World Wind Map Tile System

From Wikiteer

World Wind uses map imagery in the Plate Carree projection (aka geographic projection).

For performance reasons, World Wind stores multiple copies of the same map in successively higher resolutions. Each additional layer quadruples the number of tiles (and size).

Each tile is a 512x512 pixel square that can be stored in any image format such as PNG, JPG, DDS, etc.

The coordinate system for World Wind starts at the lower left corner.

The base layer divides the world into 36x36 degree pieces starting at level 0.

level 0	36 degrees	50 tiles (10x5)
level 1	18 degrees	200 tiles (20x10)
level 2	9 degrees	800 tiles (40x20)
level 3	4.5 degrees	3200 tiles (80x40)
level n	36/2^n degrees	50*4^n tiles (Failed to parse (Can't write to or create math temp directory): 10*2^n xFailed to parse (Can't write to or create math temp directory): 5*2^n )

• 
• 
• Failed to parse (Can't write to or create math temp directory): x=\\lfloor (long+180)/360 \\rfloor *10*2^n

• Failed to parse (Can't write to or create math temp directory): y=\\lfloor (lat+90)/180) \\rfloor *5*2^n

http://www.ceteranet.com/nww-tile-struct.pdf