How is airport pattern altitude on the Airports page determined?

The Airports page depicts the Traffic Pattern Altitude (TPA) as published by the FAA. The FAA publishes non-standard traffic pattern altitudes in the chart supplement. If a non-standard pattern altitude is not published, the standard pattern altitude is applied. In some cases, ForeFlight will depict AOPA TPA information which utilizes local knowledge to determine the TPA.

Standard traffic pattern altitude is defined by AIM 4-3-3 as: 

1. 1,000 feet above ground level (AGL) for Propeller−driven aircraft. 

2. Large and turbine−powered aircraft enter the traffic pattern at an altitude of not less than 1,500 feet AGL or 500 feet above the established pattern altitude.

3. Helicopters operating in the traffic pattern may fly a pattern similar to the fixed−wing aircraft
pattern, but at a lower altitude (500 AGL) and closer to the runway. This pattern may be on the opposite side of the runway from fixed−wing traffic when airspeed requires or for practice power−off landings (autorotation) and if local policy permits. Landings not to the runway must avoid the flow of fixed wing traffic.