The SuperCalibrator concept was introduced to take advantage of the characteristics of GPSsynchronized equipment (PMUs). Specifically, GPS-synchronized equipment has the capacity to provide precise phase measurements (to 0.01 degrees accuracy) and relatively good quality magnitude measurements (up to 0.1% accuracy). However in a practical environment this precision is not achieved for a variety of reasons, such as errors from instrumentation, system unbalanced conditions, etc. The SuperCalibrator concept is based on a statistical estimation process that fits GPS-synchronized measurements and all other available standard data into a three-phase, breaker-oriented, instrumentation inclusive model. In this paper, this concept has been extended to provide a decentralized state estimator for power systems. The decentralized state estimator operates on substation data. The resulting substation state estimate is globally valid as long as there is a valid GPS-synchronized measurement at the substation. The paper describes the SuperCalibartor methodology. Presently the concept is implemented on five substations. Numerical experiments with these systems illustrate the superiority of this approach. The paper also describes preliminary implementation and performance issues. The implications of the overall approach are substantial.