]> git.mxchange.org Git - flightgear.git/blobdiff - src/FDM/flight.cxx
Removed useless divisions - As a side effect, it removes the risk of divisions by...
[flightgear.git] / src / FDM / flight.cxx
index f1b88d36540fe89d570fde0d1b6f726ba4db397c..431605a9f9957713c977c6857376578e6580e7d4 100644 (file)
@@ -29,7 +29,6 @@
 #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>
@@ -45,23 +44,13 @@ static inline void assign(double* ptr, const SGVec3d& vec)
   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();
 }
@@ -71,33 +60,18 @@ FGInterface::~FGInterface() {
     // unbind();                   // FIXME: should be called explicitly
 }
 
-
 int
 FGInterface::_calc_multiloop (double dt)
 {
+  // Since some time the simulation time increments we get here are
+  // already a multiple of the basic update freqency.
+  // So, there is no need to do our own multiloop rounding with all bad
+  // roundoff problems when we already have nearly accurate values.
+  // Only the speedup thing must be still handled here
   int hz = fgGetInt("/sim/model-hz");
+  int multiloop = SGMiscd::roundToInt(dt*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);
+  return multiloop * speedup;
 }
 
 
@@ -144,6 +118,7 @@ FGInterface::_setup ()
     runway_altitude=0;
     climb_rate=0;
     altitude_agl=0;
+    track=0;
 }
 
 void
@@ -164,8 +139,7 @@ FGInterface::common_init ()
 
     set_inited( true );
 
-//     stamp();
-//     set_remainder( 0 );
+    ground_cache.set_cache_time_offset(globals->get_sim_time_sec());
 
     // Set initial position
     SG_LOG( SG_FLIGHT, SG_INFO, "...initializing position..." );
@@ -205,6 +179,15 @@ FGInterface::common_init ()
     double slr = SGGeodesy::SGGeodToSeaLevelRadius(geodetic_position_v);
     _set_Sea_level_radius( slr * SG_METER_TO_FEET );
 
+    // 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 );
+
     // Set initial velocities
     SG_LOG( SG_FLIGHT, SG_INFO, "...initializing velocities..." );
     if ( !fgHasNode("/sim/presets/speed-set") ) {
@@ -233,14 +216,11 @@ FGInterface::common_init ()
         }
     }
 
-    // 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 );
+    if ( fgHasNode("/sim/presets/glideslope-deg") )
+        set_Gamma_vert_rad( fgGetDouble("/sim/presets/glideslope-deg")
+                              * SGD_DEGREES_TO_RADIANS );
+    else if ( fgHasNode( "/velocities/vertical-speed-fps") )
+        set_Climb_Rate( fgGetDouble("/velocities/vertical-speed-fps") );
 
     SG_LOG( SG_FLIGHT, SG_INFO, "End common FDM init" );
 }
@@ -260,16 +240,6 @@ 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,
@@ -287,7 +257,7 @@ FGInterface::bind ()
         false);
   fgSetArchivable("/position/altitude-ft");
   fgTie("/position/altitude-agl-ft", this,
-        &FGInterface::get_Altitude_AGL); // read-only
+        &FGInterface::get_Altitude_AGL, &FGInterface::set_AltitudeAGL, false);
   fgSetArchivable("/position/ground-elev-ft");
   fgTie("/position/ground-elev-ft", this,
         &FGInterface::get_Runway_altitude); // read-only
@@ -298,34 +268,44 @@ FGInterface::bind ()
         &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
+        &FGInterface::get_Sea_level_radius,
+        &FGInterface::_set_Sea_level_radius, false);
 
                                // Orientation
   fgTie("/orientation/roll-deg", this,
        &FGInterface::get_Phi_deg,
-       &FGInterface::set_Phi_deg);
+       &FGInterface::set_Phi_deg, false);
   fgSetArchivable("/orientation/roll-deg");
   fgTie("/orientation/pitch-deg", this,
        &FGInterface::get_Theta_deg,
-       &FGInterface::set_Theta_deg);
+       &FGInterface::set_Theta_deg, false);
   fgSetArchivable("/orientation/pitch-deg");
   fgTie("/orientation/heading-deg", this,
        &FGInterface::get_Psi_deg,
-       &FGInterface::set_Psi_deg);
+       &FGInterface::set_Psi_deg, false);
   fgSetArchivable("/orientation/heading-deg");
+  fgTie("/orientation/track-deg", this,
+       &FGInterface::get_Track); // read-only
 
   // Body-axis "euler rates" (rotation speed, but in a funny
   // representation).
   fgTie("/orientation/roll-rate-degps", this,
-       &FGInterface::get_Phi_dot_degps);
+       &FGInterface::get_Phi_dot_degps,
+       &FGInterface::set_Phi_dot_degps, false);
   fgTie("/orientation/pitch-rate-degps", this,
-       &FGInterface::get_Theta_dot_degps);
+       &FGInterface::get_Theta_dot_degps,
+       &FGInterface::set_Theta_dot_degps, false);
   fgTie("/orientation/yaw-rate-degps", this,
-       &FGInterface::get_Psi_dot_degps);
+       &FGInterface::get_Psi_dot_degps,
+       &FGInterface::set_Psi_dot_degps, false);
 
+  fgTie("/orientation/p-body", this, &FGInterface::get_P_body); // read-only
+  fgTie("/orientation/q-body", this, &FGInterface::get_Q_body); // read-only
+  fgTie("/orientation/r-body", this, &FGInterface::get_R_body); // read-only
+  
                                 // Ground speed knots
   fgTie("/velocities/groundspeed-kt", this,
-        &FGInterface::get_V_ground_speed_kt);
+        &FGInterface::get_V_ground_speed_kt); // read-only
 
                                // Calibrated airspeed
   fgTie("/velocities/airspeed-kt", this,
@@ -333,6 +313,9 @@ FGInterface::bind ()
        &FGInterface::set_V_calibrated_kts,
        false);
 
+    fgTie("/velocities/equivalent-kt", this,
+        &FGInterface::get_V_equiv_kts); // read-only
+
                                // Mach number
   fgTie("/velocities/mach", this,
        &FGInterface::get_Mach_number,
@@ -357,11 +340,19 @@ FGInterface::bind ()
                                // LaRCSim are fixed (LaRCSim adds the
                                // earth's rotation to the east velocity).
   fgTie("/velocities/speed-north-fps", this,
-       &FGInterface::get_V_north);
+       &FGInterface::get_V_north, &FGInterface::set_V_north, false);
   fgTie("/velocities/speed-east-fps", this,
-       &FGInterface::get_V_east);
+       &FGInterface::get_V_east, &FGInterface::set_V_east, false);
   fgTie("/velocities/speed-down-fps", this,
-       &FGInterface::get_V_down);
+       &FGInterface::get_V_down, &FGInterface::set_V_down, false);
+
+  fgTie("/velocities/north-relground-fps", this,
+    &FGInterface::get_V_north_rel_ground); // read-only
+  fgTie("/velocities/east-relground-fps", this,
+    &FGInterface::get_V_east_rel_ground); // read-only
+  fgTie("/velocities/down-relground-fps", this,
+    &FGInterface::get_V_down_rel_ground); // read-only
+
 
                                // Relative wind
                                // FIXME: temporarily archivable, until
@@ -385,34 +376,37 @@ FGInterface::bind ()
                                // Climb and slip (read-only)
   fgTie("/velocities/vertical-speed-fps", this,
        &FGInterface::get_Climb_Rate,
-  &FGInterface::set_Climb_Rate ); 
+        &FGInterface::set_Climb_Rate, false );
   fgTie("/velocities/glideslope", this,
   &FGInterface::get_Gamma_vert_rad,
-  &FGInterface::set_Gamma_vert_rad );
+  &FGInterface::set_Gamma_vert_rad, false );
   fgTie("/orientation/side-slip-rad", this,
-       &FGInterface::get_Beta); // read-only
+       &FGInterface::get_Beta, &FGInterface::_set_Beta, false);
   fgTie("/orientation/side-slip-deg", this,
   &FGInterface::get_Beta_deg); // read-only
   fgTie("/orientation/alpha-deg", this,
-  &FGInterface::get_Alpha_deg); // read-only
+  &FGInterface::get_Alpha_deg, &FGInterface::set_Alpha_deg, false);
   fgTie("/accelerations/nlf", this,
   &FGInterface::get_Nlf); // read-only
 
                                 // NED accelerations
   fgTie("/accelerations/ned/north-accel-fps_sec",
-        this, &FGInterface::get_V_dot_north);
+        this, &FGInterface::get_V_dot_north); // read-only
   fgTie("/accelerations/ned/east-accel-fps_sec",
-        this, &FGInterface::get_V_dot_east);
+        this, &FGInterface::get_V_dot_east); // read-only
   fgTie("/accelerations/ned/down-accel-fps_sec",
-        this, &FGInterface::get_V_dot_down);
+        this, &FGInterface::get_V_dot_down); // read-only
 
                                 // Pilot accelerations
   fgTie("/accelerations/pilot/x-accel-fps_sec",
-        this, &FGInterface::get_A_X_pilot);
+        this, &FGInterface::get_A_X_pilot, &FGInterface::set_A_X_pilot, false);
   fgTie("/accelerations/pilot/y-accel-fps_sec",
-        this, &FGInterface::get_A_Y_pilot);
+        this, &FGInterface::get_A_Y_pilot, &FGInterface::set_A_Y_pilot, false);
   fgTie("/accelerations/pilot/z-accel-fps_sec",
-        this, &FGInterface::get_A_Z_pilot);
+        this, &FGInterface::get_A_Z_pilot, &FGInterface::set_A_Z_pilot, false);
+        
+  fgTie("/accelerations/n-z-cg-fps_sec",
+        this, &FGInterface::get_N_Z_cg); // read-only
 
 }
 
@@ -426,12 +420,12 @@ FGInterface::bind ()
 void
 FGInterface::unbind ()
 {
+  if (!bound) {
+    return;
+  }
+  
   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");
@@ -443,18 +437,26 @@ FGInterface::unbind ()
   fgUntie("/orientation/roll-deg");
   fgUntie("/orientation/pitch-deg");
   fgUntie("/orientation/heading-deg");
+  fgUntie("/orientation/track-deg");
   fgUntie("/orientation/roll-rate-degps");
   fgUntie("/orientation/pitch-rate-degps");
   fgUntie("/orientation/yaw-rate-degps");
+  fgUntie("/orientation/p-body");
+  fgUntie("/orientation/q-body");
+  fgUntie("/orientation/r-body");
   fgUntie("/orientation/side-slip-rad");
   fgUntie("/orientation/side-slip-deg");
   fgUntie("/orientation/alpha-deg");
   fgUntie("/velocities/airspeed-kt");
   fgUntie("/velocities/groundspeed-kt");
+  fgUntie("/velocities/equivalent-kt");
   fgUntie("/velocities/mach");
   fgUntie("/velocities/speed-north-fps");
   fgUntie("/velocities/speed-east-fps");
   fgUntie("/velocities/speed-down-fps");
+  fgUntie("/velocities/north-relground-fps");
+  fgUntie("/velocities/east-relground-fps");
+  fgUntie("/velocities/down-relground-fps");
   fgUntie("/velocities/uBody-fps");
   fgUntie("/velocities/vBody-fps");
   fgUntie("/velocities/wBody-fps");
@@ -467,6 +469,7 @@ FGInterface::unbind ()
   fgUntie("/accelerations/ned/north-accel-fps_sec");
   fgUntie("/accelerations/ned/east-accel-fps_sec");
   fgUntie("/accelerations/ned/down-accel-fps_sec");
+  fgUntie("/accelerations/n-z-cg-fps_sec");
 }
 
 /**
@@ -481,6 +484,7 @@ FGInterface::update (double dt)
 
 void FGInterface::_updatePositionM(const SGVec3d& cartPos)
 {
+    TrackComputer tracker( track, geodetic_position_v );
     cartesian_position_v = cartPos;
     geodetic_position_v = SGGeod::fromCart(cartesian_position_v);
     geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
@@ -491,6 +495,7 @@ void FGInterface::_updatePositionM(const SGVec3d& cartPos)
 
 void FGInterface::_updatePosition(const SGGeod& geod)
 {
+    TrackComputer tracker( track, geodetic_position_v );
     geodetic_position_v = geod;
     cartesian_position_v = SGVec3d::fromGeod(geodetic_position_v);
     geocentric_position_v = SGGeoc::fromCart(cartesian_position_v);
@@ -502,6 +507,7 @@ void FGInterface::_updatePosition(const SGGeod& geod)
 
 void FGInterface::_updatePosition(const SGGeoc& geoc)
 {
+    TrackComputer tracker( track, geodetic_position_v );
     geocentric_position_v = geoc;
     cartesian_position_v = SGVec3d::fromGeoc(geocentric_position_v);
     geodetic_position_v = SGGeod::fromCart(cartesian_position_v);
@@ -644,18 +650,21 @@ void FGInterface::_busdump(void) {
 }
 
 bool
-FGInterface::prepare_ground_cache_m(double ref_time, const double pt[3],
-                                    double rad)
+FGInterface::prepare_ground_cache_m(double startSimTime, double endSimTime,
+                                    const double pt[3], double rad)
 {
-  return ground_cache.prepare_ground_cache(ref_time, SGVec3d(pt), rad);
+  return ground_cache.prepare_ground_cache(startSimTime, endSimTime,
+                                           SGVec3d(pt), rad);
 }
 
-bool FGInterface::prepare_ground_cache_ft(double ref_time, const double pt[3],
-                                          double rad)
+bool
+FGInterface::prepare_ground_cache_ft(double startSimTime, double endSimTime,
+                                     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);
+  return ground_cache.prepare_ground_cache(startSimTime, endSimTime,
+                                           pt_ft, rad*SG_FEET_TO_METER);
 }
 
 bool
@@ -705,108 +714,108 @@ FGInterface::get_cat_ft(double t, const double pt[3],
   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)
+FGInterface::get_body_m(double t, simgear::BVHNode::Id id,
+                        double bodyToWorld[16], double linearVel[3],
+                        double angularVel[3])
 {
-  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;
+  SGMatrixd _bodyToWorld;
+  SGVec3d _linearVel, _angularVel;
+  if (!ground_cache.get_body(t, _bodyToWorld, _linearVel, _angularVel, id))
+    return false;
+
+  assign(linearVel, _linearVel);
+  assign(angularVel, _angularVel);
+  for (unsigned i = 0; i < 16; ++i)
+      bodyToWorld[i] = _bodyToWorld.data()[i];
+
+  return true;
 }
 
 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);
+FGInterface::get_agl_m(double t, const double pt[3], double max_altoff,
+                       double contact[3], double normal[3],
+                       double linearVel[3], double angularVel[3],
+                       SGMaterial const*& material, simgear::BVHNode::Id& id)
+{
+  SGVec3d pt_m = SGVec3d(pt) - max_altoff*ground_cache.get_down();
+  SGVec3d _contact, _normal, _linearVel, _angularVel;
+  material = 0;
+  bool ret = ground_cache.get_agl(t, pt_m, _contact, _normal, _linearVel,
+                                  _angularVel, id, material);
+  // correct the linear velocity, since the line intersector delivers
+  // values for the start point and the get_agl function should
+  // traditionally deliver for the contact point
+  _linearVel += cross(_angularVel, _contact - pt_m);
+
   assign(contact, _contact);
   assign(normal, _normal);
-  assign(vel, _vel);
+  assign(linearVel, _linearVel);
+  assign(angularVel, _angularVel);
   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)
+FGInterface::get_agl_ft(double t, const double pt[3], double max_altoff,
+                        double contact[3], double normal[3],
+                        double linearVel[3], double angularVel[3],
+                        SGMaterial const*& material, simgear::BVHNode::Id& id)
 {
   // Convert units and do the real work.
-  SGVec3d pt_m = SG_FEET_TO_METER*SGVec3d(pt);
+  SGVec3d pt_m = SGVec3d(pt) - max_altoff*ground_cache.get_down();
+  pt_m *= SG_FEET_TO_METER;
+  SGVec3d _contact, _normal, _linearVel, _angularVel;
+  material = 0;
+  bool ret = ground_cache.get_agl(t, pt_m, _contact, _normal, _linearVel,
+                                  _angularVel, id, material);
+  // correct the linear velocity, since the line intersector delivers
+  // values for the start point and the get_agl function should
+  // traditionally deliver for the contact point
+  _linearVel += cross(_angularVel, _contact - pt_m);
 
-  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;
-  }
+  assign( linearVel, SG_METER_TO_FEET*_linearVel );
+  assign( angularVel, _angularVel );
   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)
+FGInterface::get_nearest_m(double t, const double pt[3], double maxDist,
+                           double contact[3], double normal[3],
+                           double linearVel[3], double angularVel[3],
+                           SGMaterial const*& material,
+                           simgear::BVHNode::Id& id)
 {
-  SGVec3d _contact, _normal, _vel;
-  bool found = ground_cache.get_agl(t, SGVec3d(pt), max_altoff, _contact,
-                                    _normal, _vel, type, material, agl);
+  SGVec3d _contact, _linearVel, _angularVel;
+  if (!ground_cache.get_nearest(t, SGVec3d(pt), maxDist, _contact, _linearVel,
+                                _angularVel, id, material))
+      return false;
+
   assign(contact, _contact);
-  assign(normal, _normal);
-  assign(vel, _vel);
-  return found;
+  assign(linearVel, _linearVel);
+  assign(angularVel, _angularVel);
+  return true;
 }
 
 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)
+FGInterface::get_nearest_ft(double t, const double pt[3], double maxDist,
+                            double contact[3], double normal[3],
+                            double linearVel[3], double angularVel[3],
+                            SGMaterial const*& material,
+                            simgear::BVHNode::Id& id)
 {
-  // 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;
+  SGVec3d _contact, _linearVel, _angularVel;
+  if (!ground_cache.get_nearest(t, SG_FEET_TO_METER*SGVec3d(pt),
+                                SG_FEET_TO_METER*maxDist, _contact, _linearVel,
+                                _angularVel, id, material))
+      return false;
+
+  assign(contact, SG_METER_TO_FEET*_contact);
+  assign(linearVel, SG_METER_TO_FEET*_linearVel);
+  assign(angularVel, _angularVel);
+  return true;
 }
 
 double
@@ -823,43 +832,50 @@ FGInterface::get_groundlevel_m(const SGGeod& geod)
 
   // FIXME: how to handle t - ref_time differences ???
   SGVec3d cpos;
-  double ref_time, radius;
+  double ref_time = 0, 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);
+    double startTime = ref_time;
+    double endTime = startTime + 1;
+    bool ok = prepare_ground_cache_m(startTime, endTime, 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));
+      pos = SGVec3d::fromGeod(SGGeod::fromGeodM(geod, 10000));
       /// If there is still no ground, return sea level radius
-      if (!prepare_ground_cache_m(ref_time, pos.data(), 10))
+      if (!prepare_ground_cache_m(startTime, endTime, pos.data(), 10))
         return 0;
     }
   } else if (radius*radius <= distSqr(pos, cpos)) {
+    double startTime = ref_time;
+    double endTime = startTime + 1;
+
     /// 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);
+    bool ok = prepare_ground_cache_m(startTime, endTime, 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));
+      pos = SGVec3d::fromGeod(SGGeod::fromGeodM(geod, 10000));
       /// If there is still no ground, return sea level radius
-      if (!prepare_ground_cache_m(ref_time, pos.data(), radius))
+      if (!prepare_ground_cache_m(startTime, endTime, pos.data(), radius))
         return 0;
     }
   }
   
-  double contact[3], normal[3], vel[3], agl;
-  int type;
+  double contact[3], normal[3], vel[3], angvel[3];
+  const SGMaterial* material;
+  simgear::BVHNode::Id id;
   // 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);
+  get_agl_m(ref_time, pos.data(), 2.0, contact, normal, vel, angvel,
+            material, id);
   return SGGeod::fromCart(SGVec3d(contact)).getElevationM();
 }
   
@@ -915,6 +931,3 @@ FGInterface::release_wire(void)
   ground_cache.release_wire();
 }
 
-void fgToggleFDMdataLogging(void) {
-  cur_fdm_state->ToggleDataLogging();
-}