private List <RefPoint> getRefPoints(Trajectory trj)
{
if (trj.Count == 0)
{
return(null);
}
List <RefPoint> refPoints = new List <RefPoint>();
for (int i = 0; i < trj.Count; ++i)
{
MotionVector mv = trj[i];
RefPoint refPoint = null;
if (mv.e != null)
{
double distance = mv.e.DistOnLine(mv.e.Start.Point, mv.point);
refPoint = new RefPoint(mv.t, mv.e, distance);
}
else
{
refPoint = new RefPoint(mv.t, mv.point);
}
refPoints.Add(refPoint);
}
// calcualte the deviation between trj and the ref points
//String tempFileName = Path.Combine(Constants.TRJ_DIR, "1000099465_short_ref");
//StreamWriter sw = new StreamWriter(tempFileName);
//for (int i = 0; i < trj.Count; ++i)
//{
// MotionVector mv = trj[i];
// double dev = GeoPoint.GetDistance(mv.point, refPoints[i].Point);
// sw.WriteLine("{0},{1},{2},{3},{4}", mv.t, mv.point.Lat, mv.point.Lng, mv.EdgeId, dev);
//}
//sw.Close();
return(refPoints);
}
/// <summary>
/// Original version of compress
/// The use of shortest path results in some drawbacks...
/// </summary>
/// <param name="trj"></param>
/// <returns></returns>
public VCompressedTrj Compress_v1(Trajectory trj)
{
if (trj.Count == 0)
{
return(null);
}
List <RefPoint> refPoints = getRefPoints(trj);
VCompressedTrj cTrj = new VCompressedTrj();
VCompressedTrj.Item item = new VCompressedTrj.Item();
double dist = 0, appDist = 0;
Edge lastEdge = refPoints[0].e;
item.RefPoint = refPoints[0];
for (int i = 1; i < refPoints.Count; ++i)
{
RefPoint cur = refPoints[i], prev = refPoints[i - 1];
double distance = 0.0, v = 0;
byte roundV = 0, si = (byte)(cur.t - prev.t);
if (cur.e == prev.e)
{
distance = cur.distance - prev.distance;
}
else if (cur.e.Start == prev.e.End)
{
distance = prev.e.Length - prev.distance + cur.distance;
}
else
{
distance = prev.e.Length - prev.distance;
var path = _g.FindPath(prev.e.End, cur.e.Start);
foreach (var e in path)
{
distance += e.Length;
}
distance += cur.distance;
}
v = distance / si;
roundV = (byte)(Math.Round(v) / _binSize);
dist += distance;
appDist += roundV * si * _binSize;
if (Math.Abs(dist - appDist) >= _maxDev)
{
// insert the reference point
cTrj.Items.Add(item);
// clear
item = new VCompressedTrj.Item();
item.RefPoint = cur;
dist = 0;
appDist = 0;
}
else
{
item.Points.Add(new VCompressedMV(si, cur.eid, roundV));
}
}
cTrj.Items.Add(item);
return(cTrj);
}
