## 5 Experiment Verification  
### Experimental Programme  
The correctness of the multi-source data datum alignment and transfer method and the validity of the simulation accuracy in the truss structure stability experiment are verified. The truss structure is placed in a constant temperature clean assembly laboratory, and the structure is placed above a 3 m \(\times\) 3 m \(\times\) 0.5 m granite datum platform. Standard target spheres are placed at the corners of the datum platform for coordinate system datum alignment. We use a reference prism to transfer the coordinate system to solve the problem of a single instrument station not being able to take into account the entire measurement site due to the limitations of the measurement site. All our experiments are carried out in an ISO7-compliant laboratory, with room temperature variations within 20\({}^{\circ}\)\(\pm\) 0.5\({}^{\circ}\). Before the experiment, we had placed the experimental truss structure for 24 h.  
Four Leica TM6100A electronic theodolites were placed in the site as shown in Figure 10. T1 and T2 are placed at approximately 3 m and 2 m from the truss structure, collimating the cubic prism 2 on the M1&Instruments holder. T3 and T4 are placed at approximately 6 m from the truss structure, collimating the cubic prism 3 on the M2 holder. The transformation matrix \(M_{CS-CB}\) from cubic prism 2 to cubic prism 3 is obtained through the theodolite intersection measurement principle. Similarly, the transformation matrix \(M_{CB-CO}\) for cubic prism 1 to cubic prism 2 is obtained. As shown in Figure 11, the Leica AT960 laser tracker was placed at about 2.5 m in the truss structure. In turn, the characteristic points \(X_{n}\), \(Y_{n}\) (\(n\) = 1, 2, 3...) and the measuring datum \({}_{\rm Zn}\) (\(n\) = 1, 2, 3...) on the surface of the truss structure are measured. The M1&Instruments holder coordinate system \(O_{B}\) (\(O_{B}\)-\(X_{B}Y_{B}Z_{B}\)), the M2 holder coordinate system \(O_{S}\) (\(O_{S}\)-\(X_{S}Y_{S}Z_{S}\)), and the datum platform coordinate system \(O_{O}\) (\(O_{O}\)-\(X_{O}Y_{O}Z_{O}\)) are established. The transformation matrices \(M_{CS-S}\), \(M_{CB-B}\), and \(M_{CO-O}\) are obtained by the method described in Section 3.3. We use a laser tracker to correlate the reference cubic prism coordinate system with the truss structure coordinate system. We use theodolite to associate the datum cubic prism coordinate system with the truss structure measurement cubic prism coordinate system. The specific experimental setup is as follows. Figure 9: Distribution of rotation angle simulation values: (**a–c**) corresponds to (1); (**d–f**) corresponds to (2); and (**g–i**) corresponds to (3). As shown in Figure 12a,b, we photographed the measurement targets attached to the surface of the truss structure at \(L_{n}\) (\(n=1\), 2, 3...8) stations with a handheld CIM-3 camera at approximately 2 m, 5 m, and 8 m from the ground at a total of 24 camera positions. Multiple digital images taken from different angles are resolved by bundle adjustment to obtain accurate \(XYZ\) coordinate values. Alignment of photogrammetric data to the datum transfer test data by the method described in Section 3.2. The datum coordinate system transfer was carried out in the stability experiments, and Figure 13 illustrates how the individual coordinate system datums were transferred during the experiments. Experimental verification of the correctness of the datum transfer mathematical model and the repeatability of the datum transfer. Figure 14 shows the experimental site. Figure 15 shows the flow of the experiment. Figure 11: Diagram of laser tracker coordinate acquisition. Figure 10: Diagram of theodolite angle intersection measurement. Figure 12: Diagram of the photogrammetric coordinate acquisition. (**a**) distribution of camera angle positions; (**b**) distribution of camera height positions. Figure 13: Coordinate system transfer method.