One thing to note is the presence of ground vehicles (e.g. "OPS7"). Using my RTL-SDR dongle, I can pick up trucks driving around LAX, 20 miles away, because the airport is creating synthetic ADS-B targets for them and broadcasting packets as though they were any other aircraft--with appropriate flags sent so you can tell 1. it's a ground vehicle, and 2. it's a synthetic target, not a direct response from an ADS-B transponder.