Dual-Satellite Alternate Switching Ranging/INS Integrated Navigation Algorithm for Broadband LEO Constellation Independent of Altimeter and Continuous Observation  
[PERSON]  
1 School of Electronic and Information Engineering, Xi'an Jiao Tong University (XJTU), Xi'an 710049, China; [EMAIL_ADDRESS] (L.Y. ); [EMAIL_ADDRESS] (X.J.) 1  
[PERSON]  
1 School of Electronic and Information Engineering, Xi'an Jiao Tong University (XJTU), Xi'an 710049, China; [EMAIL_ADDRESS] (L.Y. ); [EMAIL_ADDRESS] (X.J.) 1  
[PERSON]  
1 School of Electronic and Information Engineering, Xi'an Jiao Tong University (XJTU), Xi'an 710049, China; [EMAIL_ADDRESS] (L.Y. ); [EMAIL_ADDRESS] (X.J.) 1  
[PERSON]  
2 State Key Laboratory of Astronautical Dynamics, Xi'an Satellite Control Center, Xi'an 710049, China; [EMAIL_ADDRESS] 2  
[PERSON]  
3 Southwest China Institute of Electronic Technology, Chengdu 610036, China; [EMAIL_ADDRESS]3.com 4  
Footnote 1: [[https://www.mdpi.com/journal/renotesensing](https://www.mdpi.com/journal/renotesensing)]([https://www.mdpi.com/journal/renotesensing](https://www.mdpi.com/journal/renotesensing))  
[PERSON]  
4 Institute of Optics and Electronics, Chinese Academy of Sciences, BOX 305, Chengdu 610209, China; [EMAIL_ADDRESS] 45 Key Laboratory of Beam Control, Chinese Academy of Sciences, Chengdu 610209, China 5  
Footnote 2: [[https://www.mdpi.com/journals/](https://www.mdpi.com/journals/)]([https://www.mdpi.com/journals/](https://www.mdpi.com/journals/))  
needs continuous observation, which delays positioning results [2], and means that real-time performance cannot be guaranteed. Therefore, to address location service demands in challenging environments with only two visible satellites, a low-cost positioning scheme with precise real-time positioning is urgently needed. Global coverage can be achieved with low earth orbit (LEO) constellations, due to the huge number available. The use of LEO constellations has the advantages of small path loss, short transmission delay, relatively stronger signal power and so forth. Moreover, since the rapid motion of LEO satellites enriches the geometric characteristics of the satellites and enables rapid convergence of positioning results, the real-time positioning performance of the LEO constellations is very strong, meaning that they can be used for wireless communication services, as well as navigation and positioning services [3]. Related research into broadband LEO constellations is a current research hotspot, and is developing in a similar direction as research on future navigation and positioning. While navigation and wireless communication have very similar theoretical and technical foundations, they have different emphases on signal measurement and information transmission, and therefore develop along different pathways. However, with the rapid development of autonomous driving and wireless interconnection technologies, the functions of navigation and communication have become closely related, and the necessity of their integration is being more widely acknowledged [4; 5; 6]. In recent years, the rapid development of large LEO constellations has provided an opportunity to solve navigation and positioning problems in challenging environments. Several studies [7; 8; 9; 10; 11] have analyzed the feasibility of the inertial navigation system (INS)+dual satellite (INS+ dual satellite) positioning combination, and proposed possible countermeasures to issues in the application of integrated navigation on aircraft, however, these algorithms require continuous observation to complete positioning. The authors of [12] introduced the concept of similar ellipsoids and proposed a positioning solution method for the dual-satellite positioning system, deriving an accurate model of the third observation related to the user's elevation in the dual-satellite positioning system, and then establishing the user's positioning algorithm, however, the algorithm requires the help of an altimeter to complete navigation and positioning.