## 3 Experiment and Analyses
### Dynamic Experiment  
#### 3.2.1 Fault Identification  
A dynamic experiment is carried out in this chapter (named Experiment 2). Firstly, the static measurement of the rover station at the initial position is maintained and then the rover station is controlled to move back and forth on the fixed rail for two periods. Each period possesses two datasets. The horizontal coordinate of the start point is about (1.2, 0.3) and the endpoint coincides with the start point. The positioning results are shown in Figures 10 and 11. The color bar represents the epochs. The red line represents the reference trajectory. According to Figure 10, it can be found that the positioning results are basically inconsistent with the reference line, which indicates a large deviation comparing with the actual situation. This conclusion can also be drawn from Figure 11. Although the ambiguity fixed rate is 31.7%, it is fixed incorrectly. High-precision positioning cannot be guaranteed, and the results are not reliable. Similar to Experiment 1, judging whether reference pseudolite performs normally is the first step and reference pseudolite in Experiment 2 is PL6. Figure 12 presents the DD carrier-phase observations of four pseudolites groups. Since Experiment 2 takes \"stationary--motion--stationary--motion--stationary\" as a period, the observations are periodic and contain two cycles in theory. Figure 12 shows that DD carrier-phase observations of PL6-1, PL6-4, and PL6-5 remain normal, which confirms the regular pattern of two motion periods and observations are stable. The reason for such regular observations is that the pseudolite constellation is fixed. The observations will maintain this periodicity as long as the rover station moves back and forth along the fixed rail. Frequent cycle slips and data interruptions only occur in DD carrier-phase observations of PL6-8, indicating that the reference pseudolite PL6 is normal in Experiment 2 and the signals of PL8 may be faulty. It is possible that some environmental factors (such as multipath, shelters) lead to frequent signals interruption and cycle slips of PL8. However, further fault identification is required to determine faulty pseudolite or epochs theoretically. The test statistics and threshold for fault identification in Experiment 2 are shown in Figure 13.  
Figure 11: Results in X, Y Components of Experiment 2. Figure 10: (a) The trajectory of Experiment 2, (b) The Equipment of Experiment 2.  
in Figure 13. The construction of test statistics and the determination of thresholdare shown in (12) and (13). The CRAIM test statistics in Figure 13a obviously exceeds the threshold. It is less than or close to the threshold in some epochs, where the signal of PL8 is interrupted instead of returning to normal. The number of visible pseudolites (# npl) has also changed from five to four. When the number of visible pseudolites is four, the test statistics wireless than the threshold. At this moment, the receivers lose lock to PL8 signals.It indicates that other pseudolites' observations are normal except PL8. Besides, the incorrect ambiguity fixed solutions in Figures 10 and 11 are also verified, because a wrong ambiguity value can cause slow growth effects in both test statistics and position error. The PRAIM test statistics in Figure 11b also exceed the threshold in very few epochs and it is not as significant as test statistics of CRAIM. According to the introduction, pseudorange is greatly affected by indoor environments, such as multipath, clock, noise and so on. Sometimes the pseudorange-based test statistics cannot truly reflect the fault because test statistics may become very large due to other factors even if there is no fault. More importantly, the PRAIM test statistics can only reflect noise and multipath but cannot  
Figure 12: DD Carrier Phase Observations of Experiment 2. Figure 13: (**a**) The Test Statistics Based on Carrier Phase Observations, (**b**) The Test Statistics Based on Pseudorange Observations. recognize cycle slips.