visibility
as defined in Commission Implementing Regulation (EU) 2017/373 of 1 March 2017 laying down…
visibility for aeronautical purposes, which is the greater of: (a) the greatest distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognised when observed against a bright background; (b) the greatest distance at which lights in the vicinity of 1 000 candelas can be seen and identified against an unlit background