Icons and symbols should be large enough for the user to perceive the representation and discriminate it from other icons and symbols.
Additional Information:
When a displayed symbol of complex shape is to be distinguished from another symbol shape that is also complex, the symbol should subtend not less than 20 minutes of arc at the required viewing distance. VDU-displayed symbols that must be distinguished from other complex shapes should have a minimum of 10 resolution elements for the longest dimension of the symbol.