-// 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.
+/**
+ * Convert from geocentric coordinates to geodetic coordinates
+ * @param lat_geoc (in) Geocentric latitude, radians, + = North
+ * @param radius (in) C.G. radius to earth center (meters)
+ * @param lat_geod (out) Geodetic latitude, radians, + = North
+ * @param alt (out) C.G. altitude above mean sea level (meters)
+ * @param sea_level_r (out) 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);
+
+
+/**
+ * Convert from geodetic coordinates to geocentric coordinates.
+ * WARNING: this function is non-reversible. Due to the fact that
+ * "up" is a different direction for geocentric and geodetic frames,
+ * you can not simply add your "alt" parameter to the "sl_radius"
+ * result and get back (via sgGeodToGeoc()) to the coordinates you
+ * started with. The error under normal conditions will be of
+ * centimeter order; whether that is important or not is application
+ * dependent. Consider using sgGeodToCart() instead.
*
- * Revision 1.4 1993/12/14 21:06:47 bjax
- * Removed global variable references Altitude and Latitude. EBJ
+ * @param lat_geod (in) Geodetic latitude, radians, + = North
+ * @param alt (in) C.G. altitude above mean sea level (meters)
+ * @param sl_radius (out) SEA LEVEL radius to earth center (meters)
+ * @param lat_geoc (out) Geocentric latitude, radians, + = North
+ */
+void sgGeodToGeoc(double lat_geod, double alt,
+ double *sl_radius, double *lat_geoc );
+
+/**
+ * Convert a cartesian point to a geodetic lat/lon/altitude.
*
- * 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.
+ * @param xyz (in) Pointer to cartesian point.
+ * @param lat (out) Latitude, in radians
+ * @param lon (out) Longitude, in radians
+ * @param alt (out) Altitude, in meters above the WGS84 ellipsoid
+ */
+void sgCartToGeod(const double* xyz, double* lat, double* lon, double* alt);
+
+/**
+ * Convert a cartesian point to a geodetic lat/lon/altitude.
+ * Alternate form using Point3D objects.
*
+ * @param cartesian point
+ * @return geodetic point
+ */
+inline Point3D sgCartToGeod(const Point3D& p)
+{
+ double lat, lon, alt, xyz[3];
+ xyz[0] = p.x(); xyz[1] = p.y(); xyz[2] = p.z();
+ sgCartToGeod(xyz, &lat, &lon, &alt);
+ return Point3D(lon, lat, alt);
+}
-----------------------------------------------------------------------------
-
- 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.
---------------------------------------------------------------------------*/
+/**
+ * Convert a geodetic lat/lon/altitude to a cartesian point.
+ *
+ * @param lat (in) Latitude, in radians
+ * @param lon (in) Longitude, in radians
+ * @param alt (in) Altitude, in meters above the WGS84 ellipsoid
+ * @param xyz (out) Pointer to cartesian point.
+ */
+void sgGeodToCart(double lat, double lon, double alt, double* xyz);
+
+/**
+ * Convert a geodetic lat/lon/altitude to a cartesian point.
+ * Alternate form using Point3D objects.
+ *
+ * @param geodetic point
+ * @return cartesian point
+ */
+inline Point3D sgGeodToCart(const Point3D& geod)
+{
+ double xyz[3];
+ sgGeodToCart(geod.lat(), geod.lon(), geod.elev(), xyz);
+ return Point3D(xyz[0], xyz[1], xyz[2]);
+}
+/**
+ * Given a starting position and an offset radial and distance,
+ * calculate an ending positon on a wgs84 ellipsoid.
+ * @param alt (in) meters
+ * @param lat1 (in) degrees
+ * @param lon1 (in) degrees
+ * @param az1 (in) degrees
+ * @param s (in) distance in meters
+ * @param lat2 (out) degrees
+ * @param lon2 (out) degrees
+ * @param az2 (out) return course in degrees
+ */
+int geo_direct_wgs_84 ( double alt, double lat1,
+ double lon1, double az1,
+ double s, double *lat2, double *lon2,
+ double *az2 );
+
+
+/**
+ * Given an altitude and two sets of (lat, lon) calculate great circle
+ * distance between them as well as the starting and ending azimuths.
+ * @param alt (in) meters
+ * @param lat1 (in) degrees
+ * @param lon1 (in) degrees
+ * @param lat2 (in) degrees
+ * @param lon2 (in) degrees
+ * @param az1 (out) start heading degrees
+ * @param az2 (out) end heading degrees
+ * @param s (out) distance meters
+ */
+int geo_inverse_wgs_84( double alt, double lat1,
+ double lon1, double lat2,
+ double lon2, double *az1, double *az2,
+ double *s );
#endif // _SG_GEODESY_HXX
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