ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-NearestNeighbor.cpp

@@ -0,0 +1,140 @@
+// Example of using the GeographicLib::NearestNeighbor class.  WARNING: this
+// creates a file, pointset.xml or pointset.txt, in the current directory.
+// Read lat/lon locations from locations.txt and lat/lon queries from
+// queries.txt.  For each query print to standard output: the index for the
+// closest location and the distance to it.  Print statistics to standard error
+// at the end.
+
+#include <iostream>
+#include <exception>
+#include <vector>
+#include <fstream>
+#include <string>
+
+#if !defined(GEOGRAPHICLIB_HAVE_BOOST_SERIALIZATION)
+#define GEOGRAPHICLIB_HAVE_BOOST_SERIALIZATION 0
+#endif
+
+#if GEOGRAPHICLIB_HAVE_BOOST_SERIALIZATION
+// If Boost serialization is available, use it.
+#include <boost/archive/xml_iarchive.hpp>
+#include <boost/archive/xml_oarchive.hpp>
+#endif
+
+#include <GeographicLib/NearestNeighbor.hpp>
+#include <GeographicLib/Geodesic.hpp>
+#include <GeographicLib/DMS.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+// A structure to hold a geographic coordinate.
+struct pos {
+  double _lat, _lon;
+  pos(double lat = 0, double lon = 0) : _lat(lat), _lon(lon) {}
+};
+
+// A class to compute the distance between 2 positions.
+class DistanceCalculator {
+private:
+  Geodesic _geod;
+public:
+  explicit DistanceCalculator(const Geodesic& geod) : _geod(geod) {}
+  double operator() (const pos& a, const pos& b) const {
+    double d;
+    _geod.Inverse(a._lat, a._lon, b._lat, b._lon, d);
+    if ( !(d >= 0) )
+      // Catch illegal positions which result in d = NaN
+      throw GeographicErr("distance doesn't satisfy d >= 0");
+    return d;
+  }
+};
+
+int main() {
+  try {
+    // Read in locations
+    vector<pos> locs;
+    double lat, lon;
+    string sa, sb;
+    {
+      ifstream is("locations.txt");
+      if (!is.good())
+        throw GeographicErr("locations.txt not readable");
+      while (is >> sa >> sb) {
+        DMS::DecodeLatLon(sa, sb, lat, lon);
+        locs.push_back(pos(lat, lon));
+      }
+      if (locs.size() == 0)
+        throw GeographicErr("need at least one location");
+    }
+
+    // Define a distance function object
+    DistanceCalculator distance(Geodesic::WGS84());
+
+    // Create NearestNeighbor object
+    NearestNeighbor<double, pos, DistanceCalculator> pointset;
+
+    {
+      // Used saved object if it is available
+#if GEOGRAPHICLIB_HAVE_BOOST_SERIALIZATION
+      ifstream is("pointset.xml");
+      if (is.good()) {
+        boost::archive::xml_iarchive ia(is);
+        ia >> BOOST_SERIALIZATION_NVP(pointset);
+      }
+#else
+      ifstream is("pointset.txt");
+      if (is.good())
+        is >> pointset;
+#endif
+    }
+    // Is the saved pointset up-to-date?
+    if (pointset.NumPoints() != int(locs.size())) {
+      // else initialize it
+      pointset.Initialize(locs, distance);
+      // and save it
+#if GEOGRAPHICLIB_HAVE_BOOST_SERIALIZATION
+      ofstream os("pointset.xml");
+      if (!os.good())
+        throw GeographicErr("cannot write to pointset.xml");
+      boost::archive::xml_oarchive oa(os);
+      oa << BOOST_SERIALIZATION_NVP(pointset);
+#else
+      ofstream os("pointset.txt");
+      if (!os.good())
+        throw GeographicErr("cannot write to pointset.txt");
+      os << pointset << "\n";
+#endif
+    }
+
+    ifstream is("queries.txt");
+    double d;
+    int count = 0;
+    vector<int> k;
+    while (is >> sa >> sb) {
+      ++count;
+      DMS::DecodeLatLon(sa, sb, lat, lon);
+      d = pointset.Search(locs, distance, pos(lat, lon), k);
+      if (k.size() != 1)
+          throw GeographicErr("unexpected number of results");
+      cout << k[0] << " " << d << "\n";
+    }
+    int setupcost, numsearches, searchcost, mincost, maxcost;
+    double mean, sd;
+    pointset.Statistics(setupcost, numsearches, searchcost,
+                        mincost, maxcost, mean, sd);
+    int
+      totcost = setupcost + searchcost,
+      exhaustivecost = count * pointset.NumPoints();
+    cerr
+      << "Number of distance calculations = " << totcost << "\n"
+      << "With an exhaustive search = " << exhaustivecost << "\n"
+      << "Ratio = " << double(totcost) / exhaustivecost << "\n"
+      << "Efficiency improvement = "
+      << 100 * (1 - double(totcost) / exhaustivecost) << "%\n";
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}