diff --git a/projects/VC90/FlightGear/FlightGear.vcproj b/projects/VC90/FlightGear/FlightGear.vcproj
index 8d70c4028..98fde43d6 100644
--- a/projects/VC90/FlightGear/FlightGear.vcproj
+++ b/projects/VC90/FlightGear/FlightGear.vcproj
@@ -3437,6 +3437,14 @@
 				RelativePath="..\..\..\src\Environment\presets.hxx"
 				>
 			</File>
+			<File
+				RelativePath="..\..\..\src\Environment\gravity.cxx"
+				>
+			</File>
+			<File
+				RelativePath="..\..\..\src\Environment\gravity.hxx"
+				>
+			</File>
 		</Filter>
 		<Filter
 			Name="Lib_Model"
diff --git a/src/Autopilot/route_mgr.cxx b/src/Autopilot/route_mgr.cxx
index 1b37fa256..044c624c8 100644
--- a/src/Autopilot/route_mgr.cxx
+++ b/src/Autopilot/route_mgr.cxx
@@ -40,6 +40,7 @@
 
 #include <simgear/misc/strutils.hxx>
 #include <simgear/structure/exception.hxx>
+#include <simgear/structure/commands.hxx>
 #include <simgear/misc/sgstream.hxx>
 
 #include <simgear/props/props_io.hxx>
@@ -109,6 +110,151 @@ PropertyWatcher* createWatcher(T* obj, void (T::*m)())
   return new MethodPropertyWatcher<T>(obj, m);
 }
 
+static bool commandLoadFlightPlan(const SGPropertyNode* arg)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  SGPath path(arg->getStringValue("path"));
+  return self->loadRoute(path);
+}
+
+static bool commandSaveFlightPlan(const SGPropertyNode* arg)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  SGPath path(arg->getStringValue("path"));
+  return self->saveRoute(path);
+}
+
+static bool commandActivateFlightPlan(const SGPropertyNode* arg)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  bool activate = arg->getBoolValue("activate", true);
+  if (activate) {
+    self->activate();
+  } else {
+    
+  }
+  
+  return true;
+}
+
+static bool commandClearFlightPlan(const SGPropertyNode*)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  self->clearRoute();
+  return true;
+}
+
+static bool commandSetActiveWaypt(const SGPropertyNode* arg)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  int index = arg->getIntValue("index");
+  if ((index < 0) || (index >= self->numWaypts())) {
+    return false;
+  }
+  
+  self->jumpToIndex(index);
+  return true;
+}
+
+static bool commandInsertWaypt(const SGPropertyNode* arg)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  int index = arg->getIntValue("index");
+  std::string ident(arg->getStringValue("id"));
+  int alt = arg->getIntValue("altitude-ft", -999);
+  int ias = arg->getIntValue("speed-knots", -999);
+  
+  WayptRef wp;
+// lat/lon may be supplied to narrow down navaid search, or to specify
+// a raw waypoint
+  SGGeod pos;
+  if (arg->hasChild("longitude-deg")) {
+    pos = SGGeod::fromDeg(arg->getDoubleValue("longitude-deg"),
+                               arg->getDoubleValue("latitude-deg"));
+  }
+  
+  if (arg->hasChild("navaid")) {
+    FGPositionedRef p = FGPositioned::findClosestWithIdent(arg->getStringValue("navaid"), pos);
+    
+    if (arg->hasChild("navaid", 1)) {
+      // intersection of two radials
+      FGPositionedRef p2 = FGPositioned::findClosestWithIdent(arg->getStringValue("navaid[1]"), pos);
+      if (!p2) {
+        SG_LOG( SG_AUTOPILOT, SG_INFO, "Unable to find FGPositioned with ident:" << arg->getStringValue("navaid[1]"));
+        return false;
+      }
+      
+      double r1 = arg->getDoubleValue("radial"),
+        r2 = arg->getDoubleValue("radial[1]");
+      
+      SGGeod intersection;
+      bool ok = SGGeodesy::radialIntersection(p->geod(), r1, p2->geod(), r2, intersection);
+      if (!ok) {
+        SG_LOG(SG_AUTOPILOT, SG_INFO, "no valid intersection for:" << p->ident() 
+                << "," << p2->ident());
+        return false;
+      }
+      
+      std::string name = p->ident() + "-" + p2->ident();
+      wp = new BasicWaypt(intersection, name, NULL);
+    } else if (arg->hasChild("offset-nm") && arg->hasChild("radial")) {
+      // offset radial from navaid
+      double radial = arg->getDoubleValue("radial");
+      double distanceNm = arg->getDoubleValue("offset-nm");
+      //radial += magvar->getDoubleValue(); // convert to true bearing
+      wp = new OffsetNavaidWaypoint(p, NULL, radial, distanceNm);
+    } else {
+      wp = new NavaidWaypoint(p, NULL);
+    }
+  } else if (arg->hasChild("airport")) {
+    const FGAirport* apt = fgFindAirportID(arg->getStringValue("airport"));
+    if (!apt) {
+      SG_LOG(SG_AUTOPILOT, SG_INFO, "no such airport" << arg->getStringValue("airport"));
+      return false;
+    }
+    
+    if (arg->hasChild("runway")) {
+      if (!apt->hasRunwayWithIdent(arg->getStringValue("runway"))) {
+        SG_LOG(SG_AUTOPILOT, SG_INFO, "No runway: " << arg->getStringValue("runway") << " at " << apt->ident());
+        return false;
+      }
+      
+      FGRunway* runway = apt->getRunwayByIdent(arg->getStringValue("runway"));
+      wp = new RunwayWaypt(runway, NULL);
+    } else {
+      wp = new NavaidWaypoint((FGAirport*) apt, NULL);
+    }
+  } else if (arg->hasChild("text")) {
+    wp = self->waypointFromString(arg->getStringValue("text"));
+  } else if (!(pos == SGGeod())) {
+    // just a raw lat/lon
+    wp = new BasicWaypt(pos, ident, NULL);
+  } else {
+    return false; // failed to build waypoint
+  }
+  
+  if (alt >= 0) {
+    wp->setAltitude(alt, flightgear::RESTRICT_AT);
+  }
+  
+  if (ias > 0) {
+    wp->setSpeed(ias, flightgear::RESTRICT_AT);
+  }
+
+  self->insertWayptAtIndex(wp, index);
+  return true;
+}
+
+static bool commandDeleteWaypt(const SGPropertyNode* arg)
+{
+  FGRouteMgr* self = (FGRouteMgr*) globals->get_subsystem("route-manager");
+  int index = arg->getIntValue("index");
+  self->removeWayptAtIndex(index);
+  return true;
+}
+
+/////////////////////////////////////////////////////////////////////////////
+
 FGRouteMgr::FGRouteMgr() :
   _currentIndex(0),
   input(fgGetNode( RM "input", true )),
@@ -117,6 +263,14 @@ FGRouteMgr::FGRouteMgr() :
   listener = new InputListener(this);
   input->setStringValue("");
   input->addChangeListener(listener);
+  
+  SGCommandMgr::instance()->addCommand("load-flightplan", commandLoadFlightPlan);
+  SGCommandMgr::instance()->addCommand("save-flightplan", commandSaveFlightPlan);
+  SGCommandMgr::instance()->addCommand("activate-flightplan", commandActivateFlightPlan);
+  SGCommandMgr::instance()->addCommand("clear-flightplan", commandClearFlightPlan);
+  SGCommandMgr::instance()->addCommand("set-active-waypt", commandSetActiveWaypt);
+  SGCommandMgr::instance()->addCommand("insert-waypt", commandInsertWaypt);
+  SGCommandMgr::instance()->addCommand("delete-waypt", commandDeleteWaypt);
 }
 
 
@@ -227,7 +381,7 @@ void FGRouteMgr::postinit()
   SGPath path(_pathNode->getStringValue());
   if (path.exists()) {
     SG_LOG(SG_AUTOPILOT, SG_INFO, "loading flight-plan from:" << path.str());
-    loadRoute();
+    loadRoute(path);
   }
   
 // this code only matters for the --wp option now - perhaps the option
@@ -897,11 +1051,11 @@ void FGRouteMgr::InputListener::valueChanged(SGPropertyNode *prop)
     else if (!strcmp(s, "@ACTIVATE"))
         mgr->activate();
     else if (!strcmp(s, "@LOAD")) {
-      mgr->loadRoute();
+      SGPath path(mgr->_pathNode->getStringValue());
+      mgr->loadRoute(path);
     } else if (!strcmp(s, "@SAVE")) {
-      mgr->saveRoute();
-    } else if (!strcmp(s, "@POP")) {
-      SG_LOG(SG_AUTOPILOT, SG_WARN, "route-manager @POP command is deprecated");
+      SGPath path(mgr->_pathNode->getStringValue());
+      mgr->saveRoute(path);
     } else if (!strcmp(s, "@NEXT")) {
       mgr->jumpToIndex(mgr->_currentIndex + 1);
     } else if (!strcmp(s, "@PREVIOUS")) {
@@ -1119,9 +1273,8 @@ Waypt* FGRouteMgr::wayptAtIndex(int index) const
   return _route[index];
 }
 
-void FGRouteMgr::saveRoute()
+bool FGRouteMgr::saveRoute(const SGPath& path)
 {
-  SGPath path(_pathNode->getStringValue());
   SG_LOG(SG_IO, SG_INFO, "Saving route to " << path.str());
   try {
     SGPropertyNode_ptr d(new SGPropertyNode);
@@ -1148,18 +1301,19 @@ void FGRouteMgr::saveRoute()
       wpt->saveAsNode(routeNode->getChild("wp", i, true));
     } // of waypoint iteration
     writeProperties(path.str(), d, true /* write-all */);
+    return true;
   } catch (sg_exception& e) {
     SG_LOG(SG_IO, SG_WARN, "failed to save flight-plan:" << e.getMessage());
+    return false;
   }
 }
 
-void FGRouteMgr::loadRoute()
+bool FGRouteMgr::loadRoute(const SGPath& path)
 {
   // deactivate route first
   active->setBoolValue(false);
   
   SGPropertyNode_ptr routeData(new SGPropertyNode);
-  SGPath path(_pathNode->getStringValue());
   
   SG_LOG(SG_IO, SG_INFO, "going to read flight-plan from:" << path.str());
     
@@ -1167,8 +1321,7 @@ void FGRouteMgr::loadRoute()
     readProperties(path.str(), routeData);
   } catch (sg_exception& ) {
     // if XML parsing fails, the file might be simple textual list of waypoints
-    loadPlainTextRoute(path);
-    return;
+    return loadPlainTextRoute(path);
   }
   
   try {
@@ -1180,9 +1333,11 @@ void FGRouteMgr::loadRoute()
     } else {
       throw sg_io_exception("unsupported XML route version");
     }
+    return true;
   } catch (sg_exception& e) {
     SG_LOG(SG_IO, SG_WARN, "failed to load flight-plan (from '" << e.getOrigin()
       << "'):" << e.getMessage());
+    return false;
   }
 }
 
@@ -1299,11 +1454,11 @@ WayptRef FGRouteMgr::parseVersion1XMLWaypt(SGPropertyNode* aWP)
   return w;
 }
 
-void FGRouteMgr::loadPlainTextRoute(const SGPath& path)
+bool FGRouteMgr::loadPlainTextRoute(const SGPath& path)
 {
   sg_gzifstream in(path.str().c_str());
   if (!in.is_open()) {
-    return;
+    return false;
   }
   
   try {
@@ -1330,8 +1485,10 @@ void FGRouteMgr::loadPlainTextRoute(const SGPath& path)
     } // of line iteration
   
     _route = wpts;
+    return true;
   } catch (sg_exception& e) {
     SG_LOG(SG_IO, SG_WARN, "failed to load route from:" << path.str() << ":" << e.getMessage());
+    return false;
   }
 }
 
diff --git a/src/Autopilot/route_mgr.hxx b/src/Autopilot/route_mgr.hxx
index 16b4adc4b..31336f96a 100644
--- a/src/Autopilot/route_mgr.hxx
+++ b/src/Autopilot/route_mgr.hxx
@@ -118,13 +118,22 @@ public:
    */
   void jumpToIndex(int index);
   
-  void saveRoute();
-  void loadRoute();
+  bool saveRoute(const SGPath& p);
+  bool loadRoute(const SGPath& p);
   
   /**
    * Helper command to setup current airport/runway if necessary
    */
   void initAtPosition();
+  
+    /**
+     * Create a WayPoint from a string in the following format:
+     *  - simple identifier
+     *  - decimal-lon,decimal-lat
+     *  - airport-id/runway-id
+     *  - navaid/radial-deg/offset-nm
+     */
+    flightgear::WayptRef waypointFromString(const std::string& target);
 private:
   flightgear::WayptVec _route;
   int _currentIndex;
@@ -188,17 +197,7 @@ private:
     SGPropertyNode_ptr weightOnWheels;
     
     InputListener *listener;
-    SGPropertyNode_ptr mirror;
-
-    /**
-     * Create a SGWayPoint from a string in the following format:
-     *  - simple identifier
-     *  - decimal-lon,decimal-lat
-     *  - airport-id/runway-id
-     *  - navaid/radial-deg/offset-nm
-     */
-    flightgear::WayptRef waypointFromString(const std::string& target);
-    
+    SGPropertyNode_ptr mirror;    
     
     void departureChanged();
     void buildDeparture(flightgear::WayptRef enroute, flightgear::WayptVec& wps);
@@ -229,7 +228,7 @@ private:
     bool checkFinished();
     
     
-    void loadPlainTextRoute(const SGPath& path);
+    bool loadPlainTextRoute(const SGPath& path);
     
     void loadVersion1XMLRoute(SGPropertyNode_ptr routeData);
     void loadVersion2XMLRoute(SGPropertyNode_ptr routeData);
diff --git a/src/Environment/CMakeLists.txt b/src/Environment/CMakeLists.txt
index 69fa003ed..ada06638e 100644
--- a/src/Environment/CMakeLists.txt
+++ b/src/Environment/CMakeLists.txt
@@ -16,6 +16,7 @@ set(SOURCES
 	ridge_lift.cxx
 	terrainsampler.cxx
 	presets.cxx
+	gravity.cxx
 	)
 	
 flightgear_component(Environment "${SOURCES}")
diff --git a/src/Environment/Makefile.am b/src/Environment/Makefile.am
index c3b1b5fbf..876f4f797 100644
--- a/src/Environment/Makefile.am
+++ b/src/Environment/Makefile.am
@@ -17,6 +17,7 @@ libEnvironment_a_SOURCES = \
 	ridge_lift.cxx ridge_lift.hxx \
 	ephemeris.cxx ephemeris.hxx \
 	terrainsampler.cxx terrainsampler.cxx \
-	presets.cxx presets.hxx
+	presets.cxx presets.hxx \
+	gravity.cxx gravity.hxx
 
 INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/src
diff --git a/src/Environment/atmosphere.hxx b/src/Environment/atmosphere.hxx
index 1ee4e1b6b..466cba270 100644
--- a/src/Environment/atmosphere.hxx
+++ b/src/Environment/atmosphere.hxx
@@ -31,8 +31,6 @@
 #include <cmath>
 #include <utility>
 
-using namespace std;
-
 /**
  * Model the atmosphere in a way consistent with the laws
  * of physics.
diff --git a/src/Environment/environment_mgr.cxx b/src/Environment/environment_mgr.cxx
index 42023ea84..97c81b9b9 100644
--- a/src/Environment/environment_mgr.cxx
+++ b/src/Environment/environment_mgr.cxx
@@ -42,6 +42,7 @@
 #include "ridge_lift.hxx"
 #include "terrainsampler.hxx"
 #include "Airports/simple.hxx"
+#include "gravity.hxx"
 
 class SGSky;
 extern SGSky *thesky;
@@ -50,7 +51,7 @@ FGEnvironmentMgr::FGEnvironmentMgr () :
   _environment(new FGEnvironment()),
   fgClouds(new FGClouds()),
   _cloudLayersDirty(true),
-  _altitudeNode(fgGetNode("/position/altitude-ft", true)),
+  _altitude_n(fgGetNode("/position/altitude-ft", true)),
   _longitude_n(fgGetNode( "/position/longitude-deg", true )),
   _latitude_n( fgGetNode( "/position/latitude-deg", true )),
   _positionTimeToLive(0.0)
@@ -98,10 +99,11 @@ FGEnvironmentMgr::init ()
   SGSubsystemGroup::init();
   fgClouds->Init();
 
+  // FIXME: is this really part of the environment_mgr?
   // Initialize the longitude, latitude and altitude to the initial position
   // of the aircraft so that the atmospheric properties (pressure, temperature
   // and density) can be initialized accordingly.
-  _altitudeNode->setDoubleValue(fgGetDouble("/sim/presets/altitude-ft"));
+  _altitude_n->setDoubleValue(fgGetDouble("/sim/presets/altitude-ft"));
   _longitude_n->setDoubleValue(fgGetDouble("/sim/presets/longitude-deg"));
   _latitude_n->setDoubleValue(fgGetDouble("/sim/presets/latitude-deg"));
 }
@@ -201,7 +203,7 @@ FGEnvironmentMgr::update (double dt)
 {
   SGSubsystemGroup::update(dt);
 
-  _environment->set_elevation_ft( _altitudeNode->getDoubleValue() );
+  _environment->set_elevation_ft( _altitude_n->getDoubleValue() );
 
   simgear::Particles::setWindFrom( _environment->get_wind_from_heading_deg(),
                                    _environment->get_wind_speed_kt() );
@@ -210,6 +212,14 @@ FGEnvironmentMgr::update (double dt)
     fgClouds->set_update_event( fgClouds->get_update_event()+1 );
   }
 
+
+  fgSetDouble( "/environment/gravitational-acceleration-mps2", 
+    Environment::Gravity::instance()->getGravity(SGGeod::fromDegFt(
+      _longitude_n->getDoubleValue(),
+      _latitude_n->getDoubleValue(),
+      _altitude_n->getDoubleValue()
+  )));
+
   _positionTimeToLive -= dt;
   if( _positionTimeToLive <= 0.0 )
   {
diff --git a/src/Environment/environment_mgr.hxx b/src/Environment/environment_mgr.hxx
index 67d929ec8..18b1668bc 100644
--- a/src/Environment/environment_mgr.hxx
+++ b/src/Environment/environment_mgr.hxx
@@ -95,7 +95,7 @@ private:
   FGEnvironment * _environment;	// always the same, for now
   FGClouds *fgClouds;
   bool _cloudLayersDirty;
-  SGPropertyNode_ptr _altitudeNode;
+  SGPropertyNode_ptr _altitude_n;
   SGPropertyNode_ptr _longitude_n;
   SGPropertyNode_ptr _latitude_n;
   double _positionTimeToLive;
diff --git a/src/Environment/fgclouds.cxx b/src/Environment/fgclouds.cxx
index d5d9fbbc0..6cc4d49ef 100644
--- a/src/Environment/fgclouds.cxx
+++ b/src/Environment/fgclouds.cxx
@@ -45,6 +45,9 @@
 
 extern SGSky *thesky;
 
+static bool do_delete_3Dcloud (const SGPropertyNode *arg);
+static bool do_move_3Dcloud (const SGPropertyNode *arg);
+static bool do_add_3Dcloud (const SGPropertyNode *arg);
 
 FGClouds::FGClouds() :
 #if 0
@@ -158,7 +161,7 @@ double FGClouds::buildCloud(SGPropertyNode *cloud_def_root, SGPropertyNode *box_
 				y = w * (y - 0.5) + pos[1]; // E/W
 				z = h * z + pos[2]; // Up/Down. pos[2] is the cloudbase
 
-				SGVec3f newpos = SGVec3f(x, y, z);
+				//SGVec3f newpos = SGVec3f(x, y, z);
 				SGNewCloud cld = SGNewCloud(texture_root, cld_def);
 
 				//layer->addCloud(newpos, cld.genCloud());
diff --git a/src/Environment/fgclouds.hxx b/src/Environment/fgclouds.hxx
index 61ccaccfe..7eab7f128 100644
--- a/src/Environment/fgclouds.hxx
+++ b/src/Environment/fgclouds.hxx
@@ -64,9 +64,5 @@ public:
 
 };
 
-static bool do_delete_3Dcloud (const SGPropertyNode *arg);
-static bool do_move_3Dcloud (const SGPropertyNode *arg);
-static bool do_add_3Dcloud (const SGPropertyNode *arg);
-
 #endif // _FGCLOUDS_HXX
 
diff --git a/src/Environment/gravity.cxx b/src/Environment/gravity.cxx
new file mode 100644
index 000000000..cd32feeb4
--- /dev/null
+++ b/src/Environment/gravity.cxx
@@ -0,0 +1,88 @@
+// gravity.cxx -- interface for earth gravitational model
+//
+// Written by Torsten Dreyer, June 2011
+//
+// Copyright (C) 2011  Torsten Dreyer - torsten (at) t3r _dot_ de
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+
+#include "gravity.hxx"
+
+#include <simgear/structure/exception.hxx>
+
+namespace Environment {
+
+/*
+http://de.wikipedia.org/wiki/Normalschwereformel
+*/
+class Somigliana : public Gravity {
+public:
+    Somigliana();
+    virtual ~Somigliana();
+    virtual double getGravity( const SGGeod & position ) const;
+};
+
+Somigliana::Somigliana()
+{
+}
+
+Somigliana::~Somigliana()
+{
+}
+
+double Somigliana::getGravity( const SGGeod & position ) const
+{
+// Geodetic Reference System 1980 parameter
+#define A 6378137.0 // equatorial radius of earth
+#define B 6356752.3141 // semiminor axis
+#define AGA (A*9.7803267715) // A times normal gravity at equator
+#define BGB (B*9.8321863685) // B times normal gravity at pole
+  // forumla of Somigliana
+  double cosphi = ::cos(position.getLatitudeRad());
+  double cos2phi = cosphi*cosphi;
+  double sinphi = ::sin(position.getLatitudeRad());
+  double sin2phi = sinphi*sinphi;
+  double g0 = (AGA * cos2phi + BGB * sin2phi) / sqrt( A*A*cos2phi+B*B*sin2phi );
+
+  static const double k1 = 3.15704e-7;
+  static const double k2 = 2.10269e-9;
+  static const double k3 = 7.37452e-14;
+
+  double h = position.getElevationM();
+  
+  return g0*(1-(k1-k2*sin2phi)*h+k3*h*h);
+}
+
+static Somigliana _somigliana;
+
+/* --------------------- Gravity implementation --------------------- */
+Gravity * Gravity::_instance = NULL;
+
+Gravity::~Gravity()
+{
+}
+
+//double Gravity::getGravity( const SGGeoc & position ) = 0;
+
+const Gravity * Gravity::instance()
+{
+    if( _instance == NULL )
+        _instance = &_somigliana;
+
+    return _instance;
+}
+    
+} // namespace
diff --git a/src/Environment/gravity.hxx b/src/Environment/gravity.hxx
new file mode 100644
index 000000000..d99ca1867
--- /dev/null
+++ b/src/Environment/gravity.hxx
@@ -0,0 +1,43 @@
+// gravity.hxx -- interface for earth gravitational model
+//
+// Written by Torsten Dreyer, June 2011
+//
+// Copyright (C) 2011  Torsten Dreyer - torsten (at) t3r _dot_ de
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+
+#ifndef __GRAVITY_HXX
+#define __GRAVITY_HXX
+
+#include <simgear/math/SGMath.hxx>
+
+namespace Environment {
+
+class Gravity 
+{
+public:
+    virtual ~Gravity();
+    virtual double getGravity( const SGGeod & position ) const = 0;
+
+    const static Gravity * instance();
+
+private:
+    static Gravity * _instance;
+    
+};
+
+} // namespace
+#endif // __GRAVITY_HXX
diff --git a/src/Environment/metarproperties.cxx b/src/Environment/metarproperties.cxx
index 171d716af..11971f08c 100644
--- a/src/Environment/metarproperties.cxx
+++ b/src/Environment/metarproperties.cxx
@@ -301,9 +301,6 @@ void MetarProperties::set_metar( const char * metar )
         }
     }
 
-    vector<SGMetarCloud> cv = m->getClouds();
-    vector<SGMetarCloud>::const_iterator cloud, cloud_end = cv.end();
-
     {
         static const char * LAYER = "layer";
         SGPropertyNode_ptr cloudsNode = _rootNode->getNode("clouds", true );
diff --git a/src/Environment/terrainsampler.cxx b/src/Environment/terrainsampler.cxx
index 0d08af84e..293eb2c86 100644
--- a/src/Environment/terrainsampler.cxx
+++ b/src/Environment/terrainsampler.cxx
@@ -285,6 +285,7 @@ void AreaSampler::analyse()
         }
     }
 
+/*
     double alt_low_min = 0.0;
     double n_max = 0.0;
     sum = 0.0;
@@ -296,7 +297,7 @@ void AreaSampler::analyse()
             break;
         }
     }
-
+*/
     _altLayered = 0.5 * (_altMin + _altOffset);
 
 #if 0