for (Map.Entry<CoordinateBounds, STRtree> entry : _treesByBounds.entrySet()) {
CoordinateBounds b = entry.getKey();
Envelope env = new Envelope(b.getMinLon(), b.getMaxLon(), b.getMinLat(),
b.getMaxLat());
STRtree tree = entry.getValue();
tree.build();
parentTree.insert(env, tree);
}
parentTree.build();
return new HierarchicalSTRtree<T>(parentTree);