ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-LocalCartesian.cpp

@@ -0,0 +1,37 @@
+// Example of using the GeographicLib::LocalCartesian class
+
+#include <iostream>
+#include <exception>
+#include <cmath>
+#include <GeographicLib/Geocentric.hpp>
+#include <GeographicLib/LocalCartesian.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+int main() {
+  try {
+    Geocentric earth(Constants::WGS84_a(), Constants::WGS84_f());
+    // Alternatively: const Geocentric& earth = Geocentric::WGS84();
+    const double lat0 = 48 + 50/60.0, lon0 = 2 + 20/60.0; // Paris
+    LocalCartesian proj(lat0, lon0, 0, earth);
+    {
+      // Sample forward calculation
+      double lat = 50.9, lon = 1.8, h = 0; // Calais
+      double x, y, z;
+      proj.Forward(lat, lon, h, x, y, z);
+      cout << x << " " << y << " " << z << "\n";
+    }
+    {
+      // Sample reverse calculation
+      double x = -38e3, y = 230e3, z = -4e3;
+      double lat, lon, h;
+      proj.Reverse(x, y, z, lat, lon, h);
+      cout << lat << " " << lon << " " << h << "\n";
+    }
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}