RRC unnecessary for DGPS messages

The range rate correction (RRC) was useful in reducing the latency error of pseudo-range correction (PRC), and the data baud rate. With selective availability (SA) removed, the temporal variations in the corrections are much smaller, so the issue has been raised as to whether the RRC term is still necessary. We provide results on PRC and RRC variation that account for seasonal, diurnal, and regional differences in the atmosphere and receiver noise statistics. We concluded that setting RRC to zero would help to reduce latency error, and supported this conclusion by static and dynamic tests using commercial receivers and the Radio Technical Commission for Marine Services (RTCM) correction message. The results will be used for defining differential correction messages in the new version 3 standard. The U.S. Coast Guard is conducting tests to address these issues based on results to date because of the potential benefits of reducing the data requirements for differential corrections and thus making available new services over the existing radio-beacon broadcast links. The results of this paper are expected to provide a thorough understanding of the factors affecting the temporal variations of the corrections, and will support the development of standards worldwide