ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-OSGB.cpp

@@ -0,0 +1,44 @@
+// Example of using the GeographicLib::OSGB class
+
+#include <iostream>
+#include <iomanip>
+#include <exception>
+#include <string>
+#include <GeographicLib/OSGB.hpp>
+#include <GeographicLib/DMS.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+int main() {
+  try {
+    {
+      // Sample forward calculation from
+      // A guide to coordinate systems in Great Britain
+      double
+        lat = DMS::Decode(52,39,27.2531),
+        lon = DMS::Decode( 1,43, 4.5177);
+      double x, y;
+      OSGB::Forward(lat, lon, x, y);
+      string gridref;
+      OSGB::GridReference(x, y, 2, gridref);
+      cout << fixed << setprecision(3)
+           << x << " " << y << " " << gridref << "\n";
+    }
+    {
+      // Sample reverse calculation
+      string gridref = "TG5113";
+      double x, y;
+      int prec;
+      OSGB::GridReference(gridref, x, y, prec);
+      double lat, lon;
+      OSGB::Reverse(x, y, lat, lon);
+      cout << fixed << setprecision(8)
+           << prec << " " << lat << " " << lon << "\n";
+    }
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}