# given a location and zoom, return a short string representing it.
def self.encode(lon, lat, z)
code = interleave_bits(((lon + 180.0) * 2**32 / 360.0).to_i,
# given a location and zoom, return a short string representing it.
def self.encode(lon, lat, z)
code = interleave_bits(((lon + 180.0) * 2**32 / 360.0).to_i,