/// <summary>
/// Get initial candidates, i.e., adjacent vertices
/// </summary>
/// <param name="head"></param>
/// <param name="openTable"></param>
/// <param name="currentIdx"></param>
/// <returns>the currentIdx, larger than or equal to the given value</returns>
private int getInitialCands(SortedSet <TrjTreeNode> openTable, int currentIdx)
{
double baseDist = GPS_ERROR_DISTANCE;
bool initialVertexFound = false;
int trjCount = trj.Count;
while (openTable.Count == 0 && currentIdx < trjCount - 1)
{
GeoPoint currentPoint = trj[currentIdx].point;
GeoPoint anotherPoint = trj[currentIdx + 1].point;
HashSet <Vertex> currentVertices = graph.VertexRangeQuery(currentPoint, baseDist);
foreach (Vertex v in currentVertices)
{
double tmpDist = Polyline.DistFrom(currentPoint, anotherPoint, v.Point);
if (tmpDist <= baseDist)
{
TrjTreeNode node = new TrjTreeNode()
{
v = v,
path = null,
parent = null,
idx = currentIdx,
score = 0
};
initialVertexFound = true;
openTable.Add(node);
}
}
if (!initialVertexFound)
{
currentIdx++;
}
}
return(currentIdx);
}
public override RoadNetwork.Trajectory match(RoadNetwork.Trajectory trajectory)
{
this.trj = trajectory;
double cellSize = 50;
GridTrj trjIndex = new GridTrj(trj, cellSize);
SortedSet <TrjTreeNode> openTable = new SortedSet <TrjTreeNode>(new TrjTreeNodeComparer());
List <TrjTreeNode> closeTable = new List <TrjTreeNode>();
int trjCount = trj.Count;
int currentIdx = 0;
while (currentIdx < trjCount - 1)
{
//1. get initial candidates
if (openTable.Count == 0)
{
currentIdx = getInitialCands(openTable, currentIdx);
}
//2. Create candidate paths
TrjTreeNode currentNode = null;
while (openTable.Count > 0)
{
Debug.Assert(currentIdx < trjCount);
//2.1.get the first node
currentNode = openTable.Min;
openTable.Remove(currentNode);
closeTable.Add(currentNode);
//2.2. create candidate paths
List <TrjTreeNode> cands = createCands(trjIndex, currentNode);
foreach (var cand in cands)
{
//2.3. check parallel paths
if (openTable.Contains(cand))
{
var tempCand = openTable.Where((n) => n == cand);
Trace.Assert(tempCand.Count() == 1, "More than two parallel paths were found!");
TrjTreeNode bestCand = getBestPath(cand, tempCand.First());
openTable.Add(bestCand);
}
else
{
openTable.Add(cand);
}
}
//2.3 prune and confirm
if (openTable.Count > 3)
{
openTable = pruneConfirm(openTable);
}
currentIdx = currentNode.idx + 1; //for breaking the loop
}
}
//3. Get the matched result
Trajectory newTrj = getMatchedResult(closeTable);
return(newTrj);
}
/// <summary>
/// Build paths within the error ellipse
/// </summary>
/// <param name="currentNode"></param>
/// <returns></returns>
private List <EdgePath> buildPath(TrjTreeNode currentNode)
{
Vertex startV = currentNode.v;
int predIdx = currentNode.idx;
int currentIdx = currentNode.idx + 1;
GeoPoint currentPoint = trj[currentIdx].point;
GeoPoint nextPoint = trj[currentIdx + 1].point;
int interval = (int)(trj[currentIdx + 1].t - trj[currentIdx].t);
double maxSpeed = Constants.MAX_SPEED;
Queue <EdgePath> rawCandidatePaths = new Queue <EdgePath>();
List <EdgePath> candidatePaths = new List <EdgePath>();
//define the maximum allowed distance, i.e., the 2c of the error ellipse
double maxDistance = Math.Min(interval * maxSpeed, Math.Max(GeoPoint.GetDistance(currentPoint, nextPoint) * 2, GeoPoint.GetDistance(currentPoint, nextPoint) + GPS_ERROR_DISTANCE));
//get initial candidate
if (currentNode.path != null && currentNode.path.Count > 0)
{
rawCandidatePaths.Enqueue(new EdgePath()
{
currentNode.path.LastEdge
});
}
else
{
Trace.Assert(currentNode.v.InEdges.Count > 0);
//Choose the first element of the InEdges
EdgePath path = new EdgePath(currentNode.v);
rawCandidatePaths.Enqueue(path);
}
while (rawCandidatePaths.Count > 0)
{
EdgePath path = rawCandidatePaths.Dequeue();
//extend it
foreach (Edge e in path.End.OutEdges)
{
if (path.Contains(e.End)) //avoid duplicate vertices
{
continue;
}
EdgePath newPath = new EdgePath(path);
newPath.Add(e);
GeoPoint p = e.End.Point;
GeoPoint result;
int projectType = e.projectFrom(nextPoint, out result);
double distance = GeoPoint.GetDistance(result, nextPoint);
if (projectType == 0 && distance < GPS_ERROR_DISTANCE)
{
candidatePaths.Add(newPath);
}
else if (GeoPoint.GetDistance(p, currentPoint) + GeoPoint.GetDistance(p, nextPoint) < maxDistance)
{
//need further extension
rawCandidatePaths.Enqueue(newPath);
}
}
}
return(candidatePaths);
}
/// <summary>
/// Choose the best path from the two parallel paths by considering the cost similarity <br/>
/// However, if the speed limit information is not available, only the distance and difference between the trajectory and the real path will be used.
/// </summary>
/// <param name="cand"></param>
/// <param name="tempCand"></param>
/// <returns></returns>
private TrjTreeNode getBestPath(TrjTreeNode cand, TrjTreeNode tempCand)
{
//1. get lowest common ancestor
//2. get the two paths
//3. evaluate the two paths
return(cand);
}
/// <summary>
/// Create candidate paths
/// </summary>
/// <param name="trjIndex"></param>
/// <param name="currentNode"></param>
/// <returns></returns>
private List <TrjTreeNode> createCands(GridTrj trjIndex, TrjTreeNode currentNode)
{
//1.get candidate paths for the current node
List <EdgePath> paths = buildPath(currentNode);
List <TrjTreeNode> cands = new List <TrjTreeNode>();
List <EdgePath> newPaths = new List <EdgePath>();
double baseDist = GPS_ERROR_DISTANCE;
int currentIdx = currentNode.idx;
//2.find the trajectory point near the end vertex of the path
foreach (EdgePath path in paths)
{
GeoPoint endPoint = path.End.Point;
HashSet <int> idxs = trjIndex.RangeQuery(endPoint, baseDist);
if (idxs.Count > 0)
{
double minDist = baseDist;
int bestIdx = -1;
foreach (int idx in idxs)
{
if (idx >= currentIdx)
{
//Filter by real distance
double distance = Polyline.DistFrom(trj[idx].point, trj[idx + 1].point, endPoint);
if (distance <= minDist)
{
minDist = distance;
bestIdx = idx;
}
}
}
if (bestIdx >= 0)
{
//Create new node
TrjTreeNode node = new TrjTreeNode(currentNode);
node.idx = bestIdx;
node.path = path;
node.v = path.End;
cands.Add(node);
}
}
}
return(cands);
}