Map Data Pre-process(3)

With the help of ethereal packet capturing, I analyzed the http request send to Google server.
http://mt1.google.com/mt?n=404&v=w2.52&x=841&y=608&zoom=7

Zoom can be value from -2 to 17 while for each zoom level, x, y can vary from 0 to 2 ^(17-zoom)-1

* Each tile is 256X256*4 = 256K, this is the maximum; normally a tile size is much less than 256K.

X is horizontal , Y is vertical , if using latitude/longitude X is 360。 , Y is 180。.
As motioned before, there’s another method to retrieve the map pictures using longitude and latitude:
http://google.com/mapdata?latitude_e6=-31900000&longitude_e6=115900000&zm=1000&w=256&h=288&cc=US
So what’s the relation between the 2 methods?

continue the analysis tomorrow.