'Initializes the Google Zoom object.'

def __init__(self, num_zoom=19, tilesize=256):

    self._tilesize = tilesize
    self._nzoom = num_zoom
    self._degpp = []
    self._radpp = []
    self._npix = []
    z = tilesize
    for i in xrange(num_zoom):
        self._degpp.append((z / 360.0))
        self._radpp.append((z / (2 * pi)))
        self._npix.append((z / 2))
        z *= 2
