Map Data Pre-process(2)

The following several blogs will talk about how to extract map data from Google map server. Currently I have found there are two methods to download map pictures from Google map server, but some request parameters I am still not very sure about it. Hope later I can find out.
Method 1:
http://mt1.google.com/mt?n=404&v=w2.52&x=111&y=76&zoom=10

Where mt0, mt1, mt2, mt3.google.com are the servers provides the same services, I assume Google uses the 4 server to balance the server load.

n=404&v=w2.52 ,don’t know the exact meaning, but it looks it keeps the same for all request.

X=111, y=76 are the column and row index of the map picture, Google divides the map into a serial of 256X256 tiles.
Zoom=10 ,zoom level
http://mt1.google.com/mt?n=404&v=w2.52&x=116627&y=73536&zoom=0

And it looks like x, y and zoom has some relations. Need to find out.

Method 2:
http://google.com/mapdata?latitude_e6=-31900000&longitude_e6=115900000&zm=1000&w=256&h=288&cc=US

latitude_e6 and longitude_e6 specify the longitude and latitude of the upper left corner of the map picture.
Zoom gives the zoom level (in meters)
w , h gives the width and height of the map picture.

All the URL gives the map picture, then it’s easy to write an application to download the map pictures automatically.