origin) - HALF_PI;
96  if (fabs(con) <= EPSLN)
97  {
98  if (lat_origin >= 0.0)
99  {
100  *lon = adjust_lon(lon_center + atan2(x, -y));
101  return(OK);
102  }
103  else
104  {
105  *lon = adjust_lon(lon_center - atan2(-x, y));
106  return(OK);
107  }
108  }
109  else
110  {
111  con = cosz - sin_p10 * sin(*lat);
112  if ((fabs(con) < EPSLN) && (fabs(x) < EPSLN))
113  return(OK);
114  else
115  *lon = adjust_lon(lon_center + atan2((x * sinz * cos_p10), (con * rh)));
116  }
117  }
118 
119 return(OK);
120 }
void gctp_print_origin(double A)
Definition: gctp_report.c:65
void gctp_print_title(const char *proj_name)
Definition: gctp_report.c:14
float * lat
double adjust_lon(double x)
Definition: proj_cproj.c:349
#define HALF_PI
Definition: proj_define.h:84
void gctp_print_offsetp(double A, double B)
Definition: gctp_report.c:91
#define OK
Definition: ancil.h:30
#define sincos
Definition: proj_define.h:108
void gctp_print_cenlonmer(double A)
Definition: gctp_report.c:48
#define fabs(a)
Definition: misc.h:93
long sterinvint(double r_maj, double center_lon, double center_lat, double false_east, double false_north)
Definition: sterinv.c:35
float * lon
void gctp_print_radius(double radius)
Definition: gctp_report.c:22
long sterinv(double x, double y, double *lon, double *lat)
Definition: sterinv.c:67
#define EPSLN
Definition: proj_define.h:86