STRtree implementation output contains random points

Question

I'm using JTS with Netbeans to implement STRtrees . I'm trying to build an STRtree for a set of points( coordinates ) . Here is my code :

package example;

import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Envelope;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.index.ArrayListVisitor;
import com.vividsolutions.jts.index.strtree.STRtree;
import java.util.List;

public class Example {


public static void main(String[] args) {
    //Getting input from the user as points

    GeometryFactory gf = new GeometryFactory();
    Coordinate coord = new Coordinate( 1, 1 );
    Point point=gf.createPoint( coord );
     coord = new Coordinate( 3,2 );
    Point point2=gf.createPoint( coord );
    coord = new Coordinate( 2,4 );
    Point point3=gf.createPoint( coord );
     coord = new Coordinate( 4,1 );
    Point point4=gf.createPoint( coord );
     coord = new Coordinate( 5,2);
    Point point5=gf.createPoint( coord );
     coord = new Coordinate( 4,5);
    Point point6=gf.createPoint( coord );
    coord = new Coordinate( 3,6 );
    Point point7=gf.createPoint( coord );
     coord = new Coordinate( 1,6 );
    Point point8=gf.createPoint( coord );
     coord = new Coordinate( 6,2 );
    Point point9=gf.createPoint( coord );
     coord = new Coordinate( 7,1 );
    Point point10=gf.createPoint( coord );
    coord = new Coordinate( 6,4 );
    Point point11=gf.createPoint( coord );
     coord = new Coordinate( 9,2);
    Point point12=gf.createPoint( coord );
    coord = new Coordinate( 3,8);
    Point point13=gf.createPoint( coord );
     coord = new Coordinate( 1,7);
    Point point14=gf.createPoint( coord );
    coord = new Coordinate( 3,7 );
    Point point15=gf.createPoint( coord );
     coord = new Coordinate( 5,7 );
    Point point16=gf.createPoint( coord );
    //Building the str object
    STRtree strTree=new STRtree();
    //inserting the points into the tree
    strTree.insert(point.getEnvelopeInternal(), point);
    strTree.insert(point2.getEnvelopeInternal(), point2);
    strTree.insert(point3.getEnvelopeInternal(), point3);
     strTree.insert(point4.getEnvelopeInternal(), point4);
    strTree.insert(point5.getEnvelopeInternal(), point5);
    strTree.insert(point6.getEnvelopeInternal(), point6);
     strTree.insert(point7.getEnvelopeInternal(), point7);
    strTree.insert(point8.getEnvelopeInternal(), point8);
    strTree.insert(point9.getEnvelopeInternal(), point9);
     strTree.insert(point10.getEnvelopeInternal(), point10);
    strTree.insert(point11.getEnvelopeInternal(), point11);
    strTree.insert(point12.getEnvelopeInternal(), point12);
     strTree.insert(point13.getEnvelopeInternal(), point13);
    strTree.insert(point14.getEnvelopeInternal(), point14);
    strTree.insert(point15.getEnvelopeInternal(), point15);
    strTree.insert(point16.getEnvelopeInternal(), point16);
    //Building the tree
    strTree.build();
    Coordinate coord2 = new Coordinate( 0,0 );
    Coordinate coord3 = new Coordinate( 5,5);
     Envelope e1=new Envelope(coord2,coord3);
     List List1 = strTree.query(e1);
     System.out.println(List1);
}
}

The code complies and runs, but I was expecting the points to get sorted in this order( roots->children->leaves ) . But my output contains random points in the enveloped region. Where did I go wrong?

Answer 1

The R-tree stores all points in the leaf nodes.

The "order" that you are looking for does not exist; all results must be from the leaves.

The JTS API looks like it's painfully expensive. Coordinates wrapped in Points wrapped in Envelopes. You may want to have a look at ELKI, which I found to have very high performance. In contrast to popular belief, I have found ELKI R-trees (at least when STR bulk loaded) to still work very well in 32 dimensions (popular knowledge claims that R-trees only work up to 10 dimensions).