Speed in a closed circuit measures an object's ( aeroplane,helicopter, car or boat) speed over a specified number of laps, normally 2.
The average speed of all the laps are used to publish the speed.
Speed measurement is done by camera, and the gate or area that you have to fly pass the camera to be registered is set to be a bottom distance 5 meters from the ground and the top distance 35 meters from the ground.
The gate's that you have to fly through, represent the pylons at both ends of the circuit. Physical pylons can be used if required but does have no effect on the measurement.
In this dicipline you do not gain height to get speed, as you have to turn around as quickly as possible when through the gate.
Aeroplane simulation in a figure 8
A figure 8 circuit is safer for spectators because you would never fly directly towards them on a circuit.