Abstract: Processing GPS signals received at moving targets and at a fixed location near instrumentation associated with timing and recording an event allows the determination of instantaneous target position to be made without a requirement for additional active tracking. An example is the recording and display of a test event involving a missile intercepting a target. The missile, target, and an instrumentation site all receive GPS signals. The signals are time tagged and the data contained thereon verified by a source and forwarded from each platform to a ground station. The data is correlated with other test data to provide a real time record and display of the missile intercepting the target. Both Time Space Position Information (TSPI) and Miss Distance Indication (MDI) are derived to a very high degree of accuracy using double difference error correction techniques. Both absolute and relative position information can be derived.