Since a pixel count must be a whole number, in Wide VGA displays it is generally rounded up to 854 to ensure inclusion of the entire image.
[2][3] Standard definition has always been a 4:3 aspect ratio with a pixel resolution of 720 × 480 at 60 Hz for NTSC regions, and 720 or 768 × 576 for PAL regions (1024 wide for widescreen displays).
However, standard definition defines a 15.7k Hz horizontal scanrate, which means that interlacing has to be used for those resolution modes.
The ATSC digital television standards define 480p with 640×480p (4:3) pixel resolutions, at 24, 30, or 60 frames per second.
In both cases the spatial resolution doesn't change, but the conversion to a interlaced format allows a direct digital to analog conversion for eventual broadcast on the analog television network.