I am for measuring before deciding.
Maybe as simple as before the whole host looses its arrows, the best archer fires a single shot to check range?
Maybe scouts measured the distance a few days prior?
If modern then weapon ranges are such that almost certainly everyone is in range, and if doubt is there, then modern tech can measure range pretty accurately.
I don’t mind games that don’t allow as I am pretty good at that sort of thing, which can cause issues when the other person is not.
Maybe you could have a commander rating, if the commander is inexperienced that unit/division/whatever can not measure.
But if your commander is experienced, that unit can measure?
Could be a way to represent better commanders rather than a die modifier?