ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-GeodesicLineExact.cpp

@@ -0,0 +1,49 @@
+// Example of using the GeographicLib::GeodesicLineExact class
+
+#include <iostream>
+#include <iomanip>
+#include <exception>
+#include <cmath>
+#include <GeographicLib/GeodesicExact.hpp>
+#include <GeographicLib/GeodesicLineExact.hpp>
+#include <GeographicLib/Constants.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+int main() {
+  try {
+    // Print waypoints between JFK and SIN
+    GeodesicExact geod(Constants::WGS84_a(), Constants::WGS84_f());
+    // Alternatively: const GeodesicExact& geod = GeodesicExact::WGS84();
+    double
+      lat1 = 40.640, lon1 = -73.779, // JFK
+      lat2 =  1.359, lon2 = 103.989; // SIN
+    GeodesicLineExact line = geod.InverseLine(lat1, lon1, lat2, lon2);
+    double ds0 = 500e3;             // Nominal distance between points = 500 km
+    int num = int(ceil(line.Distance() / ds0)); // The number of intervals
+    cout << fixed << setprecision(3);
+    {
+      // Use intervals of equal length
+      double ds = line.Distance() / num;
+      for (int i = 0; i <= num; ++i) {
+        double lat, lon;
+       line.Position(i * ds, lat, lon);
+       cout << i << " " << lat << " " << lon << "\n";
+      }
+    }
+    {
+      // Slightly faster, use intervals of equal arc length
+      double da = line.Arc() / num;
+      for (int i = 0; i <= num; ++i) {
+        double lat, lon;
+       line.ArcPosition(i * da, lat, lon);
+       cout << i << " " << lat << " " << lon << "\n";
+      }
+    }
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}