the algorithm works this way: The geolocation acquired by the webpage is in the form of latitude and longitude. Let's say it is lat: 10.123456, long: 30.123456

I want to approximate it to 3 mile accuracy (diagonal of a box, so in one dimension, would be sqrt(3^2 /2) = 2.12 mile in lat or long). 3 mile, in geographical coordinate would be equivalent to : 3 mile / 3960 mile (Earth radius) * 180 deg / pi rad = 0.0434 degree. I divide each dimension by 0.0434, and round it to a whole number (essentially, mod 0.0434). Then, I multiply that number by 0.0434 and save that as the location.

This means that a user's location can lie anywhere inside a box with 3 mile diagonal length at that geolocation.

If you see inconsistency in my logic, please let me know.