<commit_before>// sg_geodesy.cxx -- routines to convert between geodetic and geocentric 
//                   coordinate systems.
//
// Copied and adapted directly from LaRCsim/ls_geodesy.c
//
// See below for the complete original LaRCsim comments.
//
// $Id$

#include <simgear/compiler.h>

#ifdef FG_HAVE_STD_INCLUDES
# include <cmath>
# include <cerrno>
# include <cstdio>
#else
# include <math.h>
# include <errno.h>
# include <stdio.h>
#endif

#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>

#include "point3d.hxx"
#include "sg_geodesy.hxx"
#include "localconsts.hxx"


#ifndef FG_HAVE_NATIVE_SGI_COMPILERS
FG_USING_STD(cout);
#endif

// ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
#define ONE_SECOND 4.848136811E-6


#define DOMAIN_ERR_DEBUG 1


// sgGeocToGeod(lat_geoc, radius, *lat_geod, *alt, *sea_level_r)
//     INPUTS:	
//         lat_geoc	Geocentric latitude, radians, + = North
//         radius	C.G. radius to earth center (meters)
//
//     OUTPUTS:
//         lat_geod	Geodetic latitude, radians, + = North
//         alt		C.G. altitude above mean sea level (meters)
//         sea_level_r	radius from earth center to sea level at
//                      local vertical (surface normal) of C.G. (meters)


void sgGeocToGeod( double lat_geoc, double radius, double
		   *lat_geod, double *alt, double *sea_level_r )
{
#ifdef DOMAIN_ERR_DEBUG
    errno = 0;			// start with error zero'd
#endif

    double t_lat, x_alpha, mu_alpha, delt_mu, r_alpha, l_point, rho_alpha;
    double sin_mu_a, denom,delt_lambda, lambda_sl, sin_lambda_sl;

    if( ( (FG_PI_2 - lat_geoc) < ONE_SECOND )        // near North pole
	|| ( (FG_PI_2 + lat_geoc) < ONE_SECOND ) )   // near South pole
    {
	*lat_geod = lat_geoc;
	*sea_level_r = EQUATORIAL_RADIUS_M*E;
	*alt = radius - *sea_level_r;
    } else {
	// cout << "  lat_geoc = " << lat_geoc << endl;
	t_lat = tan(lat_geoc);
	// cout << "  tan(t_lat) = " << t_lat << endl;
	x_alpha = E*EQUATORIAL_RADIUS_M/sqrt(t_lat*t_lat + E*E);
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" << t_lat*t_lat + E*E << ")" );
	}
#endif
	// cout << "  x_alpha = " << x_alpha << endl;
	double tmp = sqrt(RESQ_M - x_alpha * x_alpha);
	if ( tmp < 0.0 ) { tmp = 0.0; }
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" << RESQ_M - x_alpha * x_alpha
		    << ")" );
	}
#endif
	mu_alpha = atan2(tmp,E*x_alpha);
	if (lat_geoc < 0) mu_alpha = - mu_alpha;
	sin_mu_a = sin(mu_alpha);
	delt_lambda = mu_alpha - lat_geoc;
	r_alpha = x_alpha/cos(lat_geoc);
	l_point = radius - r_alpha;
	*alt = l_point*cos(delt_lambda);

	denom = sqrt(1-EPS*EPS*sin_mu_a*sin_mu_a);
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" <<
		    1-EPS*EPS*sin_mu_a*sin_mu_a << ")" );
	}
#endif
	rho_alpha = EQUATORIAL_RADIUS_M*(1-EPS)/
	    (denom*denom*denom);
	delt_mu = atan2(l_point*sin(delt_lambda),rho_alpha + *alt);
	*lat_geod = mu_alpha - delt_mu;
	lambda_sl = atan( E*E * tan(*lat_geod) ); // SL geoc. latitude
	sin_lambda_sl = sin( lambda_sl );
	*sea_level_r = 
	    sqrt(RESQ_M / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" <<
		    RESQ_M / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl)
		    << ")" );
	}
#endif

    }

}


// sgGeodToGeoc( lat_geod, alt, *sl_radius, *lat_geoc )
//     INPUTS:	
//         lat_geod	Geodetic latitude, radians, + = North
//         alt		C.G. altitude above mean sea level (meters)
//
//     OUTPUTS:
//         sl_radius	SEA LEVEL radius to earth center (meters)
//                      (add Altitude to get true distance from earth center.
//         lat_geoc	Geocentric latitude, radians, + = North
//


void sgGeodToGeoc( double lat_geod, double alt, double *sl_radius,
		      double *lat_geoc )
{
    double lambda_sl, sin_lambda_sl, cos_lambda_sl, sin_mu, cos_mu, px, py;
    
    lambda_sl = atan( E*E * tan(lat_geod) ); // sea level geocentric latitude
    sin_lambda_sl = sin( lambda_sl );
    cos_lambda_sl = cos( lambda_sl );
    sin_mu = sin(lat_geod);                  // Geodetic (map makers') latitude
    cos_mu = cos(lat_geod);
    *sl_radius = <commit_msg>Tweaks to errno checking and perror.<commit_after>// sg_geodesy.cxx -- routines to convert between geodetic and geocentric 
//                   coordinate systems.
//
// Copied and adapted directly from LaRCsim/ls_geodesy.c
//
// See below for the complete original LaRCsim comments.
//
// $Id$

#include <simgear/compiler.h>

#ifdef FG_HAVE_STD_INCLUDES
# include <cmath>
# include <cerrno>
# include <cstdio>
#else
# include <math.h>
# include <errno.h>
# include <stdio.h>
#endif

#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>

#include "point3d.hxx"
#include "sg_geodesy.hxx"
#include "localconsts.hxx"


#ifndef FG_HAVE_NATIVE_SGI_COMPILERS
FG_USING_STD(cout);
#endif

// ONE_SECOND is pi/180/60/60, or about 100 feet at earths' equator
#define ONE_SECOND 4.848136811E-6


#define DOMAIN_ERR_DEBUG 1


// sgGeocToGeod(lat_geoc, radius, *lat_geod, *alt, *sea_level_r)
//     INPUTS:	
//         lat_geoc	Geocentric latitude, radians, + = North
//         radius	C.G. radius to earth center (meters)
//
//     OUTPUTS:
//         lat_geod	Geodetic latitude, radians, + = North
//         alt		C.G. altitude above mean sea level (meters)
//         sea_level_r	radius from earth center to sea level at
//                      local vertical (surface normal) of C.G. (meters)


void sgGeocToGeod( double lat_geoc, double radius, double
		   *lat_geod, double *alt, double *sea_level_r )
{
#ifdef DOMAIN_ERR_DEBUG
    errno = 0;			// start with error zero'd
#endif

    double t_lat, x_alpha, mu_alpha, delt_mu, r_alpha, l_point, rho_alpha;
    double sin_mu_a, denom,delt_lambda, lambda_sl, sin_lambda_sl;

    if( ( (FG_PI_2 - lat_geoc) < ONE_SECOND )        // near North pole
	|| ( (FG_PI_2 + lat_geoc) < ONE_SECOND ) )   // near South pole
    {
	*lat_geod = lat_geoc;
	*sea_level_r = EQUATORIAL_RADIUS_M*E;
	*alt = radius - *sea_level_r;
    } else {
	// cout << "  lat_geoc = " << lat_geoc << endl;
	t_lat = tan(lat_geoc);
	// cout << "  tan(t_lat) = " << t_lat << endl;
	x_alpha = E*EQUATORIAL_RADIUS_M/sqrt(t_lat*t_lat + E*E);
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" << t_lat*t_lat + E*E << ")" );
	}
#endif
	// cout << "  x_alpha = " << x_alpha << endl;
	double tmp = sqrt(RESQ_M - x_alpha * x_alpha);
	if ( tmp < 0.0 ) { tmp = 0.0; }
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" << RESQ_M - x_alpha * x_alpha
		    << ")" );
	}
#endif
	mu_alpha = atan2(tmp,E*x_alpha);
	if (lat_geoc < 0) mu_alpha = - mu_alpha;
	sin_mu_a = sin(mu_alpha);
	delt_lambda = mu_alpha - lat_geoc;
	r_alpha = x_alpha/cos(lat_geoc);
	l_point = radius - r_alpha;
	*alt = l_point*cos(delt_lambda);

	denom = sqrt(1-EPS*EPS*sin_mu_a*sin_mu_a);
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" <<
		    1-EPS*EPS*sin_mu_a*sin_mu_a << ")" );
	}
#endif
	rho_alpha = EQUATORIAL_RADIUS_M*(1-EPS)/
	    (denom*denom*denom);
	delt_mu = atan2(l_point*sin(delt_lambda),rho_alpha + *alt);
	*lat_geod = mu_alpha - delt_mu;
	lambda_sl = atan( E*E * tan(*lat_geod) ); // SL geoc. latitude
	sin_lambda_sl = sin( lambda_sl );
	*sea_level_r = 
	    sqrt(RESQ_M / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
#ifdef DOMAIN_ERR_DEBUG
	if ( errno ) {
	    perror("fgGeocToGeod()");
	    FG_LOG( FG_GENERAL, FG_ALERT, "sqrt(" <<
		    RESQ_M / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl)
		    << ")" );
	}
#endif

    }

}


// sgGeodToGeoc( lat_geod, alt, *sl_radius, *lat_geoc )
//     INPUTS:	
//         lat_geod	Geodetic latitude, radians, + = North
//         alt		C.G. altitude above mean sea level (meters)
//
//     OUTPUTS:
//         sl_radius	SEA LEVEL radius to earth center (meters)
//                      (add Altitude to get true distance from earth center.
//         lat_geoc	Geocentric latitude, radians, + = North
//


void sgGeodToGeoc( double lat_geod, double alt, double *sl_radius,
		      double *lat_geoc )
{
    double lambda_sl, sin_lambda_sl, cos_lambda_sl, sin_mu, cos_mu, px, py;
    
#ifdef DOMAIN_ERR_DEBUG
    errno = 0;
#endif

    lambda_sl = atan( E*E * tan(lat_geod) ); // sea level geocentric latitude
    sin_lambda_sl = sin( lambda_sl );
    cos_lambda_sl = cos( lambda_sl );
    sin_mu = sin(lat_geod);                  // Geodetic (map makers') latitude
    cos_mu = cos(lat_geod);
    *sl_radius = 
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