utils.py

#!/usr/bin/env python
# -*- coding:utf-8 -*-


# reference: https://github.com/vinsci/geohash
def geohash_encode(latitude, longitude, precision=12):
    """
    Encode a position given in float arguments latitude, longitude to
    a geohash which will have the character count precision.
    """
    lat_interval, lon_interval = (-90.0, 90.0), (-180.0, 180.0)
    base32 = '0123456789bcdefghjkmnpqrstuvwxyz'
    geohash = []
    bits = [16, 8, 4, 2, 1]
    bit = 0
    ch = 0
    even = True
    while len(geohash) < precision:
        if even:
            mid = (lon_interval[0] + lon_interval[1]) / 2
            if longitude > mid:
                ch |= bits[bit]
                lon_interval = (mid, lon_interval[1])
            else:
                lon_interval = (lon_interval[0], mid)
        else:
            mid = (lat_interval[0] + lat_interval[1]) / 2
            if latitude > mid:
                ch |= bits[bit]
                lat_interval = (mid, lat_interval[1])
            else:
                lat_interval = (lat_interval[0], mid)
        even = not even
        if bit < 4:
            bit += 1
        else:
            geohash += base32[ch]
            bit = 0
            ch = 0
    return ''.join(geohash)