A new system for RTK performance evaluation

Real-time kinematic (RTK) systems use GPS signals to deliver almost instantaneous positions with centimeter-level accuracy. RTK techniques are used for applications such as surveying, engineering, mining and automation. RTK technology has been commercially available since 1993. A critical factor in RTK system performance is the initialization time and reliability of estimating the carrier phase ambiguities. The time-to-initialize governs how long the user must operate with meter-level accuracy. A system that resolves ambiguities very quickly but incorrectly has serious ramifications. There is a trade-off between initialization time and reliability. Manufacturers seek to minimize initialization time while ensuring that reliability exceeds a tolerable threshold. A system has been developed to automatically evaluate RTK initialization performance. The system consists of a network of continuously logging GPS receivers, configured over a variety of baseline lengths and multipath/obstruction scenarios. Each week data is downloaded and processed over all baselines in a real-time fashion. The same engine that is used in RTK receivers is used to process the data. In some cases, multiple RTK engines are operated for comparison purposes. Statistical summaries of the results are automatically generated and electronically distributed for review. The RTK evaluation system aids algorithm refinement and helps specify system performance for users. Results from approximately 2.5 million trials produced an average initialization time of 46 seconds, and an initialization reliability of 99.9%.