Faster Compressed Quadtrees
  Real-world point sets tend to be clustered, so using a machine word for each point is wasteful. In this paper we first show how a compact representation of quadtrees using $\Oh{1}$ bits per node can break this bound on clustered point sets, while offering efficient range searches. We then describe a new compact quadtree representation based on heavy path decompositions, which supports queries faster than previous compact structures. We present experimental evidence showing that our structure is competitive in practice. 
Guillermo de Bernardo, Travis Gagie, Susana Ladra, Gonzalo Navarro and   Diego Seco
cs.DS