Preliminary analysis of URA characterization for GPS real-time precise orbit and clock products

International GNSS Service (IGS) launched an open-access Real Time Service (RTS) for Real Time Precise Point Positioning (RT-PPP). At present, RTS mainly includes the real-time precision orbit and clock products. Although User Range Accuracy (URA) is reserved according to Radio Technical Commission for Maritime services-State Space Representation (RTCM-SSR) protocol, none of the real-time products broadcast URA. As an indication of quality of orbit and clock products, the value of URA is of great importance for the quality controlling and integrity monitoring. In this paper, we mainly analyze the real time precision orbit and clock product from Centre National d'Etudes Spatiales (CNES). The accuracy and error distribution characteristics of real-time products can be obtained firstly. And then, we analyzed the correlation among the radial, along, cross errors of orbit and clock errors. Finally, We studied the computational strategy of URE and URA. URE is mainly affected by satellite clock errors, and do not satisfy Gaussian distribution. URA value is about 0.03-0.35 m getting from Root Mean Square (RMS) estimation of URE. URA has no obvious correlation with satellite type, but it is different with different satellites, which need to be accounted for high precision and high integrity navigational applications.