Improvements of USCG RTK Positioning Performance Using External NOAA Tropospheric Corrections Integrated with a Multiple Reference Station Approach

Marine navigation has been revolutionized with the advent of the Global Positioning System (GPS), and the deployment of the United States Coast Guard (USCG) Differential GPS (DGPS) Service. The reference station spacing of this network ranges from 30 to 500 km. The high level of correlated errors on measurements from long baselines can reduce the effectiveness of carrier phasebased positioning, especially when only one reference station is used. The first objective of this paper is to evaluate the effectiveness of a multiple reference station approach on the USCG network. The GPS-Met Observing Systems Branch (GPS-Met) (2002) within the Forecast Systems Laboratory (FSL) in the National Oceanic and Atmospheric Administration (NOAA) develops and assesses techniques to measure atmospheric water vapor using ground-based GPS receivers. This includes a test bed for tropospheric corrections, located in the Northeastern United States. The second objective of this paper is to evaluate the improvement due to the use of external NOAA tropospheric corrections on the USCG network. This paper presents potential DGPS system enhancements and initiatives. Some are merely concepts at this time, while others are underway. The intent of this paper is to