is there any convenient API in JTS that would help to

  • find two most distant points in line
  • find two most distant points in polygon
up vote 4 down vote accepted

I think all of the JTS methods relating to distance are looking for the nearest or shortest. But providing you don't have too many vertices then you could do a brute force O(N*N) search:

GeometryFactory gf = new GeometryFactory();
double maxDist = 0;
Point start = null, end = null;
for (Coordinate c : geom.getCoordinates()) {
  Point p = gf.createPoint(c);
  for (Coordinate c2 : geom.getCoordinates()) {
    Point p2 = gf.createPoint(c2);
    double d = DistanceOp.distance(p, p2);
    if (d > maxDist) {
      maxDist = d;
      start = p;
      end = p2;
    }
  }
} 

And if you need to consider points along the lines then add

geom = Densifier.densify(geom, .01);

before you start, though obviously this pushes N up.

enter image description here

  • Thanks @Ian! I had a hope I don't have to do it. – Sergey Oct 20 at 15:30

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