Differential corrections provide a method to improve the real-time accuracy and precision of GPS, but there are several sources of differential corrections and each have an associated accuracy and precision. In dynamic applications, the speed and heading of the rover may also have an effect on the accuracy and precision reported by the GPS receiver. These factors may have more of an effect on one differential correction method than another. An experiment was designed to test the differential correction methods under dynamic conditions. No corrections, OmniStar HP corrections, and RT2 corrections from a local base station were tested at several speeds and headings. The experiment was designed to determine what relationship, if any, exists between these factors and positional accuracy and precision of the differential correction sources. The results of the experiment will help designers choose the most effective solution for their positioning needs. The experiment showed that local RT2 corrections offered the most precision under dynamic conditions. The precision of OmniStar HP was close to that of RT2 corrections. The system with no corrections was the least precise of the three tested. The speed and direction of the vehicle were not observed to have a significant affect on the precision of the systems tested. The type of differential corrections used was not seen to have any influence on relative accuracy. The speed and direction of the vehicle did have an influence on the relative accuracy of the systems. / Master of Science