sinfor.c

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/*******************************************************************************
NAME                        SINUSOIDAL
 
PURPOSE:    Transforms input longitude and latitude to Easting and
        Northing for the Sinusoidal projection.  The
        longitude and latitude must be in radians.  The Easting
        and Northing values will be returned in meters.
 
This function was adapted from the Sinusoidal projection code (FORTRAN) in the 
General Cartographic Transformation Package software which is available from 
the U.S. Geological Survey National Mapping Division.
 
ALGORITHM REFERENCES
 
1.  Snyder, John P., "Map Projections--A Working Manual", U.S. Geological
    Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
    State Government Printing Office, Washington D.C., 1987.
 
2.  "Software Documentation for GCTP General Cartographic Transformation
    Package", U.S. Geological Survey National Mapping Division, May 1982.
*******************************************************************************/
#include "oli_cproj.h"
#include "oli_local.h"
 
/* Variables common to all subroutines in this code file
  -----------------------------------------------------*/
static double lon_center;   /* Center longitude (projection center) */
static double R;        /* Radius of the earth (sphere)     */
static double false_easting;    /* x offset in meters           */
static double false_northing;   /* y offset in meters           */
 
/* Initialize the Sinusoidal projection
  ------------------------------------*/
long sinforint
(
    double r,           /* (I) Radius of the earth (sphere)     */
    double center_long,     /* (I) Center longitude         */
    double false_east,      /* x offset in meters           */
    double false_north      /* y offset in meters           */
)
{
/* Place parameters in static storage for common use
  -------------------------------------------------*/
R = r;
lon_center = center_long;
false_easting = false_east;
false_northing = false_north;
 
/* Report parameters to the user
  -----------------------------*/
gctp_print_title("SINUSOIDAL"); 
gctp_print_radius(r);
gctp_print_cenlon(center_long);
gctp_print_offsetp(false_easting,false_northing);
return(OK);
}

/* Sinusoidal forward equations--mapping lat,long to x,y
  -----------------------------------------------------*/
long sinfor
(
    double lon,         /* (I) Longitude */
    double lat,         /* (I) Latitude */
    double *x,          /* (O) X projection coordinate */
    double *y           /* (O) Y projection coordinate */
)
{
double delta_lon;   /* Delta longitude (Given longitude - center */
 
/* Forward equations
  -----------------*/
delta_lon = adjust_lon(lon - lon_center);
*x = R * delta_lon * cos(lat) + false_easting;
*y = R * lat + false_northing;
return(OK);
}