https://github.com/yinqiwen/ardb/wiki/Spatial-Index
https://en.wikipedia.org/wiki/Geohash
Based on the github for the Radius Meters 2500km and 626km, the HashBits length 8 and 12, however based on the wikipedia for 2500km and 630 km error, the lat bits lng bits 2 and 3, and 5 and 5.
16, 156544.7188
14, 313089.4375
**12, 626178.875**
10, 1252357.75
**8, 2504715.5**
6, 5009431
4, 10018863
why these two are different? more exactly how to calculate the HashBits based on the Radius Meters, such as for Radius Meters 2500km ,why HashBits is 8 , and 626km why HashBits is 12, how these values 8 and 12 calculated ? or how to calculate the Radius Meters 2500km and 626km based on the HashBits length 8 and 12 ? any formula exists?
