I have built a spatial index structure that I am trying to compare with other existing spatial index structures. I have to either code (in Java) the same logic that PostGIS uses or find a java library that uses this logic (and I have been unable to find one).
PostGIS says that their spatial index structure is an R-tree on top of GiST.
I have read this post.
I have 3 questions:
1) What is the main difference between a regular R-tree and an R-tree on top of GiST?
2) Do you know any disk-based R-tree libraries in Java? The ones I have found are in-memory R-trees.
3) If I were to find an R-tree implementation (or write on my own), how difficult is it to make this implementation into an "R-tree on top of GiST"? I know how R-trees work.