An Entropy Maximizing Geohash for Distributed Spatiotemporal Database Indexing

Abstract

We present a modification of the standard geohash algorithm based on maximum entropy encoding in which the data volume is approximately constant for a given hash prefix length. Distributed spatiotemporal databases, which typically require interleaving spatial and temporal elements into a single key, reap large benefits from a balanced geohash by creating a consistent ratio between spatial and temporal precision even across areas of varying data density. This property is also useful for indexing purely spatial datasets, where the load distribution of large range scans is an important aspect of query performance. We apply our algorithm to data generated proportional to population as given by census block population counts provided from the US Census Bureau.