# Testing and Validation of Automotive Point-Cloud Sensors in Adverse Weather Conditions
## 3 Results  
### Fog Chamber Results  
Here, variation values of range measurements for each LiDAR under different meteorological visibility conditions are presented. The aim of this test scenario is to estimate in the target area how the individual points reflected from the calibration plates varied at different fog densities. Strong variation indicates a less confident value of range measurement. Values are calculated from all the data points collected during the measuring period. Figure 4 shows results with the target being at 10.5 m from the LiDAR setup. With meteorological visibility at 10 m, all but Cepton failed to see past the \"wall\" created by the dense fog. At this distance, Cepton performed constantly even though its variation value is the highest. Other tested LiDARs began detecting after the visibility increased to 15 m. After that, Velodyne and Ibeo seemed to perform steadily but Ouster's values vary. In Figure 5, the results for the 5% reflective target at a distance of 10.5 m are shown. Again, Cepton performed steadily starting from the visibility of 10 m but its variation values are higher than other sensors, excluding Velodyne. Velodyne did not detect the target until at 30 m visibility. Ibeo reached its reference level after the visibility had cleared to 15 m. Ouster had a peak at this distance, which was caused by a few outlier points in the point cloud data. Therefore, Ouster detects the black target when the visibility is increased to 25 m and even then, its variation values are significantly higher than the reference value. Figure 4: Standard deviation of range values from echo points reflected from the 90% target located at 10 m.  
When the target was moved 5 m further away to 15.5 m from the LiDAR setup, Cepton also lost the view at first but recovered when visibility increased to 15 m. Again, Cepton's accuracy after this was constant regarding the variation in range measurements (Figure 6). [PERSON] and [PERSON] were able to detect the target after visibility of 20 m was reached, although their range measurement accuracy showed some variation after this and did not reach the reference level any more, even though the visibility increased. Velodyne returned to its variation level once visibility reached 25 m.  
Figure 5: Standard deviation of range values from echo points reflected from the 5% target located at 10 m.  
Figure 6: Standard deviation of range values from echo points reflected from the 90% target located at 15 m.  
[PERSON] detected the 5% reflective target with the same accuracy as the 90% target (Figure 7) when visibility was more than 10 m. [PERSON] and [PERSON] were not able to detect the target until visibility had increased to 25 m. After that, their variation values increased even though the fog cleared. [PERSON]'s view may have been slightly blocked by the smaller targets, thus increasing the variation. Ouster, in general, tended to be more sensitive and gather outliers in even less dense fog. Velodyne detected the black target the first time at 30 m visibility. In the last distance (targets 20.5 m from the sensors), the two densest visibility values (10 and 15 m) are not used in the measurements. The assumption is that none of the sensors are able to detect targets this far in such dense fog. It is also notable that for Ibeo, the reference measurement is missing. When the 90% target is located at 20.5 m, detecting it in the fog became a challenging task for all the LiDARs. However, once they did, the distance measurements were nearly as accurate as without the fog (Figure 8). Again, Cepton was the first to detect the target and returned similar variation values similar to those that it did as for the reference visibility. Both [PERSON] and [PERSON] were able to see the target at visibility 25 m, from which their variation values increased despite the fog clearing. Velodyne detected the target at 30 m and returned to its performance level regarding the range measurement accuracy. As expected, the 5% target at 20.5 m was the most difficult to detect (Figure 9).