Converting Between 2 Google Map Tile Types

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        Google maps is a marvelous app.
I try to program a prototype of it on pys60
http://bigbold.com/snippets/posts/show/458

There I only show the default map, not the satellite images.
Retrieving a different mode isn't that difficult.
I read the info from here
http://intepid.com/2005-07-17/21.50/
Then I begin comparing the 2 tile types of the same area
(around California)
http://mt.google.com/mt?v=w2.5&x=20&y=49&zoom=10 (map)
http://kh.google.com/kh?v=3&t=tqtsqrqt (satellite)

Here's the conversion routine between x,y,zoom and quadtree

def quadtree(x,y, zoom):
	out = []
	m = {(0,0):'q', (0,1):'t', (1,0):'r', (1,1):'s'}
	for i in range(17-zoom):
		x, rx = divmod(x, 2)
		y, ry = divmod(y, 2)
		out.insert(0, m[(rx,ry)])
	return 't' + ''.join(out)

Then to convert back

def xyzoom(quad):
	x, y, z = 0, 0, 17
	m = {'q':(0,0), 't':(0,1), 'r':(1,0), 's':(1,1)}
 	for c in quad[1:]:
		x = x*2 + m[c][0]
		y = y*2 + m[c][1]
		z -= 1
	return x, y, z

Using them is simple

>>> quadtree(20,49,10)
'tqtsqrqt'
>>> xyzoom('tqtsqrqt')
(20, 49, 10)
>>> sat_url = 'http://kh.google.com/kh?v=3&t=' + quadtree(20,49,10)

Tags:
• conversion
• Google
• map
• Python
• tile