@Pongo:
480i is really only 240 lines of resolution for each image. These are displayed 60 times per second alternating between upper and lower fields.
a 480p display will update the entire 480 lines of resolution 60 times per second, so you will get twice the vertical resolution.
480i and 480p isn't the same resolution?
one is interlaced and other is progressive, but the same resolution. 480pixels height
480i is 240lines per field, so 240+240=480lines but only 240lines viewed at one time.
480p show always 480lines on screen.