Current GeoPointField LUCENE-6450 computes a set of ranges along the space-filling curve that represent a provided bounding box. This determines which terms to visit in the terms dictionary and which to skip. This is suboptimal for large bounding boxes as we may end up visiting all terms (which could be quite large).
This incremental improvement is to improve GeoPointField to only visit high precision terms in boundary ranges and use the postings list for ranges that are completely within the target bounding box.
A separate improvement is to switch over to auto-prefix and build an Automaton representing the bounding box. That can be tracked in a separate issue.