]> git.mxchange.org Git - flightgear.git/blobdiff - src/AIModel/AIBallistic.cxx
Merge branch 'next' of git://gitorious.org/fg/flightgear into next
[flightgear.git] / src / AIModel / AIBallistic.cxx
index 6ade9f411e27c63e232f3dcbc6016a758966bc25..16b15fe1d93f3aec36cb81a45ad6631c09a3398c 100644 (file)
@@ -3,7 +3,7 @@
 // Written by David Culp, started November 2003.
 // - davidculp2@comcast.net
 //
-// With major additions by Mathias Froehlich & Vivian Meazza 2004-2007
+// With major additions by Mathias Froehlich & Vivian Meazza 2004-2008
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the GNU General Public License as
 #  include <config.h>
 #endif
 
-#include <simgear/math/point3d.hxx>
 #include <simgear/math/sg_random.h>
-#include <simgear/scene/material/mat.hxx>
 #include <simgear/math/sg_geodesy.hxx>
+#include <simgear/scene/model/modellib.hxx>
 
 #include <Scenery/scenery.hxx>
 
 #include "AIBallistic.hxx"
 
-const double FGAIBallistic::slugs_to_kgs = 14.5939029372;
+#include <Main/util.hxx>
+
+using namespace simgear;
 
-FGAIBallistic::FGAIBallistic() :
-    FGAIBase(otBallistic),
-    _elevation(0),
-    _aero_stabilised(false),
-    _drag_area(0.007),
-    _life_timer(0.0),
-    _gravity(32),
-    _buoyancy(0),
-    _random(false),
-    _ht_agl_ft(0),
-    _load_resistance(0),
-    _solid(false),
-    _report_collision(false),
-    _report_impact(false),
-    _impact_report_node(fgGetNode("/ai/models/model-impact", true)),
-    _external_force(false)
+const double FGAIBallistic::slugs_to_kgs = 14.5939029372;
+const double FGAIBallistic::slugs_to_lbs = 32.1740485564;
+
+FGAIBallistic::FGAIBallistic(object_type ot) :
+FGAIBase(ot),
+_height(0.0),
+_speed(0),
+_ht_agl_ft(0.0),
+_azimuth(0.0),
+_elevation(0.0),
+_rotation(0.0),
+hs(0),
+_elapsed_time(0),
+_aero_stabilised(false),
+_drag_area(0.007),
+_life_timer(0.0),
+_gravity(32.1740485564),
+_buoyancy(0),
+_wind(true),
+_mass(0),
+_random(false),
+_load_resistance(0),
+_solid(false),
+_force_stabilised(false),
+_slave_to_ac(false),
+_slave_load_to_ac(false),
+_contents_lb(0),
+_report_collision(false),
+_report_impact(false),
+_external_force(false),
+_report_expiry(false),
+_impact_report_node(fgGetNode("/ai/models/model-impact", true)),
+_old_height(0)
 
 {
     no_roll = false;
@@ -59,79 +77,229 @@ FGAIBallistic::~FGAIBallistic() {
 }
 
 void FGAIBallistic::readFromScenario(SGPropertyNode* scFileNode) {
-    if (!scFileNode)
+    if (!scFileNode){
         return;
+    }
 
     FGAIBase::readFromScenario(scFileNode);
 
+    //setPath(scFileNode->getStringValue("model", "Models/Geometry/rocket.ac")); 
+    setRandom(scFileNode->getBoolValue("random", false));
     setAzimuth(scFileNode->getDoubleValue("azimuth", 0.0));
-    setElevation(scFileNode->getDoubleValue("elevation", 0.0));
+    setElevation(scFileNode->getDoubleValue("elevation", 0));
     setDragArea(scFileNode->getDoubleValue("eda", 0.007));
     setLife(scFileNode->getDoubleValue("life", 900.0));
     setBuoyancy(scFileNode->getDoubleValue("buoyancy", 0));
-    setWind_from_east(scFileNode->getDoubleValue("wind_from_east", 0));
-    setWind_from_north(scFileNode->getDoubleValue("wind_from_north", 0));
+    //setWind_from_east(scFileNode->getDoubleValue("wind_from_east", 0));
+    //setWind_from_north(scFileNode->getDoubleValue("wind_from_north", 0));
     setWind(scFileNode->getBoolValue("wind", false));
     setRoll(scFileNode->getDoubleValue("roll", 0.0));
     setCd(scFileNode->getDoubleValue("cd", 0.029));
-    setMass(scFileNode->getDoubleValue("mass", 0.007));
-    setStabilisation(scFileNode->getBoolValue("aero_stabilized", false));
+    //setMass(scFileNode->getDoubleValue("mass", 0.007));
+    setWeight(scFileNode->getDoubleValue("weight", 0.25));
+    setStabilisation(scFileNode->getBoolValue("aero-stabilised", false));
     setNoRoll(scFileNode->getBoolValue("no-roll", false));
-    setRandom(scFileNode->getBoolValue("random", false));
     setImpact(scFileNode->getBoolValue("impact", false));
+    setExpiry(scFileNode->getBoolValue("expiry", false));
+    setCollision(scFileNode->getBoolValue("collision", false));
     setImpactReportNode(scFileNode->getStringValue("impact-reports"));
-    setName(scFileNode->getStringValue("name", "Bomb"));
+    setName(scFileNode->getStringValue("name", "Rocket"));
     setFuseRange(scFileNode->getDoubleValue("fuse-range", 0.0));
     setSMPath(scFileNode->getStringValue("submodel-path", ""));
     setSubID(scFileNode->getIntValue("SubID", 0));
+    setExternalForce(scFileNode->getBoolValue("external-force", false));
+    setForcePath(scFileNode->getStringValue("force-path", ""));
+    setForceStabilisation(scFileNode->getBoolValue("force-stabilised", false));
+    setXoffset(scFileNode->getDoubleValue("x-offset", 0.0));
+    setYoffset(scFileNode->getDoubleValue("y-offset", 0.0));
+    setZoffset(scFileNode->getDoubleValue("z-offset", 0.0));
+    setPitchoffset(scFileNode->getDoubleValue("pitch-offset", 0.0));
+    setRolloffset(scFileNode->getDoubleValue("roll-offset", 0.0));
+    setYawoffset(scFileNode->getDoubleValue("yaw-offset", 0.0));
+    setGroundOffset(scFileNode->getDoubleValue("ground-offset", 0.0));
+    setLoadOffset(scFileNode->getDoubleValue("load-offset", 0.0));
+    setSlaved(scFileNode->getBoolValue("slaved", false));
+    setSlavedLoad(scFileNode->getBoolValue("slaved-load", false));
+    setContentsPath(scFileNode->getStringValue("contents"));
+    setParentName(scFileNode->getStringValue("parent"));
 }
 
 bool FGAIBallistic::init(bool search_in_AI_path) {
     FGAIBase::init(search_in_AI_path);
 
+    _impact_reported = false;
+    _collision_reported = false;
+    _expiry_reported = false;
+
+    _impact_lat = 0;
+    _impact_lon = 0;
+    _impact_elev = 0;
+    _impact_hdg = 0;
+    _impact_pitch = 0;
+    _impact_roll = 0;
+    _impact_speed = 0;
+
+    invisible = false;
+
+    _elapsed_time += (sg_random() * 100);
+
     props->setStringValue("material/name", "");
     props->setStringValue("name", _name.c_str());
-    props->setStringValue("submodels/path", _submodel.c_str());
+    props->setStringValue("submodels/path", _path.c_str());
+
+    if (_slave_to_ac){
+        props->setStringValue("force/path", _force_path.c_str());
+        props->setStringValue("contents/path", _contents_path.c_str());
+    }
+
+    //if(_parent != ""){
+    //    setParentNode();
+    //}
+
+    //setParentNodes(_selected_ac);
+
+    //props->setStringValue("vector/path", _vector_path.c_str());
 
     // start with high value so that animations don't trigger yet
     _ht_agl_ft = 1e10;
     hdg = _azimuth;
     pitch = _elevation;
     roll = _rotation;
+
     Transform();
 
+    if(_parent != ""){
+        setParentNode();
+    }
+
+    setParentNodes(_selected_ac);
+
     return true;
 }
 
 void FGAIBallistic::bind() {
     //    FGAIBase::bind();
+
     props->tie("sim/time/elapsed-sec",
         SGRawValueMethods<FGAIBallistic,double>(*this,
         &FGAIBallistic::_getTime));
-    props->tie("material/load-resistance",
-                SGRawValuePointer<double>(&_load_resistance));
+    //props->tie("mass-slug",
+    //    SGRawValueMethods<FGAIBallistic,double>(*this,
+    //    &FGAIBallistic::getMass));
+
     props->tie("material/solid",
-                SGRawValuePointer<bool>(&_solid));
+        SGRawValuePointer<bool>(&_solid));
     props->tie("altitude-agl-ft",
-                SGRawValuePointer<double>(&_ht_agl_ft));
+        SGRawValuePointer<double>(&_ht_agl_ft));
+    props->tie("controls/slave-to-ac",
+        SGRawValueMethods<FGAIBallistic,bool>
+        (*this, &FGAIBallistic::getSlaved, &FGAIBallistic::setSlaved));
+    props->tie("controls/invisible",
+        SGRawValuePointer<bool>(&invisible));
+
+    if(_external_force || _slave_to_ac){
+        props->tie("controls/force_stabilized",
+            SGRawValuePointer<bool>(&_force_stabilised));
+        props->tie("position/global-x", 
+            SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosX, 0));
+        props->tie("position/global-y",
+            SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosY, 0));
+        props->tie("position/global-z",
+            SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getCartPosZ, 0));
+        props->tie("velocities/vertical-speed-fps",
+            SGRawValuePointer<double>(&vs));
+        props->tie("velocities/true-airspeed-kt",
+            SGRawValuePointer<double>(&speed));
+        props->tie("velocities/horizontal-speed-fps",
+            SGRawValuePointer<double>(&hs));
+        props->tie("position/altitude-ft",
+            SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getElevationFt, &FGAIBase::_setAltitude));
+        props->tie("position/latitude-deg", 
+            SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLatitude, &FGAIBase::_setLatitude));
+        props->tie("position/longitude-deg",
+            SGRawValueMethods<FGAIBase,double>(*this, &FGAIBase::_getLongitude, &FGAIBase::_setLongitude));
+        props->tie("orientation/hdg-deg",
+            SGRawValuePointer<double>(&hdg));
+        props->tie("orientation/pitch-deg",
+            SGRawValuePointer<double>(&pitch));
+        props->tie("orientation/roll-deg",
+            SGRawValuePointer<double>(&roll));
+        props->tie("controls/slave-load-to-ac",
+            SGRawValueMethods<FGAIBallistic,bool>
+            (*this, &FGAIBallistic::getSlavedLoad, &FGAIBallistic::setSlavedLoad));
+        props->tie("position/load-offset",
+            SGRawValueMethods<FGAIBallistic,double>
+            (*this, &FGAIBallistic::getLoadOffset, &FGAIBallistic::setLoadOffset));
+        props->tie("load/distance-to-hitch-ft",
+            SGRawValueMethods<FGAIBallistic,double>
+            (*this, &FGAIBallistic::getDistanceToHitch));
+        props->tie("load/elevation-to-hitch-deg",
+            SGRawValueMethods<FGAIBallistic,double>
+            (*this, &FGAIBallistic::getElevToHitch));
+        props->tie("load/bearing-to-hitch-deg",
+            SGRawValueMethods<FGAIBallistic,double>
+            (*this, &FGAIBallistic::getBearingToHitch));
+        props->tie("material/load-resistance",
+        SGRawValuePointer<double>(&_load_resistance));
+    }
+
 }
 
 void FGAIBallistic::unbind() {
-    //    FGAIBase::unbind();
+//    FGAIBase::unbind();
+
     props->untie("sim/time/elapsed-sec");
-    props->untie("material/load-resistance");
+    props->untie("mass-slug");
     props->untie("material/solid");
     props->untie("altitude-agl-ft");
+    props->untie("controls/slave-to-ac");
+    props->untie("controls/invisible");
+
+    if(_external_force || _slave_to_ac){
+        props->untie("position/global-y");
+        props->untie("position/global-x");
+        props->untie("position/global-z");
+        props->untie("velocities/vertical-speed-fps");
+        props->untie("velocities/true-airspeed-kt");
+        props->untie("velocities/horizontal-speed-fps");
+        props->untie("position/altitude-ft");
+        props->untie("position/latitude-deg");
+        props->untie("position/longitude-deg");
+        props->untie("position/ht-agl-ft");
+        props->untie("orientation/hdg-deg");
+        props->untie("orientation/pitch-deg");
+        props->untie("orientation/roll-deg");
+        props->untie("controls/force_stabilized");
+        props->untie("position/load-offset");
+        props->untie("load/distance-to-hitch-ft");
+        props->untie("load/elevation-to-hitch-deg");
+        props->untie("load/bearing-to-hitch-deg");
+        props->untie("material/load-resistance");
+    }
 }
 
 void FGAIBallistic::update(double dt) {
     FGAIBase::update(dt);
-    Run(dt);
-    Transform();
+    _setUserPos();
+
+    if (_slave_to_ac){
+        slaveToAC(dt);
+        Transform();
+    } else if (!invisible){
+        Run(dt);
+        Transform();
+    }
+
 }
 
 void FGAIBallistic::setAzimuth(double az) {
-    hdg = _azimuth = az;
+
+    if (_random)
+        hdg = _azimuth = (az - 5 ) + (10 * sg_random());
+    else 
+        hdg = _azimuth = az;
+
+    //cout << _name << " init hdg " << hdg << " random " << _random << endl;
 }
 
 void FGAIBallistic::setElevation(double el) {
@@ -139,13 +307,17 @@ void FGAIBallistic::setElevation(double el) {
 }
 
 void FGAIBallistic::setRoll(double rl) {
-    _rotation = rl;
+    roll = _rotation = rl;
 }
 
 void FGAIBallistic::setStabilisation(bool val) {
     _aero_stabilised = val;
 }
 
+void FGAIBallistic::setForceStabilisation(bool val) {
+    _force_stabilised = val;
+}
+
 void FGAIBallistic::setNoRoll(bool nr) {
     no_roll = nr;
 }
@@ -155,7 +327,12 @@ void FGAIBallistic::setDragArea(double a) {
 }
 
 void FGAIBallistic::setLife(double seconds) {
-    life = seconds;
+
+    if (_random){
+        life = seconds * _randomness + (seconds * (1 -_randomness) * sg_random());
+        //cout << "life " << life << endl;
+    } else
+        life = seconds;
 }
 
 void FGAIBallistic::setBuoyancy(double fpss) {
@@ -182,6 +359,14 @@ void FGAIBallistic::setMass(double m) {
     _mass = m;
 }
 
+void FGAIBallistic::setWeight(double w) {
+    _weight_lb = w;
+}
+
+void FGAIBallistic::setRandomness(double r) {
+    _randomness = r;
+}
+
 void FGAIBallistic::setRandom(bool r) {
     _random = r;
 }
@@ -194,6 +379,10 @@ void FGAIBallistic::setCollision(bool c) {
     _report_collision = c;
 }
 
+void FGAIBallistic::setExpiry(bool e) {
+    _report_expiry = e;
+}
+
 void FGAIBallistic::setExternalForce(bool f) {
     _external_force = f;
 }
@@ -204,12 +393,9 @@ void FGAIBallistic::setImpactReportNode(const string& path) {
         _impact_report_node = fgGetNode(path.c_str(), true);
 }
 
-void FGAIBallistic::setName(const string& n) {
-    _name = n;
-}
-
 void FGAIBallistic::setSMPath(const string& s) {
-    _submodel = s;
+    _path = s;
+    //cout << "submodel path " << _path << endl;
 }
 
 void FGAIBallistic::setFuseRange(double f) {
@@ -218,13 +404,112 @@ void FGAIBallistic::setFuseRange(double f) {
 
 void FGAIBallistic::setSubID(int i) {
     _subID = i;
-    //cout << "sub id " << _subID << " name " << _name << endl;
 }
 
 void FGAIBallistic::setSubmodel(const string& s) {
     _submodel = s;
 }
 
+void FGAIBallistic::setGroundOffset(double g) {
+    _ground_offset = g;
+}
+
+void FGAIBallistic::setLoadOffset(double l) {
+    _load_offset = l;
+}
+
+double FGAIBallistic::getLoadOffset() const {
+    return _load_offset;
+}
+
+void FGAIBallistic::setSlaved(bool s) {
+    _slave_to_ac = s;
+}
+
+void FGAIBallistic::setContentsPath(const string& path) {
+
+    _contents_path = path;
+
+    if (!path.empty()) {
+        _contents_node = fgGetNode(path.c_str(), true);
+    }
+}
+
+void FGAIBallistic::setContentsNode(SGPropertyNode_ptr node) {
+
+    if (node != 0) {
+        _contents_node = node;
+        _contents_path = _contents_node->getDisplayName();
+    }
+}
+
+void FGAIBallistic::setParentNodes(SGPropertyNode_ptr node) {
+
+    if (node != 0) {
+        _pnode = node;
+        _p_pos_node = _pnode->getChild("position", 0, true);
+        _p_lat_node = _p_pos_node->getChild("latitude-deg", 0, true);
+        _p_lon_node = _p_pos_node->getChild("longitude-deg", 0, true);
+        _p_alt_node = _p_pos_node->getChild("altitude-ft", 0, true);
+        _p_agl_node = _p_pos_node->getChild("altitude-agl-ft", 0, true);
+
+
+        _p_ori_node = _pnode->getChild("orientation", 0, true);
+        _p_pch_node = _p_ori_node->getChild("pitch-deg", 0, true);
+        _p_rll_node = _p_ori_node->getChild("roll-deg", 0, true);
+        _p_hdg_node = _p_ori_node->getChild("true-heading-deg",0, true);
+
+        _p_vel_node = _pnode->getChild("velocities", 0, true);
+        _p_spd_node = _p_vel_node->getChild("true-airspeed-kt", 0, true);
+    }
+
+}
+
+void FGAIBallistic::setParentPos() {
+
+    if (_pnode != 0) { 
+        //cout << "set parent pos" << endl;
+
+        double lat = _p_lat_node->getDoubleValue();
+        double lon = _p_lon_node->getDoubleValue();
+        double alt = _p_alt_node->getDoubleValue();
+
+        _parentpos.setLongitudeDeg(lon);
+        _parentpos.setLatitudeDeg(lat);
+        _parentpos.setElevationFt(alt);
+
+    }
+
+}
+
+bool FGAIBallistic::getSlaved() const {
+    return _slave_to_ac;
+}
+
+double FGAIBallistic::getMass() const {
+    return _mass;
+}
+
+double FGAIBallistic::getContents() {
+    if(_contents_node){
+        _contents_lb = _contents_node->getChild("level-lbs",0,1)->getDoubleValue();
+    }
+    return _contents_lb;
+}
+
+void FGAIBallistic::setContents(double c) {
+    if(_contents_node) 
+        _contents_lb = _contents_node->getChild("level-gal_us",0,1)->setDoubleValue(c);
+}
+
+void FGAIBallistic::setSlavedLoad(bool l) {
+    _slave_load_to_ac = l;
+}
+
+bool FGAIBallistic::getSlavedLoad() const {
+    return _slave_load_to_ac;
+}
+
 void FGAIBallistic::setForcePath(const string& p) {
     _force_path = p;
     if (!_force_path.empty()) {
@@ -235,15 +520,169 @@ void FGAIBallistic::setForcePath(const string& p) {
     }
 }
 
+bool FGAIBallistic::getHtAGL(double start){
+
+    if (getGroundElevationM(SGGeod::fromGeodM(pos, start),
+        _elevation_m, &_material)) {
+            _ht_agl_ft = pos.getElevationFt() - _elevation_m * SG_METER_TO_FEET;
+
+            if (_material) {
+                const vector<string>& names = _material->get_names();
+                _solid = _material->get_solid();
+                _load_resistance = _material->get_load_resistance();
+                _frictionFactor =_material->get_friction_factor();
+
+                if (!names.empty())
+                    props->setStringValue("material/name", names[0].c_str());
+                else
+                    props->setStringValue("material/name", "");
+
+                _mat_name = names[0];
+
+                //cout << "material " << _mat_name 
+                //<< " solid " << _solid 
+                //<< " load " << _load_resistance
+                //<< " frictionFactor " << _frictionFactor
+                //<< endl;
+
+            }
+
+            return true;
+    } else {
+        return false;
+    }
+
+}
+
+double FGAIBallistic::getRecip(double az){
+    // calculate the reciprocal of the input azimuth 
+    if(az - 180 < 0){
+        return az + 180;
+    } else {
+        return az - 180; 
+    }
+}
+
+void FGAIBallistic::setPch(double e, double dt, double coeff){
+    double c = dt / (coeff + dt);
+    pitch = (e * c) + (pitch * (1 - c));
+}
+
+void FGAIBallistic::setBnk(double r, double dt, double coeff){
+    double c = dt / (coeff + dt);
+    roll = (r * c) + (roll * (1 - c));
+}
+
+void FGAIBallistic::setSpd(double s, double dt, double coeff){
+    double c = dt / (coeff + dt);
+    _speed = (s * c) + (_speed * (1 - c));
+}
+
+void FGAIBallistic::setHt(double h, double dt, double coeff){
+    double c = dt / (coeff + dt);
+    _height = (h * c) + (_height * (1 - c));
+}
+
+int FGAIBallistic::setHdg(double tgt_hdg, double dt, double coeff){
+    double recip = getRecip(hdg);
+    double c = dt / (coeff + dt);
+    //we need to ensure that we turn the short way to the new hdg
+    if (tgt_hdg < recip && tgt_hdg < hdg && hdg > 180) {
+        hdg = ((tgt_hdg + 360) * c) + (hdg * (1 - c));
+//        cout << "case 1: right turn" << endl;
+    } else if (tgt_hdg > recip && tgt_hdg > hdg && hdg <= 180){
+        hdg = ((tgt_hdg - 360) * c) + (hdg * (1 - c));
+//        cout << "case 2: left turn" << endl;
+    } else {
+        hdg = (tgt_hdg * c) + (hdg * (1 - c));
+//        cout << "case 4: left turn" << endl;
+    }
+    return -1;
+}
+
+double  FGAIBallistic::getTgtXOffset() const {
+    return _tgt_x_offset;
+}
+
+double  FGAIBallistic::getTgtYOffset() const {
+    return _tgt_y_offset;
+} 
+
+double  FGAIBallistic::getTgtZOffset() const {
+    return _tgt_z_offset;
+}
+
+void FGAIBallistic::setTgtXOffset(double x){
+    _tgt_x_offset = x;
+}
+
+void FGAIBallistic::setTgtYOffset(double y){
+    _tgt_y_offset = y;
+}
+
+void FGAIBallistic::setTgtZOffset(double z){
+    _tgt_z_offset = z;
+}
+
+void FGAIBallistic::slaveToAC(double dt){
+
+    double hdg, pch, rll, agl = 0;
+
+    if (_pnode != 0) {
+        setParentPos();
+        hdg = _p_hdg_node->getDoubleValue();
+        pch = _p_pch_node->getDoubleValue();
+        rll = _p_rll_node->getDoubleValue();
+        agl = _p_agl_node->getDoubleValue();
+        setOffsetPos(_parentpos, hdg, pch, rll);
+        setSpeed(_p_spd_node->getDoubleValue());
+    }else {
+        hdg = manager->get_user_heading();
+        pch = manager->get_user_pitch();
+        rll = manager->get_user_roll();
+        agl = manager->get_user_agl();
+        setOffsetPos(userpos, hdg, pch, rll);
+        setSpeed(manager->get_user_speed());
+    }
+
+    pos.setLatitudeDeg(_offsetpos.getLatitudeDeg());
+    pos.setLongitudeDeg(_offsetpos.getLongitudeDeg());
+    pos.setElevationFt(_offsetpos.getElevationFt());
+    setHeading(hdg);
+    setPitch(pch + _pitch_offset);
+    setBank(rll + _roll_offset);
+    setOffsetVelocity(dt, pos);
+
+    //update the mass (slugs)
+    _mass = (_weight_lb + getContents()) / slugs_to_lbs;
+
+    _impact_reported = false;
+
+    //cout << _name << " _mass "<<_mass <<" " << getContents() 
+    //<< " " << getContents() / slugs_to_lbs << " weight " << _weight_lb << endl;
+    //    cout << _name << " update hs " << hs << " vs " << vs << endl;
+}
+
 void FGAIBallistic::Run(double dt) {
     _life_timer += dt;
-     //cout << "life timer" <<_name <<" " << _life_timer <<  dt << endl;
-    if (_life_timer > life)
-        setDie(true);
 
-    //randomise Cd by +- 5%
+    // if life = -1 the object does not die
+    if (_life_timer > life && life != -1){
+
+        if (_report_expiry && !_expiry_reported && !_impact_reported && !_collision_reported){
+            //cout<<"AIBallistic: expiry"<< endl;
+            handle_expiry();
+        } else
+            setDie(true);
+
+    }
+
+    //set the contents in the appropriate tank or other property in the parent to zero
+    setContents(0);
+
+    //randomise Cd by +- 10%
     if (_random)
-        _Cd = _Cd * 0.95 + (0.05 * sg_random());
+        _Cd = _Cd * 0.90 + (0.10 * sg_random());
 
     // Adjust Cd by Mach number. The equations are based on curves
     // for a conventional shell/bullet (no boat-tail).
@@ -256,7 +695,8 @@ void FGAIBallistic::Run(double dt) {
     else
         Cdm = 0.2965 * pow(Mach, -1.1506) + _Cd;
 
-    //cout << " Mach , " << Mach << " , Cdm , " << Cdm << " ballistic speed kts //"<< speed <<  endl;
+    //cout <<_name << " Mach " << Mach << " Cdm " << Cdm 
+    //    << " ballistic speed kts "<< speed <<  endl;
 
     // drag = Cd * 0.5 * rho * speed * speed * drag_area;
     // rho is adjusted for altitude in void FGAIBase::update,
@@ -270,7 +710,7 @@ void FGAIBallistic::Run(double dt) {
         speed = 0.0;
 
     double speed_fps = speed * SG_KT_TO_FPS;
-    double hs;
+    //double hs;
 
     // calculate vertical and horizontal speed components
     if (speed == 0.0) {
@@ -292,125 +732,197 @@ void FGAIBallistic::Run(double dt) {
     if (!_wind) {
         _wind_from_north = 0;
         _wind_from_east = 0;
+    } else {
+        _wind_from_north = manager->get_wind_from_north();
+        _wind_from_east = manager->get_wind_from_east();
     }
 
-    // convert wind speed (fps) to degrees lat/lon per second
-    double wind_speed_from_north_deg_sec = _wind_from_north / ft_per_deg_lat;
-    double wind_speed_from_east_deg_sec  = _wind_from_east / ft_per_deg_lon;
-
     //calculate velocity due to external force
     double force_speed_north_deg_sec = 0;
     double force_speed_east_deg_sec = 0;
-    double vs_force_fps = 0;
+//    double vs_force_fps = 0;
     double hs_force_fps = 0;
     double v_force_acc_fpss = 0;
     double force_speed_north_fps = 0;
     double force_speed_east_fps = 0;
+    double h_force_lbs = 0;
+    double normal_force_lbs = 0;
+    double normal_force_fpss = 0;
+    double static_friction_force_lbs = 0;
+    double dynamic_friction_force_lbs = 0;
+    double friction_force_speed_north_fps = 0;
+    double friction_force_speed_east_fps = 0;
+    double friction_force_speed_north_deg_sec = 0;
+    double friction_force_speed_east_deg_sec = 0;
+    double force_elevation_deg = 0;
 
     if (_external_force) {
+        //cout << _name << " external force" << endl;
+
         SGPropertyNode *n = fgGetNode(_force_path.c_str(), true);
         double force_lbs            = n->getChild("force-lb", 0, true)->getDoubleValue();
-        double force_elevation_deg  = n->getChild("force-elevation-deg", 0, true)->getDoubleValue();
+        force_elevation_deg         = n->getChild("force-elevation-deg", 0, true)->getDoubleValue();
         double force_azimuth_deg    = n->getChild("force-azimuth-deg", 0, true)->getDoubleValue();
-
+        
         //resolve force into vertical and horizontal components:
         double v_force_lbs = force_lbs * sin( force_elevation_deg * SG_DEGREES_TO_RADIANS );
-        double h_force_lbs = force_lbs * cos( force_elevation_deg * SG_DEGREES_TO_RADIANS );
+        h_force_lbs = force_lbs * cos( force_elevation_deg * SG_DEGREES_TO_RADIANS );
+
+        //ground interaction 
+
+        if (getHtAGL(10000)){
+            double deadzone = 0.1;
+
+            if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
+                normal_force_lbs = (_mass * slugs_to_lbs) - v_force_lbs;
+
+                if ( normal_force_lbs < 0 )
+                    normal_force_lbs = 0;
+
+                pos.setElevationFt(0 + _ground_offset);
+                if (vs < 0) 
+                    vs = -vs * 0.5;
+
+                // calculate friction
+                // we assume a static Coefficient of Friction (mu) of 0.62 (wood on concrete)
+                double mu = 0.62;
+
+                static_friction_force_lbs = mu * normal_force_lbs * _frictionFactor;
+
+                //adjust horizontal force. We assume that a speed of <= 5 fps is static 
+                if (h_force_lbs <= static_friction_force_lbs && hs <= 5){
+                    h_force_lbs = hs = 0;
+                    speed_north_fps = speed_east_fps = 0;
+                } else
+                    dynamic_friction_force_lbs = (static_friction_force_lbs * 0.95);
+
+                //ignore wind when on the ground for now
+                //TODO fix this
+                _wind_from_north = 0;
+                _wind_from_east = 0;
+
+            }
+
+        }
 
         //acceleration = (force(lbsf)/mass(slugs))
-        v_force_acc_fpss = (v_force_lbs/_mass);
-        double h_force_acc_fpss = (h_force_lbs/_mass);
+        v_force_acc_fpss = v_force_lbs/_mass;
+        normal_force_fpss = normal_force_lbs/_mass;
+        double h_force_acc_fpss = h_force_lbs/_mass;
+        double dynamic_friction_acc_fpss = dynamic_friction_force_lbs/_mass;
 
         // velocity = acceleration * dt
         hs_force_fps = h_force_acc_fpss * dt;
+        double friction_force_fps = dynamic_friction_acc_fpss * dt;
 
-        //resolve horizontal speed into north and east components:
+        //resolve horizontal speeds into north and east components:
         force_speed_north_fps   = cos(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
         force_speed_east_fps    = sin(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
 
+        friction_force_speed_north_fps = cos(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
+        friction_force_speed_east_fps  = sin(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
+
         // convert horizontal speed (fps) to degrees per second
-        double force_speed_north_deg_sec = force_speed_north_fps / ft_per_deg_lat;
-        double force_speed_east_deg_sec  = force_speed_east_fps / ft_per_deg_lon;
-
-        //recombine the horizontal velocity components
-        hs = sqrt(((speed_north_fps + force_speed_north_fps) * (speed_north_fps + force_speed_north_fps))
-            + ((speed_east_fps + force_speed_east_fps) * (speed_east_fps + force_speed_east_fps)));
-
-        /*cout << "mass " << _mass 
-        << " force " << force_lbs 
-        << " elevation " << force_elevation_deg
-        << " azimuth " << force_azimuth_deg
-        << endl; */
-
-        //cout << " _hs_force_fps " << hs_force_fps 
-        //<< " force_speed_north_fps " << force_speed_north_fps 
-        //<< " force_speed_east_fps " << force_speed_east_fps 
-        //<< " speed_north_fps " << speed_north_fps 
-        //<< " speed_east_fps " << speed_east_fps
-        //<< endl;
+        force_speed_north_deg_sec = force_speed_north_fps / ft_per_deg_lat;
+        force_speed_east_deg_sec  = force_speed_east_fps / ft_per_deg_lon;
+
+        friction_force_speed_north_deg_sec = friction_force_speed_north_fps / ft_per_deg_lat;
+        friction_force_speed_east_deg_sec  = friction_force_speed_east_fps / ft_per_deg_lon;
     }
 
-    // set new position
-    pos.setLatitudeDeg( pos.getLatitudeDeg()
-        + (speed_north_deg_sec - wind_speed_from_north_deg_sec + force_speed_north_deg_sec) * dt );
-    pos.setLongitudeDeg( pos.getLongitudeDeg()
-        + (speed_east_deg_sec - wind_speed_from_east_deg_sec + force_speed_east_deg_sec) * dt );
+    // convert wind speed (fps) to degrees lat/lon per second
+    double wind_speed_from_north_deg_sec = _wind_from_north / ft_per_deg_lat;
+    double wind_speed_from_east_deg_sec  = _wind_from_east / ft_per_deg_lon;
+
+    //recombine the horizontal velocity components
+    hs = sqrt(((speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps) 
+        * (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
+        + ((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps) 
+        * (speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)));
+
+    if (hs <= 0.00001)
+        hs = 0;
 
     // adjust vertical speed for acceleration of gravity, buoyancy, and vertical force
-    //v_force_acc_fpss = 0;
-    vs -= (_gravity - _buoyancy - v_force_acc_fpss) * dt;
+    vs -= (_gravity - _buoyancy - v_force_acc_fpss - normal_force_fpss) * dt;
+
+    if (vs <= 0.00001 && vs >= -0.00001)
+        vs = 0;
 
-    // adjust altitude (feet) and set new elevation
-    altitude_ft += vs * dt;
-    pos.setElevationFt(altitude_ft);
+    // set new position
+    if(_slave_load_to_ac) {
+        setOffsetPos(pos, 
+            manager->get_user_heading(),
+            manager->get_user_pitch(), 
+            manager->get_user_roll()
+            );
+        pos.setLatitudeDeg(_offsetpos.getLatitudeDeg());
+        pos.setLongitudeDeg(_offsetpos.getLongitudeDeg());
+        pos.setElevationFt(_offsetpos.getElevationFt());
+
+        if (getHtAGL(10000)){
+            double deadzone = 0.1;
+
+            if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
+                pos.setElevationFt(0 + _ground_offset);
+            } else {
+                pos.setElevationFt(_offsetpos.getElevationFt() + _load_offset);
+            }
+
+        }
+    } else {
+        pos.setLatitudeDeg( pos.getLatitudeDeg()
+            + (speed_north_deg_sec - wind_speed_from_north_deg_sec 
+            + force_speed_north_deg_sec + friction_force_speed_north_deg_sec) * dt );
+        pos.setLongitudeDeg( pos.getLongitudeDeg()
+            + (speed_east_deg_sec - wind_speed_from_east_deg_sec 
+            + force_speed_east_deg_sec + friction_force_speed_east_deg_sec) * dt );
+        pos.setElevationFt(pos.getElevationFt() + vs * dt);
+    }
+
+//    cout << _name << " run hs " << hs << " vs " << vs << endl;
+
+    // recalculate total speed
+    if ( vs == 0 && hs == 0)
+        speed = 0;
+    else
+        speed = sqrt( vs * vs + hs * hs) / SG_KT_TO_FPS;
 
     // recalculate elevation and azimuth (velocity vectors)
     _elevation = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
-    _azimuth =  atan2((speed_east_fps + force_speed_east_fps), 
-        (speed_north_fps + force_speed_north_fps)) * SG_RADIANS_TO_DEGREES;
+    _azimuth =  atan2((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps), 
+        (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
+        * SG_RADIANS_TO_DEGREES;
 
     // rationalise azimuth
-    if (_azimuth < 0) _azimuth += 360;
+    if (_azimuth < 0)
+        _azimuth += 360;
 
     if (_aero_stabilised) { // we simulate rotational moment of inertia by using a filter
+        //cout<< "_aero_stabilised "<< endl;
         const double coeff = 0.9;
-        double c = dt / (coeff + dt);
-        double recip;
-
-        // calculate the recip
-        if(hdg - 180 < 0){
-            recip = hdg + 180;
-        } else {
-            recip = hdg - 180;
-        }
-        //cout << "recip " << recip << endl;
 
         // we assume a symetrical MI about the pitch and yaw axis
-        pitch = (_elevation * c) + (pitch * (1 - c));
-
-        //we need to ensure that we turn the short way to the new hdg
-        if (_azimuth < recip && _azimuth < hdg && hdg > 180) {
-            //cout <<  "_azimuth - hdg 1 " << _azimuth << " " << hdg << endl;
-            hdg = ((_azimuth + 360) * c) + (hdg * (1 - c));
-        } else if (_azimuth > recip && _azimuth > hdg && hdg <= 180){
-            //cout <<  "_azimuth - hdg 2 " << _azimuth <<" " << hdg << endl;
-            hdg = ((_azimuth - 360) * c) + (hdg * (1 - c));
-        } else {
-            //cout <<  "_azimuth - hdg 3 " << _azimuth <<" " << hdg << endl;
-            hdg = (_azimuth * c) + (hdg * (1 - c));
-        }
+        setPch(_elevation, dt, coeff);
+        setHdg(_azimuth, dt, coeff);
+    } else if (_force_stabilised) { // we simulate rotational moment of inertia by using a filter
+        //cout<< "_force_stabilised "<< endl;
+        
+        const double coeff = 0.9;
+        double ratio = h_force_lbs/(_mass * slugs_to_lbs);
 
-    }
+        if (ratio >  1) ratio =  1;
+        if (ratio < -1) ratio = -1;
 
-    // recalculate total speed
-    speed = sqrt( vs * vs + hs * hs) / SG_KT_TO_FPS;
+        double force_pitch = acos(ratio) * SG_RADIANS_TO_DEGREES;
 
-    /*cout << "_elevation " << _elevation
-    << " pitch " << pitch
-    <<" _yaw " << _yaw 
-    << " hdg " << hdg 
-    << " speed " << speed
-    << endl;*/
+        if (force_pitch <= force_elevation_deg)
+            force_pitch = force_elevation_deg;
+
+        // we assume a symetrical MI about the pitch and yaw axis
+        setPch(force_pitch,dt, coeff);
+        setHdg(_azimuth, dt, coeff);
+    }
 
     //do impacts and collisions
     if (_report_impact && !_impact_reported)
@@ -420,58 +932,56 @@ void FGAIBallistic::Run(double dt) {
         handle_collision();
 
     // set destruction flag if altitude less than sea level -1000
-    if (altitude_ft < -1000.0)
+    if (altitude_ft < -1000.0 && life != -1)
         setDie(true);
 
 }  // end Run
 
 double FGAIBallistic::_getTime() const {
-    //    cout << "life timer 2" << _life_timer << endl;
     return _life_timer;
 }
 
 void FGAIBallistic::handle_impact() {
-    double elevation_m;
-    const SGMaterial* material;
 
     // try terrain intersection
-    if (!globals->get_scenery()->get_elevation_m(pos.getLatitudeDeg(), pos.getLongitudeDeg(),
-            10000.0, elevation_m, &material))
-        return;
+    double start = pos.getElevationM() + 10;
 
-    if (material) {
-        const vector<string> names = material->get_names();
-        string mat_name;
-
-        if (!names.empty())
-            mat_name = names[0].c_str();
-
-        _solid = material->get_solid();
-        _load_resistance = material->get_load_resistance();
-        props->setStringValue("material/name", mat_name.c_str());
-        //cout << "material " << mat_name << " solid " << _solid << " load " << _load_resistance << endl;
-    }
-
-    _ht_agl_ft = pos.getElevationFt() - elevation_m * SG_METER_TO_FEET;
+    if(!getHtAGL(start)) 
+        return;
 
     if (_ht_agl_ft <= 0) {
         SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: terrain impact");
-        report_impact(elevation_m);
+        report_impact(_elevation_m);
         _impact_reported = true;
 
-        // kill the AIObject if there is no subsubmodel
-        if (_subID == 0)
+        if (life == -1){
+            invisible = true;
+        } else if (_subID == 0)  // kill the AIObject if there is no subsubmodel
             setDie(true);
+    } 
+}
+
+void FGAIBallistic::handle_expiry() {
+
+    SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: handle_expiry " << pos.getElevationM());
+
+    report_impact(pos.getElevationM());
+    _expiry_reported = true;
+
+    if (life == -1){
+        invisible = true;
+    } else if (_subID == 0){  // kill the AIObject if there is no subsubmodel
+        setDie(true);
     }
+
 }
 
 void FGAIBallistic::handle_collision()
 {
     const FGAIBase *object = manager->calcCollision(pos.getElevationFt(),
-            pos.getLatitudeDeg(),pos.getLongitudeDeg(), _fuse_range);
+        pos.getLatitudeDeg(),pos.getLongitudeDeg(), _fuse_range);
 
     if (object) {
-        SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: object hit");
         report_impact(pos.getElevationM(), object);
         _collision_reported = true;
     }
@@ -488,11 +998,14 @@ void FGAIBallistic::report_impact(double elevation, const FGAIBase *object)
     _impact_roll   = roll;
 
     SGPropertyNode *n = props->getNode("impact", true);
+
     if (object)
         n->setStringValue("type", object->getTypeString());
     else
         n->setStringValue("type", "terrain");
 
+    SG_LOG(SG_GENERAL, SG_DEBUG, "AIBallistic: object impact" << _name << " lon " <<_impact_lon);
+
     n->setDoubleValue("longitude-deg", _impact_lon);
     n->setDoubleValue("latitude-deg", _impact_lat);
     n->setDoubleValue("elevation-m", _impact_elev);
@@ -504,5 +1017,238 @@ void FGAIBallistic::report_impact(double elevation, const FGAIBase *object)
     _impact_report_node->setStringValue(props->getPath());
 }
 
-// end AIBallistic
+SGVec3d FGAIBallistic::getCartUserPos() const {
+    SGVec3d cartUserPos = SGVec3d::fromGeod(userpos);
+    return cartUserPos;
+}
+
+SGVec3d FGAIBallistic::getCartHitchPos() const{
+
+    // convert geodetic positions to geocentered
+    SGVec3d cartuserPos = SGVec3d::fromGeod(userpos);
+    //SGVec3d cartPos = getCartPos();
+
+    // Transform to the right coordinate frame, configuration is done in
+    // the x-forward, y-right, z-up coordinates (feet), computation
+    // in the simulation usual body x-forward, y-right, z-down coordinates
+    // (meters) )
+    SGVec3d _off(_x_offset * SG_FEET_TO_METER,
+            _y_offset * SG_FEET_TO_METER,
+            -_z_offset * SG_FEET_TO_METER);
+
+    // Transform the user position to the horizontal local coordinate system.
+    SGQuatd hlTrans = SGQuatd::fromLonLat(userpos);
+
+    // and postrotate the orientation of the user model wrt the horizontal
+    // local frame
+    hlTrans *= SGQuatd::fromYawPitchRollDeg(
+        manager->get_user_heading(),
+        manager->get_user_pitch(),
+        manager->get_user_roll());
+
+    // The offset converted to the usual body fixed coordinate system
+    // rotated to the earth-fixed coordinates axis
+    SGVec3d off = hlTrans.backTransform(_off);
+
+    // Add the position offset of the user model to get the geocentered position
+    SGVec3d offsetPos = cartuserPos + off;
+
+    return offsetPos;
+}
+
+void FGAIBallistic::setOffsetPos(SGGeod inpos, double heading, double pitch, double roll){
+    // convert the hitch geocentered position to geodetic
 
+    SGVec3d cartoffsetPos = getCartOffsetPos(inpos, heading, pitch, roll);
+
+    //SGVec3d cartoffsetPos = getCartHitchPos();
+
+    //SGGeodesy::SGCartToGeod(cartoffsetPos, hitchpos);
+    SGGeodesy::SGCartToGeod(cartoffsetPos, _offsetpos);
+
+}
+
+double FGAIBallistic::getDistanceToHitch() const {
+    //calculate the distance load to hitch 
+    SGVec3d carthitchPos = getCartHitchPos();
+    SGVec3d cartPos = getCartPos();
+
+    SGVec3d diff = carthitchPos - cartPos;
+    double distance = norm(diff);
+    return distance * SG_METER_TO_FEET;
+}
+
+double FGAIBallistic::getElevToHitch() const {
+    // now the angle, positive angles are upwards
+    double distance = getDistanceToHitch() * SG_FEET_TO_METER;
+    double angle = 0;
+    double daltM = _offsetpos.getElevationM() - pos.getElevationM();
+
+    if (fabs(distance) < SGLimits<float>::min()) {
+        angle = 0;
+    } else {
+        double sAngle = daltM/distance;
+        sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
+        angle = SGMiscd::rad2deg(asin(sAngle));
+    }
+
+    return angle;
+}
+
+double FGAIBallistic::getBearingToHitch() const {
+    //calculate the bearing and range of the second pos from the first
+    double distance = getDistanceToHitch() * SG_FEET_TO_METER;
+    double az1, az2;
+
+    geo_inverse_wgs_84(pos, _offsetpos, &az1, &az2, &distance);
+
+    return az1;
+}
+
+double FGAIBallistic::getRelBrgHitchToUser() const {
+    //calculate the relative bearing 
+    double az1, az2, distance;
+
+    geo_inverse_wgs_84(_offsetpos, userpos, &az1, &az2, &distance);
+
+    double rel_brg = az1 - hdg;
+
+    SG_NORMALIZE_RANGE(rel_brg, -180.0, 180.0);
+
+    return rel_brg;
+}
+
+double FGAIBallistic::getElevHitchToUser() const {
+
+    //calculate the distance from the user position
+    SGVec3d carthitchPos = getCartHitchPos();
+    SGVec3d cartuserPos = getCartUserPos();
+
+    SGVec3d diff = cartuserPos - carthitchPos;
+
+    double distance = norm(diff);
+    double angle = 0;
+
+    double daltM = userpos.getElevationM() - _offsetpos.getElevationM();
+
+    // now the angle, positive angles are upwards
+    if (fabs(distance) < SGLimits<float>::min()) {
+        angle = 0;
+    } else {
+        double sAngle = daltM/distance;
+        sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
+        angle = SGMiscd::rad2deg(asin(sAngle));
+    }
+
+    return angle;
+}
+
+void FGAIBallistic::setTgtOffsets(double dt, double coeff){
+    double c = dt / (coeff + dt);
+
+    _x_offset = (_tgt_x_offset * c) + (_x_offset * (1 - c));
+    _y_offset = (_tgt_y_offset * c) + (_y_offset * (1 - c));
+    _z_offset = (_tgt_z_offset * c) + (_z_offset * (1 - c));
+}
+
+
+void FGAIBallistic::calcVSHS(){
+    // calculate vertical and horizontal speed components
+    double speed_fps = speed * SG_KT_TO_FPS;
+
+    if (speed == 0.0) {
+        hs = vs = 0.0;
+    } else {
+        vs = sin( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
+        hs = cos( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
+    }
+}
+
+void FGAIBallistic::calcNE(){
+    //resolve horizontal speed into north and east components:
+    _speed_north_fps = cos(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
+    _speed_east_fps = sin(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
+
+    // convert horizontal speed (fps) to degrees per second
+    speed_north_deg_sec = _speed_north_fps / ft_per_deg_lat;
+    speed_east_deg_sec  = _speed_east_fps / ft_per_deg_lon;
+
+}
+
+SGVec3d FGAIBallistic::getCartOffsetPos(SGGeod inpos, double user_heading, 
+                                        double user_pitch, double user_roll
+                                        ) const{
+
+    // convert geodetic positions to geocentered
+     SGVec3d cartuserPos = SGVec3d::fromGeod(inpos);
+    //SGVec3d cartuserPos = getCartUserPos();
+    //SGVec3d cartPos = getCartPos();
+
+    // Transform to the right coordinate frame, configuration is done in
+    // the x-forward, y-right, z-up coordinates (feet), computation
+    // in the simulation usual body x-forward, y-right, z-down coordinates
+    // (meters) )
+    SGVec3d _off(_x_offset * SG_FEET_TO_METER,
+            _y_offset * SG_FEET_TO_METER,
+            -_z_offset * SG_FEET_TO_METER);
+
+    // Transform the user position to the horizontal local coordinate system.
+    SGQuatd hlTrans = SGQuatd::fromLonLat(inpos);
+
+    // and postrotate the orientation of the user model wrt the horizontal
+    // local frame
+    hlTrans *= SGQuatd::fromYawPitchRollDeg(
+        user_heading,
+        user_pitch,
+        user_roll);
+
+    // The offset converted to the usual body fixed coordinate system
+    // rotated to the earth-fixed coordinates axis
+    SGVec3d off = hlTrans.backTransform(_off);
+
+    // Add the position offset of the user model to get the geocentered position
+    SGVec3d offsetPos = cartuserPos + off;
+
+    return offsetPos;
+}
+
+void FGAIBallistic::setOffsetVelocity(double dt, SGGeod offsetpos) {
+    //calculate the distance from the previous offset position
+    SGVec3d cartoffsetPos = SGVec3d::fromGeod(offsetpos);
+    SGVec3d diff = cartoffsetPos - _oldcartoffsetPos;
+
+    double distance = norm(diff);
+    //calculate speed knots
+    speed = (distance/dt) * SG_MPS_TO_KT;
+
+    //now calulate the angle between the old and current postion positions (degrees)
+    double angle = 0;
+    double daltM = offsetpos.getElevationM() - _oldoffsetpos.getElevationM();
+
+    if (fabs(distance) < SGLimits<float>::min()) {
+        angle = 0;
+    } else {
+        double sAngle = daltM/distance;
+        sAngle = SGMiscd::min(1, SGMiscd::max(-1, sAngle));
+        angle = SGMiscd::rad2deg(asin(sAngle));
+    }
+
+    _elevation = angle;
+
+    //calculate vertical and horizontal speed components
+    calcVSHS();
+
+    //calculate the bearing of the new offset position from the old
+    double az1, az2, dist;
+    geo_inverse_wgs_84(_oldoffsetpos, offsetpos, &az1, &az2, &dist);
+    _azimuth = az1;
+
+    //resolve horizontal speed into north and east components:
+    calcNE();
+
+    // and finally store the new values
+    _oldcartoffsetPos = cartoffsetPos;
+    _oldoffsetpos = offsetpos;
+}
+
+// end AIBallistic