Here's a couple suggestions to check and double check your yardages while on the 3D course.

1. Judge the yardage to the target in 10 yard increments.....

2. Most people know what 20 yards looks like, judge 20 yards and then how much more to the target.....not another 20 so I'll pick 10 yards beyond the 20 yard mark and then what's left to the target..... or if it's not another 10 yards, micro judge it.

3. Pick half way, judge the distance to the half way mark and then double it.

4. Judge 20 yards back from the target.....pick a spot that would be 20 yards from the target and then judge from that point back to where your standing.

5. Simply go on impression of target..the more you shoot the more you'll learn what a target looks like at different distances....it's instinct then double check it with the methods above.