For NTSC it should be 720 by 480 for SD video and 720 by 576 for PAL SD video, so there is a difference between the two systems. For the graphic you are looking for, you may find something by using Google to locate animated overlays, something with crosshairs, numbers and text moving about the screen or animated graphs on it. I think I know the kind of thing you are looking for, something Terminator style. Try and get one that is an 'x-ray' view or 'infra-red' (just alter the colours to invert or negative, it doesnt have to be that elaborate). Then overlay it on a video layer/track and use a blend mode to mix the graphic/animated background with the underlying video track (from the aliens POV).