sphdz.c

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/*******************************************************************************
NAME                           SPHDZ 
 
PURPOSE:        This function assigns values to the semimajor axis, semiminor
                axis, and radius of sphere.  If the spheroid code is negative,
                the first two values in the parameter array (parm) are used
                to define the values as follows:
 
                --If parm[0] is a non-zero value and parm[1] is greater than
                  one, the semimajor axis and radius are set to parm[0] and
                  the semiminor axis is set to parm[1]. 
 
                --If parm[0] is nonzero and parm[1] is greater than zero but
                  less than or equal to one, the semimajor axis and radius
                  are set to parm[0] and the semiminor axis is computed
                  from the eccentricity squared value parm[1].  This
                  algorithm is given below.
 
                --If parm[0] is nonzero and parm[1] is equal to zero, the
                  semimajor axis, radius, and semiminor axis are set to
                  parm[0].
 
                --If parm[0] equals zero and parm[1] is greater than zero,
                  the default Clarke 1866 is used to assign values to the
                  semimajor axis, radius and semiminor axis.
 
                --If parm[0] and parm[1] equals zero, the semimajor axis
                  and radius are set to 6370997.0 (This value is represented
                  as the last value in the spheroid code array) and the
                  semiminor axis is set to zero.
 
                if a spheroid code is zero or greater, the semimajor and
                semiminor axis are defined by the spheroid code, listed below
                in the array assignment, and the radius is set to 6370997.0
                (or 6371007.181 if the sphere number is 31).
                If the spheroid code is greater than SPHDCT the default
                spheroid, Clarke 1866, is used to define the semimajor
                and semiminor axis and radius is set to 6370997.0.
 
                The algorithm to define the semiminor axis using the
                eccentricity squared value is as follows:
 
                      semiminor = sqrt(1.0 - ES) * semimajor   where
                      ES = eccentricity squared
 
                
 
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.  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.
*******************************************************************************/
 
/* Assign the radius value to the radius argument if a spheroid is assigned */
#define RADVAL 19
 
#include "oli_cproj.h"
#include "oli_local.h"
 
        /* Semi-Major axis of supported Spheroids */
static double major[SPHDCT] = {
                6378206.4,              /* 0: Clarke 1866 (default) */
                6378249.145,            /* 1: Clarke 1880 */
                6377397.155,            /* 2: Bessel */
                6378157.5,              /* 3: International 1967 */
                6378388.0,              /* 4: International 1909 */
                6378135.0,              /* 5: WGS 72 */
                6377276.3452,           /* 6: Everest */
                6378145.0,              /* 7: WGS 66 */
                6378137.0,              /* 8: GRS 1980 */
                6377563.396,            /* 9: Airy */
                6377304.063,            /* 10: Modified Everest */
                6377340.189,            /* 11: Modified Airy */
                6378137.0,              /* 12: WGS 84 */
                6378155.0,              /* 13: Southeast Asia */
                6378160.0,              /* 14: Australian National */
                6378245.0,              /* 15: Krassovsky */
                6378270.0,              /* 16: Hough */
                6378166.0,              /* 17: Mercury 1960 */
                6378150.0,              /* 18: Modified Mercury 1968 */
                6370997.0,              /* 19: Sphere of Radius 6370997 meters*/
                6377483.865,            /* 20: Bessel 1841(Namibia) */
                6377298.556,            /* 21: Everest (Sabah & Sarawak) */
                6377301.243,            /* 22: Everest (India 1956) */
                6377295.664,            /* 23: Everest (Malaysia 1969) */
                6377304.063,            /* 24: Everest (Malay & Singapr 1948)*/
                6377309.613,            /* 25: Everest (Pakistan) */
                6378388.0,              /* 26: Hayford */
                6378200.0,              /* 27: Helmert 1906 */
                6378160.000,            /* 28: Indonesian 1974 */
                6378160.0,              /* 29: South American 1969 */
                6378165.0,              /* 30: WGS 60 */
                6371007.181             /* 31: MODIS Sphere */
};
 
        /* Semi-Minor axis of supported Spheroids */
static double minor[SPHDCT] = {
                6356583.8,              /* 0: Clarke 1866 (default) */
                6356514.86955,          /* 1: Clarke 1880 */
                6356078.96284,          /* 2: Bessel */
                6356772.2,              /* 3: International 1967 */
                6356911.94613,          /* 4: International 1909 */
                6356750.519915,         /* 5: WGS 72 */
                6356075.4133,           /* 6: Everest */
                6356759.769356,         /* 7: WGS 66 */
                6356752.31414,          /* 8: GRS 1980 */
                6356256.91,             /* 9: Airy */
                6356103.039,            /* 10: Modified Everest */
                6356034.448,            /* 11: Modified Airy */
                6356752.314245,         /* 12: WGS 84 */
                6356773.3205,           /* 13: Southeast Asia */
                6356774.719,            /* 14: Australian National */
                6356863.0188,           /* 15: Krassovsky */
                6356794.343479,         /* 16: Hough */
                6356784.283666,         /* 17: Mercury 1960 */
                6356768.337303,         /* 18: Modified Mercury 1968 */
                6370997.0,              /* 19: Sphere of Radius 6370997 meters*/
                6356165.382966,         /* 20: Bessel 1841(Namibia) */
                6356097.571445,         /* 21: Everest (Sabah & Sarawak) */
                6356100.228368,         /* 22: Everest (India 1956) */
                6356094.667915,         /* 23: Everest (Malaysia 1969) */
                6356103.038993,         /* 24: Everest (Malay & Singapr 1948)*/
                6356108.570542,         /* 25: Everest (Pakistan) */
                6356911.946128,         /* 26: Hayford */
                6356818.169,            /* 27: Helmert 1906 */
                6356774.504086,         /* 28: Indonesian 1974 */
                6356774.719,            /* 29: South American 1969 */
                6356783.287,            /* 30: WGS 60 */
                6371007.181             /* 31: MODIS Sphere */
};
 
/* Finds the correct ellipsoid axis
---------------------------------*/
 
void sphdz
(
    long isph,          /* spheroid code number                         */
    const double *parm, /* projection parameters                        */
    double *r_major,    /* major axis                                   */
    double *r_minor,    /* minor axis                                   */
    double *radius      /* radius                                       */
)
{
    double t_major;         /* temporary major axis                         */
    double t_minor;         /* temporary minor axis                         */
    long jsph;              /* spheroid code number                         */
 
    if (isph < 0)
    {
        /* if the spheroid code is a negative number, get the semi-major and 
           semi-minor axis from the projection array
           -----------------------------------------------------------------*/
        t_major = fabs(parm[0]);
        t_minor = fabs(parm[1]);
 
        if (t_major  > 0.0) 
        {
            if (t_minor > 1.0)
            {
                /* The semimajor axis and the semiminor axis are in the array, 
                   assign them directly
                   -----------------------------------------------------------*/
                *r_major = t_major;
                *r_minor = t_minor;
                *radius = t_major;
            } 
            else if (t_minor > 0.0)
            {
                /* The semimajor axis and the eccentricity squared values are 
                   in the array, therefore, the semiminor axis is computed 
                   from the eccentricity squared value parm[1]
                   ----------------------------------------------------------*/
                *r_major = t_major;
                *radius = t_major;
                *r_minor = (sqrt(1.0 - t_minor)) * t_major; 
            }
            else
            {
                /* The semiminor axis is zero or less, assign the semimajor 
                   axis to the semiminor axis.
                   --------------------------------------------------------*/
                *r_major = t_major;
                *radius = t_major;
                *r_minor = t_major;
            }
        }
        else if (t_minor > 0.0)   /* t_major = 0 */
        {
            /* Assign Clarke 1866 semi-major and semi-minor axis
               -------------------------------------------------*/
            *r_major = major[0];
            *radius = major[0];
            *r_minor = minor[0];
        }
        else
        {
            /* Assign Spheroid radius to semi-major and semi-minor axis
               --------------------------------------------------------*/
            *r_major = major[RADVAL];
            *radius = major[RADVAL];
            *r_minor = major[RADVAL];
        }
    }
    else            /* isph >= 0 */
    {
        /* Use the spheroid code to assign the semi-major and semi-minor axis
           -----------------------------------------------------------------*/
        jsph = isph;
 
        if (jsph > (SPHDCT - 1))
        {
            /* The spheroid code is out of range, assign Clarke 1866
               -----------------------------------------------------*/
            GCTP_PRINT_ERROR("Invalid spheroid selection");
            GCTP_PRINT_ERROR("Reset to 0");
            jsph = 0;
        }
        /* Assign the radius argument to the standard radius value
           -------------------------------------------------------*/
        *r_major = major[jsph];
        *r_minor = minor[jsph];
 
        /* for the projections that are only defined for a sphere, use sphere 19
           unless the sphere is the MODIS sphere */
        if (jsph != 31)
            *radius = major[RADVAL];
        else
            *radius = major[jsph];
    }
}