A method for measuring air mass flow into a compressor section of a gas turbine engine is provided. Air is introduced into a chamber upstream from an inlet of the compressor section. The chamber includes filter packages with at least some of the filter packages including a flow sensor and a filter structure, the filter structure filtering the air. The flow sensors measure the velocity of the air flowing through the corresponding filter package. A controller uses the air flow sensor signal data to characterize a two dimensional flow field through the chamber. Additionally, a plurality of temperature, humidity, and static pressure sensors are disposed throughout the filter packages. The controller uses the temperature, humidity, and static pressure sensor signal data to characterize a two dimensional density field through the chamber. The controller combines the flow field with the density field to calculate a two dimensional air mass flow field.