Pretty sure there are no "known yardage" classes in IBO, however ASA has opened up a couple of new classes and I think one of them is what you are looking for. In my opinion the whole point to 3D competition is judging distance, any spot shooter can come out to a 3D shoot and rack up high scores when the yardage is known but throw that same guy in the mix of unknown's and he is all over the place like the rest of us! If you are looking to know your yardage than you may possibly look into Field or FITA competitions.