## 3 Experiment and Analyses
### Static Experiment with Zero-Baseline
#### 3.1.2 Fault Exclusion  
Two strategies are considered for fault exclusion to ensure the reliability of positioning. The first one called Strategy 1 is to replace the reference pseudolite from PL5 to PL6 and retain the observations of original reference pseudolite. The other one named Strategy 2 is eliminating PL5 directly. In theory, Strategy 1 is more rigorous because subsequent observations return to normal. After the 10 th epoch, the STD of PL6-5 for DD pseudorange observations is 0.27 m and 0.04 cycles forthe DD carrier phase. Therefore, after observations return to normal, the signals of PL5 should continue to be received. Figure 7 shows the DD pseudorange and carrier phase observations after using both two strategies. Figure 8 shows the test statistics after applying two strategies. The construction of test statistics and the determination of thresholdare shown in expression (12) and (13). Figure 6: (**a**) Double Differenced (DD) Observations of Pseudorange, (**b1–b4**) DD Observations of the Carrier Phase. Figure 8: (**a**) CRAIM Test Statistic after Using Strategy 1, (**b**) CRAIM TestStatistic after Using Strategy 2. Figure 7: (**a**) DD Pseudorange Observations after Using Strategy 1, (**b**) DD Pseudorange Observations after Using Strategy 2, (**c1–c4**) DD Carrier Phase Observations after Using Strategy 1. According to Figure 7, the DD observations of all pseudolites return to normal after the reference pseudolite is replaced. When using Strategy 1, the test statistics exceed threshold during the previous 10 epochs because the data quality of PL5 is poor, but test statistics remain normal in the last 10 epochs. When using Strategy 2, test statistics are below the threshold since PL5 is removed. It can be considered that the fault has been excluded and high-precision positioning can be performed. In theory, as long as PL5 returns to normal, the test statistics are less than the set threshold due to a large reduction in residuals of DD observations. In Experiment 1, the faulty pseudolite PL5 is the reference pseudolite, so the method of replacing reference PL is used in Strategy 1. However, even if the reference PL is replaced, PL5 is still in a faulty state in the first 10 epochs and test statistics are higher than the threshold. However, PL5 is eliminated in Strategy 2 and test statistics are less than the threshold, which can ensure that there is no obvious deviation in the whole positioning process. After PL5 returns to normal, more redundant observations will be received in Strategy 1 and the theoretical positioning precision will be higher than Strategy 2. Figure 9 shows the results of horizontal positioning with two strategies and the color bar represents epochs. Figure 9: **(a1,a2)** Results of Experiment 1 when Using Strategy 1, **(b1,b2)** Results of Experiment 1 when Using Strategy 2. According to Figure 9, it can be found that the fixed rate has been increased to 50% and the results of the fixed solution are close to true value when using Strategy 1. The STD of horizontal results is 5.4 mm (X direction is 2.7 mm and Y direction 4.7 mm). When applying Strategy 2, the fixed rate has been increased to 100% and the STD of horizontal results is 9.8 mm (X direction is 3.7 mm and Y direction 9.1 mm). This phenomenon is also mutually confirmed with the previous analysis. In Strategy 1, when PL5 is faulty, the positioning result shows a large deviation and correct ambiguity fixed solutions cannot be obtained. At present, the positioning results of Strategy 2 are stabilized near true value. After PL5 returns to normal, the positioning result of Strategy 1 is also close to a true value and STD is better than Strategy 2. Nevertheless, we cannot decide which strategy is better without in combination with specific scenarios. The applicable scenarios of the two strategies and the best methods in the dynamic scenario will be discussed in this article. Combined with Figure 6, the following conclusions can be obtained: if observations return to normal, PL5 can be resumed for positioning.