I don't know either. My guess is that's for very laze search mechanism. It's especially useful for geohash, so you can look for other pictures in the same small / wide area.

Maybe less so for lat/lon.
https://www.pubnub.com/guides/what-is-geohashing/ 

 I might modify the script to only do incrementally sized geohash and just have a single lat/lon coordinate.