http://www.dtic.mil/ndia/2005smallarms/tuesday/trohanowsky.pdf
As an example I've linked to a study of a 120mm mortars accuracy.
In Arma 3 (and 2) mortars are/were insanly accurate... inface I think they may impact exactly where you indicate when using the trajectory computer (in RL this helps/does with calculations NOT add GPS guided mortar shells).
Please change this to include a firing signature or grouping size, see pic! {F17438} {F17439} {F17440}