Some preliminary information follows. For NTSC, SD media is almost always $720\times480$ interlaced (the format in the United States, US). For PAL, SD media is almost always $720\times576$ interlaced (Europe, EU, and most of the world). An SD can conceivably be created with a lower resolution – for example $352\times240$ MPEG-1 -- but it is not useful. Aspect ratio for either NTSC or PAL can be $4:3$ or $16:9$.
Some preliminary information follows. For NTSC, SD media is almost always $720\times480$ interlaced (the format in the United States, US). For PAL, SD media is almost always $720\times576$ interlaced (Europe, EU, and most of the world). An SD can conceivably be created with a lower resolution – for example $352\times240$ MPEG-1 -- but it is not useful. Aspect ratio for either NTSC or PAL can be $4:3$ or $16:9$.