ABSTRACTDevelopment and testing of a prototype GPS receiver housed in a commercial inertial reference system has recently been completed. A flight test program in 1986 demonstrated dynamic performance in maneuvering flight, operation in low signal/noise environments, and operation at zero degree satellite elevation angles with 20–30 m typical accuracies using the Block I GPS satellites. The effects of altitude and clock aiding were also demonstrated.Many of the recognized limitations of an inertial system (including unbounded position error and pilot initialization as well as stand‐alone GPS limitations such as poor satellite geometry, dynamic noise and satellite masking) are overcome with this integrated design approach. This paper describes the advantages of GPS/IRS integration as well as a design approach that utilizes them. The paper also summarizes some test results of the prototype GPS recei