Toyon Research Corporation proposes to develop and demonstrate a prototype low-cost precision navigation system using commercial-grade gyroscopes and accelerometers. During the Phase I effort an uncalibrated brassboard system was built and flight tested using a manned biplane. The brassboard system comprised an experimental single-channel (L1-only) software GPS receiver, and a 720 deg/hr inertial measurement unit (IMU) costing only $1k. The performance of the brassboard system was comparable to that of a $42k precision reference system that comprised a dual-channel (L1 and L2) GPS receiver and antenna, and a tactical-grade (1 deg/hr) IMU ($24k). This tactical-grade performance was achieved by fusing low-cost inertial measurements with attitude and position measurements from a GPS-based attitude (GPS/A) sensor. The Miniature Integrated Direction-finding Attitude-determining Anti-jam System (MIDAAS(TM)) obtains position, velocity, attitude, and time (PVAT) measurements directly from GPS signals and employs an innovative small single-aperture antenna to compute full 3-D attitude (roll, pitch and yaw) using only two RF channels, leading to a smaller, simpler, lower-cost GPS/A receiver system. During the Phase II program, a form-fit-function prototype system will be designed, built, and flight tested in an operational environment. The prototype performance will be compared with that of a higher-accuracy, more expensive attitude reference system.