The semi circle was introduced to ensure that all players were 13 metres from the player taking a penalty.It has no relevance regarding a kick out presently but in the past when kick outs were taken at different points whether it be a wide or a score it had relevance. With the kick out from the 13 m line after a wide or a score it done away with this requirement
You asked how does a referee know how they know if a ball has traveled 13m. The same way he/she makes a judgement if a player is too close to a player taking a sideline or a free - it is a judgement call.
The introduction of the semi circle by a rules revision committee some years back who thought it would be a good idea but there was a knock on effect on the existing rules in force at that time for both football and hurling and had to be revised. This is something I feel Rules Revision Committees do not take into consideration - the consequences of proposed rule changes and how it affects other rules.
You asked how does a referee know how they know if a ball has traveled 13m. The same way he/she makes a judgement if a player is too close to a player taking a sideline or a free - it is a judgement call.
The introduction of the semi circle by a rules revision committee some years back who thought it would be a good idea but there was a knock on effect on the existing rules in force at that time for both football and hurling and had to be revised. This is something I feel Rules Revision Committees do not take into consideration - the consequences of proposed rule changes and how it affects other rules.