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src/Environment/gravity.hxx

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+// 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