Converting between 2 google map tile types

korakot (Korakot Chaovavanich) — Sat, 30 Jul 2005 13:11:40 GMT

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)

DZone Snippets: tile code

Converting between 2 google map tile types