--- /dev/null
+/**************************************************************************
+ * fg_geodesy.c -- 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.
+ *
+ * $Id$
+ * (Log is kept at end of this file)
+ **************************************************************************/
+
+
+#include <math.h>
+
+#include "fg_geodesy.h"
+#include "../constants.h"
+
+
+/* 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, 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.
+ */
+
+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_KM*E;
+ *alt = radius - *sea_level_r;
+ } else {
+ t_lat = tan(lat_geoc);
+ x_alpha = E*EQUATORIAL_RADIUS_KM/sqrt(t_lat*t_lat + E*E);
+ mu_alpha = atan2(sqrt(RESQ_KM - x_alpha*x_alpha),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);
+ rho_alpha = EQUATORIAL_RADIUS_KM*(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_KM / (1 + ((1/(E*E))-1)*sin_lambda_sl*sin_lambda_sl));
+ }
+}
+
+
+/* fgGeodToGeoc( lat_geod, alt, *sl_radius, *lat_geoc )
+ * INPUTS:
+ * lat_geod Geodetic latitude, radians, + = North
+ * alt C.G. altitude above mean sea level, ft
+ *
+ * OUTPUTS:
+ * sl_radius SEA LEVEL radius to earth center, ft (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_KM / (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 );
+}
+
+
+/***************************************************************************
+
+ 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:
+
+$Header$
+$Log$
+Revision 1.1 1997/07/31 23:13:14 curt
+Initial revision.
+
+Revision 1.1 1997/05/29 00:09:56 curt
+Initial Flight Gear revision.
+
+ * 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.
+
+--------------------------------------------------------------------------*/
+
+
+/* $Log$
+/* Revision 1.1 1997/07/31 23:13:14 curt
+/* Initial revision.
+/*
+ */
--- /dev/null
+/**************************************************************************
+ * fg_geodesy.h -- 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.
+ *
+ * $Id$
+ * (Log is kept at end of this file)
+ **************************************************************************/
+
+
+#ifndef FG_GEODESY_H
+#define FG_GEODESY_H
+
+
+/* fgGeocToGeod(lat_geoc, radius, *lat_geod, *alt, *sea_level_r)
+ * 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.
+ */
+
+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, ft
+ *
+ * OUTPUTS:
+ * sl_radius SEA LEVEL radius to earth center, ft (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 );
+
+
+
+/***************************************************************************
+
+ 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:
+
+$Header$
+$Log$
+Revision 1.1 1997/07/31 23:13:14 curt
+Initial revision.
+
+Revision 1.1 1997/05/29 00:09:56 curt
+Initial Flight Gear revision.
+
+ * 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_H */
+
+
+/* $Log$
+/* Revision 1.1 1997/07/31 23:13:14 curt
+/* Initial revision.
+/*
+ */
projects / simgear.git / commitdiff