lulu

https://github.com/gene-ressler/lulu

Lulu merges the closest overlapping pair of map markers into a one whose area is the sum of the original two, located at their centroid. It repeats this until no overlaps remain. Some interesting data structures make this quite fast for all but pathologically bad data. Markers can be circles or squares. The user may provide a scale factor allowing the marker radius to have a different scale than distance between markers.