diff --git a/src/ATC/AIEntity.hxx b/src/ATC/AIEntity.hxx
index 2ff757049..deab859e2 100644
--- a/src/ATC/AIEntity.hxx
+++ b/src/ATC/AIEntity.hxx
@@ -58,7 +58,7 @@ protected:
     double pitch;	//degrees
 
     char* model_path;	//Path to the 3D model
-    FGModelPlacement aip;
+    SGModelPlacement aip;
 
     void Transform();
 };
diff --git a/src/ATC/AILocalTraffic.cxx b/src/ATC/AILocalTraffic.cxx
index 7cf30c5f3..4a7b0da31 100644
--- a/src/ATC/AILocalTraffic.cxx
+++ b/src/ATC/AILocalTraffic.cxx
@@ -157,7 +157,7 @@ bool FGAILocalTraffic::Init(string ICAO, OperatingState initialState, PatternLeg
 	string planepath = "Aircraft/c172/Models/c172-dpm.ac";
 	SGPath path = globals->get_fg_root();
 	path.append(planepath);
-        ssgBranch *model = fgLoad3DModel( path.str(),
+        ssgBranch *model = sgLoad3DModel( path.str(),
                                           planepath.c_str(),
                                           globals->get_props(),
                                           globals->get_sim_time_sec() );
@@ -404,8 +404,8 @@ void FGAILocalTraffic::Update(double dt) {
 		//cout << "In IN_PATTERN\n";
 		if(!inAir) DoGroundElev();
 		if(!elevInitGood) {
-			if(aip.getFGLocation()->get_cur_elev_m() > -9990.0) {
-				pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+			if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
+				pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 				//cout << "TAKEOFF_ROLL, POS = " << pos.lon() << ", " << pos.lat() << ", " << pos.elev() << '\n';
 				//Transform();
 				aip.setVisible(true);
@@ -421,8 +421,8 @@ void FGAILocalTraffic::Update(double dt) {
 		//cout << "*" << flush;
 		if(!elevInitGood) {
 			//DoGroundElev();
-			if(aip.getFGLocation()->get_cur_elev_m() > -9990.0) {
-				pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+			if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
+				pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 				//Transform();
 				aip.setVisible(true);
 				//Transform();
@@ -469,8 +469,8 @@ void FGAILocalTraffic::Update(double dt) {
 		//cout << "In PARKED\n";
 		if(!elevInitGood) {
 			DoGroundElev();
-			if(aip.getFGLocation()->get_cur_elev_m() > -9990.0) {
-				pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+			if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
+				pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 				//Transform();
 				aip.setVisible(true);
 				//Transform();
@@ -613,8 +613,8 @@ void FGAILocalTraffic::FlyTrafficPattern(double dt) {
 			double dveldt = 5.0;
 			vel += dveldt * dt;
 		}
-		if(aip.getFGLocation()->get_cur_elev_m() > -9990.0) {
-			pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+		if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
+			pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 		}
 		IAS = vel + (cos((hdg - wind_from) * DCL_DEGREES_TO_RADIANS) * wind_speed);
 		if(IAS >= 70) {
@@ -743,8 +743,8 @@ void FGAILocalTraffic::FlyTrafficPattern(double dt) {
 			               	// for us in update(...) when the inAir flag is false.
 		}
 		if(pos.elev() < (rwy.threshold_pos.elev()+10.0+wheelOffset)) {
-			if(aip.getFGLocation()->get_cur_elev_m() > -9990.0) {
-				if((aip.getFGLocation()->get_cur_elev_m() + wheelOffset) > pos.elev()) {
+			if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
+				if((aip.getSGLocation()->get_cur_elev_m() + wheelOffset) > pos.elev()) {
 					slope = 0.0;
 					pitch = 0.0;
 					leg = LANDING_ROLL;
@@ -755,8 +755,8 @@ void FGAILocalTraffic::FlyTrafficPattern(double dt) {
 		break;
 	case LANDING_ROLL:
 		//inAir = false;
-		if(aip.getFGLocation()->get_cur_elev_m() > -9990.0) {
-			pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+		if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
+			pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 		}
 		track = rwy.hdg;
 		double dveldt = -5.0;
@@ -1063,8 +1063,8 @@ void FGAILocalTraffic::Taxi(double dt) {
 		double slope = 0.0;
 		pos = dclUpdatePosition(pos, track, slope, dist);
 		//cout << "Updated position...\n";
-		if(aip.getFGLocation()->get_cur_elev_m() > -9990) {
-			pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+		if(aip.getSGLocation()->get_cur_elev_m() > -9990) {
+			pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 		} // else don't change the elev until we get a valid ground elev again!
 	} else if(lastNode) {
 		if(taxiState == TD_LINING_UP) {
@@ -1082,8 +1082,8 @@ void FGAILocalTraffic::Taxi(double dt) {
 				double slope = 0.0;
 				pos = dclUpdatePosition(pos, track, slope, dist);
 				//cout << "Updated position...\n";
-				if(aip.getFGLocation()->get_cur_elev_m() > -9990) {
-					pos.setelev(aip.getFGLocation()->get_cur_elev_m() + wheelOffset);
+				if(aip.getSGLocation()->get_cur_elev_m() > -9990) {
+					pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 				} // else don't change the elev until we get a valid ground elev again!
 				if(fabs(hdg - rwy.hdg) <= 1.0) {
 					operatingState = IN_PATTERN;
@@ -1117,14 +1117,14 @@ void FGAILocalTraffic::DoGroundElev() {
 	// answer with one call to the function, but what I tried in the two commented-out lines
 	// below only intermittently worked, and I haven't quite groked why yet.
 	//SGBucket buck(pos.lon(), pos.lat());
-	//aip.getFGLocation()->set_tile_center(Point3D(buck.get_center_lon(), buck.get_center_lat(), 0.0));
+	//aip.getSGLocation()->set_tile_center(Point3D(buck.get_center_lon(), buck.get_center_lat(), 0.0));
 	
 	double visibility_meters = fgGetDouble("/environment/visibility-m");
 	//globals->get_tile_mgr()->prep_ssg_nodes( acmodel_location,
-	globals->get_tile_mgr()->prep_ssg_nodes( aip.getFGLocation(),	visibility_meters );
+	globals->get_tile_mgr()->prep_ssg_nodes( aip.getSGLocation(),	visibility_meters );
         Point3D scenery_center = globals->get_scenery()->get_center();
-	globals->get_tile_mgr()->update( aip.getFGLocation(), visibility_meters, (aip.getFGLocation())->get_absolute_view_pos( scenery_center ) );
-	// save results of update in FGLocation for fdm...
+	globals->get_tile_mgr()->update( aip.getSGLocation(), visibility_meters, (aip.getSGLocation())->get_absolute_view_pos( scenery_center ) );
+	// save results of update in SGLocation for fdm...
 	
 	//if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
 	//	acmodel_location->
@@ -1132,10 +1132,10 @@ void FGAILocalTraffic::DoGroundElev() {
 	//}
 	
 	// The need for this here means that at least 2 consecutive passes are needed :-(
-	aip.getFGLocation()->set_tile_center( globals->get_scenery()->get_next_center() );
+	aip.getSGLocation()->set_tile_center( globals->get_scenery()->get_next_center() );
 	
 	//cout << "Transform Elev is " << globals->get_scenery()->get_cur_elev() << '\n';
-	aip.getFGLocation()->set_cur_elev_m(globals->get_scenery()->get_cur_elev());
+	aip.getSGLocation()->set_cur_elev_m(globals->get_scenery()->get_cur_elev());
 	//return(globals->get_scenery()->get_cur_elev());
 }
 
diff --git a/src/Cockpit/panel.hxx b/src/Cockpit/panel.hxx
index fc2afda00..9f1d42445 100644
--- a/src/Cockpit/panel.hxx
+++ b/src/Cockpit/panel.hxx
@@ -228,7 +228,7 @@ private:
  * or joystick, but they are tied to specific mouse actions in
  * rectangular areas of the panel.
  */
-class FGPanelAction : public FGConditional
+class FGPanelAction : public SGConditional
 {
 public:
   FGPanelAction ();
@@ -288,7 +288,7 @@ private:
 /**
  * A transformation for a layer.
  */
-class FGPanelTransformation : public FGConditional
+class FGPanelTransformation : public SGConditional
 {
 public:
 
@@ -327,7 +327,7 @@ public:
  * on current FGFS instrument readings: for example, a texture
  * representing a needle can rotate to show the airspeed.
  */
-class FGInstrumentLayer : public FGConditional
+class FGInstrumentLayer : public SGConditional
 {
 public:
 
@@ -369,7 +369,7 @@ protected:
  * may show up in the future (some complex instruments could be 
  * entirely hand-coded, for example).
  */
-class FGPanelInstrument : public FGConditional
+class FGPanelInstrument : public SGConditional
 {
 public:
   FGPanelInstrument ();
@@ -491,7 +491,7 @@ public:
     DOUBLE_VALUE
   };
 
-  class Chunk : public FGConditional
+  class Chunk : public SGConditional
   {
   public:
     Chunk (const string &text, const string &fmt = "%s");
diff --git a/src/Cockpit/panel_io.cxx b/src/Cockpit/panel_io.cxx
index 88fe30c4a..28435e20f 100644
--- a/src/Cockpit/panel_io.cxx
+++ b/src/Cockpit/panel_io.cxx
@@ -132,12 +132,12 @@ readTexture (const SGPropertyNode * node)
 ////////////////////////////////////////////////////////////////////////
 
 static void
-readConditions (FGConditional * component, const SGPropertyNode * node)
+readConditions (SGConditional *component, const SGPropertyNode *node)
 {
   const SGPropertyNode * conditionNode = node->getChild("condition");
   if (conditionNode != 0)
 				// The top level is implicitly AND
-    component->setCondition(fgReadCondition(globals->get_props(),
+    component->setCondition(sgReadCondition(globals->get_props(),
                                             conditionNode) );
 }
 
diff --git a/src/FDM/LaRCsim.cxx b/src/FDM/LaRCsim.cxx
index 3a27172e4..8ab20ab23 100644
--- a/src/FDM/LaRCsim.cxx
+++ b/src/FDM/LaRCsim.cxx
@@ -190,7 +190,7 @@ void FGLaRCsim::update( double dt ) {
 
     // Inform LaRCsim of the local terrain altitude
     // Runway_altitude = get_Runway_altitude();
-    Runway_altitude = getACModel()->get3DModel()->getFGLocation()->get_cur_elev_m() * SG_METER_TO_FEET;
+    Runway_altitude = getACModel()->get3DModel()->getSGLocation()->get_cur_elev_m() * SG_METER_TO_FEET;
     // Weather
     /* V_north_airmass = get_V_north_airmass();
        V_east_airmass =  get_V_east_airmass();
diff --git a/src/FDM/YASim/YASim.cxx b/src/FDM/YASim/YASim.cxx
index 6173f2d5f..f65c627f4 100644
--- a/src/FDM/YASim/YASim.cxx
+++ b/src/FDM/YASim/YASim.cxx
@@ -253,7 +253,7 @@ void YASim::copyToYASim(bool copyState)
     wind[2] = get_V_down_airmass() * FT2M * -1.0;
 
     // Get ground elevation from the FGinterface's FGlocation data
-    double ground = getACModel()->get3DModel()->getFGLocation()->get_cur_elev_m();
+    double ground = getACModel()->get3DModel()->getSGLocation()->get_cur_elev_m();
     // cout << "YASIM: ground = " << ground << endl;
 
     float pressure = fgGetFloat("/environment/pressure-inhg") * INHG2PA;
diff --git a/src/FDM/flight.cxx b/src/FDM/flight.cxx
index 9274166f1..1f9d650c0 100644
--- a/src/FDM/flight.cxx
+++ b/src/FDM/flight.cxx
@@ -201,7 +201,7 @@ FGInterface::common_init ()
                   * SGD_DEGREES_TO_RADIANS );
     double ground_elev_m = globals->get_scenery()->get_cur_elev();
     double ground_elev_ft = ground_elev_m * SG_METER_TO_FEET;
-    _acmodel->get3DModel()->getFGLocation()->set_cur_elev_m( ground_elev_m );
+    _acmodel->get3DModel()->getSGLocation()->set_cur_elev_m( ground_elev_m );
     _set_Runway_altitude ( ground_elev_ft );
     if ( fgGetBool("/sim/presets/onground")
          || fgGetDouble("/sim/presets/altitude-ft") < ground_elev_ft ) {
@@ -504,7 +504,7 @@ void FGInterface::_updateGeodeticPosition( double lat, double lon, double alt )
 
     _set_Sea_level_radius( sl_radius * SG_METER_TO_FEET );
     if ( getACModel() != NULL ) {
-        _set_Runway_altitude( getACModel()->get3DModel()->getFGLocation()->get_cur_elev_m() * SG_METER_TO_FEET );
+        _set_Runway_altitude( getACModel()->get3DModel()->getSGLocation()->get_cur_elev_m() * SG_METER_TO_FEET );
     }
 
     _set_sin_lat_geocentric( lat_geoc );
@@ -561,7 +561,7 @@ void FGInterface::_updateGeocentricPosition( double lat_geoc, double lon,
     _set_Geodetic_Position( lat_geod, lon, alt );
 
     _set_Sea_level_radius( sl_radius2 * SG_METER_TO_FEET );
-    _set_Runway_altitude( getACModel()->get3DModel()->getFGLocation()->get_cur_elev_m() * SG_METER_TO_FEET );
+    _set_Runway_altitude( getACModel()->get3DModel()->getSGLocation()->get_cur_elev_m() * SG_METER_TO_FEET );
 
     _set_sin_lat_geocentric( lat_geoc );
     _set_cos_lat_geocentric( lat_geoc );
diff --git a/src/Input/input.cxx b/src/Input/input.cxx
index a2419ca9b..9e236f269 100644
--- a/src/Input/input.cxx
+++ b/src/Input/input.cxx
@@ -104,7 +104,7 @@ FGBinding::read (const SGPropertyNode * node)
 {
   const SGPropertyNode * conditionNode = node->getChild("condition");
   if (conditionNode != 0)
-    setCondition(fgReadCondition(globals->get_props(), conditionNode));
+    setCondition(sgReadCondition(globals->get_props(), conditionNode));
 
   _command_name = node->getStringValue("command", "");
   if (_command_name.empty()) {
diff --git a/src/Input/input.hxx b/src/Input/input.hxx
index 2dc81f5a5..2ca5568a6 100644
--- a/src/Input/input.hxx
+++ b/src/Input/input.hxx
@@ -62,7 +62,7 @@ SG_USING_STD(vector);
  * keyboard key, a joystick button or axis, or even a panel
  * instrument.</p>
  */
-class FGBinding : public FGConditional
+class FGBinding : public SGConditional
 {
 public:
 
diff --git a/src/Main/fg_init.cxx b/src/Main/fg_init.cxx
index f71573cff..adf2f936b 100644
--- a/src/Main/fg_init.cxx
+++ b/src/Main/fg_init.cxx
@@ -980,19 +980,22 @@ fgInitNav ()
 bool fgInitPosition() {
     bool set_pos = false;
 
-    // Do a first guess if we should be on the ground or in the air
-    // (to be refined later based on other input.
+    // If glideslope is specified, then calculate offset-distance or
+    // altitude relative to glide slope if either of those was not
+    // specified.
+    if ( fgGetDouble("/sim/presets/glideslope-deg") > 0.1 ) {
+        fgSetDistOrAltFromGlideSlope();
+    }
+
+    // Select ground or air start depending on if an altitude is
+    // specified (this choice can be refined later based on other
+    // input.)
     if ( fgGetDouble("/sim/presets/altitude-ft") > -9990.0 ) {
         fgSetBool("/sim/presets/onground", false);
     } else {
         fgSetBool("/sim/presets/onground", true);
     }
 
-    // If glideslope is specified, then calculate offset-distance or
-    // altitude relative to glide slope if either of those was not
-    // specified.
-    fgSetDistOrAltFromGlideSlope();
-
     // If we have an explicit, in-range lon/lat, don't change it, just use it.
     // If not, check for an airport-id and use that.
     // If not, default to the middle of the KSFO field.
@@ -1045,33 +1048,18 @@ bool fgInitPosition() {
     if ( !set_pos && !vor.empty() ) {
         // a VOR is requested
         if ( fgSetPosFromNAV( vor, vor_freq ) ) {
-            if ( fgGetDouble("/sim/presets/altitude-ft") > -9990.0 ) {
-                fgSetBool("/sim/presets/onground", false);
-            } else {
-                fgSetBool("/sim/presets/onground", true);
-            }
             set_pos = true;
         }
     }
     if ( !set_pos && !ndb.empty() ) {
         // an NDB is requested
         if ( fgSetPosFromNAV( ndb, ndb_freq ) ) {
-            if ( fgGetDouble("/sim/presets/altitude-ft") > -9990.0 ) {
-                fgSetBool("/sim/presets/onground", false);
-            } else {
-                fgSetBool("/sim/presets/onground", true);
-            }
             set_pos = true;
         }
     }
     if ( !set_pos && !fix.empty() ) {
         // a Fix is requested
         if ( fgSetPosFromFix( fix ) ) {
-            if ( fgGetDouble("/sim/presets/altitude-ft") > -9990.0 ) {
-                fgSetBool("/sim/presets/onground", false);
-            } else {
-                fgSetBool("/sim/presets/onground", true);
-            }
             set_pos = true;
         }
     }
diff --git a/src/Main/globals.hxx b/src/Main/globals.hxx
index 606cb79ec..4a6dda600 100644
--- a/src/Main/globals.hxx
+++ b/src/Main/globals.hxx
@@ -52,6 +52,7 @@ class SGEphemeris;
 
 class SGCommandMgr;
 class SGMagVar;
+class SGModelLoader;
 class SGPropertyNode;
 class SGRoute;
 class SGTime;
@@ -66,7 +67,6 @@ class FGControls;
 class FGEnvironment;
 class FGEnvironmentMgr;
 class FGIO;
-class FGModelLoader;
 class FGModelMgr;
 class FGScenery;
 #ifdef FG_MPLAYER_AS
@@ -159,7 +159,7 @@ private:
 
     SGCommandMgr *commands;
 
-    FGModelLoader * model_loader;
+    SGModelLoader * model_loader;
 
     FGAircraftModel *acmodel;
 
@@ -275,9 +275,9 @@ public:
 
     inline SGCommandMgr *get_commands () { return commands; }
 
-    inline FGModelLoader * get_model_loader () { return model_loader; }
+    inline SGModelLoader * get_model_loader () { return model_loader; }
 
-    inline void set_model_loader (FGModelLoader * loader) {
+    inline void set_model_loader (SGModelLoader * loader) {
         model_loader = loader;
     }
 
diff --git a/src/Main/main.cxx b/src/Main/main.cxx
index fae900537..d7c3c38d5 100644
--- a/src/Main/main.cxx
+++ b/src/Main/main.cxx
@@ -497,7 +497,7 @@ void fgRenderFrame() {
         }
         // Keep resetting sim time while the sim is initializing
         globals->set_sim_time_sec( 0.0 );
-        Animation::set_sim_time_sec( 0.0 );
+        SGAnimation::set_sim_time_sec( 0.0 );
     } else {
         // idle_state is now 1000 meaning we've finished all our
         // initializations and are running the main loop, so this will
@@ -1025,7 +1025,7 @@ static void fgMainLoop( void ) {
         delta_time_sec = 0;
     last_time_stamp = current_time_stamp;
     globals->inc_sim_time_sec( delta_time_sec );
-    Animation::set_sim_time_sec( globals->get_sim_time_sec() );
+    SGAnimation::set_sim_time_sec( globals->get_sim_time_sec() );
 
     static long remainder = 0;
     long elapsed;
@@ -1042,9 +1042,9 @@ static void fgMainLoop( void ) {
     sglog().setLogLevels( SG_ALL, (sgDebugPriority)fgGetInt("/sim/log-level") );
     sglog().setLogLevels( SG_ALL, SG_INFO );
 
-    FGLocation * acmodel_location = 0;
+    SGLocation * acmodel_location = 0;
     if(cur_fdm_state->getACModel() != 0) {
-      acmodel_location = (FGLocation *)  cur_fdm_state->getACModel()->get3DModel()->getFGLocation();
+      acmodel_location = (SGLocation *)  cur_fdm_state->getACModel()->get3DModel()->getSGLocation();
     }
 
     SG_LOG( SG_ALL, SG_DEBUG, "Running Main Loop");
@@ -1250,14 +1250,14 @@ static void fgMainLoop( void ) {
 
     // update tile manager for FDM...
     // ...only if location is different than the viewer (to avoid duplicating effort)
-    if( acmodel_location != current_view->getFGLocation() ) {
+    if( acmodel_location != current_view->getSGLocation() ) {
       if( acmodel_location != 0 ) {
         globals->get_tile_mgr()->prep_ssg_nodes( acmodel_location,
                                                  visibility_meters );
         globals->get_tile_mgr()->
             update( acmodel_location, visibility_meters,
                     acmodel_location->get_absolute_view_pos(globals->get_scenery()->get_center()) );
-        // save results of update in FGLocation for fdm...
+        // save results of update in SGLocation for fdm...
         if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
           acmodel_location->
               set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
@@ -1267,24 +1267,24 @@ static void fgMainLoop( void ) {
       }
     }
 
-    globals->get_tile_mgr()->prep_ssg_nodes( current_view->getFGLocation(),
+    globals->get_tile_mgr()->prep_ssg_nodes( current_view->getSGLocation(),
                                              visibility_meters );
     // update tile manager for view...
     // IMPORTANT!!! the tilemgr update for view location _must_ be done last 
     // after the FDM's until all of Flight Gear code references the viewer's location
     // for elevation instead of the "scenery's" current elevation.
-    FGLocation *view_location = globals->get_current_view()->getFGLocation();
+    SGLocation *view_location = globals->get_current_view()->getSGLocation();
     globals->get_tile_mgr()->update( view_location, visibility_meters,
                                      current_view->get_absolute_view_pos() );
-    // save results of update in FGLocation for fdm...
+    // save results of update in SGLocation for fdm...
     if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
-      current_view->getFGLocation()->set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
+      current_view->getSGLocation()->set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
     }
-    current_view->getFGLocation()->set_tile_center( globals->get_scenery()->get_next_center() );
+    current_view->getSGLocation()->set_tile_center( globals->get_scenery()->get_next_center() );
 
     // If fdm location is same as viewer's then we didn't do the update for fdm location 
-    //   above so we need to save the viewer results in the fdm FGLocation as well...
-    if( acmodel_location == current_view->getFGLocation() ) {
+    //   above so we need to save the viewer results in the fdm SGLocation as well...
+    if( acmodel_location == current_view->getSGLocation() ) {
       if( acmodel_location != 0 ) {
         if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
           acmodel_location->set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
@@ -1697,7 +1697,7 @@ static bool fgMainInit( int argc, char **argv ) {
     // Initialize the general model subsystem.
     ////////////////////////////////////////////////////////////////////
 
-    globals->set_model_loader(new FGModelLoader);
+    globals->set_model_loader(new SGModelLoader);
     globals->set_model_mgr(new FGModelMgr);
     globals->get_model_mgr()->init();
     globals->get_model_mgr()->bind();
diff --git a/src/Main/viewer.cxx b/src/Main/viewer.cxx
index cf56c96a0..b32e93d2d 100644
--- a/src/Main/viewer.cxx
+++ b/src/Main/viewer.cxx
@@ -186,15 +186,15 @@ void
 FGViewer::init ()
 {
   if ( _from_model )
-    _location = (FGLocation *) globals->get_aircraft_model()->get3DModel()->getFGLocation();
+    _location = (SGLocation *) globals->get_aircraft_model()->get3DModel()->getSGLocation();
   else
-    _location = (FGLocation *) new FGLocation;
+    _location = (SGLocation *) new SGLocation;
 
   if ( _type == FG_LOOKAT ) {
     if ( _at_model )
-      _target_location = (FGLocation *) globals->get_aircraft_model()->get3DModel()->getFGLocation();
+      _target_location = (SGLocation *) globals->get_aircraft_model()->get3DModel()->getSGLocation();
     else
-      _target_location = (FGLocation *) new FGLocation;
+      _target_location = (SGLocation *) new SGLocation;
   }
 }
 
@@ -477,20 +477,20 @@ FGViewer::getZeroElevViewPos ()
 }
 
 void
-FGViewer::updateFromModelLocation (FGLocation * location)
+FGViewer::updateFromModelLocation (SGLocation * location)
 {
   sgCopyMat4(LOCAL, location->getCachedTransformMatrix());
 }
 
 void
-FGViewer::updateAtModelLocation (FGLocation * location)
+FGViewer::updateAtModelLocation (SGLocation * location)
 {
   sgCopyMat4(ATLOCAL, 
              location->getCachedTransformMatrix());
 }
 
 void
-FGViewer::recalcOurOwnLocation (FGLocation * location, double lon_deg, double lat_deg, double alt_ft, 
+FGViewer::recalcOurOwnLocation (SGLocation * location, double lon_deg, double lat_deg, double alt_ft, 
                         double roll_deg, double pitch_deg, double heading_deg)
 {
   // update from our own data...
@@ -668,7 +668,7 @@ FGViewer::recalcLookAt ()
 }
 
 // copy results from location class to viewer...
-// FIXME: some of these should be changed to reference directly to FGLocation...
+// FIXME: some of these should be changed to reference directly to SGLocation...
 void
 FGViewer::copyLocationData()
 {
diff --git a/src/Main/viewer.hxx b/src/Main/viewer.hxx
index 291f4a491..890d35187 100644
--- a/src/Main/viewer.hxx
+++ b/src/Main/viewer.hxx
@@ -255,7 +255,7 @@ public:
     inline void set_clean() { _dirty = false; }
     
     // return eye location...
-    virtual FGLocation * getFGLocation () const { return _location; }
+    virtual SGLocation * getSGLocation () const { return _location; }
 
 
 private:
@@ -322,8 +322,8 @@ private:
     bool _at_model;
     int _at_model_index;  // number of model (for multi model)
 
-    FGLocation * _location;
-    FGLocation * _target_location;
+    SGLocation * _location;
+    SGLocation * _target_location;
 
     // the nominal field of view (angle, in degrees)
     double _fov_deg; 
@@ -372,9 +372,9 @@ private:
     void recalcLookFrom();
     void recalcLookAt();
     void copyLocationData();
-    void updateFromModelLocation (FGLocation * location);
-    void updateAtModelLocation (FGLocation * location);
-    void recalcOurOwnLocation (FGLocation * location, double lon_deg, double lat_deg, double alt_ft,
+    void updateFromModelLocation (SGLocation * location);
+    void updateAtModelLocation (SGLocation * location);
+    void recalcOurOwnLocation (SGLocation * location, double lon_deg, double lat_deg, double alt_ft,
                  double roll_deg, double pitch_deg, double heading_deg);
 
     // add to _heading_offset_deg
diff --git a/src/Model/acmodel.cxx b/src/Model/acmodel.cxx
index 14d996b12..90a70f8f6 100644
--- a/src/Model/acmodel.cxx
+++ b/src/Model/acmodel.cxx
@@ -53,7 +53,7 @@ FGAircraftModel::~FGAircraftModel ()
 void 
 FGAircraftModel::init ()
 {
-  _aircraft = new FGModelPlacement;
+  _aircraft = new SGModelPlacement;
   string path = fgGetString("/sim/model/path", "Models/Geometry/glider.ac");
   try {
     ssgBranch *model = fgLoad3DModelPanel( globals->get_fg_root(),
diff --git a/src/Model/acmodel.hxx b/src/Model/acmodel.hxx
index b2674e70f..0e6fe2235 100644
--- a/src/Model/acmodel.hxx
+++ b/src/Model/acmodel.hxx
@@ -21,7 +21,7 @@ SG_USING_STD(vector);
 // Don't pull in the headers, since we don't need them here.
 class ssgRoot;
 class ssgSelector;
-class FGModelPlacement;
+class SGModelPlacement;
 
 
 class FGAircraftModel : public FGSubsystem
@@ -36,11 +36,11 @@ public:
   virtual void unbind ();
   virtual void update (double dt);
   virtual void draw ();
-  virtual FGModelPlacement * get3DModel() { return _aircraft; }
+  virtual SGModelPlacement * get3DModel() { return _aircraft; }
 
 private:
 
-  FGModelPlacement * _aircraft;
+  SGModelPlacement * _aircraft;
   ssgSelector * _selector;
   ssgRoot * _scene;
   float _nearplane;
diff --git a/src/Model/model_panel.cxx b/src/Model/model_panel.cxx
index b06d83c8a..3c197f661 100644
--- a/src/Model/model_panel.cxx
+++ b/src/Model/model_panel.cxx
@@ -84,7 +84,7 @@ fgLoad3DModelPanel( const string &fg_root, const string &path,
   ssgTransform * alignmainmodel = new ssgTransform;
   alignmainmodel->addKid(model);
   sgMat4 res_matrix;
-  fgMakeOffsetsMatrix(&res_matrix,
+  sgMakeOffsetsMatrix(&res_matrix,
                       props.getFloatValue("/offsets/heading-deg", 0.0),
                       props.getFloatValue("/offsets/roll-deg", 0.0),
                       props.getFloatValue("/offsets/pitch-deg", 0.0),
@@ -111,7 +111,7 @@ fgLoad3DModelPanel( const string &fg_root, const string &path,
     const char * name = animation_nodes[i]->getStringValue("name", 0);
     vector<SGPropertyNode_ptr> name_nodes =
       animation_nodes[i]->getChildren("object-name");
-    fgMakeAnimation( model, name, name_nodes, prop_root, animation_nodes[i],
+    sgMakeAnimation( model, name, name_nodes, prop_root, animation_nodes[i],
                      sim_time_sec);
   }
 
@@ -121,7 +121,7 @@ fgLoad3DModelPanel( const string &fg_root, const string &path,
     SGPropertyNode_ptr node = model_nodes[i];
     ssgTransform * align = new ssgTransform;
     sgMat4 res_matrix;
-    fgMakeOffsetsMatrix(&res_matrix,
+    sgMakeOffsetsMatrix(&res_matrix,
                         node->getFloatValue("offsets/heading-deg", 0.0),
                         node->getFloatValue("offsets/roll-deg", 0.0),
                         node->getFloatValue("offsets/pitch-deg", 0.0),
@@ -130,7 +130,7 @@ fgLoad3DModelPanel( const string &fg_root, const string &path,
                         node->getFloatValue("offsets/z-m", 0.0));
     align->setTransform(res_matrix);
 
-    ssgBranch * kid = fgLoad3DModel( fg_root, node->getStringValue("path"),
+    ssgBranch * kid = sgLoad3DModel( fg_root, node->getStringValue("path"),
                                      prop_root, sim_time_sec );
     align->addKid(kid);
     model->addKid(align);
diff --git a/src/Model/model_panel.hxx b/src/Model/model_panel.hxx
index 98b5ffe71..fb0554e11 100644
--- a/src/Model/model_panel.hxx
+++ b/src/Model/model_panel.hxx
@@ -53,7 +53,7 @@ class FGLocation;
  * list wrapper to add animations to the model.
  *
  * Subsystems should not normally invoke this function directly;
- * instead, they should use the FGModelLoader declared in loader.hxx.
+ * instead, they should use the SGModelLoader declared in loader.hxx.
  */
 ssgBranch *fgLoad3DModelPanel( const string& fg_root, const string &path,
                                SGPropertyNode *prop_root,
diff --git a/src/Model/modelmgr.cxx b/src/Model/modelmgr.cxx
index a1d92a962..432b31862 100644
--- a/src/Model/modelmgr.cxx
+++ b/src/Model/modelmgr.cxx
@@ -45,10 +45,10 @@ FGModelMgr::init ()
     SG_LOG(SG_GENERAL, SG_INFO,
 	   "Adding model " << node->getStringValue("name", "[unnamed]"));
     Instance * instance = new Instance;
-    FGModelPlacement *model = new FGModelPlacement;
+    SGModelPlacement *model = new SGModelPlacement;
     instance->model = model;
     ssgBranch *object
-        = fgLoad3DModel( globals->get_fg_root(),
+        = sgLoad3DModel( globals->get_fg_root(),
                          node->getStringValue("path",
                                               "Models/Geometry/glider.ac"),
                          globals->get_props(),
@@ -117,7 +117,7 @@ FGModelMgr::update (double dt)
 {
   for (unsigned int i = 0; i < _instances.size(); i++) {
     Instance * instance = _instances[i];
-    FGModelPlacement * model = instance->model;
+    SGModelPlacement * model = instance->model;
 
 				// Optionally set position from properties
     if (instance->lon_deg_node != 0)
diff --git a/src/Model/modelmgr.hxx b/src/Model/modelmgr.hxx
index 87ee0fe76..664e48425 100644
--- a/src/Model/modelmgr.hxx
+++ b/src/Model/modelmgr.hxx
@@ -21,7 +21,7 @@ SG_USING_STD(vector);
 // Don't pull in headers, since we don't need them here.
 class ssgSelector;
 class SGPropertyNode;
-class FGModelPlacement;
+class SGModelPlacement;
 
 
 /**
@@ -37,18 +37,18 @@ public:
    * The model manager uses the property nodes to update the model's
    * position and orientation; any of the property node pointers may
    * be set to zero to avoid update.  Normally, a caller should
-   * load the model by instantiating FGModelPlacement with the path
+   * load the model by instantiating SGModelPlacement with the path
    * to the model or its XML wrapper, then assign any relevant
    * property node pointers.
    *
-   * @see FGModelPlacement
+   * @see SGModelPlacement
    * @see FGModelMgr#add_instance
    */
   struct Instance
   {
     Instance ();
     virtual ~Instance ();
-    FGModelPlacement * model;
+    SGModelPlacement * model;
     SGPropertyNode * lon_deg_node;
     SGPropertyNode * lat_deg_node;
     SGPropertyNode * elev_ft_node;
diff --git a/src/Objects/obj.cxx b/src/Objects/obj.cxx
index 523f55ec5..85395e309 100644
--- a/src/Objects/obj.cxx
+++ b/src/Objects/obj.cxx
@@ -89,7 +89,7 @@ bool fgGenTile( const string& path, SGBucket b,
                       double *bounding_radius,
                       ssgBranch* geometry )
 {
-    FGNewMat *newmat;
+    SGMaterial *newmat;
 
     ssgSimpleState *state = NULL;
 
@@ -283,7 +283,7 @@ class LeafUserData : public ssgBase
 public:
     bool is_filled_in;
     ssgLeaf * leaf;
-    FGNewMat * mat;
+    SGMaterial * mat;
     ssgBranch * branch;
     float sin_lat;
     float cos_lat;
@@ -306,13 +306,13 @@ public:
   float * p3;
     sgVec3 center;
     double area;
-  FGNewMat::ObjectGroup * object_group;
+  SGMaterial::ObjectGroup * object_group;
   ssgBranch * branch;
     LeafUserData * leafData;
   unsigned int seed;
 
     void fill_in_triangle();
-    void add_object_to_triangle(FGNewMat::Object * object);
+    void add_object_to_triangle(SGMaterial::Object * object);
     void makeWorldMatrix (sgMat4 ROT, double hdg_deg );
 };
 
@@ -333,7 +333,7 @@ void TriUserData::fill_in_triangle ()
     int nObjects = object_group->get_object_count();
 
     for (int i = 0; i < nObjects; i++) {
-      FGNewMat::Object * object = object_group->get_object(i);
+      SGMaterial::Object * object = object_group->get_object(i);
       double num = area / object->get_coverage_m2();
 
       // place an object each unit of area
@@ -353,11 +353,11 @@ void TriUserData::fill_in_triangle ()
     }
 }
 
-void TriUserData::add_object_to_triangle (FGNewMat::Object * object)
+void TriUserData::add_object_to_triangle (SGMaterial::Object * object)
 {
     // Set up the random heading if required.
     double hdg_deg = 0;
-    if (object->get_heading_type() == FGNewMat::Object::HEADING_RANDOM)
+    if (object->get_heading_type() == SGMaterial::Object::HEADING_RANDOM)
         hdg_deg = sg_random() * 360;
 
     sgMat4 mat;
@@ -539,7 +539,7 @@ void LeafUserData::setup_triangle (int i )
     int num_groups = mat->get_object_group_count();
     for (int j = 0; j < num_groups; j++) {
                                 // Look up the random object.
-        FGNewMat::ObjectGroup * group = mat->get_object_group(j);
+        SGMaterial::ObjectGroup * group = mat->get_object_group(j);
 
                                 // Set up the range selector for the entire
                                 // triangle; note that we use the object
@@ -670,7 +670,7 @@ gen_random_surface_objects (ssgLeaf *leaf,
       return;
 
                                 // Get the material for this surface.
-    FGNewMat * mat = material_lib.find(material_name);
+    SGMaterial * mat = material_lib.find(material_name);
     if (mat == 0) {
       SG_LOG(SG_INPUT, SG_ALERT, "Unknown material " << material_name);
       return;
@@ -743,7 +743,7 @@ ssgLeaf *gen_leaf( const string& path,
     ssgSimpleState *state = NULL;
     float coverage = -1;
 
-    FGNewMat *newmat = material_lib.find( material );
+    SGMaterial *newmat = material_lib.find( material );
     if ( newmat == NULL ) {
         // see if this is an on the fly texture
         string file = path;
diff --git a/src/Objects/pt_lights.cxx b/src/Objects/pt_lights.cxx
index aa287ae2e..96f05e83d 100644
--- a/src/Objects/pt_lights.cxx
+++ b/src/Objects/pt_lights.cxx
@@ -117,7 +117,7 @@ ssgLeaf *gen_directional_light( sgVec3 pt, sgVec3 dir, sgVec3 up,
     ssgLeaf *leaf = 
         new ssgVtxTable ( GL_TRIANGLES, vl, nl, NULL, cl );
 
-    FGNewMat *newmat = material_lib.find( material );
+    SGMaterial *newmat = material_lib.find( material );
 
     if ( newmat != NULL ) {
         leaf->setState( newmat->get_state() );
@@ -234,7 +234,7 @@ ssgTransform *gen_dir_light_group( const point_list &nodes,
     ssgLeaf *leaf = 
         new ssgVtxTable ( GL_TRIANGLES, vl, nl, NULL, cl );
 
-    FGNewMat *newmat = material_lib.find( material );
+    SGMaterial *newmat = material_lib.find( material );
 
     if ( newmat != NULL ) {
         leaf->setState( newmat->get_state() );
@@ -319,7 +319,7 @@ ssgTransform *gen_reil_lights( const point_list &nodes,
     ssgLeaf *leaf = 
         new ssgVtxTable ( GL_TRIANGLES, vl, nl, NULL, cl );
 
-    FGNewMat *newmat = material_lib.find( "RWY_WHITE_LIGHTS" );
+    SGMaterial *newmat = material_lib.find( "RWY_WHITE_LIGHTS" );
 
     if ( newmat != NULL ) {
         leaf->setState( newmat->get_state() );
@@ -393,7 +393,7 @@ ssgTransform *gen_odals_lights( const point_list &nodes,
             new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
 
         // we don't want directional lights here
-        FGNewMat *newmat = material_lib.find( "GROUND_LIGHTS" );
+        SGMaterial *newmat = material_lib.find( "GROUND_LIGHTS" );
 
         if ( newmat != NULL ) {
             leaf->setState( newmat->get_state() );
@@ -428,7 +428,7 @@ ssgTransform *gen_odals_lights( const point_list &nodes,
         new ssgVtxTable ( GL_POINTS, vl, NULL, NULL, cl );
 
     // we don't want directional lights here
-    FGNewMat *newmat = material_lib.find( "GROUND_LIGHTS" );
+    SGMaterial *newmat = material_lib.find( "GROUND_LIGHTS" );
 
     if ( newmat != NULL ) {
         leaf->setState( newmat->get_state() );
@@ -527,7 +527,7 @@ ssgTransform *gen_rabbit_lights( const point_list &nodes,
         ssgLeaf *leaf = 
             new ssgVtxTable ( GL_TRIANGLES, vl, nl, NULL, cl );
 
-        FGNewMat *newmat = material_lib.find( "RWY_WHITE_LIGHTS" );
+        SGMaterial *newmat = material_lib.find( "RWY_WHITE_LIGHTS" );
 
         if ( newmat != NULL ) {
             leaf->setState( newmat->get_state() );
@@ -584,7 +584,7 @@ ssgLeaf *gen_normal_line( sgVec3 pt, sgVec3 dir, sgVec3 up ) {
     ssgLeaf *leaf = 
         new ssgVtxTable ( GL_LINES, vl, NULL, NULL, cl );
 
-    FGNewMat *newmat = material_lib.find( "GROUND_LIGHTS" );
+    SGMaterial *newmat = material_lib.find( "GROUND_LIGHTS" );
     leaf->setState( newmat->get_state() );
 
     return leaf;
diff --git a/src/Scenery/FGTileLoader.hxx b/src/Scenery/FGTileLoader.hxx
index 74d237f34..5d7d98492 100644
--- a/src/Scenery/FGTileLoader.hxx
+++ b/src/Scenery/FGTileLoader.hxx
@@ -155,7 +155,7 @@ private:
      * Lock and synchronize access to tile queue.
      */
     SGMutex mutex;
-    SGCondition frame_cond;
+    SGPthreadCond frame_cond;
 
     /**
      * Thread cleanup handler.
diff --git a/src/Scenery/tileentry.cxx b/src/Scenery/tileentry.cxx
index 3a5704684..a307620bc 100644
--- a/src/Scenery/tileentry.cxx
+++ b/src/Scenery/tileentry.cxx
@@ -525,7 +525,7 @@ ssgLeaf* FGTileEntry::gen_lights( ssgVertexArray *lights, int inc, float bright
         new ssgVtxTable ( GL_POINTS, vl, nl, tl, cl );
 
     // assign state
-    FGNewMat *newmat = material_lib.find( "GROUND_LIGHTS" );
+    SGMaterial *newmat = material_lib.find( "GROUND_LIGHTS" );
     leaf->setState( newmat->get_state() );
     leaf->setCallback( SSG_CALLBACK_PREDRAW, fgLightsPredraw );
     leaf->setCallback( SSG_CALLBACK_POSTDRAW, fgLightsPostdraw );
diff --git a/src/Scenery/tilemgr.cxx b/src/Scenery/tilemgr.cxx
index bc94fc620..47e72427e 100644
--- a/src/Scenery/tilemgr.cxx
+++ b/src/Scenery/tilemgr.cxx
@@ -354,7 +354,7 @@ void FGTileMgr::update_queues()
 // disk.
 int FGTileMgr::update( double visibility_meters )
 {
-    FGLocation *location = globals->get_current_view()->getFGLocation();
+    SGLocation *location = globals->get_current_view()->getSGLocation();
     sgdVec3 abs_pos_vector;
     sgdCopyVec3( abs_pos_vector,
                  globals->get_current_view()->get_absolute_view_pos() );
@@ -362,7 +362,7 @@ int FGTileMgr::update( double visibility_meters )
 }
 
 
-int FGTileMgr::update( FGLocation *location, double visibility_meters,
+int FGTileMgr::update( SGLocation *location, double visibility_meters,
                        sgdVec3 abs_pos_vector )
 {
     longitude = location->getLongitude_deg();
@@ -470,7 +470,7 @@ int FGTileMgr::updateCurrentElevAtPos(sgdVec3 abs_pos_vector, Point3D center) {
 }
 
 
-void FGTileMgr::prep_ssg_nodes( FGLocation *location, float vis ) {
+void FGTileMgr::prep_ssg_nodes( SGLocation *location, float vis ) {
 
     // traverse the potentially viewable tile list and update range
     // selector and transform
diff --git a/src/Scenery/tilemgr.hxx b/src/Scenery/tilemgr.hxx
index 34abff2ce..990a6fd05 100644
--- a/src/Scenery/tilemgr.hxx
+++ b/src/Scenery/tilemgr.hxx
@@ -163,7 +163,7 @@ public:
     // local chunks.  If the chunk isn't already in the cache, then
     // read it from disk.
     int update( double visibility_meters );
-    int update( FGLocation *location, double visibility_meters,
+    int update( SGLocation *location, double visibility_meters,
                 sgdVec3 abs_pos_vector );
 
     int updateCurrentElevAtPos(sgdVec3 abs_pos_vector, Point3D center );
@@ -183,7 +183,7 @@ public:
     // tile, set the ssg transform and update it's range selector
     // based on current visibilty void prep_ssg_nodes( float
     // visibility_meters );
-    void prep_ssg_nodes( FGLocation *location, float visibility_meters );
+    void prep_ssg_nodes( SGLocation *location, float visibility_meters );
 
     // Set flag with event manager so that non-moving view refreshes
     // tiles...