# File lib/pr_geohash.rb, line 37
  def encode(latitude, longitude, precision=12)
    latlng = [latitude, longitude]
    points = [[-90.0, 90.0], [-180.0, 180.0]]
    is_lng = 1
    (0...precision).map {
      ch = 0
      5.times do |bit|
        mid = (points[is_lng][0] + points[is_lng][1]) / 2
        points[is_lng][latlng[is_lng] > mid ? 0 : 1] = mid
        ch |=  BITS[bit] if latlng[is_lng] > mid
        is_lng ^= 1
      end
      BASE32[ch,1]
    }.join
  end