For those that don't know, it is illegal to hunt with a bow (any bow) in the UK, so with the exception of a handful of guys who travel overseas for their hunting, the choices are FITA, Field and 3D.
I'm not a FITA archer, I have a good bow for it, but it's not really my thing, so I shoot field and 3D only. I've attached a couple of pics from the National 3D Championship a couple of years ago. I did OK with a 5th in class, after a poor first days shooting, but won the Welsh Open 3D in my (finger release) class later the same year.
I've had a break for about 18 months, due to work, and am just about to get back into the competition scene, I can't wait.
Most 3D comps are shot unmarked distance and no range finders are allowed, so it's down to good old fashioned experience and judgement. I have done one marked distance round, but I still used my own judgement, and put in the top score (in my class) of the day.
The last pic shows a bedded Elk, which was full size, HUGE and a lot further away than it looked.