// flight.cxx -- a general interface to the various flight models
//
// Written by Curtis Olson, started May 1997.
//
// Copyright (C) 1997  Curtis L. Olson  - http://www.flightgear.org/~curt
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program 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
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
//
// $Id: flight.cxx,v 1.35 2007-11-09 05:39:13 frohlich Exp $

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "flight.hxx"

#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>
#include <simgear/math/SGMath.hxx>
#include <simgear/scene/material/mat.hxx>
#include <simgear/timing/timestamp.hxx>

#include <Scenery/scenery.hxx>
#include <Main/globals.hxx>
#include <Main/fg_props.hxx>
#include <FDM/groundcache.hxx>


static inline void assign(double* ptr, const SGVec3d& vec)
{
  ptr[0] = vec[0];
  ptr[1] = vec[1];
  ptr[2] = vec[2];
}

// base_fdm_state is the internal state that is updated in integer
// multiples of "dt".  This leads to "jitter" with respect to the real
// world time, so we introduce cur_fdm_state which is extrapolated by
// the difference between sim time and real world time

FGInterface *cur_fdm_state = 0;
FGInterface base_fdm_state;

// Constructor
FGInterface::FGInterface()
  : remainder(0)
{
    _setup();
}

FGInterface::FGInterface( double dt )
  : remainder(0)
{
    _setup();
}

// Destructor
FGInterface::~FGInterface() {
    // unbind();                   // FIXME: should be called explicitly
}


int
FGInterface::_calc_multiloop (double dt)
{
  int hz = fgGetInt("/sim/model-hz");
  int speedup = fgGetInt("/sim/speed-up");

  dt += remainder;
  remainder = 0;
  double ml = dt * hz;
  // Avoid roundoff problems by adding the roundoff itself.
  // ... ok, two times the roundoff to have enough room.
  int multiloop = int(floor(ml * (1.0 + 2.0*DBL_EPSILON)));
  remainder = (ml - multiloop) / hz;

  // If we artificially inflate ml above by a tiny amount to get the
  // closest integer, then subtract the integer from the original
  // slightly smaller value, we can get a negative remainder.
  // Logically this should never happen, and we definitely don't want
  // to carry a negative remainder over to the next iteration, so
  // never let the remainder go below zero.
  // 
  // Note: this fixes a problem where we run 1, 3, 1, 3, 1, 3... loops
  // of the FDM when in fact we want to run 2, 2, 2, 2, 2...
  if ( remainder < 0 ) { remainder = 0; }

  return (multiloop * speedup);
}


/**
 * Set default values for the state of the FDM.
 *
 * This method is invoked by the constructors.
 */
void
FGInterface::_setup ()
{
    inited = false;
    bound = false;

    d_cg_rp_body_v = SGVec3d::zeros();
    v_dot_local_v = SGVec3d::zeros();
    v_dot_body_v = SGVec3d::zeros();
    a_cg_body_v = SGVec3d::zeros();
    a_pilot_body_v = SGVec3d::zeros();
    n_cg_body_v = SGVec3d::zeros();
    v_local_v = SGVec3d::zeros();
    v_local_rel_ground_v = SGVec3d::zeros();
    v_local_airmass_v = SGVec3d::zeros();
    v_wind_body_v = SGVec3d::zeros();
    omega_body_v = SGVec3d::zeros();
    euler_rates_v = SGVec3d::zeros();
    geocentric_rates_v = SGVec3d::zeros();
    geodetic_position_v = SGGeod::fromRadM(0, 0, 0);
    cartesian_position_v = SGVec3d::fromGeod(geodetic_position_v);
    geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
    euler_angles_v = SGVec3d::zeros();
    
    nlf=0;
    v_rel_wind=v_true_kts=0;
    v_ground_speed=v_equiv_kts=0;
    v_calibrated_kts=0;
    alpha=beta=0;
    gamma_vert_rad=0;
    density=mach_number=0;
    static_pressure=total_pressure=0;
    dynamic_pressure=0;
    static_temperature=total_temperature=0;
    sea_level_radius=earth_position_angle=0;
    runway_altitude=0;
    climb_rate=0;
    altitude_agl=0;
}

void
FGInterface::init () {}

/**
 * Initialize the state of the FDM.
 *
 * Subclasses of FGInterface may do their own, additional initialization,
 * but there is some that is common to all.  Normally, they should call
 * this before they begin their own init to make sure the basic structures
 * are set up properly.
 */
void
FGInterface::common_init ()
{
    SG_LOG( SG_FLIGHT, SG_INFO, "Start common FDM init" );

    set_inited( true );

//     stamp();
//     set_remainder( 0 );

    // Set initial position
    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing position..." );
    double lon = fgGetDouble("/sim/presets/longitude-deg")
      * SGD_DEGREES_TO_RADIANS;
    double lat = fgGetDouble("/sim/presets/latitude-deg")
      * SGD_DEGREES_TO_RADIANS;
    double alt_ft = fgGetDouble("/sim/presets/altitude-ft");
    double alt_m = alt_ft * SG_FEET_TO_METER;
    set_Longitude( lon );
    set_Latitude( lat );
    SG_LOG( SG_FLIGHT, SG_INFO, "Checking for lon = "
            << lon*SGD_RADIANS_TO_DEGREES << "deg, lat = "
            << lat*SGD_RADIANS_TO_DEGREES << "deg, alt = "
            << alt_ft << "ft");

    double ground_elev_m = get_groundlevel_m(lat, lon, alt_m);
    double ground_elev_ft = ground_elev_m * SG_METER_TO_FEET;
    _set_Runway_altitude ( ground_elev_ft );
    if ( fgGetBool("/sim/presets/onground") || alt_ft < ground_elev_ft ) {
        fgSetDouble("/position/altitude-ft", ground_elev_ft + 0.1);
        set_Altitude( ground_elev_ft + 0.1);
    } else {
        set_Altitude( alt_ft );
    }

    // Set ground elevation
    SG_LOG( SG_FLIGHT, SG_INFO,
            "...initializing ground elevation to " << ground_elev_ft
            << "ft..." );

    // Set sea-level radius
    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing sea-level radius..." );
    SG_LOG( SG_FLIGHT, SG_INFO, " lat = "
            << fgGetDouble("/sim/presets/latitude-deg")
            << " alt = " << get_Altitude() );
    double slr = SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v);
    _set_Sea_level_radius( slr * SG_METER_TO_FEET );

    // Set initial velocities
    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing velocities..." );
    if ( !fgHasNode("/sim/presets/speed-set") ) {
        set_V_calibrated_kts(0.0);
    } else {
        const string speedset = fgGetString("/sim/presets/speed-set");
        if ( speedset == "knots" || speedset == "KNOTS" ) {
            set_V_calibrated_kts( fgGetDouble("/sim/presets/airspeed-kt") );
        } else if ( speedset == "mach" || speedset == "MACH" ) {
            set_Mach_number( fgGetDouble("/sim/presets/mach") );
        } else if ( speedset == "UVW" || speedset == "uvw" ) {
            set_Velocities_Wind_Body(
                                     fgGetDouble("/sim/presets/uBody-fps"),
                                     fgGetDouble("/sim/presets/vBody-fps"),
                                     fgGetDouble("/sim/presets/wBody-fps") );
        } else if ( speedset == "NED" || speedset == "ned" ) {
            set_Velocities_Local(
                                 fgGetDouble("/sim/presets/speed-north-fps"),
                                 fgGetDouble("/sim/presets/speed-east-fps"),
                                 fgGetDouble("/sim/presets/speed-down-fps") );
        } else {
            SG_LOG( SG_FLIGHT, SG_ALERT,
                    "Unrecognized value for /sim/presets/speed-set: "
                    << speedset);
            set_V_calibrated_kts( 0.0 );
        }
    }

    // Set initial Euler angles
    SG_LOG( SG_FLIGHT, SG_INFO, "...initializing Euler angles..." );
    set_Euler_Angles( fgGetDouble("/sim/presets/roll-deg")
                        * SGD_DEGREES_TO_RADIANS,
                      fgGetDouble("/sim/presets/pitch-deg")
                        * SGD_DEGREES_TO_RADIANS,
                      fgGetDouble("/sim/presets/heading-deg")
                        * SGD_DEGREES_TO_RADIANS );

    SG_LOG( SG_FLIGHT, SG_INFO, "End common FDM init" );
}


/**
 * Bind getters and setters to properties.
 *
 * The bind() method will be invoked after init().  Note that unlike
 * the usual implementations of FGSubsystem::bind(), this method does
 * not automatically pick up existing values for the properties at
 * bind time; instead, all values are set explicitly in the init()
 * method.
 */
void
FGInterface::bind ()
{
  bound = true;

                                // Time management (read-only)
//   fgTie("/fdm/time/delta_t", this,
//         &FGInterface::get_delta_t); // read-only
//   fgTie("/fdm/time/elapsed", this,
//         &FGInterface::get_elapsed); // read-only
//   fgTie("/fdm/time/remainder", this,
//         &FGInterface::get_remainder); // read-only
//   fgTie("/fdm/time/multi_loop", this,
//         &FGInterface::get_multi_loop); // read-only

			// Aircraft position
  fgTie("/position/latitude-deg", this,
        &FGInterface::get_Latitude_deg,
        &FGInterface::set_Latitude_deg,
        false);
  fgSetArchivable("/position/latitude-deg");
  fgTie("/position/longitude-deg", this,
        &FGInterface::get_Longitude_deg,
        &FGInterface::set_Longitude_deg,
        false);
  fgSetArchivable("/position/longitude-deg");
  fgTie("/position/altitude-ft", this,
        &FGInterface::get_Altitude,
        &FGInterface::set_Altitude,
        false);
  fgSetArchivable("/position/altitude-ft");
  fgTie("/position/altitude-agl-ft", this,
        &FGInterface::get_Altitude_AGL); // read-only
  fgSetArchivable("/position/ground-elev-ft");
  fgTie("/position/ground-elev-ft", this,
        &FGInterface::get_Runway_altitude); // read-only
  fgSetArchivable("/position/ground-elev-m");
  fgTie("/position/ground-elev-m", this,
        &FGInterface::get_Runway_altitude_m); // read-only
  fgTie("/environment/ground-elevation-m", this,
        &FGInterface::get_Runway_altitude_m); // read-only
  fgSetArchivable("/position/sea-level-radius-ft");
  fgTie("/position/sea-level-radius-ft", this,
        &FGInterface::get_Sea_level_radius); // read-only

				// Orientation
  fgTie("/orientation/roll-deg", this,
	&FGInterface::get_Phi_deg,
	&FGInterface::set_Phi_deg);
  fgSetArchivable("/orientation/roll-deg");
  fgTie("/orientation/pitch-deg", this,
	&FGInterface::get_Theta_deg,
	&FGInterface::set_Theta_deg);
  fgSetArchivable("/orientation/pitch-deg");
  fgTie("/orientation/heading-deg", this,
	&FGInterface::get_Psi_deg,
	&FGInterface::set_Psi_deg);
  fgSetArchivable("/orientation/heading-deg");

  // Body-axis "euler rates" (rotation speed, but in a funny
  // representation).
  fgTie("/orientation/roll-rate-degps", this,
	&FGInterface::get_Phi_dot_degps);
  fgTie("/orientation/pitch-rate-degps", this,
	&FGInterface::get_Theta_dot_degps);
  fgTie("/orientation/yaw-rate-degps", this,
	&FGInterface::get_Psi_dot_degps);

                                // Ground speed knots
  fgTie("/velocities/groundspeed-kt", this,
        &FGInterface::get_V_ground_speed_kt);

				// Calibrated airspeed
  fgTie("/velocities/airspeed-kt", this,
	&FGInterface::get_V_calibrated_kts,
	&FGInterface::set_V_calibrated_kts,
	false);

				// Mach number
  fgTie("/velocities/mach", this,
	&FGInterface::get_Mach_number,
	&FGInterface::set_Mach_number,
	false);

				// Local velocities
//   fgTie("/velocities/speed-north-fps", this,
// 	&FGInterface::get_V_north,
// 	&FGInterface::set_V_north);
//   fgSetArchivable("/velocities/speed-north-fps");
//   fgTie("/velocities/speed-east-fps", this,
// 	&FGInterface::get_V_east,
// 	&FGInterface::set_V_east);
//   fgSetArchivable("/velocities/speed-east-fps");
//   fgTie("/velocities/speed-down-fps", this,
// 	&FGInterface::get_V_down,
// 	&FGInterface::set_V_down);
//   fgSetArchivable("/velocities/speed-down-fps");
				// FIXME: Temporarily read-only, until the
				// incompatibilities between JSBSim and
				// LaRCSim are fixed (LaRCSim adds the
				// earth's rotation to the east velocity).
  fgTie("/velocities/speed-north-fps", this,
	&FGInterface::get_V_north);
  fgTie("/velocities/speed-east-fps", this,
	&FGInterface::get_V_east);
  fgTie("/velocities/speed-down-fps", this,
	&FGInterface::get_V_down);

				// Relative wind
				// FIXME: temporarily archivable, until
				// the NED problem is fixed.
  fgTie("/velocities/uBody-fps", this,
	&FGInterface::get_uBody,
	&FGInterface::set_uBody,
	false);
  fgSetArchivable("/velocities/uBody-fps");
  fgTie("/velocities/vBody-fps", this,
	&FGInterface::get_vBody,
	&FGInterface::set_vBody,
	false);
  fgSetArchivable("/velocities/vBody-fps");
  fgTie("/velocities/wBody-fps", this,
	&FGInterface::get_wBody,
	&FGInterface::set_wBody,
	false);
  fgSetArchivable("/velocities/wBody-fps");

				// Climb and slip (read-only)
  fgTie("/velocities/vertical-speed-fps", this,
	&FGInterface::get_Climb_Rate,
  &FGInterface::set_Climb_Rate ); 
  fgTie("/velocities/glideslope", this,
  &FGInterface::get_Gamma_vert_rad,
  &FGInterface::set_Gamma_vert_rad );
  fgTie("/orientation/side-slip-rad", this,
	&FGInterface::get_Beta); // read-only
  fgTie("/orientation/side-slip-deg", this,
  &FGInterface::get_Beta_deg); // read-only
  fgTie("/orientation/alpha-deg", this,
  &FGInterface::get_Alpha_deg); // read-only
  fgTie("/accelerations/nlf", this,
  &FGInterface::get_Nlf); // read-only

                                // NED accelerations
  fgTie("/accelerations/ned/north-accel-fps_sec",
        this, &FGInterface::get_V_dot_north);
  fgTie("/accelerations/ned/east-accel-fps_sec",
        this, &FGInterface::get_V_dot_east);
  fgTie("/accelerations/ned/down-accel-fps_sec",
        this, &FGInterface::get_V_dot_down);

                                // Pilot accelerations
  fgTie("/accelerations/pilot/x-accel-fps_sec",
        this, &FGInterface::get_A_X_pilot);
  fgTie("/accelerations/pilot/y-accel-fps_sec",
        this, &FGInterface::get_A_Y_pilot);
  fgTie("/accelerations/pilot/z-accel-fps_sec",
        this, &FGInterface::get_A_Z_pilot);

}


/**
 * Unbind any properties bound to this FDM.
 *
 * This method allows the FDM to release properties so that a new
 * FDM can bind them instead.
 */
void
FGInterface::unbind ()
{
  bound = false;

  // fgUntie("/fdm/time/delta_t");
  // fgUntie("/fdm/time/elapsed");
  // fgUntie("/fdm/time/remainder");
  // fgUntie("/fdm/time/multi_loop");
  fgUntie("/position/latitude-deg");
  fgUntie("/position/longitude-deg");
  fgUntie("/position/altitude-ft");
  fgUntie("/position/altitude-agl-ft");
  fgUntie("/position/ground-elev-ft");
  fgUntie("/position/ground-elev-m");
  fgUntie("/environment/ground-elevation-m");
  fgUntie("/position/sea-level-radius-ft");
  fgUntie("/orientation/roll-deg");
  fgUntie("/orientation/pitch-deg");
  fgUntie("/orientation/heading-deg");
  fgUntie("/orientation/roll-rate-degps");
  fgUntie("/orientation/pitch-rate-degps");
  fgUntie("/orientation/yaw-rate-degps");
  fgUntie("/orientation/side-slip-rad");
  fgUntie("/orientation/side-slip-deg");
  fgUntie("/orientation/alpha-deg");
  fgUntie("/velocities/airspeed-kt");
  fgUntie("/velocities/groundspeed-kt");
  fgUntie("/velocities/mach");
  fgUntie("/velocities/speed-north-fps");
  fgUntie("/velocities/speed-east-fps");
  fgUntie("/velocities/speed-down-fps");
  fgUntie("/velocities/uBody-fps");
  fgUntie("/velocities/vBody-fps");
  fgUntie("/velocities/wBody-fps");
  fgUntie("/velocities/vertical-speed-fps");
  fgUntie("/velocities/glideslope");
  fgUntie("/accelerations/nlf");
  fgUntie("/accelerations/pilot/x-accel-fps_sec");
  fgUntie("/accelerations/pilot/y-accel-fps_sec");
  fgUntie("/accelerations/pilot/z-accel-fps_sec");
  fgUntie("/accelerations/ned/north-accel-fps_sec");
  fgUntie("/accelerations/ned/east-accel-fps_sec");
  fgUntie("/accelerations/ned/down-accel-fps_sec");
}

/**
 * Update the state of the FDM (i.e. run the equations of motion).
 */
void
FGInterface::update (double dt)
{
    SG_LOG(SG_FLIGHT, SG_ALERT, "dummy update() ... SHOULDN'T BE CALLED!");
}


void FGInterface::_updatePositionM(const SGVec3d& cartPos)
{
    cartesian_position_v = cartPos;
    geodetic_position_v = SGGeod::fromCart(cartesian_position_v);
    geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
    _set_Sea_level_radius( SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v)*SG_METER_TO_FEET );
    _update_ground_elev_at_pos();
}


void FGInterface::_updatePosition(const SGGeod& geod)
{
    geodetic_position_v = geod;
    cartesian_position_v = SGVec3d::fromGeod(geodetic_position_v);
    geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);

    _set_Sea_level_radius( SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v)*SG_METER_TO_FEET );
    _update_ground_elev_at_pos();
}


void FGInterface::_updatePosition(const SGGeoc& geoc)
{
    geocentric_position_v = geoc;
    cartesian_position_v = SGVec3d::fromGeoc(geocentric_position_v);
    geodetic_position_v = SGGeod::fromCart(cartesian_position_v);

    _set_Sea_level_radius( SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v)*SG_METER_TO_FEET );
    _update_ground_elev_at_pos();
}


void FGInterface::_updateGeodeticPosition( double lat, double lon, double alt )
{
    _updatePosition(SGGeod::fromRadFt(lon, lat, alt));
}


void FGInterface::_updateGeocentricPosition( double lat, double lon,
					     double alt )
{
    _updatePosition(SGGeoc::fromRadFt(lon, lat, get_Sea_level_radius() + alt));
}

void FGInterface::_update_ground_elev_at_pos( void ) {
    double groundlevel_m = get_groundlevel_m(geodetic_position_v);
    _set_Runway_altitude( groundlevel_m * SG_METER_TO_FEET );
}

// Positions
void FGInterface::set_Latitude(double lat) {
    geodetic_position_v.setLatitudeRad(lat);
}

void FGInterface::set_Longitude(double lon) {
    geodetic_position_v.setLongitudeRad(lon);
}

void FGInterface::set_Altitude(double alt) {
    geodetic_position_v.setElevationFt(alt);
}

void FGInterface::set_AltitudeAGL(double altagl) {
    altitude_agl=altagl;
}

// Velocities
void FGInterface::set_V_calibrated_kts(double vc) {
    v_calibrated_kts = vc;
}

void FGInterface::set_Mach_number(double mach) {
    mach_number = mach;
}

void FGInterface::set_Velocities_Local( double north, 
					double east, 
					double down ){
    v_local_v[0] = north;
    v_local_v[1] = east;
    v_local_v[2] = down;
}

void FGInterface::set_Velocities_Wind_Body( double u, 
					    double v, 
					    double w){
    v_wind_body_v[0] = u;
    v_wind_body_v[1] = v;
    v_wind_body_v[2] = w;
}

// Euler angles 
void FGInterface::set_Euler_Angles( double phi, 
				    double theta, 
				    double psi ) {
    euler_angles_v[0] = phi;
    euler_angles_v[1] = theta;
    euler_angles_v[2] = psi;                                            
}  

// Flight Path
void FGInterface::set_Climb_Rate( double roc) {
    climb_rate = roc;
}

void FGInterface::set_Gamma_vert_rad( double gamma) {
    gamma_vert_rad = gamma;
}

void FGInterface::set_Static_pressure(double p) { static_pressure = p; }
void FGInterface::set_Static_temperature(double T) { static_temperature = T; }
void FGInterface::set_Density(double rho) { density = rho; }

void FGInterface::set_Velocities_Local_Airmass (double wnorth, 
						double weast, 
						double wdown ) {
    v_local_airmass_v[0] = wnorth;
    v_local_airmass_v[1] = weast;
    v_local_airmass_v[2] = wdown;
}


void FGInterface::_busdump(void) {

    SG_LOG(SG_FLIGHT,SG_INFO,"d_cg_rp_body_v: " << d_cg_rp_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"v_dot_local_v: " << v_dot_local_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"v_dot_body_v: " << v_dot_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"a_cg_body_v: " << a_cg_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"a_pilot_body_v: " << a_pilot_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"n_cg_body_v: " << n_cg_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"v_local_v: " << v_local_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"v_local_rel_ground_v: " << v_local_rel_ground_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"v_local_airmass_v: " << v_local_airmass_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"v_wind_body_v: " << v_wind_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"omega_body_v: " << omega_body_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"euler_rates_v: " << euler_rates_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"geocentric_rates_v: " << geocentric_rates_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"geocentric_position_v: " << geocentric_position_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"geodetic_position_v: " << geodetic_position_v);
    SG_LOG(SG_FLIGHT,SG_INFO,"euler_angles_v: " << euler_angles_v);

    SG_LOG(SG_FLIGHT,SG_INFO,"nlf: " << nlf );
    SG_LOG(SG_FLIGHT,SG_INFO,"v_rel_wind: " << v_rel_wind );
    SG_LOG(SG_FLIGHT,SG_INFO,"v_true_kts: " << v_true_kts );
    SG_LOG(SG_FLIGHT,SG_INFO,"v_ground_speed: " << v_ground_speed );
    SG_LOG(SG_FLIGHT,SG_INFO,"v_equiv_kts: " << v_equiv_kts );
    SG_LOG(SG_FLIGHT,SG_INFO,"v_calibrated_kts: " << v_calibrated_kts );
    SG_LOG(SG_FLIGHT,SG_INFO,"alpha: " << alpha );
    SG_LOG(SG_FLIGHT,SG_INFO,"beta: " << beta );
    SG_LOG(SG_FLIGHT,SG_INFO,"gamma_vert_rad: " << gamma_vert_rad );
    SG_LOG(SG_FLIGHT,SG_INFO,"density: " << density );
    SG_LOG(SG_FLIGHT,SG_INFO,"mach_number: " << mach_number );
    SG_LOG(SG_FLIGHT,SG_INFO,"static_pressure: " << static_pressure );
    SG_LOG(SG_FLIGHT,SG_INFO,"total_pressure: " << total_pressure );
    SG_LOG(SG_FLIGHT,SG_INFO,"dynamic_pressure: " << dynamic_pressure );
    SG_LOG(SG_FLIGHT,SG_INFO,"static_temperature: " << static_temperature );
    SG_LOG(SG_FLIGHT,SG_INFO,"total_temperature: " << total_temperature );
    SG_LOG(SG_FLIGHT,SG_INFO,"sea_level_radius: " << sea_level_radius );
    SG_LOG(SG_FLIGHT,SG_INFO,"earth_position_angle: " << earth_position_angle );
    SG_LOG(SG_FLIGHT,SG_INFO,"runway_altitude: " << runway_altitude );
    SG_LOG(SG_FLIGHT,SG_INFO,"climb_rate: " << climb_rate );
    SG_LOG(SG_FLIGHT,SG_INFO,"altitude_agl: " << altitude_agl );
}

bool
FGInterface::prepare_ground_cache_m(double ref_time, const double pt[3],
                                    double rad)
{
  return ground_cache.prepare_ground_cache(ref_time, SGVec3d(pt), rad);
}

bool FGInterface::prepare_ground_cache_ft(double ref_time, const double pt[3],
                                          double rad)
{
  // Convert units and do the real work.
  SGVec3d pt_ft = SG_FEET_TO_METER*SGVec3d(pt);
  return ground_cache.prepare_ground_cache(ref_time, pt_ft, rad*SG_FEET_TO_METER);
}

bool
FGInterface::is_valid_m(double *ref_time, double pt[3], double *rad)
{
  SGVec3d _pt;
  bool valid = ground_cache.is_valid(*ref_time, _pt, *rad);
  assign(pt, _pt);
  return valid;
}

bool FGInterface::is_valid_ft(double *ref_time, double pt[3], double *rad)
{
  // Convert units and do the real work.
  SGVec3d _pt;
  bool found_ground = ground_cache.is_valid(*ref_time, _pt, *rad);
  assign(pt, SG_METER_TO_FEET*_pt);
  *rad *= SG_METER_TO_FEET;
  return found_ground;
}

double
FGInterface::get_cat_m(double t, const double pt[3],
                       double end[2][3], double vel[2][3])
{
  SGVec3d _end[2], _vel[2];
  double dist = ground_cache.get_cat(t, SGVec3d(pt), _end, _vel);
  for (int k=0; k<2; ++k) {
    assign( end[k], _end[k] );
    assign( vel[k], _vel[k] );
  }
  return dist;
}

double
FGInterface::get_cat_ft(double t, const double pt[3],
                        double end[2][3], double vel[2][3])
{
  // Convert units and do the real work.
  SGVec3d pt_m = SG_FEET_TO_METER*SGVec3d(pt);
  SGVec3d _end[2], _vel[2];
  double dist = ground_cache.get_cat(t, pt_m, _end, _vel);
  for (int k=0; k<2; ++k) {
    assign( end[k], SG_METER_TO_FEET*_end[k] );
    assign( vel[k], SG_METER_TO_FEET*_vel[k] );
  }
  return dist*SG_METER_TO_FEET;
}

// Legacy interface just kept because of JSBSim
bool
FGInterface::get_agl_m(double t, const double pt[3],
                       double contact[3], double normal[3], double vel[3],
                       int *type, double *loadCapacity,
                       double *frictionFactor, double *agl)
{
  const SGMaterial* material;
  SGVec3d _contact, _normal, _vel;
  bool ret = ground_cache.get_agl(t, SGVec3d(pt), 2.0, _contact, _normal,
                                  _vel, type, &material, agl);
  assign(contact, _contact);
  assign(normal, _normal);
  assign(vel, _vel);
  if (material) {
    *loadCapacity = material->get_load_resistance();
    *frictionFactor = material->get_friction_factor();

  } else {
    *loadCapacity = DBL_MAX;
    *frictionFactor = 1.0;
  }
  return ret;
}

bool
FGInterface::get_agl_m(double t, const double pt[3],
                       double contact[3], double normal[3], double vel[3],
                       int *type, const SGMaterial **material, double *agl)
{
  SGVec3d _contact, _normal, _vel;
  bool ret = ground_cache.get_agl(t, SGVec3d(pt), 2.0, _contact, _normal,
                                  _vel, type, material, agl);
  assign(contact, _contact);
  assign(normal, _normal);
  assign(vel, _vel);
  return ret;
}

// Legacy interface just kept because of JSBSim
bool
FGInterface::get_agl_ft(double t, const double pt[3],
                        double contact[3], double normal[3], double vel[3],
                        int *type, double *loadCapacity,
                        double *frictionFactor, double *agl)
{
  // Convert units and do the real work.
  SGVec3d pt_m = SG_FEET_TO_METER*SGVec3d(pt);

  const SGMaterial* material;
  SGVec3d _contact, _normal, _vel;
  bool ret = ground_cache.get_agl(t, pt_m, 2.0, _contact, _normal, _vel,
                                  type, &material, agl);
  // Convert units back ...
  assign( contact, SG_METER_TO_FEET*_contact );
  assign( vel, SG_METER_TO_FEET*_vel );
  assign( normal, _normal );
  *agl *= SG_METER_TO_FEET;

  // return material properties if available
  if (material) {
    // FIXME: convert units?? now pascal to lbf/ft^2
    *loadCapacity = 0.020885434*material->get_load_resistance();
    *frictionFactor = material->get_friction_factor();
  } else {
    *loadCapacity = DBL_MAX;
    *frictionFactor = 1.0;
  }
  return ret;
}

bool
FGInterface::get_agl_m(double t, const double pt[3], double max_altoff,
                       double contact[3], double normal[3], double vel[3],
                       int *type, const SGMaterial** material, double *agl)
{
  SGVec3d _contact, _normal, _vel;
  bool found = ground_cache.get_agl(t, SGVec3d(pt), max_altoff, _contact,
                                    _normal, _vel, type, material, agl);
  assign(contact, _contact);
  assign(normal, _normal);
  assign(vel, _vel);
  return found;
}

bool
FGInterface::get_agl_ft(double t, const double pt[3], double max_altoff,
                        double contact[3], double normal[3], double vel[3],
                        int *type, const SGMaterial** material, double *agl)
{
  // Convert units and do the real work.
  SGVec3d pt_m = SG_FEET_TO_METER*SGVec3d(pt);
  SGVec3d _contact, _normal, _vel;
  bool ret = ground_cache.get_agl(t, pt_m, SG_FEET_TO_METER * max_altoff,
                                  _contact, _normal, _vel,
                                  type, material, agl);
  // Convert units back ...
  assign( contact, SG_METER_TO_FEET*_contact );
  assign( vel, SG_METER_TO_FEET*_vel );
  assign( normal, _normal );
  *agl *= SG_METER_TO_FEET;
  return ret;
}

double
FGInterface::get_groundlevel_m(double lat, double lon, double alt)
{
  return get_groundlevel_m(SGGeod::fromRadM(lon, lat, alt));
}

double
FGInterface::get_groundlevel_m(const SGGeod& geod)
{
  // Compute the cartesian position of the given lat/lon/alt.
  SGVec3d pos = SGVec3d::fromGeod(geod);

  // FIXME: how to handle t - ref_time differences ???
  SGVec3d cpos;
  double ref_time, radius;
  // Prepare the ground cache for that position.
  if (!is_valid_m(&ref_time, cpos.data(), &radius)) {
    bool ok = prepare_ground_cache_m(ref_time, pos.data(), 10);
    /// This is most likely the case when the given altitude is
    /// too low, try with a new altitude of 10000m, that should be
    /// sufficient to find a ground level below everywhere on our planet
    if (!ok) {
      pos = SGVec3d::fromGeod(SGGeod::fromRadM(geod.getLongitudeRad(), geod.getLatitudeRad(), 10000));
      /// If there is still no ground, return sea level radius
      if (!prepare_ground_cache_m(ref_time, pos.data(), 10))
        return 0;
    }
  } else if (radius*radius <= distSqr(pos, cpos)) {
    /// We reuse the old radius value, but only if it is at least 10 Meters ..
    if (!(10 < radius)) // Well this strange compare is nan safe
      radius = 10;

    bool ok = prepare_ground_cache_m(ref_time, pos.data(), radius);
    /// This is most likely the case when the given altitude is
    /// too low, try with a new altitude of 10000m, that should be
    /// sufficient to find a ground level below everywhere on our planet
    if (!ok) {
      pos = SGVec3d::fromGeod(SGGeod::fromRadM(geod.getLongitudeRad(), geod.getLatitudeRad(), 10000));
      /// If there is still no ground, return sea level radius
      if (!prepare_ground_cache_m(ref_time, pos.data(), radius))
        return 0;
    }
  }
  
  double contact[3], normal[3], vel[3], agl;
  int type;
  // Ignore the return value here, since it just tells us if
  // the returns stem from the groundcache or from the coarse
  // computations below the groundcache. The contact point is still something
  // valid, the normals and the other returns just contain some defaults.
  get_agl_m(ref_time, pos.data(), 2.0, contact, normal, vel, &type, 0, &agl);
  return SGGeod::fromCart(SGVec3d(contact)).getElevationM();
}
  
bool
FGInterface::caught_wire_m(double t, const double pt[4][3])
{
  SGVec3d pt_m[4];
  for (int i=0; i<4; ++i)
    pt_m[i] = SGVec3d(pt[i]);
  
  return ground_cache.caught_wire(t, pt_m);
}

bool
FGInterface::caught_wire_ft(double t, const double pt[4][3])
{
  // Convert units and do the real work.
  SGVec3d pt_m[4];
  for (int i=0; i<4; ++i)
    pt_m[i] = SG_FEET_TO_METER*SGVec3d(pt[i]);
    
  return ground_cache.caught_wire(t, pt_m);
}
  
bool
FGInterface::get_wire_ends_m(double t, double end[2][3], double vel[2][3])
{
  SGVec3d _end[2], _vel[2];
  bool ret = ground_cache.get_wire_ends(t, _end, _vel);
  for (int k=0; k<2; ++k) {
    assign( end[k], _end[k] );
    assign( vel[k], _vel[k] );
  }
  return ret;
}

bool
FGInterface::get_wire_ends_ft(double t, double end[2][3], double vel[2][3])
{
  // Convert units and do the real work.
  SGVec3d _end[2], _vel[2];
  bool ret = ground_cache.get_wire_ends(t, _end, _vel);
  for (int k=0; k<2; ++k) {
    assign( end[k], SG_METER_TO_FEET*_end[k] );
    assign( vel[k], SG_METER_TO_FEET*_vel[k] );
  }
  return ret;
}

void
FGInterface::release_wire(void)
{
  ground_cache.release_wire();
}

void fgToggleFDMdataLogging(void) {
  cur_fdm_state->ToggleDataLogging();
}
