C# QuadTreeLib example for indexing and querying point items

In GIS, quad trees are usually used for spatial indexing of geographical features. I found this great C# QuadTree Implementation (QuadTreeLib) library project at http://blog.bluetoque.ca/products/quadtree/. The library project comes with an example of indexing rectangles but not for points. So I thought of posting a simple example for points. In this example, the points in a LiDAR LAS file is read and spatially indexed using this library.

//include these name spaces

using System.Drawing;

using QuadTreeLib;

//Implement the QuadTreeLib's IHasPoint interface as my own class e.g. PointItem.

class PointItem : QuadTreeLib.IHasPoint

{

private PointF _point;

private uint _seq;

public PointF Point

{

get { return _point; }

}

public uint Seq

{

get { return _seq; }

}

public PointItem(double x, double y,uint seq)

{

PointF p = new PointF((float)x, (float)y);

_point = p;

_seq = seq;

}

}

//...etc...

//Declare and initialize the PointQuadTree for storing PointItem classes

private PointQuadTree<PointItem> quadTree = null;

static void Main(string[] args)

{    

//...etc...

LASReader reader = new LASReader(@"C:\Temp\myfile.las");

LASHeader header = reader.GetHeader().Copy();

//Create a rectangle encompassing the dataset bounds

System.Drawing.RectangleF lasRect = new System.Drawing.RectangleF((float)header.GetMinX(), (float)header.GetMinY(), (float)(header.GetMaxX()-header.GetMinX()),(float)(header.GetMaxY()-header.GetMinY()));

//Create the PointQuadTree class

quadTree = new PointQuadTree<PointItem>(lasRect);

//Populate the quad tree with the points from the LiDAR file

uint counter = 0;

while (reader.GetNextPoint())

{

counter++;

LASPoint lasPnt = reader.GetPoint().Copy();

PointItem p = new PointItem(lasPnt.X, lasPnt.Y, counter);

quadTree.Insert(p);

lasPnt.Dispose();

}

header.Dispose();

reader.Dispose();

//Define a query window bounds

double xlo = 0;

double xhi = 100000;

double ylo = 0;

double yhi = 200000;

//Query the quad tree and get the points within the window

ArrayList candidates = GetCandidates(xlo, ylo, xhi, yhi);

}

public ArrayList GetCandidates(double xlo, double ylo, double xhi, double yhi)

{

ArrayList candidates = new ArrayList();

RectangleF window = new RectangleF((float)xlo, (float)ylo, (float) (xhi - xlo), (float) (yhi - ylo));

//Call the PointQuadTree's Query method to find all the points within the window

List<PointItem> list = quadTree.Query(window);

for (int i = 0; i < list.Count; i++)

{

PointItem p = (PointItem) list[i];

candidates.Add(p.Seq);

}

return candidates;

}