As the Nation becomes more and more reliant on positioning, navigation, and timing solutions, greater accuracy and greater reliability are needed. This project represents a subset of the overall High Accuracy-Nationwide Differential Global Positioning System effort. It is broken into separate tracks, but working together for the common goal of defining what can be achieved for positioning, navigation, and timing services with global positioning systems (GPS) and when GPS has failed. This Small Business Innovative Research Project recently completed phase I and is moving into phase II. The findings of phase I indicate that Nationwide Differential Global Positioning System and High Accuracy-Nationwide Differential Global Positioning System work well as a base framework for supporting positioning, navigation, and timing when GPS is unavailable. Phase II will develop the ideas further, identifying broadcast signal characteristics that will aid in improving the accuracy possible from the current broadcast, and developing hardware for implementation of this approach.