_Applied_  
_sciences_  
_Article_  
**A Holistic Approach to Guarantee the Reliability of Positioning Based on Carrier Phase for**  
**Indoor Pseudolite**  
**[PERSON] 1,2,3,4,5,6, [PERSON] 1,7,8,9, [PERSON] 1,1,1,1, [PERSON] 1,2, [PERSON] 1, [PERSON] 4,6, [PERSON] 5 and [PERSON] 1,3**  
1 School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China; [EMAIL_ADDRESS] (Y.Z.); [EMAIL_ADDRESS] (P.Z.); [EMAIL_ADDRESS] (D.Z.); [EMAIL_ADDRESS] (FY.)  
2 Research Center for High Accuracy Location Awareness, Wuhan University, Wuhan 430079, China  
3 Guangxi Key Laboratory of Spatial Information and Geomatics, Guilin 541004, China  
4 College of Geology Engineering and Geomatics, Chang'an University, Xi'an 710054, Shannxi, China; [EMAIL_ADDRESS]  
5 State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China; [EMAIL_ADDRESS]  
* Correspondence: [EMAIL_ADDRESS] (J.G.); [EMAIL_ADDRESS] (J.Z.); Tel.: +86-1330-862-0798 (J.G.); +86-1338-757-1063 (J.Z)  
Received: 15 January 2020; Accepted: 6 February 2020; Published: 11 February 2020  
**Featured Application: This work is potentially applied to indoor high-precision engineering/industrial measurement, such as parts installation, tunnel engineering, dynamic rail inspection, path planning, etc. Especially in case of pseudolite faulty, the reliability and availability of positioning can be guaranteed.**  
**Abstract: The integrity monitoring algorithm based on pseudorange observations has been widely used outdoors and plays an important role in ensuring the reliability of positioning. However, pseudorange observations are greatly affected by the error sources such as multipath, clock drift, and noise in indoor pseudolite system, thus the pseudorange observations cannot be applied to high-precision indoor positioning. In general, double differenced (DD) carrier phase observations are used to obtain a high-precision indoor positioning result. What's more, the carrier phase-based integrity monitoring (CRAIM) algorithm is applied to identify and exclude potential faults of the pseudolites. In this article, a holistic method is proposed to ensure the accuracy and reliability of positioning results. Firstly, if the reference pseudolite operates normally, extended Kalman filter is used for parameter estimation on the premise that the number of common pseudolites meets positioning requirements. Secondly, the innovation sequence in the Kalman filter is applied to construct test statistics and the corresponding threshold is determined from the Chi distribution with a given probability of false alert. The pseudolitehorizontal protection level (HPL) is calculated by the threshold and a prior probability of missed detection. Finally, compared the test statistics with the threshold to exclude the faultypseudolite for the reliability of positioning. The experiment results show that the proposed method improves the accuracy and stability of the results through faults detection and exclusion. This method ensures accuracies at the centimeter level for dynamic experiments and millimeter levels for static ones.**  
**Keywords: carrier phase; differential pseudolite system; extended Kalman filter; reliability; integrity monitoring**