ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-PolarStereographic.cpp

@@ -0,0 +1,37 @@
+// Example of using the GeographicLib::PolarStereographic class
+
+#include <iostream>
+#include <iomanip>
+#include <exception>
+#include <GeographicLib/PolarStereographic.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+int main() {
+  try {
+    PolarStereographic proj(Constants::WGS84_a(), Constants::WGS84_f(),
+                            Constants::UPS_k0());
+    // Alternatively:
+    // const PolarStereographic& proj = PolarStereographic::UPS();
+    bool northp = true;
+    {
+      // Sample forward calculation
+      double lat = 61.2, lon = -149.9; // Anchorage
+      double x, y;
+      proj.Forward(northp, lat, lon, x, y);
+      cout << x << " " << y << "\n";
+    }
+    {
+      // Sample reverse calculation
+      double x = -1637e3, y = 2824e3;
+      double lat, lon;
+      proj.Reverse(northp, x, y, lat, lon);
+      cout << lat << " " << lon << "\n";
+    }
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}