An apparatus for converting aircraft altitude encoder measurements into higher resolution values, including a microprocessor connected to monitor the aircraft altitude encoder output signals, a pressure transducer and converter network for providing incremental pressure change readings, also connected to the microprocessor; the microprocessor being programmed to utilize the incremental pressure readings to calculate corresponding incremental altitude signals between transition points of the aircraft altitude encoder readings. The method of the invention includes the steps of monitoring aircraft altitude encoder transition points, reading incremental pressure variations between transition points, and calculating incremental altitude variations between altitude encoder transition points.
