I think that is how you get your "megapixels" on cameras - it's the area. i.e. 4500px x 2300px equals about 10 Megapixels.I always thought 480x320 is the amount of pixels when you multiply it out.
It is like a graph in math. 480 pixels on the x axis and 320 on the y
So, if you multiply out 480x320 you get 153,600 pixels, 1.5 decapixels? *shrugs*