public List<T> getWithin(Point point, double threshold) {
    build();
    Coordinate coord = point.getCoordinate();
    // pre-filter by rectangular envelope
    Envelope envelope = point.getEnvelopeInternal();
    envelope.expandBy(threshold);
    List<?> items = index.query(envelope);
    List<T> result = new ArrayList<>(items.size());
    // then post-filter by circular radius
    for (Object item : items) {
      if (item instanceof GeomWithData<?> value) {
        double distance = value.coord.distance(coord);
        if (distance <= threshold) {
          @SuppressWarnings("unchecked") T t = (T) value.data;
          result.add(t);
        }
      }
    }
    return result;
  }
Returns the data associated with all indexed points within a radius from {@code point}.
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/PointIndex.java