#define RESQ_FT 437882827922500. // ft
#define RESQ_M 40680645877797.1344 // meter
+#if 0
// Value of earth flattening parameter from ref [8]
//
// Note: FP = f
// E = 1-f
// EPS = sqrt(1-(1-f)^2)
//
-
+
#define FP 0.003352813178
#define E 0.996647186
#define EPS 0.081819221
#define MJD0 2415020.0
#define J2000 (2451545.0 - MJD0)
#define SIDRATE .9972695677
-
+#endif
// Conversions
// this means client for now
sock = make_client_socket();
- // TODO: check for error.
+ // TODO: check for error.
if ( sock_style == SOCK_DGRAM ) {
// Non-blocking UDP
nonblock();
}
+ } else if ( dir == SG_IO_BI && sock_style == SOCK_STREAM ) {
+ // this means server for TCP sockets
+
+ // Setup socket to listen on. Set "port" before making this
+ // call. A port of "0" indicates that we want to let the os
+ // pick any available port.
+ sock = make_server_socket();
+ // TODO: check for error.
+
+ FG_LOG( FG_IO, FG_INFO, "socket is connected to port = " << port );
+
+ // Blocking TCP
+ // Specify the maximum length of the connection queue
+ listen( sock, SG_MAX_SOCKET_QUEUE );
} else {
FG_LOG( FG_IO, FG_ALERT,
- "Error: bidirection mode not available yet for sockets." );
+ "Error: bidirection mode not available for UDP sockets." );
return false;
}
lib_LIBRARIES = libsgmath.a
include_HEADERS = \
- fg_geodesy.hxx \
fg_memory.h \
fg_random.h \
interpolater.hxx \
leastsqs.hxx \
+ localconsts.hxx \
point3d.hxx \
polar3d.hxx \
+ sg_geodesy.hxx \
sg_types.hxx \
vector.hxx
EXTRA_DIST = linintp2.h linintp2.inl sphrintp.h sphrintp.inl
libsgmath_a_SOURCES = \
- fg_geodesy.cxx \
fg_random.c \
interpolater.cxx \
leastsqs.cxx \
polar3d.cxx \
+ sg_geodesy.cxx \
vector.cxx
INCLUDES += -I$(top_srcdir) $(ZLIB_INCL)
+++ /dev/null
-// fg_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>
-#else
-# include <math.h>
-# include <errno.h>
-#endif
-
-#include <simgear/constants.h>
-#include <simgear/debug/logstream.hxx>
-
-#include "point3d.hxx"
-#include "fg_geodesy.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
-
-
-// fgGeocToGeod(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 fgGeocToGeod( double lat_geoc, double radius, double
- *lat_geod, double *alt, double *sea_level_r )
-{
- 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);
- // cout << " x_alpha = " << x_alpha << endl;
- double tmp = RESQ_M - x_alpha * x_alpha;
- if ( tmp < 0.0 ) { tmp = 0.0; }
- mu_alpha = atan2(sqrt(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);
-
- // check for domain error
- if ( errno == EDOM ) {
- FG_LOG( FG_GENERAL, FG_ALERT, "Domain ERROR in fgGeocToGeod!!!!" );
- *alt = 0.0;
- }
-
- denom = sqrt(1-EPS*EPS*sin_mu_a*sin_mu_a);
- 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));
-
- // check for domain error
- if ( errno == EDOM ) {
- FG_LOG( FG_GENERAL, FG_ALERT, "Domain ERROR in fgGeocToGeod!!!!" );
- *sea_level_r = 0.0;
- }
- }
-
-}
-
-
-// fgGeodToGeoc( 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 fgGeodToGeoc( 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 =
- sqrt(RESQ_M / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
- py = *sl_radius*sin_lambda_sl + alt*sin_mu;
- px = *sl_radius*cos_lambda_sl + alt*cos_mu;
- *lat_geoc = atan2( py, px );
-}
-
-
-// Direct and inverse distance functions
-//
-// Proceedings of the 7th International Symposium on Geodetic
-// Computations, 1985
-//
-// "The Nested Coefficient Method for Accurate Solutions of Direct and
-// Inverse Geodetic Problems With Any Length"
-//
-// Zhang Xue-Lian
-// pp 747-763
-//
-// modified for FlightGear to use WGS84 only -- Norman Vine
-
-#define GEOD_INV_PI FG_PI
-
-// s == distance
-// az = azimuth
-
-// for WGS_84 a = 6378137.000, rf = 298.257223563;
-
-static double M0( double e2 ) {
- //double e4 = e2*e2;
- return GEOD_INV_PI*(1.0 - e2*( 1.0/4.0 + e2*( 3.0/64.0 +
- e2*(5.0/256.0) )))/2.0;
-}
-
-
-// given, alt, lat1, lon1, az1 and distance (s), calculate lat2, lon2
-// and az2. Lat, lon, and azimuth are in degrees. distance in meters
-int geo_direct_wgs_84 ( double alt, double lat1, double lon1, double az1,
- double s, double *lat2, double *lon2, double *az2 )
-{
- double a = 6378137.000, rf = 298.257223563;
- double RADDEG = (GEOD_INV_PI)/180.0, testv = 1.0E-10;
- double f = ( rf > 0.0 ? 1.0/rf : 0.0 );
- double b = a*(1.0-f);
- double e2 = f*(2.0-f);
- double phi1 = lat1*RADDEG, lam1 = lon1*RADDEG;
- double sinphi1 = sin(phi1), cosphi1 = cos(phi1);
- double azm1 = az1*RADDEG;
- double sinaz1 = sin(azm1), cosaz1 = cos(azm1);
-
-
- if( fabs(s) < 0.01 ) { // distance < centimeter => congruency
- *lat2 = lat1;
- *lon2 = lon1;
- *az2 = 180.0 + az1;
- if( *az2 > 360.0 ) *az2 -= 360.0;
- return 0;
- } else if( cosphi1 ) { // non-polar origin
- // u1 is reduced latitude
- double tanu1 = sqrt(1.0-e2)*sinphi1/cosphi1;
- double sig1 = atan2(tanu1,cosaz1);
- double cosu1 = 1.0/sqrt( 1.0 + tanu1*tanu1 ), sinu1 = tanu1*cosu1;
- double sinaz = cosu1*sinaz1, cos2saz = 1.0-sinaz*sinaz;
- double us = cos2saz*e2/(1.0-e2);
-
- // Terms
- double ta = 1.0+us*(4096.0+us*(-768.0+us*(320.0-175.0*us)))/16384.0,
- tb = us*(256.0+us*(-128.0+us*(74.0-47.0*us)))/1024.0,
- tc = 0;
-
- // FIRST ESTIMATE OF SIGMA (SIG)
- double first = s/(b*ta); // !!
- double sig = first;
- double c2sigm, sinsig,cossig, temp,denom,rnumer, dlams, dlam;
- do {
- c2sigm = cos(2.0*sig1+sig);
- sinsig = sin(sig); cossig = cos(sig);
- temp = sig;
- sig = first +
- tb*sinsig*(c2sigm+tb*(cossig*(-1.0+2.0*c2sigm*c2sigm) -
- tb*c2sigm*(-3.0+4.0*sinsig*sinsig)
- *(-3.0+4.0*c2sigm*c2sigm)/6.0)
- /4.0);
- } while( fabs(sig-temp) > testv);
-
- // LATITUDE OF POINT 2
- // DENOMINATOR IN 2 PARTS (TEMP ALSO USED LATER)
- temp = sinu1*sinsig-cosu1*cossig*cosaz1;
- denom = (1.0-f)*sqrt(sinaz*sinaz+temp*temp);
-
- // NUMERATOR
- rnumer = sinu1*cossig+cosu1*sinsig*cosaz1;
- *lat2 = atan2(rnumer,denom)/RADDEG;
-
- // DIFFERENCE IN LONGITUDE ON AUXILARY SPHERE (DLAMS )
- rnumer = sinsig*sinaz1;
- denom = cosu1*cossig-sinu1*sinsig*cosaz1;
- dlams = atan2(rnumer,denom);
-
- // TERM C
- tc = f*cos2saz*(4.0+f*(4.0-3.0*cos2saz))/16.0;
-
- // DIFFERENCE IN LONGITUDE
- dlam = dlams-(1.0-tc)*f*sinaz*(sig+tc*sinsig*
- (c2sigm+
- tc*cossig*(-1.0+2.0*
- c2sigm*c2sigm)));
- *lon2 = (lam1+dlam)/RADDEG;
- if (*lon2 > 180.0 ) *lon2 -= 360.0;
- if (*lon2 < -180.0 ) *lon2 += 360.0;
-
- // AZIMUTH - FROM NORTH
- *az2 = atan2(-sinaz,temp)/RADDEG;
- if ( fabs(*az2) < testv ) *az2 = 0.0;
- if( *az2 < 0.0) *az2 += 360.0;
- return 0;
- } else { // phi1 == 90 degrees, polar origin
- double dM = a*M0(e2) - s;
- double paz = ( phi1 < 0.0 ? 180.0 : 0.0 );
- return geo_direct_wgs_84( alt, 0.0, lon1, paz, dM,lat2,lon2,az2 );
- }
-}
-
-
-// given alt, lat1, lon1, lat2, lon2, calculate starting and ending
-// az1, az2 and distance (s). Lat, lon, and azimuth are in degrees.
-// distance in meters
-int geo_inverse_wgs_84( double alt, double lat1, double lon1, double lat2,
- double lon2, double *az1, double *az2, double *s )
-{
- double a = 6378137.000, rf = 298.257223563;
- int iter=0;
- double RADDEG = (GEOD_INV_PI)/180.0, testv = 1.0E-10;
- double f = ( rf > 0.0 ? 1.0/rf : 0.0 );
- double b = a*(1.0-f);
- // double e2 = f*(2.0-f); // unused in this routine
- double phi1 = lat1*RADDEG, lam1 = lon1*RADDEG;
- double sinphi1 = sin(phi1), cosphi1 = cos(phi1);
- double phi2 = lat2*RADDEG, lam2 = lon2*RADDEG;
- double sinphi2 = sin(phi2), cosphi2 = cos(phi2);
-
- if( (fabs(lat1-lat2) < testv &&
- ( fabs(lon1-lon2) < testv) || fabs(lat1-90.0) < testv ) )
- {
- // TWO STATIONS ARE IDENTICAL : SET DISTANCE & AZIMUTHS TO ZERO */
- *az1 = 0.0; *az2 = 0.0; *s = 0.0;
- return 0;
- } else if( fabs(cosphi1) < testv ) {
- // initial point is polar
- int k = geo_inverse_wgs_84( alt, lat2,lon2,lat1,lon1, az1,az2,s );
- k = k; // avoid compiler error since return result is unused
- b = *az1; *az1 = *az2; *az2 = b;
- return 0;
- } else if( fabs(cosphi2) < testv ) {
- // terminal point is polar
- int k = geo_inverse_wgs_84( alt, lat1,lon1,lat1,lon1+180.0,
- az1,az2,s );
- k = k; // avoid compiler error since return result is unused
- *s /= 2.0;
- *az2 = *az1 + 180.0;
- if( *az2 > 360.0 ) *az2 -= 360.0;
- return 0;
- } else if( (fabs( fabs(lon1-lon2) - 180 ) < testv) &&
- (fabs(lat1+lat2) < testv) )
- {
- // Geodesic passes through the pole (antipodal)
- double s1,s2;
- geo_inverse_wgs_84( alt, lat1,lon1, lat1,lon2, az1,az2, &s1 );
- geo_inverse_wgs_84( alt, lat2,lon2, lat1,lon2, az1,az2, &s2 );
- *az2 = *az1;
- *s = s1 + s2;
- return 0;
- } else {
- // antipodal and polar points don't get here
- double dlam = lam2 - lam1, dlams = dlam;
- double sdlams,cdlams, sig,sinsig,cossig, sinaz,
- cos2saz, c2sigm;
- double tc,temp, us,rnumer,denom, ta,tb;
- double cosu1,sinu1, sinu2,cosu2;
-
- // Reduced latitudes
- temp = (1.0-f)*sinphi1/cosphi1;
- cosu1 = 1.0/sqrt(1.0+temp*temp);
- sinu1 = temp*cosu1;
- temp = (1.0-f)*sinphi2/cosphi2;
- cosu2 = 1.0/sqrt(1.0+temp*temp);
- sinu2 = temp*cosu2;
-
- do {
- sdlams = sin(dlams), cdlams = cos(dlams);
- sinsig = sqrt(cosu2*cosu2*sdlams*sdlams+
- (cosu1*sinu2-sinu1*cosu2*cdlams)*
- (cosu1*sinu2-sinu1*cosu2*cdlams));
- cossig = sinu1*sinu2+cosu1*cosu2*cdlams;
-
- sig = atan2(sinsig,cossig);
- sinaz = cosu1*cosu2*sdlams/sinsig;
- cos2saz = 1.0-sinaz*sinaz;
- c2sigm = (sinu1 == 0.0 || sinu2 == 0.0 ? cossig :
- cossig-2.0*sinu1*sinu2/cos2saz);
- tc = f*cos2saz*(4.0+f*(4.0-3.0*cos2saz))/16.0;
- temp = dlams;
- dlams = dlam+(1.0-tc)*f*sinaz*
- (sig+tc*sinsig*
- (c2sigm+tc*cossig*(-1.0+2.0*c2sigm*c2sigm)));
- if (fabs(dlams) > GEOD_INV_PI && iter++ > 50) {
- return iter;
- }
- } while ( fabs(temp-dlams) > testv);
-
- us = cos2saz*(a*a-b*b)/(b*b); // !!
- // BACK AZIMUTH FROM NORTH
- rnumer = -(cosu1*sdlams);
- denom = sinu1*cosu2-cosu1*sinu2*cdlams;
- *az2 = atan2(rnumer,denom)/RADDEG;
- if( fabs(*az2) < testv ) *az2 = 0.0;
- if(*az2 < 0.0) *az2 += 360.0;
-
- // FORWARD AZIMUTH FROM NORTH
- rnumer = cosu2*sdlams;
- denom = cosu1*sinu2-sinu1*cosu2*cdlams;
- *az1 = atan2(rnumer,denom)/RADDEG;
- if( fabs(*az1) < testv ) *az1 = 0.0;
- if(*az1 < 0.0) *az1 += 360.0;
-
- // Terms a & b
- ta = 1.0+us*(4096.0+us*(-768.0+us*(320.0-175.0*us)))/
- 16384.0;
- tb = us*(256.0+us*(-128.0+us*(74.0-47.0*us)))/1024.0;
-
- // GEODETIC DISTANCE
- *s = b*ta*(sig-tb*sinsig*
- (c2sigm+tb*(cossig*(-1.0+2.0*c2sigm*c2sigm)-tb*
- c2sigm*(-3.0+4.0*sinsig*sinsig)*
- (-3.0+4.0*c2sigm*c2sigm)/6.0)/
- 4.0));
- return 0;
- }
-}
-
-
-/***************************************************************************
-
- TITLE: ls_geodesy
-
-----------------------------------------------------------------------------
-
- FUNCTION: Converts geocentric coordinates to geodetic positions
-
-----------------------------------------------------------------------------
-
- MODULE STATUS: developmental
-
-----------------------------------------------------------------------------
-
- GENEALOGY: Written as part of LaRCSim project by E. B. Jackson
-
-----------------------------------------------------------------------------
-
- DESIGNED BY: E. B. Jackson
-
- CODED BY: E. B. Jackson
-
- MAINTAINED BY: E. B. Jackson
-
-----------------------------------------------------------------------------
-
- MODIFICATION HISTORY:
-
- DATE PURPOSE BY
-
- 930208 Modified to avoid singularity near polar region. EBJ
- 930602 Moved backwards calcs here from ls_step. EBJ
- 931214 Changed erroneous Latitude and Altitude variables to
- *lat_geod and *alt in routine ls_geoc_to_geod. EBJ
- 940111 Changed header files from old ls_eom.h style to ls_types,
- and ls_constants. Also replaced old DATA type with new
- SCALAR type. EBJ
-
- CURRENT RCS HEADER:
-
-$Header$
- * Revision 1.5 1994/01/11 18:47:05 bjax
- * Changed include files to use types and constants, not ls_eom.h
- * Also changed DATA type to SCALAR type.
- *
- * Revision 1.4 1993/12/14 21:06:47 bjax
- * Removed global variable references Altitude and Latitude. EBJ
- *
- * Revision 1.3 1993/06/02 15:03:40 bjax
- * Made new subroutine for calculating geodetic to geocentric; changed name
- * of forward conversion routine from ls_geodesy to ls_geoc_to_geod.
- *
-
-----------------------------------------------------------------------------
-
- REFERENCES:
-
- [ 1] Stevens, Brian L.; and Lewis, Frank L.: "Aircraft
- Control and Simulation", Wiley and Sons, 1992.
- ISBN 0-471-61397-5
-
-
-----------------------------------------------------------------------------
-
- CALLED BY: ls_aux
-
-----------------------------------------------------------------------------
-
- CALLS TO:
-
-----------------------------------------------------------------------------
-
- INPUTS:
- lat_geoc Geocentric latitude, radians, + = North
- radius C.G. radius to earth center, ft
-
-----------------------------------------------------------------------------
-
- OUTPUTS:
- lat_geod Geodetic latitude, radians, + = North
- alt C.G. altitude above mean sea level, ft
- sea_level_r radius from earth center to sea level at
- local vertical (surface normal) of C.G.
-
---------------------------------------------------------------------------*/
-
-
+++ /dev/null
-// fg_geodesy.hxx -- 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.
-//
-// $Id$
-
-
-#ifndef _FG_GEODESY_HXX
-#define _FG_GEODESY_HXX
-
-
-#ifndef __cplusplus
-# error This library requires C++
-#endif
-
-
-#include <simgear/math/point3d.hxx>
-#include <simgear/math/polar3d.hxx>
-
-
-// fgGeocToGeod(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 fgGeocToGeod( double lat_geoc, double radius, double
- *lat_geod, double *alt, double *sea_level_r );
-
-
-// fgGeodToGeoc( 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 fgGeodToGeoc( double lat_geod, double alt, double *sl_radius,
- double *lat_geoc );
-
-
-// convert a geodetic point lon(radians), lat(radians), elev(meter) to
-// a cartesian point
-
-inline Point3D fgGeodToCart(const Point3D& geod) {
- double gc_lon, gc_lat, sl_radius;
-
- // printf("A geodetic point is (%.2f, %.2f, %.2f)\n",
- // geod[0], geod[1], geod[2]);
-
- gc_lon = geod.lon();
- fgGeodToGeoc(geod.lat(), geod.radius(), &sl_radius, &gc_lat);
-
- // printf("A geocentric point is (%.2f, %.2f, %.2f)\n", gc_lon,
- // gc_lat, sl_radius+geod[2]);
-
- Point3D pp = Point3D( gc_lon, gc_lat, sl_radius + geod.radius());
- return fgPolarToCart3d(pp);
-}
-
-
-// given, alt, lat1, lon1, az1 and distance (s), calculate lat2, lon2
-// and az2. Lat, lon, and azimuth are in degrees. distance in meters
-int geo_direct_wgs_84 ( double alt, double lat1, double lon1, double az1,
- double s, double *lat2, double *lon2, double *az2 );
-
-
-// given alt, lat1, lon1, lat2, lon2, calculate starting and ending
-// az1, az2 and distance (s). Lat, lon, and azimuth are in degrees.
-// distance in meters
-int geo_inverse_wgs_84( double alt, double lat1, double lon1, double lat2,
- double lon2, double *az1, double *az2, double *s );
-
-
-/***************************************************************************
-
- TITLE: ls_geodesy
-
-----------------------------------------------------------------------------
-
- FUNCTION: Converts geocentric coordinates to geodetic positions
-
-----------------------------------------------------------------------------
-
- MODULE STATUS: developmental
-
-----------------------------------------------------------------------------
-
- GENEALOGY: Written as part of LaRCSim project by E. B. Jackson
-
-----------------------------------------------------------------------------
-
- DESIGNED BY: E. B. Jackson
-
- CODED BY: E. B. Jackson
-
- MAINTAINED BY: E. B. Jackson
-
-----------------------------------------------------------------------------
-
- MODIFICATION HISTORY:
-
- DATE PURPOSE BY
-
- 930208 Modified to avoid singularity near polar region. EBJ
- 930602 Moved backwards calcs here from ls_step. EBJ
- 931214 Changed erroneous Latitude and Altitude variables to
- *lat_geod and *alt in routine ls_geoc_to_geod. EBJ
- 940111 Changed header files from old ls_eom.h style to ls_types,
- and ls_constants. Also replaced old DATA type with new
- SCALAR type. EBJ
-
- CURRENT RCS HEADER:
-
-$Header$
-
- * Revision 1.5 1994/01/11 18:47:05 bjax
- * Changed include files to use types and constants, not ls_eom.h
- * Also changed DATA type to SCALAR type.
- *
- * Revision 1.4 1993/12/14 21:06:47 bjax
- * Removed global variable references Altitude and Latitude. EBJ
- *
- * Revision 1.3 1993/06/02 15:03:40 bjax
- * Made new subroutine for calculating geodetic to geocentric; changed name
- * of forward conversion routine from ls_geodesy to ls_geoc_to_geod.
- *
-
-----------------------------------------------------------------------------
-
- REFERENCES:
-
- [ 1] Stevens, Brian L.; and Lewis, Frank L.: "Aircraft
- Control and Simulation", Wiley and Sons, 1992.
- ISBN 0-471-61397-5
-
-
-----------------------------------------------------------------------------
-
- CALLED BY: ls_aux
-
-----------------------------------------------------------------------------
-
- CALLS TO:
-
-----------------------------------------------------------------------------
-
- INPUTS:
- lat_geoc Geocentric latitude, radians, + = North
- radius C.G. radius to earth center, ft
-
-----------------------------------------------------------------------------
-
- OUTPUTS:
- lat_geod Geodetic latitude, radians, + = North
- alt C.G. altitude above mean sea level, ft
- sea_level_r radius from earth center to sea level at
- local vertical (surface normal) of C.G.
-
---------------------------------------------------------------------------*/
-
-
-#endif // _FG_GEODESY_HXX
--- /dev/null
+// localconsts.hxx -- various constant that are shared
+//
+// Written by Curtis Olson, started September 2000.
+//
+// Copyright (C) 2000 Curtis L. Olson - curt@flightgear.org
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Library General Public
+// License as published by the Free Software Foundation; either
+// version 2 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// Library General Public License for more details.
+//
+// You should have received a copy of the GNU Library General Public
+// License along with this library; if not, write to the
+// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+// Boston, MA 02111-1307, USA.
+//
+// $Id$
+
+
+#ifndef _SG_LOCAL_CONSTS_HXX
+#define _SG_LOCAL_CONSTS_HXX
+
+
+// Value of earth flattening parameter from ref [8]
+//
+// Note: FP = f
+// E = 1-f
+// EPS = sqrt(1-(1-f)^2)
+//
+
+static const double FP = 0.003352813178;
+static const double E = 0.996647186;
+static const double EPS = 0.081819221;
+static const double INVG = 0.031080997;
+
+
+#endif // _SG_LOCAL_CONSTS_HXX
# include <math.h>
#endif
+#include "localconsts.hxx"
+
// I don't understand ... <math.h> or <cmath> should be included
// already depending on how you defined FG_HAVE_STD_INCLUDES, but I
// can go ahead and add this -- CLO
// Find the Altitude above the Ellipsoid (WGS84) given the Earth
// Centered Cartesian coordinate vector Distances are specified in
// meters.
-double fgGeodAltFromCart(const Point3D& cp);
+double sgGeodAltFromCart(const Point3D& cp);
// Convert a polar coordinate to a cartesian coordinate. Lon and Lat
-// must be specified in radians. The FG convention is for distances
+// must be specified in radians. The SG convention is for distances
// to be specified in meters
-inline Point3D fgPolarToCart3d(const Point3D& p) {
+inline Point3D sgPolarToCart3d(const Point3D& p) {
double tmp = cos( p.lat() ) * p.radius();
return Point3D( cos( p.lon() ) * tmp,
// Convert a cartesian coordinate to polar coordinates (lon/lat
// specified in radians. Distances are specified in meters.
-inline Point3D fgCartToPolar3d(const Point3D& cp) {
+inline Point3D sgCartToPolar3d(const Point3D& cp) {
return Point3D( atan2( cp.y(), cp.x() ),
FG_PI_2 -
atan2( sqrt(cp.x()*cp.x() + cp.y()*cp.y()), cp.z() ),
--- /dev/null
+// 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>
+#else
+# include <math.h>
+# include <errno.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
+
+
+// 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 )
+{
+ 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);
+ // cout << " x_alpha = " << x_alpha << endl;
+ double tmp = RESQ_M - x_alpha * x_alpha;
+ if ( tmp < 0.0 ) { tmp = 0.0; }
+ mu_alpha = atan2(sqrt(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);
+
+ // check for domain error
+ if ( errno == EDOM ) {
+ FG_LOG( FG_GENERAL, FG_ALERT, "Domain ERROR in fgGeocToGeod!!!!" );
+ *alt = 0.0;
+ }
+
+ denom = sqrt(1-EPS*EPS*sin_mu_a*sin_mu_a);
+ 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));
+
+ // check for domain error
+ if ( errno == EDOM ) {
+ FG_LOG( FG_GENERAL, FG_ALERT, "Domain ERROR in sgGeocToGeod!!!!" );
+ *sea_level_r = 0.0;
+ }
+ }
+
+}
+
+
+// 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 =
+ sqrt(RESQ_M / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
+ py = *sl_radius*sin_lambda_sl + alt*sin_mu;
+ px = *sl_radius*cos_lambda_sl + alt*cos_mu;
+ *lat_geoc = atan2( py, px );
+}
+
+
+// Direct and inverse distance functions
+//
+// Proceedings of the 7th International Symposium on Geodetic
+// Computations, 1985
+//
+// "The Nested Coefficient Method for Accurate Solutions of Direct and
+// Inverse Geodetic Problems With Any Length"
+//
+// Zhang Xue-Lian
+// pp 747-763
+//
+// modified for FlightGear to use WGS84 only -- Norman Vine
+
+#define GEOD_INV_PI FG_PI
+
+// s == distance
+// az = azimuth
+
+// for WGS_84 a = 6378137.000, rf = 298.257223563;
+
+static double M0( double e2 ) {
+ //double e4 = e2*e2;
+ return GEOD_INV_PI*(1.0 - e2*( 1.0/4.0 + e2*( 3.0/64.0 +
+ e2*(5.0/256.0) )))/2.0;
+}
+
+
+// given, alt, lat1, lon1, az1 and distance (s), calculate lat2, lon2
+// and az2. Lat, lon, and azimuth are in degrees. distance in meters
+int geo_direct_wgs_84 ( double alt, double lat1, double lon1, double az1,
+ double s, double *lat2, double *lon2, double *az2 )
+{
+ double a = 6378137.000, rf = 298.257223563;
+ double RADDEG = (GEOD_INV_PI)/180.0, testv = 1.0E-10;
+ double f = ( rf > 0.0 ? 1.0/rf : 0.0 );
+ double b = a*(1.0-f);
+ double e2 = f*(2.0-f);
+ double phi1 = lat1*RADDEG, lam1 = lon1*RADDEG;
+ double sinphi1 = sin(phi1), cosphi1 = cos(phi1);
+ double azm1 = az1*RADDEG;
+ double sinaz1 = sin(azm1), cosaz1 = cos(azm1);
+
+
+ if( fabs(s) < 0.01 ) { // distance < centimeter => congruency
+ *lat2 = lat1;
+ *lon2 = lon1;
+ *az2 = 180.0 + az1;
+ if( *az2 > 360.0 ) *az2 -= 360.0;
+ return 0;
+ } else if( cosphi1 ) { // non-polar origin
+ // u1 is reduced latitude
+ double tanu1 = sqrt(1.0-e2)*sinphi1/cosphi1;
+ double sig1 = atan2(tanu1,cosaz1);
+ double cosu1 = 1.0/sqrt( 1.0 + tanu1*tanu1 ), sinu1 = tanu1*cosu1;
+ double sinaz = cosu1*sinaz1, cos2saz = 1.0-sinaz*sinaz;
+ double us = cos2saz*e2/(1.0-e2);
+
+ // Terms
+ double ta = 1.0+us*(4096.0+us*(-768.0+us*(320.0-175.0*us)))/16384.0,
+ tb = us*(256.0+us*(-128.0+us*(74.0-47.0*us)))/1024.0,
+ tc = 0;
+
+ // FIRST ESTIMATE OF SIGMA (SIG)
+ double first = s/(b*ta); // !!
+ double sig = first;
+ double c2sigm, sinsig,cossig, temp,denom,rnumer, dlams, dlam;
+ do {
+ c2sigm = cos(2.0*sig1+sig);
+ sinsig = sin(sig); cossig = cos(sig);
+ temp = sig;
+ sig = first +
+ tb*sinsig*(c2sigm+tb*(cossig*(-1.0+2.0*c2sigm*c2sigm) -
+ tb*c2sigm*(-3.0+4.0*sinsig*sinsig)
+ *(-3.0+4.0*c2sigm*c2sigm)/6.0)
+ /4.0);
+ } while( fabs(sig-temp) > testv);
+
+ // LATITUDE OF POINT 2
+ // DENOMINATOR IN 2 PARTS (TEMP ALSO USED LATER)
+ temp = sinu1*sinsig-cosu1*cossig*cosaz1;
+ denom = (1.0-f)*sqrt(sinaz*sinaz+temp*temp);
+
+ // NUMERATOR
+ rnumer = sinu1*cossig+cosu1*sinsig*cosaz1;
+ *lat2 = atan2(rnumer,denom)/RADDEG;
+
+ // DIFFERENCE IN LONGITUDE ON AUXILARY SPHERE (DLAMS )
+ rnumer = sinsig*sinaz1;
+ denom = cosu1*cossig-sinu1*sinsig*cosaz1;
+ dlams = atan2(rnumer,denom);
+
+ // TERM C
+ tc = f*cos2saz*(4.0+f*(4.0-3.0*cos2saz))/16.0;
+
+ // DIFFERENCE IN LONGITUDE
+ dlam = dlams-(1.0-tc)*f*sinaz*(sig+tc*sinsig*
+ (c2sigm+
+ tc*cossig*(-1.0+2.0*
+ c2sigm*c2sigm)));
+ *lon2 = (lam1+dlam)/RADDEG;
+ if (*lon2 > 180.0 ) *lon2 -= 360.0;
+ if (*lon2 < -180.0 ) *lon2 += 360.0;
+
+ // AZIMUTH - FROM NORTH
+ *az2 = atan2(-sinaz,temp)/RADDEG;
+ if ( fabs(*az2) < testv ) *az2 = 0.0;
+ if( *az2 < 0.0) *az2 += 360.0;
+ return 0;
+ } else { // phi1 == 90 degrees, polar origin
+ double dM = a*M0(e2) - s;
+ double paz = ( phi1 < 0.0 ? 180.0 : 0.0 );
+ return geo_direct_wgs_84( alt, 0.0, lon1, paz, dM,lat2,lon2,az2 );
+ }
+}
+
+
+// given alt, lat1, lon1, lat2, lon2, calculate starting and ending
+// az1, az2 and distance (s). Lat, lon, and azimuth are in degrees.
+// distance in meters
+int geo_inverse_wgs_84( double alt, double lat1, double lon1, double lat2,
+ double lon2, double *az1, double *az2, double *s )
+{
+ double a = 6378137.000, rf = 298.257223563;
+ int iter=0;
+ double RADDEG = (GEOD_INV_PI)/180.0, testv = 1.0E-10;
+ double f = ( rf > 0.0 ? 1.0/rf : 0.0 );
+ double b = a*(1.0-f);
+ // double e2 = f*(2.0-f); // unused in this routine
+ double phi1 = lat1*RADDEG, lam1 = lon1*RADDEG;
+ double sinphi1 = sin(phi1), cosphi1 = cos(phi1);
+ double phi2 = lat2*RADDEG, lam2 = lon2*RADDEG;
+ double sinphi2 = sin(phi2), cosphi2 = cos(phi2);
+
+ if( (fabs(lat1-lat2) < testv &&
+ ( fabs(lon1-lon2) < testv) || fabs(lat1-90.0) < testv ) )
+ {
+ // TWO STATIONS ARE IDENTICAL : SET DISTANCE & AZIMUTHS TO ZERO */
+ *az1 = 0.0; *az2 = 0.0; *s = 0.0;
+ return 0;
+ } else if( fabs(cosphi1) < testv ) {
+ // initial point is polar
+ int k = geo_inverse_wgs_84( alt, lat2,lon2,lat1,lon1, az1,az2,s );
+ k = k; // avoid compiler error since return result is unused
+ b = *az1; *az1 = *az2; *az2 = b;
+ return 0;
+ } else if( fabs(cosphi2) < testv ) {
+ // terminal point is polar
+ int k = geo_inverse_wgs_84( alt, lat1,lon1,lat1,lon1+180.0,
+ az1,az2,s );
+ k = k; // avoid compiler error since return result is unused
+ *s /= 2.0;
+ *az2 = *az1 + 180.0;
+ if( *az2 > 360.0 ) *az2 -= 360.0;
+ return 0;
+ } else if( (fabs( fabs(lon1-lon2) - 180 ) < testv) &&
+ (fabs(lat1+lat2) < testv) )
+ {
+ // Geodesic passes through the pole (antipodal)
+ double s1,s2;
+ geo_inverse_wgs_84( alt, lat1,lon1, lat1,lon2, az1,az2, &s1 );
+ geo_inverse_wgs_84( alt, lat2,lon2, lat1,lon2, az1,az2, &s2 );
+ *az2 = *az1;
+ *s = s1 + s2;
+ return 0;
+ } else {
+ // antipodal and polar points don't get here
+ double dlam = lam2 - lam1, dlams = dlam;
+ double sdlams,cdlams, sig,sinsig,cossig, sinaz,
+ cos2saz, c2sigm;
+ double tc,temp, us,rnumer,denom, ta,tb;
+ double cosu1,sinu1, sinu2,cosu2;
+
+ // Reduced latitudes
+ temp = (1.0-f)*sinphi1/cosphi1;
+ cosu1 = 1.0/sqrt(1.0+temp*temp);
+ sinu1 = temp*cosu1;
+ temp = (1.0-f)*sinphi2/cosphi2;
+ cosu2 = 1.0/sqrt(1.0+temp*temp);
+ sinu2 = temp*cosu2;
+
+ do {
+ sdlams = sin(dlams), cdlams = cos(dlams);
+ sinsig = sqrt(cosu2*cosu2*sdlams*sdlams+
+ (cosu1*sinu2-sinu1*cosu2*cdlams)*
+ (cosu1*sinu2-sinu1*cosu2*cdlams));
+ cossig = sinu1*sinu2+cosu1*cosu2*cdlams;
+
+ sig = atan2(sinsig,cossig);
+ sinaz = cosu1*cosu2*sdlams/sinsig;
+ cos2saz = 1.0-sinaz*sinaz;
+ c2sigm = (sinu1 == 0.0 || sinu2 == 0.0 ? cossig :
+ cossig-2.0*sinu1*sinu2/cos2saz);
+ tc = f*cos2saz*(4.0+f*(4.0-3.0*cos2saz))/16.0;
+ temp = dlams;
+ dlams = dlam+(1.0-tc)*f*sinaz*
+ (sig+tc*sinsig*
+ (c2sigm+tc*cossig*(-1.0+2.0*c2sigm*c2sigm)));
+ if (fabs(dlams) > GEOD_INV_PI && iter++ > 50) {
+ return iter;
+ }
+ } while ( fabs(temp-dlams) > testv);
+
+ us = cos2saz*(a*a-b*b)/(b*b); // !!
+ // BACK AZIMUTH FROM NORTH
+ rnumer = -(cosu1*sdlams);
+ denom = sinu1*cosu2-cosu1*sinu2*cdlams;
+ *az2 = atan2(rnumer,denom)/RADDEG;
+ if( fabs(*az2) < testv ) *az2 = 0.0;
+ if(*az2 < 0.0) *az2 += 360.0;
+
+ // FORWARD AZIMUTH FROM NORTH
+ rnumer = cosu2*sdlams;
+ denom = cosu1*sinu2-sinu1*cosu2*cdlams;
+ *az1 = atan2(rnumer,denom)/RADDEG;
+ if( fabs(*az1) < testv ) *az1 = 0.0;
+ if(*az1 < 0.0) *az1 += 360.0;
+
+ // Terms a & b
+ ta = 1.0+us*(4096.0+us*(-768.0+us*(320.0-175.0*us)))/
+ 16384.0;
+ tb = us*(256.0+us*(-128.0+us*(74.0-47.0*us)))/1024.0;
+
+ // GEODETIC DISTANCE
+ *s = b*ta*(sig-tb*sinsig*
+ (c2sigm+tb*(cossig*(-1.0+2.0*c2sigm*c2sigm)-tb*
+ c2sigm*(-3.0+4.0*sinsig*sinsig)*
+ (-3.0+4.0*c2sigm*c2sigm)/6.0)/
+ 4.0));
+ return 0;
+ }
+}
+
+
+/***************************************************************************
+
+ TITLE: ls_geodesy
+
+----------------------------------------------------------------------------
+
+ FUNCTION: Converts geocentric coordinates to geodetic positions
+
+----------------------------------------------------------------------------
+
+ MODULE STATUS: developmental
+
+----------------------------------------------------------------------------
+
+ GENEALOGY: Written as part of LaRCSim project by E. B. Jackson
+
+----------------------------------------------------------------------------
+
+ DESIGNED BY: E. B. Jackson
+
+ CODED BY: E. B. Jackson
+
+ MAINTAINED BY: E. B. Jackson
+
+----------------------------------------------------------------------------
+
+ MODIFICATION HISTORY:
+
+ DATE PURPOSE BY
+
+ 930208 Modified to avoid singularity near polar region. EBJ
+ 930602 Moved backwards calcs here from ls_step. EBJ
+ 931214 Changed erroneous Latitude and Altitude variables to
+ *lat_geod and *alt in routine ls_geoc_to_geod. EBJ
+ 940111 Changed header files from old ls_eom.h style to ls_types,
+ and ls_constants. Also replaced old DATA type with new
+ SCALAR type. EBJ
+
+ CURRENT RCS HEADER:
+
+$Header$
+ * Revision 1.5 1994/01/11 18:47:05 bjax
+ * Changed include files to use types and constants, not ls_eom.h
+ * Also changed DATA type to SCALAR type.
+ *
+ * Revision 1.4 1993/12/14 21:06:47 bjax
+ * Removed global variable references Altitude and Latitude. EBJ
+ *
+ * Revision 1.3 1993/06/02 15:03:40 bjax
+ * Made new subroutine for calculating geodetic to geocentric; changed name
+ * of forward conversion routine from ls_geodesy to ls_geoc_to_geod.
+ *
+
+----------------------------------------------------------------------------
+
+ REFERENCES:
+
+ [ 1] Stevens, Brian L.; and Lewis, Frank L.: "Aircraft
+ Control and Simulation", Wiley and Sons, 1992.
+ ISBN 0-471-61397-5
+
+
+----------------------------------------------------------------------------
+
+ CALLED BY: ls_aux
+
+----------------------------------------------------------------------------
+
+ CALLS TO:
+
+----------------------------------------------------------------------------
+
+ INPUTS:
+ lat_geoc Geocentric latitude, radians, + = North
+ radius C.G. radius to earth center, ft
+
+----------------------------------------------------------------------------
+
+ OUTPUTS:
+ lat_geod Geodetic latitude, radians, + = North
+ alt C.G. altitude above mean sea level, ft
+ sea_level_r radius from earth center to sea level at
+ local vertical (surface normal) of C.G.
+
+--------------------------------------------------------------------------*/
+
+
--- /dev/null
+// sg_geodesy.hxx -- 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.
+//
+// $Id$
+
+
+#ifndef _SG_GEODESY_HXX
+#define _SG_GEODESY_HXX
+
+
+#ifndef __cplusplus
+# error This library requires C++
+#endif
+
+
+#include <simgear/math/point3d.hxx>
+#include <simgear/math/polar3d.hxx>
+
+
+// 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 );
+
+
+// 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 );
+
+
+// convert a geodetic point lon(radians), lat(radians), elev(meter) to
+// a cartesian point
+
+inline Point3D sgGeodToCart(const Point3D& geod) {
+ double gc_lon, gc_lat, sl_radius;
+
+ // printf("A geodetic point is (%.2f, %.2f, %.2f)\n",
+ // geod[0], geod[1], geod[2]);
+
+ gc_lon = geod.lon();
+ sgGeodToGeoc(geod.lat(), geod.radius(), &sl_radius, &gc_lat);
+
+ // printf("A geocentric point is (%.2f, %.2f, %.2f)\n", gc_lon,
+ // gc_lat, sl_radius+geod[2]);
+
+ Point3D pp = Point3D( gc_lon, gc_lat, sl_radius + geod.radius());
+ return sgPolarToCart3d(pp);
+}
+
+
+// given, alt, lat1, lon1, az1 and distance (s), calculate lat2, lon2
+// and az2. Lat, lon, and azimuth are in degrees. distance in meters
+int geo_direct_wgs_84 ( double alt, double lat1, double lon1, double az1,
+ double s, double *lat2, double *lon2, double *az2 );
+
+
+// given alt, lat1, lon1, lat2, lon2, calculate starting and ending
+// az1, az2 and distance (s). Lat, lon, and azimuth are in degrees.
+// distance in meters
+int geo_inverse_wgs_84( double alt, double lat1, double lon1, double lat2,
+ double lon2, double *az1, double *az2, double *s );
+
+
+/***************************************************************************
+
+ TITLE: ls_geodesy
+
+----------------------------------------------------------------------------
+
+ FUNCTION: Converts geocentric coordinates to geodetic positions
+
+----------------------------------------------------------------------------
+
+ MODULE STATUS: developmental
+
+----------------------------------------------------------------------------
+
+ GENEALOGY: Written as part of LaRCSim project by E. B. Jackson
+
+----------------------------------------------------------------------------
+
+ DESIGNED BY: E. B. Jackson
+
+ CODED BY: E. B. Jackson
+
+ MAINTAINED BY: E. B. Jackson
+
+----------------------------------------------------------------------------
+
+ MODIFICATION HISTORY:
+
+ DATE PURPOSE BY
+
+ 930208 Modified to avoid singularity near polar region. EBJ
+ 930602 Moved backwards calcs here from ls_step. EBJ
+ 931214 Changed erroneous Latitude and Altitude variables to
+ *lat_geod and *alt in routine ls_geoc_to_geod. EBJ
+ 940111 Changed header files from old ls_eom.h style to ls_types,
+ and ls_constants. Also replaced old DATA type with new
+ SCALAR type. EBJ
+
+ CURRENT RCS HEADER:
+
+$Header$
+
+ * Revision 1.5 1994/01/11 18:47:05 bjax
+ * Changed include files to use types and constants, not ls_eom.h
+ * Also changed DATA type to SCALAR type.
+ *
+ * Revision 1.4 1993/12/14 21:06:47 bjax
+ * Removed global variable references Altitude and Latitude. EBJ
+ *
+ * Revision 1.3 1993/06/02 15:03:40 bjax
+ * Made new subroutine for calculating geodetic to geocentric; changed name
+ * of forward conversion routine from ls_geodesy to ls_geoc_to_geod.
+ *
+
+----------------------------------------------------------------------------
+
+ REFERENCES:
+
+ [ 1] Stevens, Brian L.; and Lewis, Frank L.: "Aircraft
+ Control and Simulation", Wiley and Sons, 1992.
+ ISBN 0-471-61397-5
+
+
+----------------------------------------------------------------------------
+
+ CALLED BY: ls_aux
+
+----------------------------------------------------------------------------
+
+ CALLS TO:
+
+----------------------------------------------------------------------------
+
+ INPUTS:
+ lat_geoc Geocentric latitude, radians, + = North
+ radius C.G. radius to earth center, ft
+
+----------------------------------------------------------------------------
+
+ OUTPUTS:
+ lat_geod Geodetic latitude, radians, + = North
+ alt C.G. altitude above mean sea level, ft
+ sea_level_r radius from earth center to sea level at
+ local vertical (surface normal) of C.G.
+
+--------------------------------------------------------------------------*/
+
+
+#endif // _SG_GEODESY_HXX
#define RADHR(x) DEGHR(x*RAD_TO_DEG)
+static const double MJD0 = 2415020.0;
+static const double J2000 = 2451545.0 - MJD0;
+static const double SIDRATE = 0.9972695677;
+
+
SGTime::SGTime( double lon, double lat, const string& root )
{
FG_LOG( FG_EVENT, FG_INFO, "Initializing Time" );
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