Analysis of Co-located IGS Network GPS Receiver DCBs Derived by CODE and a Single Station Estimation Method

Abstract:

The Global Positioning System (GPS) is a valuable tool in the measurement and monitoring of ionospheric Total Electron Content (TEC). To obtain accurate GPS-derived TEC, satellite and receiver hardware biases, known as Differential Code Biases (DCBs), must be estimated and removed. The Centre for Orbit Determination in Europe (CODE) provides monthly averages of receiver DCBs for a number of stations in the International Global Navigation Satellite System (GNSS) Service (IGS) network. A comparison of the monthly receiver DCBs provided by CODE with DCBs estimated using the Minimization of Standard Deviations (MSD) method (Ma & Maruyama, 2003), on both daily and monthly time intervals, is presented. TEC, which has been unbiased using CODE-derived DCBs, shows inconsistencies in differenced sTEC up to 6.906 TECU, while TEC that has been unbiased using MSD-derived DCBs results in inconsistencies rarely exceeding 1.5 TECU. A number of possible factors that could be causing the CODE-derived DCB inconsistencies, such as hardware configuration, solar activity, and seasonal variations, are analyzed and discussed. It is also noted that daily MSD-derived DCBs show significant variations from day to day, with standard deviations up to 42 TECU in a given month. The magnitude of day-to-day variations was found to have a strong correlation between co-located receiver pairs. This correlation was seen regardless of hardware make, model, and configuration, which suggests that the variations are likely caused by ionospheric artifacts within the bias estimation method.