Clock-based RAIM method and its application in GPS receiver positioning

Because the signals of global positioning system （GPS） satellites are susceptible to obstructions in urban environment with many high buildings around, the number of GPS useful satellites is usually less than six. In this case, the receiver autonomous integrity monitoring （RAIM） method earmot exclude faulty satellite. In order to improve the performance of RAIM method and obtain the reliable positioning results with five satellites, the series of receiver clock bias （RCB） is regarded as one useful satellite and used to aid RAIM method. From the point of nonlinear series, a grey-Markov model for predicting the RCB series based on grey theory and Markov chain is presented. And then the model is used for aiding RAIM method in order to exclude faulty satellite. Experimental results demonstrate that the prediction model is fit for predicting the RCB series, and with the clock-based RAIM method the faulty satellite can be correctly excluded and the positioning precision of GPS receiver can be improved for the case where there are only five useful satellites.

New Method for Solving GPS Deformation Monitoring Information at Single Epoch

Based on the analyses for the characteristics of high precise GPS defor-mation monitor,according to the spatial relationship among the satellite, base point and monitoring point a new model and its corresponding algorithm were presented to solve the monitoring point deformation directly at single epoch. In this method the carrier phases is used as the basic observations, and the initial condition is precise baseline vectors obtained in the first period observations between the base point and monitoring point. This model is called the similar single difference model (SSDM). The main error sources effecting the accuracy of deformations were analyzed briefly, the single epoch algorithm of the receiver clock offset was advanced. The numerical results of test data show that the SSDM and the single epoch algorithm of receiver clock offset advanced are reliable and correct.

A new receiver clock model to enhance BDS-3 real-time PPP time transfer with the PPP-B2b service

A new Precise Point Positioning(PPP)service,called the PPP-B2b service,has been implemented in the BeiDou-3 Navigation Satellite System(BDS-3),which brings new opportunities for time transfer.However,the solution using the traditional PPP method with the PPP-B2b correction still absorbs some unknown errors and needs reconverging when there exist abnormal data.We developed a new receiver clock model to improve PPP time transfer using the PPP-B2b correction.The traditional PPP time transfers using PPP-B2b with BDS-3,Global Positioning System(GPS),and BDS-3/GPS(Scheme1)are compared with the corresponding time transfer with the proposed clock model(Scheme2).The results show that GPS-only PPP is not recommended because of low accuracy of 2 ns.BDS-3 or BDS-3/GPS PPP time transfers in Scheme1 can realize about 0.2 ns accuracy.When the new clock model is applied,the accuracy can be improved by up to 45%and 39.8%for BDS-3 and BDS-3/GPS PPP,respectively.The proposed clock model can signifcantly improve the short-term frequency stability by 57.4%,but less for the long-term stability.