ABSTRACTGPS offers significantly improved capabilities in precise positioning. Applications include 10 cm altitude determination for the Topex/Poseidon oceanographic satellite, centimeter positioning anywhere on the Earth, and precise attitude determination for synthetic aperture radar. In the pursuit of the most precise GPS‐based measurements, NASA has sponsored the development of new software and hardware tools related to GPS. The dual‐frequency Rogue receiver can track up to eight GPS satellites simultaneously. A new antenna design for the Rogue has reduced the combined effects of data noise and multipath to less than 15 cm peak with 2 min smoothing on the pseudorange. The corresponding contribution from data noise is less than 2 cm. Data noise for the carrier is insignificant, and multipath errors are about 1 cm for 2 min smoothing. The GPS Inferred Positioning SYstem (GIPSY) is a software system that includes state‐of‐the‐art Earth models, automatic data editing, and numerically stable and flexible square root filtering techniques for parameter estimation, including process noise modeling. With these tools, we have demonstrated submeter GPS orbits and measurements of positions on the Earth to a precision and accuracy of better than 20 parts pe