imolwinv.c

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/*******************************************************************************
NAME                        INTERRUPTED MOLLWEIDE
 
PURPOSE:        Transforms input Easting and Northing to longitude and
                latitude for the Interrupted Mollweide projection.  The
                Easting and Northing must be in meters.  The longitude
                and latitude values will be returned in radians.
 
ALGORITHM REFERENCES
 
1.  Snyder, John P. and Voxland, Philip M., "An Album of Map Projections",
    U.S. Geological Survey Professional Paper 1453 , United State Government
    Printing Office, Washington D.C., 1989.
 
2.  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.
*******************************************************************************/
#include "oli_cproj.h"
#include "oli_local.h"
 
/* Variables common to all subroutines in this code file
  -----------------------------------------------------*/
static double R;        /* Radius of the earth (sphere) */
static double lon_center[6];    /* Central meridians, one for each region */
static double feast[6];     /* False easting, one for each region */
 
/* Initialize the Interrupted Mollweide projection
  --------------------------------------------*/
long imolwinvint
(
    double r            /* (I) Radius of the earth (sphere) */
)
{
/* Place parameters in static storage for common use
  -------------------------------------------------*/
R = r;
 
/* Initialize central meridians for each of the 6 regions
  ------------------------------------------------------*/
lon_center[0] = 1.0471975512;       /*   60.0 degrees */
lon_center[1] = -2.96705972839;     /* -170.0 degrees */
lon_center[2] = -0.523598776;       /*  -30.0 degrees */
lon_center[3] =  1.57079632679;     /*   90.0 degrees */
lon_center[4] = -2.44346095279;     /* -140.0 degrees */
lon_center[5] = -0.34906585;        /*  -20.0 degrees */
 
/* Initialize false eastings for each of the 6 regions
  ---------------------------------------------------*/
feast[0] = R * -2.19988776387;
feast[1] = R * -0.15713484;
feast[2] = R * 2.04275292359;
feast[3] = R * -1.72848324304;
feast[4] = R * 0.31426968;
feast[5] = R * 2.19988776387;
 
/* Report parameters to the user
  -----------------------------*/
gctp_print_title("INTERRUPTED MOLLWEIDE EQUAL-AREA"); 
gctp_print_radius(r);
return(OK);
}

long imolwinv
(
    double x,       /* (I) X projection coordinate */
    double y,       /* (I) Y projection coordinate */
    double *lon,        /* (O) Longitude */
    double *lat     /* (O) Latitude */
)
{
double theta;
long region;
 
/* Inverse equations
  -----------------*/
if (y >= 0.0)
   {
   if (x <= R * -1.41421356248) region = 0;
   else if (x <= R * 0.942809042) region = 1;
   else region = 2;
   }
else
   {
   if (x <= R * -0.942809042) region = 3;
   else if (x <= R * 1.41421356248) region = 4;
   else region = 5;
   }
x = x - feast[region];
 
theta = asin(y / (1.4142135623731 * R));
*lon = adjust_lon(lon_center[region] + (x / (0.900316316158*R * cos(theta))));
*lat = asin((2.0 * theta + sin(2.0 * theta)) / PI);
 
/* Are we in a interrupted area?  If so, return status code of IN_BREAK.
  ---------------------------------------------------------------------*/
if (region == 0 && (*lon < 0.34906585 || *lon > 1.91986217719))return(IN_BREAK);
if (region == 1 && ((*lon < 1.91986217719 && *lon > 0.34906585) || 
              (*lon > -1.74532925199 && *lon < 0.34906585))) return(IN_BREAK);
if (region == 2 && (*lon < -1.745329252 || *lon > 0.34906585)) return(IN_BREAK);
if (region == 3 && (*lon < 0.34906585 || *lon > 2.44346095279))return(IN_BREAK);
if (region == 4 && ((*lon < 2.44346095279 && *lon > 0.34906585) || 
              (*lon > -1.2217304764 && *lon < 0.34906585))) return(IN_BREAK);
if (region == 5 && (*lon < -1.2217304764 || *lon> 0.34906585))return(IN_BREAK);
return(OK);
}