World Wind Map Tile System

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(Difference between revisions)
Line 10: Line 10:
{| border="1" cellpadding="2" style="text-align:center"
{| border="1" cellpadding="2" style="text-align:center"
|-
|-
-
|level 0 || 36 degrees    ||50 tiles
+
|level 0 || 36 degrees    ||50 tiles (10x5)
|-
|-
-
|level 1 || 18 degrees    ||200 tiles
+
|level 1 || 18 degrees    ||200 tiles (20x10)
|-
|-
-
|level 2 || 9 degrees      ||800 tiles
+
|level 2 || 9 degrees      ||800 tiles (40x20)
|-
|-
-
|level 3 || 4.5 degrees    ||3200 tiles
+
|level 3 || 4.5 degrees    ||3200 tiles (80x40)
|-
|-
-
|level n || 36/2^n degrees ||50*4^n tiles
+
|level n || 36/2^n degrees ||50*4^n tiles (<math>10*2^n</math>x<math>5*2^n</math>)
|}
|}

Revision as of 00:04, 29 October 2006

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 )

  • Image:Math01.png
  • Image:Math02.png
  • 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

world+wind+tile+systemt.gif

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