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Thursday, September 18, 2008

Google Maps - Quadtree tiling system

So Google and other online mapsite using a tiling system to transfer large images.

These images are cut into smaller ones, based on a nested hierachy.... known as Quadtree. Good explaination here

Google use q,r,t,s (0-3) to denote one of 4 corners of a tile.

So to find your location run this Python code....

Run it like this:

python 17 -43.525 172.616

Spherical Mercator (ESPG:900913) coordinates for lat/lon:
(19215525.222771712, -5392226.689463486)
17/128383/47899 ( TileMapService: z / x / y )
Google: 128383 83172
Quadkey: 31311030123311311 ( 14851095925 )

Substitute the QUADKEY values as follows

Then type that list of letters into this page...

Here's an example for Christchurch, NZ

Other useful info on tiling

cut your own tiles - x,y info

view tiles on one page

how it works

overlay on web your own image and create the tiles for it

use python to create a local cache of WMS tiles

Wednesday, September 17, 2008

Some Mapping links - most with source code included!

Display OpenStreetMap on a DEM!

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Adding MS VE to a .NET application!

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3D and graphics tools


3d mini terrain viewer

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connecting Wii to MS VE