Mysterious Santa Anita question

[ElPrado]

It's pretty much a spot where they get the mid point of the gate to. If the box fits, they have it square and straight. There's likely a spotter on phone or radio at the booth or an office telling them it's right or it may be a computer. Knowing tracks, more likely a spotter. It's easy to see, directly under the "S" in Santa Anita.😀