## 5 Conclusions  
The subject of this article is to study a high-precision measurement method for target point coordinates on long straight tracks, such as rocket sled test tracks, and a multi-level measurement strategy based on length-angle mixed intersection adjustment model is innovatively proposed. Initially, based on the analysis of the measurement task and characteristics of the measurement equipment, the measurement control network is divided into multiple levels: Level I includes distances between every two target points, Level II measures coordinates within a small range using laser trackers at different stations, and Level III uses a total station for global data. The length-angle mixed intersection adjustment model is used for data fusion between Level II and Level III, fully utilizing the high-precision distance information from the laser tracker and the high-precision angular information from the total station to control measurement errors. Additionally, to further enhance measurement precision, the simulation analysis of the measurement equipment layout is conducted, providing practical guidance for station placement. Finally, the methods researched are applied in a rocket sled test on a straight track approximately 669 m long, with 224 target points. After solving with the adjustment model, the distances of the target points are compared with the benchmark distances measured by the laser tracker. The deviation range was \(\pm\)1 mm, the average absolute value of the deviation was 0.10 mm, and the standard deviation of the deviation was 0.20 mm. The method proposed in this article has significant reference value for the construction of straight track measurement networks and can be applied in various engineering projects such as large-scale generator station construction, tunnel construction, and oil and gas pipeline construction. Moreover, the length-angle mixed intersection adjustment model is also applicable to measurement networks constructed by other distance or angle measuring instruments.  
Additionally, uncertainty is crucial for the assessment of the accuracy of three-dimensioal coordinates. The uncertainty sources of the length-angle mixed intersection adjustment model proposed in this article mainly include distance and angle measurement accuracy, target point run-out, measurement method, Taylor series expansion, etc. In future work, the study of uncertainty will be one of our important research topics.  
Conceptualization, Z.X. and C.L.; methodology, C.L. and Z.X.; software, H.Z., C.Z. and C.L.; validation, Z.X., C.L. and Z.Z. ([PERSON]); formal analysis, Z.X. and C.L.; investigation, C.Z.; resources, Z.X., H.Z. and C.L.; data curation, Z.Z. ([PERSON]) and C.Z.; writing--original draft preparation, Z.X. and C.L.; writing--review and editing, Z.X. and C.L.; visualization, H.Z.; supervision, Z.X. and Z.Z. ([PERSON]); project administration, Z.X. and Z.Z. ([PERSON]); funding acquisition, Z.X. All authors have read and agreed to the published version of the manuscript.  
Figure 15: Comparative analysis of distance measurement: (**a**) distance benchmark value and adjusted distance value and (**b**) deviation.  
Funding: The Key Technology of Six-degree-of-freedom Laser Automatic Precise Tracking and Measurement (2019 YFB2006100).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data will be provided by the authors upon request.  
**Conflicts of Interest:** The authors declare no conflicts of interest.