Create a world file for PNG(, which shows the entire globe)

Unlike Geotiff, PNG does not have information about coordinates of a image file.
This leads little difficulty to create a map tile of world wind.

To overcome the difficulty, we need to create a world file (extention .pgw), and the contents can be calculated with the following site:
http://egb13.net/2009/03/worldfile-calculator/

In my case, I have a image which covers the entire globe generated by combining NASA's blue marble picture, and the input parameters are 90N 180W, 90S 180E, 83200x41600 pixels.

Putting the .pgw file, world wind imaginary and elevation installation program works, which I introduced in the past.