ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-Rhumb.cpp

@@ -0,0 +1,36 @@
+// Example of using the GeographicLib::Rhumb class
+
+#include <iostream>
+#include <exception>
+#include <GeographicLib/Rhumb.hpp>
+#include <GeographicLib/Constants.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+int main() {
+  try {
+    Rhumb rhumb(Constants::WGS84_a(), Constants::WGS84_f());
+    // Alternatively: const Rhumb& rhumb = Rhumb::WGS84();
+    {
+      // Sample direct calculation, travelling about NE from JFK
+      double lat1 = 40.6, lon1 = -73.8, s12 = 5.5e6, azi12 = 51;
+      double lat2, lon2;
+      rhumb.Direct(lat1, lon1, azi12, s12, lat2, lon2);
+      cout << lat2 << " " << lon2 << "\n";
+    }
+    {
+      // Sample inverse calculation, JFK to LHR
+      double
+        lat1 = 40.6, lon1 = -73.8, // JFK Airport
+        lat2 = 51.6, lon2 = -0.5;  // LHR Airport
+      double s12, azi12;
+      rhumb.Inverse(lat1, lon1, lat2, lon2, s12, azi12);
+      cout << s12 << " " << azi12 << "\n";
+    }
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}