A Prototype WADGPS System for Real Time Sub-Meter Positioning WorldwideMany planned and proposed NASA science activities will benefit from precise real time positioning with wide area differential GPS (WADGPS). Future NASA users include orbital remote sensing instruments (altimeters, SARs, imagers) and a variety of airborne and Earth based investigations. Real time positioning requirements and goals range from a few meters to a few centimeters. Direct benefits will include the enabling of missions that are not now possible (such as precision remote sensing from the space shuttle and space station) and dramatic reduction of analysis costs for a diversity of current investigations.