Analysis of complexity measure of air traffic flow at terminal area based on approximate entropy

In order to quantitatively describe the complexity of air traffic flow system at terminal area, the model of nonlinear dynamics, approximate entropy was introduced. The approximate entropy of two actual time series of air traffic flow at terminal area was calculated. The results show that air traffic flow at terminal area can be applied to effectively measure the randomicity and nonlinearity of a system and resolve the difficult problems of short sequence and comparability in depicting the complexity of a system. They are suitable to measure the complexity of the actual air traffic flow.