src/FDM/flight.cxx

   1 // flight.cxx -- a general interface to the various flight models
   2 //
   3 // Written by Curtis Olson, started May 1997.
   4 //
   5 // Copyright (C) 1997  Curtis L. Olson  - http://www.flightgear.org/~curt
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License as
   9 // published by the Free Software Foundation; either version 2 of the
  10 // License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 // General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 //
  21 // $Id$
  22
  23 #ifdef HAVE_CONFIG_H
  24 #  include "config.h"
  25 #endif
  26
  27 #include <stdio.h>
  28
  29 #include <plib/sg.h>
  30
  31 #include <simgear/constants.h>
  32 #include <simgear/debug/logstream.hxx>
  33 #include <simgear/math/sg_geodesy.hxx>
  34 #include <simgear/scene/model/placement.hxx>
  35 #include <simgear/timing/timestamp.hxx>
  36
  37 #include <Scenery/scenery.hxx>
  38 #include <Main/globals.hxx>
  39 #include <Main/fg_props.hxx>
  40 #include <FDM/groundcache.hxx>
  41
  42 #include "flight.hxx"
  43
  44
  45 // base_fdm_state is the internal state that is updated in integer
  46 // multiples of "dt".  This leads to "jitter" with respect to the real
  47 // world time, so we introduce cur_fdm_state which is extrapolated by
  48 // the difference between sim time and real world time
  49
  50 FGInterface *cur_fdm_state = 0;
  51 FGInterface base_fdm_state;
  52
  53 inline void init_vec(FG_VECTOR_3 vec) {
  54     vec[0] = 0.0; vec[1] = 0.0; vec[2] = 0.0;
  55 }
  56
  57 // Constructor
  58 FGInterface::FGInterface()
  59   : remainder(0)
  60 {
  61     _setup();
  62 }
  63
  64 FGInterface::FGInterface( double dt )
  65   : remainder(0)
  66 {
  67     _setup();
  68 }
  69
  70 // Destructor
  71 FGInterface::~FGInterface() {
  72     // unbind();                   // FIXME: should be called explicitly
  73 }
  74
  75
  76 int
  77 FGInterface::_calc_multiloop (double dt)
  78 {
  79   int hz = fgGetInt("/sim/model-hz");
  80   int speedup = fgGetInt("/sim/speed-up");
  81
  82   dt += remainder;
  83   remainder = 0;
  84   double ml = dt * hz;
  85   // Avoid roundoff problems by adding the roundoff itself.
  86   // ... ok, two times the roundoff to have enough room.
  87   int multiloop = int(floor(ml * (1.0 + 2.0*DBL_EPSILON)));
  88   remainder = (ml - multiloop) / hz;
  89   return (multiloop * speedup);
  90 }
  91
  92
  93 /**
  94  * Set default values for the state of the FDM.
  95  *
  96  * This method is invoked by the constructors.
  97  */
  98 void
  99 FGInterface::_setup ()
 100 {
 101     inited = false;
 102     bound = false;
 103
 104     init_vec( d_pilot_rp_body_v );
 105     init_vec( d_cg_rp_body_v );
 106     init_vec( f_body_total_v );
 107     init_vec( f_local_total_v );
 108     init_vec( f_aero_v );
 109     init_vec( f_engine_v );
 110     init_vec( f_gear_v );
 111     init_vec( m_total_rp_v );
 112     init_vec( m_total_cg_v );
 113     init_vec( m_aero_v );
 114     init_vec( m_engine_v );
 115     init_vec( m_gear_v );
 116     init_vec( v_dot_local_v );
 117     init_vec( v_dot_body_v );
 118     init_vec( a_cg_body_v );
 119     init_vec( a_pilot_body_v );
 120     init_vec( n_cg_body_v );
 121     init_vec( n_pilot_body_v );
 122     init_vec( omega_dot_body_v );
 123     init_vec( v_local_v );
 124     init_vec( v_local_rel_ground_v );
 125     init_vec( v_local_airmass_v );
 126     init_vec( v_local_rel_airmass_v );
 127     init_vec( v_local_gust_v );
 128     init_vec( v_wind_body_v );
 129     init_vec( omega_body_v );
 130     init_vec( omega_local_v );
 131     init_vec( omega_total_v );
 132     init_vec( euler_rates_v );
 133     init_vec( geocentric_rates_v );
 134     init_vec( geocentric_position_v );
 135     init_vec( geodetic_position_v );
 136     init_vec( euler_angles_v );
 137     init_vec( d_cg_rwy_local_v );
 138     init_vec( d_cg_rwy_rwy_v );
 139     init_vec( d_pilot_rwy_local_v );
 140     init_vec( d_pilot_rwy_rwy_v );
 141     init_vec( t_local_to_body_m[0] );
 142     init_vec( t_local_to_body_m[1] );
 143     init_vec( t_local_to_body_m[2] );
 144
 145     mass=i_xx=i_yy=i_zz=i_xz=0;
 146     nlf=0;
 147     v_rel_wind=v_true_kts=v_rel_ground=v_inertial=0;
 148     v_ground_speed=v_equiv=v_equiv_kts=0;
 149     v_calibrated=v_calibrated_kts=0;
 150     gravity=0;
 151     centrifugal_relief=0;
 152     alpha=beta=alpha_dot=beta_dot=0;
 153     cos_alpha=sin_alpha=cos_beta=sin_beta=0;
 154     cos_phi=sin_phi=cos_theta=sin_theta=cos_psi=sin_psi=0;
 155     gamma_vert_rad=gamma_horiz_rad=0;
 156     sigma=density=v_sound=mach_number=0;
 157     static_pressure=total_pressure=impact_pressure=0;
 158     dynamic_pressure=0;
 159     static_temperature=total_temperature=0;
 160     sea_level_radius=earth_position_angle=0;
 161     runway_altitude=runway_latitude=runway_longitude=0;
 162     runway_heading=0;
 163     radius_to_rwy=0;
 164     climb_rate=0;
 165     sin_lat_geocentric=cos_lat_geocentric=0;
 166     sin_latitude=cos_latitude=0;
 167     sin_longitude=cos_longitude=0;
 168     altitude_agl=0;
 169 }
 170
 171 void
 172 FGInterface::init () {}
 173
 174 /**
 175  * Initialize the state of the FDM.
 176  *
 177  * Subclasses of FGInterface may do their own, additional initialization,
 178  * but there is some that is common to all.  Normally, they should call
 179  * this before they begin their own init to make sure the basic structures
 180  * are set up properly.
 181  */
 182 void
 183 FGInterface::common_init ()
 184 {
 185     SG_LOG( SG_FLIGHT, SG_INFO, "Start common FDM init" );
 186
 187     set_inited( true );
 188
 189 //     stamp();
 190 //     set_remainder( 0 );
 191
 192     // Set initial position
 193     SG_LOG( SG_FLIGHT, SG_INFO, "...initializing position..." );
 194     double lon = fgGetDouble("/sim/presets/longitude-deg")
 195       * SGD_DEGREES_TO_RADIANS;
 196     double lat = fgGetDouble("/sim/presets/latitude-deg")
 197       * SGD_DEGREES_TO_RADIANS;
 198     double alt_ft = fgGetDouble("/sim/presets/altitude-ft");
 199     double alt_m = alt_ft * SG_FEET_TO_METER;
 200     set_Longitude( lon );
 201     set_Latitude( lat );
 202     SG_LOG( SG_FLIGHT, SG_INFO, "Checking for lon = "
 203             << lon*SGD_RADIANS_TO_DEGREES << "deg, lat = "
 204             << lat*SGD_RADIANS_TO_DEGREES << "deg, alt = "
 205             << alt_ft << "ft");
 206
 207     double ground_elev_m = get_groundlevel_m(lat, lon, alt_m);
 208     double ground_elev_ft = ground_elev_m * SG_METER_TO_FEET;
 209     _set_Runway_altitude ( ground_elev_ft );
 210     if ( fgGetBool("/sim/presets/onground") || alt_ft < ground_elev_ft ) {
 211         fgSetDouble("/position/altitude-ft", ground_elev_ft + 0.1);
 212         set_Altitude( ground_elev_ft + 0.1);
 213     } else {
 214         set_Altitude( alt_ft );
 215     }
 216
 217     // Set ground elevation
 218     SG_LOG( SG_FLIGHT, SG_INFO,
 219             "...initializing ground elevation to " << ground_elev_ft
 220             << "ft..." );
 221
 222     // Set sea-level radius
 223     SG_LOG( SG_FLIGHT, SG_INFO, "...initializing sea-level radius..." );
 224     SG_LOG( SG_FLIGHT, SG_INFO, " lat = "
 225             << fgGetDouble("/sim/presets/latitude-deg")
 226             << " alt = " << get_Altitude() );
 227     double sea_level_radius_meters;
 228     double lat_geoc;
 229     sgGeodToGeoc( fgGetDouble("/sim/presets/latitude-deg")
 230                     * SGD_DEGREES_TO_RADIANS,
 231                   get_Altitude() * SG_FEET_TO_METER,
 232                   &sea_level_radius_meters, &lat_geoc );
 233     _set_Sea_level_radius( sea_level_radius_meters * SG_METER_TO_FEET );
 234
 235     // Set initial velocities
 236     SG_LOG( SG_FLIGHT, SG_INFO, "...initializing velocities..." );
 237     if ( !fgHasNode("/sim/presets/speed-set") ) {
 238         set_V_calibrated_kts(0.0);
 239     } else {
 240         const string speedset = fgGetString("/sim/presets/speed-set");
 241         if ( speedset == "knots" || speedset == "KNOTS" ) {
 242             set_V_calibrated_kts( fgGetDouble("/sim/presets/airspeed-kt") );
 243         } else if ( speedset == "mach" || speedset == "MACH" ) {
 244             set_Mach_number( fgGetDouble("/sim/presets/mach") );
 245         } else if ( speedset == "UVW" || speedset == "uvw" ) {
 246             set_Velocities_Wind_Body(
 247                                      fgGetDouble("/sim/presets/uBody-fps"),
 248                                      fgGetDouble("/sim/presets/vBody-fps"),
 249                                      fgGetDouble("/sim/presets/wBody-fps") );
 250         } else if ( speedset == "NED" || speedset == "ned" ) {
 251             set_Velocities_Local(
 252                                  fgGetDouble("/sim/presets/speed-north-fps"),
 253                                  fgGetDouble("/sim/presets/speed-east-fps"),
 254                                  fgGetDouble("/sim/presets/speed-down-fps") );
 255         } else {
 256             SG_LOG( SG_FLIGHT, SG_ALERT,
 257                     "Unrecognized value for /sim/presets/speed-set: "
 258                     << speedset);
 259             set_V_calibrated_kts( 0.0 );
 260         }
 261     }
 262
 263     // Set initial Euler angles
 264     SG_LOG( SG_FLIGHT, SG_INFO, "...initializing Euler angles..." );
 265     set_Euler_Angles( fgGetDouble("/sim/presets/roll-deg")
 266                         * SGD_DEGREES_TO_RADIANS,
 267                       fgGetDouble("/sim/presets/pitch-deg")
 268                         * SGD_DEGREES_TO_RADIANS,
 269                       fgGetDouble("/sim/presets/heading-deg")
 270                         * SGD_DEGREES_TO_RADIANS );
 271
 272     SG_LOG( SG_FLIGHT, SG_INFO, "End common FDM init" );
 273 }
 274
 275
 276 /**
 277  * Bind getters and setters to properties.
 278  *
 279  * The bind() method will be invoked after init().  Note that unlike
 280  * the usual implementations of FGSubsystem::bind(), this method does
 281  * not automatically pick up existing values for the properties at
 282  * bind time; instead, all values are set explicitly in the init()
 283  * method.
 284  */
 285 void
 286 FGInterface::bind ()
 287 {
 288   bound = true;
 289
 290                                 // Time management (read-only)
 291 //   fgTie("/fdm/time/delta_t", this,
 292 //         &FGInterface::get_delta_t); // read-only
 293 //   fgTie("/fdm/time/elapsed", this,
 294 //         &FGInterface::get_elapsed); // read-only
 295 //   fgTie("/fdm/time/remainder", this,
 296 //         &FGInterface::get_remainder); // read-only
 297 //   fgTie("/fdm/time/multi_loop", this,
 298 //         &FGInterface::get_multi_loop); // read-only
 299
 300                         // Aircraft position
 301   fgTie("/position/latitude-deg", this,
 302         &FGInterface::get_Latitude_deg,
 303         &FGInterface::set_Latitude_deg,
 304         false);
 305   fgSetArchivable("/position/latitude-deg");
 306   fgTie("/position/longitude-deg", this,
 307         &FGInterface::get_Longitude_deg,
 308         &FGInterface::set_Longitude_deg,
 309         false);
 310   fgSetArchivable("/position/longitude-deg");
 311   fgTie("/position/altitude-ft", this,
 312         &FGInterface::get_Altitude,
 313         &FGInterface::set_Altitude,
 314         false);
 315   fgSetArchivable("/position/altitude-ft");
 316   fgTie("/position/altitude-agl-ft", this,
 317         &FGInterface::get_Altitude_AGL); // read-only
 318   fgSetArchivable("/position/ground-elev-ft");
 319   fgTie("/position/ground-elev-ft", this,
 320         &FGInterface::get_Runway_altitude); // read-only
 321   fgSetArchivable("/position/ground-elev-m");
 322   fgTie("/position/ground-elev-m", this,
 323         &FGInterface::get_Runway_altitude_m); // read-only
 324   fgTie("/environment/ground-elevation-m", this,
 325         &FGInterface::get_Runway_altitude_m); // read-only
 326   fgSetArchivable("/position/sea-level-radius-ft");
 327   fgTie("/position/sea-level-radius-ft", this,
 328         &FGInterface::get_Sea_level_radius); // read-only
 329
 330                                 // Orientation
 331   fgTie("/orientation/roll-deg", this,
 332         &FGInterface::get_Phi_deg,
 333         &FGInterface::set_Phi_deg);
 334   fgSetArchivable("/orientation/roll-deg");
 335   fgTie("/orientation/pitch-deg", this,
 336         &FGInterface::get_Theta_deg,
 337         &FGInterface::set_Theta_deg);
 338   fgSetArchivable("/orientation/pitch-deg");
 339   fgTie("/orientation/heading-deg", this,
 340         &FGInterface::get_Psi_deg,
 341         &FGInterface::set_Psi_deg);
 342   fgSetArchivable("/orientation/heading-deg");
 343
 344   // Body-axis "euler rates" (rotation speed, but in a funny
 345   // representation).
 346   fgTie("/orientation/roll-rate-degps", this,
 347         &FGInterface::get_Phi_dot_degps);
 348   fgTie("/orientation/pitch-rate-degps", this,
 349         &FGInterface::get_Theta_dot_degps);
 350   fgTie("/orientation/yaw-rate-degps", this,
 351         &FGInterface::get_Psi_dot_degps);
 352
 353                                 // Calibrated airspeed
 354   fgTie("/velocities/airspeed-kt", this,
 355         &FGInterface::get_V_calibrated_kts,
 356         &FGInterface::set_V_calibrated_kts,
 357         false);
 358
 359                                 // Mach number
 360   fgTie("/velocities/mach", this,
 361         &FGInterface::get_Mach_number,
 362         &FGInterface::set_Mach_number,
 363         false);
 364
 365                                 // Local velocities
 366 //   fgTie("/velocities/speed-north-fps", this,
 367 //      &FGInterface::get_V_north,
 368 //      &FGInterface::set_V_north);
 369 //   fgSetArchivable("/velocities/speed-north-fps");
 370 //   fgTie("/velocities/speed-east-fps", this,
 371 //      &FGInterface::get_V_east,
 372 //      &FGInterface::set_V_east);
 373 //   fgSetArchivable("/velocities/speed-east-fps");
 374 //   fgTie("/velocities/speed-down-fps", this,
 375 //      &FGInterface::get_V_down,
 376 //      &FGInterface::set_V_down);
 377 //   fgSetArchivable("/velocities/speed-down-fps");
 378                                 // FIXME: Temporarily read-only, until the
 379                                 // incompatibilities between JSBSim and
 380                                 // LaRCSim are fixed (LaRCSim adds the
 381                                 // earth's rotation to the east velocity).
 382   fgTie("/velocities/speed-north-fps", this,
 383         &FGInterface::get_V_north);
 384   fgTie("/velocities/speed-east-fps", this,
 385         &FGInterface::get_V_east);
 386   fgTie("/velocities/speed-down-fps", this,
 387         &FGInterface::get_V_down);
 388
 389                                 // Relative wind
 390                                 // FIXME: temporarily archivable, until
 391                                 // the NED problem is fixed.
 392   fgTie("/velocities/uBody-fps", this,
 393         &FGInterface::get_uBody,
 394         &FGInterface::set_uBody,
 395         false);
 396   fgSetArchivable("/velocities/uBody-fps");
 397   fgTie("/velocities/vBody-fps", this,
 398         &FGInterface::get_vBody,
 399         &FGInterface::set_vBody,
 400         false);
 401   fgSetArchivable("/velocities/vBody-fps");
 402   fgTie("/velocities/wBody-fps", this,
 403         &FGInterface::get_wBody,
 404         &FGInterface::set_wBody,
 405         false);
 406   fgSetArchivable("/velocities/wBody-fps");
 407
 408                                 // Climb and slip (read-only)
 409   fgTie("/velocities/vertical-speed-fps", this,
 410         &FGInterface::get_Climb_Rate,
 411   &FGInterface::set_Climb_Rate );
 412   fgTie("/velocities/glideslope", this,
 413   &FGInterface::get_Gamma_vert_rad,
 414   &FGInterface::set_Gamma_vert_rad );
 415   fgTie("/orientation/side-slip-rad", this,
 416         &FGInterface::get_Beta); // read-only
 417   fgTie("/orientation/side-slip-deg", this,
 418   &FGInterface::get_Beta_deg); // read-only
 419   fgTie("/orientation/alpha-deg", this,
 420   &FGInterface::get_Alpha_deg); // read-only
 421   fgTie("/accelerations/nlf", this,
 422   &FGInterface::get_Nlf); // read-only
 423
 424                                 // NED accelerations
 425   fgTie("/accelerations/ned/north-accel-fps_sec",
 426         this, &FGInterface::get_V_dot_north);
 427   fgTie("/accelerations/ned/east-accel-fps_sec",
 428         this, &FGInterface::get_V_dot_east);
 429   fgTie("/accelerations/ned/down-accel-fps_sec",
 430         this, &FGInterface::get_V_dot_down);
 431
 432                                 // Pilot accelerations
 433   fgTie("/accelerations/pilot/x-accel-fps_sec",
 434         this, &FGInterface::get_A_X_pilot);
 435   fgTie("/accelerations/pilot/y-accel-fps_sec",
 436         this, &FGInterface::get_A_Y_pilot);
 437   fgTie("/accelerations/pilot/z-accel-fps_sec",
 438         this, &FGInterface::get_A_Z_pilot);
 439
 440 }
 441
 442
 443 /**
 444  * Unbind any properties bound to this FDM.
 445  *
 446  * This method allows the FDM to release properties so that a new
 447  * FDM can bind them instead.
 448  */
 449 void
 450 FGInterface::unbind ()
 451 {
 452   bound = false;
 453
 454   // fgUntie("/fdm/time/delta_t");
 455   // fgUntie("/fdm/time/elapsed");
 456   // fgUntie("/fdm/time/remainder");
 457   // fgUntie("/fdm/time/multi_loop");
 458   fgUntie("/position/latitude-deg");
 459   fgUntie("/position/longitude-deg");
 460   fgUntie("/position/altitude-ft");
 461   fgUntie("/position/altitude-agl-ft");
 462   fgUntie("/position/ground-elev-ft");
 463   fgUntie("/position/ground-elev-m");
 464   fgUntie("/environment/ground-elevation-m");
 465   fgUntie("/position/sea-level-radius-ft");
 466   fgUntie("/orientation/roll-deg");
 467   fgUntie("/orientation/pitch-deg");
 468   fgUntie("/orientation/heading-deg");
 469   fgUntie("/orientation/roll-rate-degps");
 470   fgUntie("/orientation/pitch-rate-degps");
 471   fgUntie("/orientation/yaw-rate-degps");
 472   fgUntie("/orientation/side-slip-rad");
 473   fgUntie("/orientation/side-slip-deg");
 474   fgUntie("/orientation/alpha-deg");
 475   fgUntie("/velocities/airspeed-kt");
 476   fgUntie("/velocities/mach");
 477   fgUntie("/velocities/speed-north-fps");
 478   fgUntie("/velocities/speed-east-fps");
 479   fgUntie("/velocities/speed-down-fps");
 480   fgUntie("/velocities/uBody-fps");
 481   fgUntie("/velocities/vBody-fps");
 482   fgUntie("/velocities/wBody-fps");
 483   fgUntie("/velocities/vertical-speed-fps");
 484   fgUntie("/velocities/glideslope");
 485   fgUntie("/accelerations/nlf");
 486   fgUntie("/accelerations/pilot/x-accel-fps_sec");
 487   fgUntie("/accelerations/pilot/y-accel-fps_sec");
 488   fgUntie("/accelerations/pilot/z-accel-fps_sec");
 489   fgUntie("/accelerations/ned/north-accel-fps_sec");
 490   fgUntie("/accelerations/ned/east-accel-fps_sec");
 491   fgUntie("/accelerations/ned/down-accel-fps_sec");
 492 }
 493
 494 /**
 495  * Update the state of the FDM (i.e. run the equations of motion).
 496  */
 497 void
 498 FGInterface::update (double dt)
 499 {
 500     SG_LOG(SG_FLIGHT, SG_ALERT, "dummy update() ... SHOULDN'T BE CALLED!");
 501 }
 502
 503
 504 void FGInterface::_updateGeodeticPosition( double lat, double lon, double alt )
 505 {
 506     double lat_geoc, sl_radius;
 507
 508     // cout << "starting sea level rad = " << get_Sea_level_radius() << endl;
 509
 510     sgGeodToGeoc( lat, alt * SG_FEET_TO_METER, &sl_radius, &lat_geoc );
 511
 512     SG_LOG( SG_FLIGHT, SG_DEBUG, "lon = " << lon
 513             << " lat_geod = " << lat
 514             << " lat_geoc = " << lat_geoc
 515             << " alt = " << alt
 516             << " sl_radius = " << sl_radius * SG_METER_TO_FEET
 517             << " Equator = " << SG_EQUATORIAL_RADIUS_FT );
 518
 519     _set_Geocentric_Position( lat_geoc, lon,
 520                               sl_radius * SG_METER_TO_FEET + alt );
 521
 522     _set_Geodetic_Position( lat, lon, alt );
 523
 524     _set_Sea_level_radius( sl_radius * SG_METER_TO_FEET );
 525     _update_ground_elev_at_pos();
 526
 527     _set_sin_lat_geocentric( lat_geoc );
 528     _set_cos_lat_geocentric( lat_geoc );
 529
 530     _set_sin_cos_longitude( lon );
 531
 532     _set_sin_cos_latitude( lat );
 533 }
 534
 535
 536 void FGInterface::_updateGeocentricPosition( double lat_geoc, double lon,
 537                                              double alt )
 538 {
 539     double lat_geod, tmp_alt, sl_radius1, sl_radius2, tmp_lat_geoc;
 540
 541     // cout << "starting sea level rad = " << get_Sea_level_radius() << endl;
 542
 543     sgGeocToGeod( lat_geoc, ( get_Sea_level_radius() + alt ) * SG_FEET_TO_METER,
 544                   &lat_geod, &tmp_alt, &sl_radius1 );
 545     sgGeodToGeoc( lat_geod, alt * SG_FEET_TO_METER, &sl_radius2, &tmp_lat_geoc );
 546
 547     SG_LOG( SG_FLIGHT, SG_DEBUG, "lon = " << lon
 548             << " lat_geod = " << lat_geod
 549             << " lat_geoc = " << lat_geoc
 550             << " alt = " << alt
 551             << " tmp_alt = " << tmp_alt * SG_METER_TO_FEET
 552             << " sl_radius1 = " << sl_radius1 * SG_METER_TO_FEET
 553             << " sl_radius2 = " << sl_radius2 * SG_METER_TO_FEET
 554             << " Equator = " << SG_EQUATORIAL_RADIUS_FT );
 555
 556     _set_Geocentric_Position( lat_geoc, lon,
 557                               sl_radius2 * SG_METER_TO_FEET + alt );
 558
 559     _set_Geodetic_Position( lat_geod, lon, alt );
 560
 561     _set_Sea_level_radius( sl_radius2 * SG_METER_TO_FEET );
 562     _update_ground_elev_at_pos();
 563
 564     _set_sin_lat_geocentric( lat_geoc );
 565     _set_cos_lat_geocentric( lat_geoc );
 566
 567     _set_sin_cos_longitude( lon );
 568
 569     _set_sin_cos_latitude( lat_geod );
 570 }
 571
 572 void FGInterface::_update_ground_elev_at_pos( void ) {
 573     double lat = get_Latitude();
 574     double lon = get_Longitude();
 575     double alt_m = get_Altitude()*SG_FEET_TO_METER;
 576     double groundlevel_m = get_groundlevel_m(lat, lon, alt_m);
 577     _set_Runway_altitude( groundlevel_m * SG_METER_TO_FEET );
 578 }
 579
 580 // Extrapolate fdm based on time_offset (in usec)
 581 void FGInterface::extrapolate( int time_offset ) {
 582     double dt = time_offset / 1000000.0;
 583
 584     // -dw- metrowerks complains about ambiguous access, not critical
 585     // to keep this ;)
 586 #ifndef __MWERKS__
 587     SG_LOG(SG_FLIGHT, SG_INFO, "extrapolating FDM by dt = " << dt);
 588 #endif
 589
 590     double lat = geodetic_position_v[0] + geocentric_rates_v[0] * dt;
 591     double lat_geoc = geocentric_position_v[0] + geocentric_rates_v[0] * dt;
 592
 593     double lon = geodetic_position_v[1] + geocentric_rates_v[1] * dt;
 594     double lon_geoc = geocentric_position_v[1] + geocentric_rates_v[1] * dt;
 595
 596     double alt = geodetic_position_v[2] + geocentric_rates_v[2] * dt;
 597     double radius = geocentric_position_v[2] + geocentric_rates_v[2] * dt;
 598
 599     geodetic_position_v[0] = lat;
 600     geocentric_position_v[0] = lat_geoc;
 601
 602     geodetic_position_v[1] = lon;
 603     geocentric_position_v[1] = lon_geoc;
 604
 605     geodetic_position_v[2] = alt;
 606     geocentric_position_v[2] = radius;
 607 }
 608
 609 // Positions
 610 void FGInterface::set_Latitude(double lat) {
 611     geodetic_position_v[0] = lat;
 612 }
 613
 614 void FGInterface::set_Longitude(double lon) {
 615     geodetic_position_v[1] = lon;
 616 }
 617
 618 void FGInterface::set_Altitude(double alt) {
 619     geodetic_position_v[2] = alt;
 620 }
 621
 622 void FGInterface::set_AltitudeAGL(double altagl) {
 623     altitude_agl=altagl;
 624 }
 625
 626 // Velocities
 627 void FGInterface::set_V_calibrated_kts(double vc) {
 628     v_calibrated_kts = vc;
 629 }
 630
 631 void FGInterface::set_Mach_number(double mach) {
 632     mach_number = mach;
 633 }
 634
 635 void FGInterface::set_Velocities_Local( double north,
 636                                         double east,
 637                                         double down ){
 638     v_local_v[0] = north;
 639     v_local_v[1] = east;
 640     v_local_v[2] = down;
 641 }
 642
 643 void FGInterface::set_Velocities_Wind_Body( double u,
 644                                             double v,
 645                                             double w){
 646     v_wind_body_v[0] = u;
 647     v_wind_body_v[1] = v;
 648     v_wind_body_v[2] = w;
 649 }
 650
 651 // Euler angles
 652 void FGInterface::set_Euler_Angles( double phi,
 653                                     double theta,
 654                                     double psi ) {
 655     euler_angles_v[0] = phi;
 656     euler_angles_v[1] = theta;
 657     euler_angles_v[2] = psi;
 658 }
 659
 660 // Flight Path
 661 void FGInterface::set_Climb_Rate( double roc) {
 662     climb_rate = roc;
 663 }
 664
 665 void FGInterface::set_Gamma_vert_rad( double gamma) {
 666     gamma_vert_rad = gamma;
 667 }
 668
 669 void FGInterface::set_Static_pressure(double p) { static_pressure = p; }
 670 void FGInterface::set_Static_temperature(double T) { static_temperature = T; }
 671 void FGInterface::set_Density(double rho) { density = rho; }
 672
 673 void FGInterface::set_Velocities_Local_Airmass (double wnorth,
 674                                                 double weast,
 675                                                 double wdown ) {
 676     v_local_airmass_v[0] = wnorth;
 677     v_local_airmass_v[1] = weast;
 678     v_local_airmass_v[2] = wdown;
 679 }
 680
 681
 682 void FGInterface::_busdump(void) {
 683
 684     SG_LOG(SG_FLIGHT,SG_INFO,"d_pilot_rp_body_v[3]: " << d_pilot_rp_body_v[0] << ", " << d_pilot_rp_body_v[1] << ", " << d_pilot_rp_body_v[2]);
 685     SG_LOG(SG_FLIGHT,SG_INFO,"d_cg_rp_body_v[3]: " << d_cg_rp_body_v[0] << ", " << d_cg_rp_body_v[1] << ", " << d_cg_rp_body_v[2]);
 686     SG_LOG(SG_FLIGHT,SG_INFO,"f_body_total_v[3]: " << f_body_total_v[0] << ", " << f_body_total_v[1] << ", " << f_body_total_v[2]);
 687     SG_LOG(SG_FLIGHT,SG_INFO,"f_local_total_v[3]: " << f_local_total_v[0] << ", " << f_local_total_v[1] << ", " << f_local_total_v[2]);
 688     SG_LOG(SG_FLIGHT,SG_INFO,"f_aero_v[3]: " << f_aero_v[0] << ", " << f_aero_v[1] << ", " << f_aero_v[2]);
 689     SG_LOG(SG_FLIGHT,SG_INFO,"f_engine_v[3]: " << f_engine_v[0] << ", " << f_engine_v[1] << ", " << f_engine_v[2]);
 690     SG_LOG(SG_FLIGHT,SG_INFO,"f_gear_v[3]: " << f_gear_v[0] << ", " << f_gear_v[1] << ", " << f_gear_v[2]);
 691     SG_LOG(SG_FLIGHT,SG_INFO,"m_total_rp_v[3]: " << m_total_rp_v[0] << ", " << m_total_rp_v[1] << ", " << m_total_rp_v[2]);
 692     SG_LOG(SG_FLIGHT,SG_INFO,"m_total_cg_v[3]: " << m_total_cg_v[0] << ", " << m_total_cg_v[1] << ", " << m_total_cg_v[2]);
 693     SG_LOG(SG_FLIGHT,SG_INFO,"m_aero_v[3]: " << m_aero_v[0] << ", " << m_aero_v[1] << ", " << m_aero_v[2]);
 694     SG_LOG(SG_FLIGHT,SG_INFO,"m_engine_v[3]: " << m_engine_v[0] << ", " << m_engine_v[1] << ", " << m_engine_v[2]);
 695     SG_LOG(SG_FLIGHT,SG_INFO,"m_gear_v[3]: " << m_gear_v[0] << ", " << m_gear_v[1] << ", " << m_gear_v[2]);
 696     SG_LOG(SG_FLIGHT,SG_INFO,"v_dot_local_v[3]: " << v_dot_local_v[0] << ", " << v_dot_local_v[1] << ", " << v_dot_local_v[2]);
 697     SG_LOG(SG_FLIGHT,SG_INFO,"v_dot_body_v[3]: " << v_dot_body_v[0] << ", " << v_dot_body_v[1] << ", " << v_dot_body_v[2]);
 698     SG_LOG(SG_FLIGHT,SG_INFO,"a_cg_body_v[3]: " << a_cg_body_v[0] << ", " << a_cg_body_v[1] << ", " << a_cg_body_v[2]);
 699     SG_LOG(SG_FLIGHT,SG_INFO,"a_pilot_body_v[3]: " << a_pilot_body_v[0] << ", " << a_pilot_body_v[1] << ", " << a_pilot_body_v[2]);
 700     SG_LOG(SG_FLIGHT,SG_INFO,"n_cg_body_v[3]: " << n_cg_body_v[0] << ", " << n_cg_body_v[1] << ", " << n_cg_body_v[2]);
 701     SG_LOG(SG_FLIGHT,SG_INFO,"n_pilot_body_v[3]: " << n_pilot_body_v[0] << ", " << n_pilot_body_v[1] << ", " << n_pilot_body_v[2]);
 702     SG_LOG(SG_FLIGHT,SG_INFO,"omega_dot_body_v[3]: " << omega_dot_body_v[0] << ", " << omega_dot_body_v[1] << ", " << omega_dot_body_v[2]);
 703     SG_LOG(SG_FLIGHT,SG_INFO,"v_local_v[3]: " << v_local_v[0] << ", " << v_local_v[1] << ", " << v_local_v[2]);
 704     SG_LOG(SG_FLIGHT,SG_INFO,"v_local_rel_ground_v[3]: " << v_local_rel_ground_v[0] << ", " << v_local_rel_ground_v[1] << ", " << v_local_rel_ground_v[2]);
 705     SG_LOG(SG_FLIGHT,SG_INFO,"v_local_airmass_v[3]: " << v_local_airmass_v[0] << ", " << v_local_airmass_v[1] << ", " << v_local_airmass_v[2]);
 706     SG_LOG(SG_FLIGHT,SG_INFO,"v_local_rel_airmass_v[3]: " << v_local_rel_airmass_v[0] << ", " << v_local_rel_airmass_v[1] << ", " << v_local_rel_airmass_v[2]);
 707     SG_LOG(SG_FLIGHT,SG_INFO,"v_local_gust_v[3]: " << v_local_gust_v[0] << ", " << v_local_gust_v[1] << ", " << v_local_gust_v[2]);
 708     SG_LOG(SG_FLIGHT,SG_INFO,"v_wind_body_v[3]: " << v_wind_body_v[0] << ", " << v_wind_body_v[1] << ", " << v_wind_body_v[2]);
 709     SG_LOG(SG_FLIGHT,SG_INFO,"omega_body_v[3]: " << omega_body_v[0] << ", " << omega_body_v[1] << ", " << omega_body_v[2]);
 710     SG_LOG(SG_FLIGHT,SG_INFO,"omega_local_v[3]: " << omega_local_v[0] << ", " << omega_local_v[1] << ", " << omega_local_v[2]);
 711     SG_LOG(SG_FLIGHT,SG_INFO,"omega_total_v[3]: " << omega_total_v[0] << ", " << omega_total_v[1] << ", " << omega_total_v[2]);
 712     SG_LOG(SG_FLIGHT,SG_INFO,"euler_rates_v[3]: " << euler_rates_v[0] << ", " << euler_rates_v[1] << ", " << euler_rates_v[2]);
 713     SG_LOG(SG_FLIGHT,SG_INFO,"geocentric_rates_v[3]: " << geocentric_rates_v[0] << ", " << geocentric_rates_v[1] << ", " << geocentric_rates_v[2]);
 714     SG_LOG(SG_FLIGHT,SG_INFO,"geocentric_position_v[3]: " << geocentric_position_v[0] << ", " << geocentric_position_v[1] << ", " << geocentric_position_v[2]);
 715     SG_LOG(SG_FLIGHT,SG_INFO,"geodetic_position_v[3]: " << geodetic_position_v[0] << ", " << geodetic_position_v[1] << ", " << geodetic_position_v[2]);
 716     SG_LOG(SG_FLIGHT,SG_INFO,"euler_angles_v[3]: " << euler_angles_v[0] << ", " << euler_angles_v[1] << ", " << euler_angles_v[2]);
 717     SG_LOG(SG_FLIGHT,SG_INFO,"d_cg_rwy_local_v[3]: " << d_cg_rwy_local_v[0] << ", " << d_cg_rwy_local_v[1] << ", " << d_cg_rwy_local_v[2]);
 718     SG_LOG(SG_FLIGHT,SG_INFO,"d_cg_rwy_rwy_v[3]: " << d_cg_rwy_rwy_v[0] << ", " << d_cg_rwy_rwy_v[1] << ", " << d_cg_rwy_rwy_v[2]);
 719     SG_LOG(SG_FLIGHT,SG_INFO,"d_pilot_rwy_local_v[3]: " << d_pilot_rwy_local_v[0] << ", " << d_pilot_rwy_local_v[1] << ", " << d_pilot_rwy_local_v[2]);
 720     SG_LOG(SG_FLIGHT,SG_INFO,"d_pilot_rwy_rwy_v[3]: " << d_pilot_rwy_rwy_v[0] << ", " << d_pilot_rwy_rwy_v[1] << ", " << d_pilot_rwy_rwy_v[2]);
 721
 722     SG_LOG(SG_FLIGHT,SG_INFO,"t_local_to_body_m[0][3]: " << t_local_to_body_m[0][0] << ", " << t_local_to_body_m[0][1] << ", " << t_local_to_body_m[0][2]);
 723     SG_LOG(SG_FLIGHT,SG_INFO,"t_local_to_body_m[1][3]: " << t_local_to_body_m[1][0] << ", " << t_local_to_body_m[1][1] << ", " << t_local_to_body_m[1][2]);
 724     SG_LOG(SG_FLIGHT,SG_INFO,"t_local_to_body_m[2][3]: " << t_local_to_body_m[2][0] << ", " << t_local_to_body_m[2][1] << ", " << t_local_to_body_m[2][2]);
 725
 726     SG_LOG(SG_FLIGHT,SG_INFO,"mass: " << mass );
 727     SG_LOG(SG_FLIGHT,SG_INFO,"i_xx: " << i_xx );
 728     SG_LOG(SG_FLIGHT,SG_INFO,"i_yy: " << i_yy );
 729     SG_LOG(SG_FLIGHT,SG_INFO,"i_zz: " << i_zz );
 730     SG_LOG(SG_FLIGHT,SG_INFO,"i_xz: " << i_xz );
 731     SG_LOG(SG_FLIGHT,SG_INFO,"nlf: " << nlf );
 732     SG_LOG(SG_FLIGHT,SG_INFO,"v_rel_wind: " << v_rel_wind );
 733     SG_LOG(SG_FLIGHT,SG_INFO,"v_true_kts: " << v_true_kts );
 734     SG_LOG(SG_FLIGHT,SG_INFO,"v_rel_ground: " << v_rel_ground );
 735     SG_LOG(SG_FLIGHT,SG_INFO,"v_inertial: " << v_inertial );
 736     SG_LOG(SG_FLIGHT,SG_INFO,"v_ground_speed: " << v_ground_speed );
 737     SG_LOG(SG_FLIGHT,SG_INFO,"v_equiv: " << v_equiv );
 738     SG_LOG(SG_FLIGHT,SG_INFO,"v_equiv_kts: " << v_equiv_kts );
 739     SG_LOG(SG_FLIGHT,SG_INFO,"v_calibrated: " << v_calibrated );
 740     SG_LOG(SG_FLIGHT,SG_INFO,"v_calibrated_kts: " << v_calibrated_kts );
 741     SG_LOG(SG_FLIGHT,SG_INFO,"gravity: " << gravity );
 742     SG_LOG(SG_FLIGHT,SG_INFO,"centrifugal_relief: " << centrifugal_relief );
 743     SG_LOG(SG_FLIGHT,SG_INFO,"alpha: " << alpha );
 744     SG_LOG(SG_FLIGHT,SG_INFO,"beta: " << beta );
 745     SG_LOG(SG_FLIGHT,SG_INFO,"alpha_dot: " << alpha_dot );
 746     SG_LOG(SG_FLIGHT,SG_INFO,"beta_dot: " << beta_dot );
 747     SG_LOG(SG_FLIGHT,SG_INFO,"cos_alpha: " << cos_alpha );
 748     SG_LOG(SG_FLIGHT,SG_INFO,"sin_alpha: " << sin_alpha );
 749     SG_LOG(SG_FLIGHT,SG_INFO,"cos_beta: " << cos_beta );
 750     SG_LOG(SG_FLIGHT,SG_INFO,"sin_beta: " << sin_beta );
 751     SG_LOG(SG_FLIGHT,SG_INFO,"cos_phi: " << cos_phi );
 752     SG_LOG(SG_FLIGHT,SG_INFO,"sin_phi: " << sin_phi );
 753     SG_LOG(SG_FLIGHT,SG_INFO,"cos_theta: " << cos_theta );
 754     SG_LOG(SG_FLIGHT,SG_INFO,"sin_theta: " << sin_theta );
 755     SG_LOG(SG_FLIGHT,SG_INFO,"cos_psi: " << cos_psi );
 756     SG_LOG(SG_FLIGHT,SG_INFO,"sin_psi: " << sin_psi );
 757     SG_LOG(SG_FLIGHT,SG_INFO,"gamma_vert_rad: " << gamma_vert_rad );
 758     SG_LOG(SG_FLIGHT,SG_INFO,"gamma_horiz_rad: " << gamma_horiz_rad );
 759     SG_LOG(SG_FLIGHT,SG_INFO,"sigma: " << sigma );
 760     SG_LOG(SG_FLIGHT,SG_INFO,"density: " << density );
 761     SG_LOG(SG_FLIGHT,SG_INFO,"v_sound: " << v_sound );
 762     SG_LOG(SG_FLIGHT,SG_INFO,"mach_number: " << mach_number );
 763     SG_LOG(SG_FLIGHT,SG_INFO,"static_pressure: " << static_pressure );
 764     SG_LOG(SG_FLIGHT,SG_INFO,"total_pressure: " << total_pressure );
 765     SG_LOG(SG_FLIGHT,SG_INFO,"impact_pressure: " << impact_pressure );
 766     SG_LOG(SG_FLIGHT,SG_INFO,"dynamic_pressure: " << dynamic_pressure );
 767     SG_LOG(SG_FLIGHT,SG_INFO,"static_temperature: " << static_temperature );
 768     SG_LOG(SG_FLIGHT,SG_INFO,"total_temperature: " << total_temperature );
 769     SG_LOG(SG_FLIGHT,SG_INFO,"sea_level_radius: " << sea_level_radius );
 770     SG_LOG(SG_FLIGHT,SG_INFO,"earth_position_angle: " << earth_position_angle );
 771     SG_LOG(SG_FLIGHT,SG_INFO,"runway_altitude: " << runway_altitude );
 772     SG_LOG(SG_FLIGHT,SG_INFO,"runway_latitude: " << runway_latitude );
 773     SG_LOG(SG_FLIGHT,SG_INFO,"runway_longitude: " << runway_longitude );
 774     SG_LOG(SG_FLIGHT,SG_INFO,"runway_heading: " << runway_heading );
 775     SG_LOG(SG_FLIGHT,SG_INFO,"radius_to_rwy: " << radius_to_rwy );
 776     SG_LOG(SG_FLIGHT,SG_INFO,"climb_rate: " << climb_rate );
 777     SG_LOG(SG_FLIGHT,SG_INFO,"sin_lat_geocentric: " << sin_lat_geocentric );
 778     SG_LOG(SG_FLIGHT,SG_INFO,"cos_lat_geocentric: " << cos_lat_geocentric );
 779     SG_LOG(SG_FLIGHT,SG_INFO,"sin_longitude: " << sin_longitude );
 780     SG_LOG(SG_FLIGHT,SG_INFO,"cos_longitude: " << cos_longitude );
 781     SG_LOG(SG_FLIGHT,SG_INFO,"sin_latitude: " << sin_latitude );
 782     SG_LOG(SG_FLIGHT,SG_INFO,"cos_latitude: " << cos_latitude );
 783     SG_LOG(SG_FLIGHT,SG_INFO,"altitude_agl: " << altitude_agl );
 784 }
 785
 786 bool
 787 FGInterface::prepare_ground_cache_m(double ref_time, const double pt[3],
 788                                     double rad)
 789 {
 790   return ground_cache.prepare_ground_cache(ref_time, pt, rad);
 791 }
 792
 793 bool FGInterface::prepare_ground_cache_ft(double ref_time, const double pt[3],
 794                                           double rad)
 795 {
 796   // Convert units and do the real work.
 797   sgdVec3 pt_ft;
 798   sgdScaleVec3( pt_ft, pt, SG_FEET_TO_METER );
 799   return ground_cache.prepare_ground_cache(ref_time, pt_ft, rad*SG_FEET_TO_METER);
 800 }
 801
 802 bool
 803 FGInterface::is_valid_m(double *ref_time, double pt[3], double *rad)
 804 {
 805   return ground_cache.is_valid(ref_time, pt, rad);
 806 }
 807
 808 bool FGInterface::is_valid_ft(double *ref_time, double pt[3], double *rad)
 809 {
 810   // Convert units and do the real work.
 811   bool found_ground = ground_cache.is_valid(ref_time, pt, rad);
 812   sgdScaleVec3(pt, SG_METER_TO_FEET);
 813   *rad *= SG_METER_TO_FEET;
 814   return found_ground;
 815 }
 816
 817 double
 818 FGInterface::get_cat_m(double t, const double pt[3],
 819                        double end[2][3], double vel[2][3])
 820 {
 821   return ground_cache.get_cat(t, pt, end, vel);
 822 }
 823
 824 double
 825 FGInterface::get_cat_ft(double t, const double pt[3],
 826                         double end[2][3], double vel[2][3])
 827 {
 828   // Convert units and do the real work.
 829   sgdVec3 pt_m;
 830   sgdScaleVec3( pt_m, pt, SG_FEET_TO_METER );
 831   double dist = ground_cache.get_cat(t, pt_m, end, vel);
 832   for (int k=0; k<2; ++k) {
 833     sgdScaleVec3( end[k], SG_METER_TO_FEET );
 834     sgdScaleVec3( vel[k], SG_METER_TO_FEET );
 835   }
 836   return dist*SG_METER_TO_FEET;
 837 }
 838
 839 bool
 840 FGInterface::get_agl_m(double t, const double pt[3],
 841                        double contact[3], double normal[3], double vel[3],
 842                        int *type, double *loadCapacity,
 843                        double *frictionFactor, double *agl)
 844 {
 845   return ground_cache.get_agl(t, pt, 2.0, contact, normal, vel, type,
 846                               loadCapacity, frictionFactor, agl);
 847 }
 848
 849 bool
 850 FGInterface::get_agl_ft(double t, const double pt[3],
 851                         double contact[3], double normal[3], double vel[3],
 852                         int *type, double *loadCapacity,
 853                         double *frictionFactor, double *agl)
 854 {
 855   // Convert units and do the real work.
 856   sgdVec3 pt_m;
 857   sgdScaleVec3( pt_m, pt, SG_FEET_TO_METER );
 858   bool ret = ground_cache.get_agl(t, pt_m, 2.0, contact, normal, vel,
 859                                   type, loadCapacity, frictionFactor, agl);
 860   // Convert units back ...
 861   sgdScaleVec3( contact, SG_METER_TO_FEET );
 862   sgdScaleVec3( vel, SG_METER_TO_FEET );
 863   *agl *= SG_METER_TO_FEET;
 864   // FIXME: scale the load limit to something in the english unit system.
 865   // Be careful with the DBL_MAX which is returned by default.
 866   return ret;
 867 }
 868
 869 bool
 870 FGInterface::get_agl_m(double t, const double pt[3], double max_altoff,
 871                        double contact[3], double normal[3], double vel[3],
 872                        int *type, double *loadCapacity,
 873                        double *frictionFactor, double *agl)
 874 {
 875   return ground_cache.get_agl(t, pt, max_altoff, contact, normal, vel, type,
 876                               loadCapacity, frictionFactor, agl);
 877 }
 878
 879 bool
 880 FGInterface::get_agl_ft(double t, const double pt[3], double max_altoff,
 881                         double contact[3], double normal[3], double vel[3],
 882                         int *type, double *loadCapacity,
 883                         double *frictionFactor, double *agl)
 884 {
 885   // Convert units and do the real work.
 886   sgdVec3 pt_m;
 887   sgdScaleVec3( pt_m, pt, SG_FEET_TO_METER );
 888   bool ret = ground_cache.get_agl(t, pt_m, SG_FEET_TO_METER * max_altoff,
 889                                   contact, normal, vel,
 890                                   type, loadCapacity, frictionFactor, agl);
 891   // Convert units back ...
 892   sgdScaleVec3( contact, SG_METER_TO_FEET );
 893   sgdScaleVec3( vel, SG_METER_TO_FEET );
 894   *agl *= SG_METER_TO_FEET;
 895   // FIXME: scale the load limit to something in the english unit system.
 896   // Be careful with the DBL_MAX which is returned by default.
 897   return ret;
 898 }
 899
 900
 901 double
 902 FGInterface::get_groundlevel_m(double lat, double lon, double alt)
 903 {
 904   sgdVec3 pos, cpos;
 905   // Compute the cartesian position of the given lat/lon/alt.
 906   sgGeodToCart(lat, lon, alt, pos);
 907
 908   // FIXME: how to handle t - ref_time differences ???
 909   double ref_time, radius;
 910   // Prepare the ground cache for that position.
 911   if (!is_valid_m(&ref_time, cpos, &radius)) {
 912     bool ok = prepare_ground_cache_m(ref_time, pos, 10);
 913     /// This is most likely the case when the given altitude is
 914     /// too low, try with a new altitude of 10000m, that should be
 915     /// sufficient to find a ground level below everywhere on our planet
 916     if (!ok) {
 917       sgGeodToCart(lat, lon, 10000, pos);
 918       /// If there is still no ground, return sea level radius
 919       if (!prepare_ground_cache_m(ref_time, pos, 10))
 920         return 0;
 921     }
 922   } else if (radius*radius <= sgdDistanceSquaredVec3(pos, cpos)) {
 923     /// We reuse the old radius value, but only if it is at least 10 Meters ..
 924     if (!(10 < radius)) // Well this strange compare is nan safe
 925       radius = 10;
 926
 927     bool ok = prepare_ground_cache_m(ref_time, pos, radius);
 928     /// This is most likely the case when the given altitude is
 929     /// too low, try with a new altitude of 10000m, that should be
 930     /// sufficient to find a ground level below everywhere on our planet
 931     if (!ok) {
 932       sgGeodToCart(lat, lon, 10000, pos);
 933       /// If there is still no ground, return sea level radius
 934       if (!prepare_ground_cache_m(ref_time, pos, radius))
 935         return 0;
 936     }
 937   }
 938
 939   double contact[3], normal[3], vel[3], lc, ff, agl;
 940   int type;
 941   // Ignore the return value here, since it just tells us if
 942   // the returns stem from the groundcache or from the coarse
 943   // computations below the groundcache. The contact point is still something
 944   // valid, the normals and the other returns just contain some defaults.
 945   get_agl_m(ref_time, pos, 2.0, contact, normal, vel, &type, &lc, &ff, &agl);
 946   Point3D geodPos = sgCartToGeod(Point3D(contact[0], contact[1], contact[2]));
 947   return geodPos.elev();
 948 }
 949
 950 bool
 951 FGInterface::caught_wire_m(double t, const double pt[4][3])
 952 {
 953   return ground_cache.caught_wire(t, pt);
 954 }
 955
 956 bool
 957 FGInterface::caught_wire_ft(double t, const double pt[4][3])
 958 {
 959   // Convert units and do the real work.
 960   double pt_m[4][3];
 961   for (int i=0; i<4; ++i)
 962     sgdScaleVec3(pt_m[i], pt[i], SG_FEET_TO_METER);
 963
 964   return ground_cache.caught_wire(t, pt_m);
 965 }
 966
 967 bool
 968 FGInterface::get_wire_ends_m(double t, double end[2][3], double vel[2][3])
 969 {
 970   return ground_cache.get_wire_ends(t, end, vel);
 971 }
 972
 973 bool
 974 FGInterface::get_wire_ends_ft(double t, double end[2][3], double vel[2][3])
 975 {
 976   // Convert units and do the real work.
 977   bool ret = ground_cache.get_wire_ends(t, end, vel);
 978   for (int k=0; k<2; ++k) {
 979     sgdScaleVec3( end[k], SG_METER_TO_FEET );
 980     sgdScaleVec3( vel[k], SG_METER_TO_FEET );
 981   }
 982   return ret;
 983 }
 984
 985 void
 986 FGInterface::release_wire(void)
 987 {
 988   ground_cache.release_wire();
 989 }
 990
 991 void fgToggleFDMdataLogging(void) {
 992   cur_fdm_state->ToggleDataLogging();
 993 }