International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / FAA is currently evaluating DGPS based CAT III Landing Systems for use as the next generation commercial aviation landing system standard. Any technique to validate such a DGPS based system must have at least equivalent accuracy. A laser position tracking system coupled with a high performance real-time computational capability was developed providing real-time analysis of performance. This real-time performance measurement system was key in enabling the quick completion of a large number of test approach and landings needed to achieve statistically accurate results.