I'm sure there are many of you who have never been exposed to what the judges view looks like at a record level (E/L/R) tournament which uses slalom gate cameras. The screen capture below is from last weeks US Nationals and is a good example of pushing the limit of the rule. Any further left (skier right) and it would have been called a missed gate.
AWSA Rule 10.08.A.2 includes a graphical example of what constitutes good and bad gates. The rule book appendix has a similar graphic and notation that "all references are to the front foot in binding". So this shot was almost exactly when the skiers front foot crossed the buoy virtually exactly down the center. Note - I'm not saying it's how you should ski it (never know if hitting the buoy is going to change your path or cause other problems).
Now to explain a bit more of what you see - The rules dictate that the camera should be approximately a 44 degree angle from the path of the boat. This angle gives a very good prespective of the skier heading straight toward the camera and takes as many "viewing angle" variables out of the equation. Point is, it's a pretty good view.
The small white circles you see on the screen are simple visual references of where the buoys are in calm water. As you can see, when the boat goes through the gates they move outward somewhat but also get briefly covered by the spray/wash from the boat so the circles help 'locate' the buoy when things fly by quickly. The gate call is NOT made relative to these small circles instead it's the actual buoy itself.
The controls on the bottom of the screen help scroll back and forth to find the frame where the front binding is closest to crossing (or passing) the buoy. Event judges see this in real time and get a "half speed" (+/-) review immediately after the pass (when using Splash Eye).
Certainly some times the spray/foam obsures the buoy, but most times you get a pretty good look at the skier coming through the gate with this set up. Technology like this which is used is all geared toward making the right call. It's not failure proof and still involves humans to operate and interpret what they see but it's generally pretty helpful.
AWSA Vice President