ADD: new track message, Entity class and Position class

libs/geographiclib/wrapper/c/cgeoid.cpp

@@ -0,0 +1,14 @@
+#include "cgeoid.h"
+#include "GeographicLib/Geoid.hpp"
+
+extern "C"
+double HeightAboveEllipsoid(double lat, double lon, double h) {
+  try {
+    // Declare static so that g is only constructed once
+    static const GeographicLib::Geoid g("egm2008-1");
+    return h + GeographicLib::Geoid::GEOIDTOELLIPSOID * g(lat, lon);
+  }
+  catch (...) {
+    return GeographicLib::Math::NaN();
+  }
+}