# Experimental Analysis of the Behavior of Mirror-like Objects in LiDAR-Based Robot Navigation
## 5 Experimental Results
### Data Collection
This was continuously corrected as the robot traveled along the mirrors and did not leave a map boundary after crossing them. At position C, solid boundaries were seen behind both mirrors. The mirror reflections of the bottom boundaries were partially formed as well (Figure 10C). The left boundary reflection map was slightly less prominently mapped than the right side. A potential cause for this could be the disturbance caused by the moving Turtlebot map. Inconsistent lighting could also cause the difference in mapping between the two boundary reflection maps. Case 4: One front mirror and two side mirrors (Figure 7d)  
Similar to the first three experiments, at point A, there was negative space in the field of view between the LiDAR and the mirror locations (Figure 11A). At point B, the reflections of the boundaries of the 12-foot sides of the environment were mapped behind the mirrors as in previous tests (Figure 11B). With respect to the mirror at the top of the environment, there was only negative space in the field of view between the LiDAR and the mirror. However, unlike case 3, where the Turtlebot was continuously mapped in the left mirror, the Turtlebot was continuously mapped in the right mirror in case 4. At position C, the top mirror also allowed for some of the reflections of the side boundaries to be mapped while also mapping the robot reflection on the surface of the mirror, normal to the robot  
Figure 10: RViz map of test case 3 at positions (**A–C**) where the mobile robot travels between two parallel plane mirrors. Figure 9: RViz map of test case 2 at positions (**A–C**) where the mobile robot travels along a plane mirror. (Figure 11C). It also left some negative space where no boundaries were in range. Solid reflections of the left and right boundaries were mapped behind both mirrors due to the faulty light transmission property. The right reflected boundary map was less dense than the left. This is likely due to disturbance caused by the robot mapping and correction as it passed through the parallel mirrors. To reinforce the understanding of detecting the robot on the surface of the mirror, a stationary test was performed by placing the robot in front of a single mirror, running the SLAM algorithm and viewing the map on the RViz visualization tool. As seen in Figure 12, a solid collection of map points was mapped on the surface of the mirror. The remaining length of the mirror was not mapped, but the reflected portion of the opposite boundary was mapped behind the mirror. According to Figure 13, there are some negative spaces where mirrors were seen consistently over multiple experiments, both before and after the mirrors. is consistent with the uniform reflection of all LiDAR scan points from the start to end of the mirror. It is possible to detect a reflection caused by any boundary that is out of the LiDAR range. Alternatively, LiDAR was unable to receive any intensity from any other nearby reflected objects. All scans that lie outside the length of the mirror are unaffected by having a mirror in the environment. That is, only the points between the mirror and the LiDAR are affected. Beyond the mirror, all LiDAR readings are false. False detection within the mirror was seen consistently when the opposite boundary was in range (Figure 14). This is consistent with the law of reflection for a plane mirror, stating that for reflection off a plane reflective surface, the angle of incidence is equal to the angle of reflection. Thus, it can be assumed that any other diffuse object placed at a distance from the mirror where the reflection of the object would be within the range of the LiDAR would also be mapped. Figure 11: RViz map of test case 4 at positions (**A**–**C**) where the mobile robot travels in a multiple mirror environment with three plane mirrors. Figure 12: RViz map of tat positions (A–C) where the mobile robot is stationary in front of a plane mirror. It is also interesting that the robot detected itself on the surface of the mirror.