# Low-Altitude Sensing Model: Analysis Leveraging ISAC in Real-World Environments
## 4 Performance Verification and Analysis
### Single Base Station Sensing Validation
According to Equation (2), the primary reason was that the UAV was not aligned with the antenna's normal direction, resulting in a decreased SNR and a reduced sensing accuracy. The overall accuracy in the OP direction was better than in the OA direction due to the difference in flight distance. OA paths generally cover longer distances, and according to Equation (1), the SNR degrades at farther points, resulting in relatively poorer accuracy in the OA direction during overall statistical analysis. The vertical accuracy fluctuated between 2.33 and 3.17 m, showing a trend consistent with the horizontal accuracy. The horizontal positioning accuracy was generally inferior to the vertical positioning accuracy due to the hardware design of the antenna array. The vertical direction had more antenna elements, and the larger element spacing caused by transmit-receive isolation resulted in a larger array aperture, providing a better angular accuracy and leading to superior vertical positioning accuracy. However, both the horizontal and vertical positioning accuracy values met the 3 GPP TR 22.837 [29] requirement for UAV intrusion sensing, which specifies a positioning accuracy of less than 10 m, aligning with the expectations. From the upward tilt direction test, it is clear that the measured farthest radial distance during upward flight was exceptionally close to the value of the theoretical model. An error of only 0.7 m represented an error ratio of approximately 0.17%. It shows that this minor deviation was primarily because of the impact of sensing accuracy. However, the deviation in the measured nearest sensing distance was relatively larger, reaching 2.2 m. The main reason for this was consistent with that in the horizontal direction. Namely, the starting point could not be set at 0 m in practical operations. It is worth noting that within the entire sensing range, when the positioning accuracy at CDF 95% was statistically analyzed, the results showed an accuracy of around 2 m, which fully met the sensing requirements. To further verify the coverage blind spots caused by the vertical elevation angle and the ability of the single base station 3D sensing model to replicate the sensing range of a real-world base station, targeted tests were conducted. According to Equation (10), the maximum horizontal distance of the blind spot was approximately 320 m. Vertical upward flights were performed at distances of 50 m, 100 m, 150 m, 200 m, 300 m, and 350 m along the antenna's normal direction (OA direction), as shown in Figure 14. To ensure data reliability, each point was tested 100 times. Subsequently, the minimum and maximum detectable heights at the corresponding positions and the horizontal and vertical positioning accuracies within the sensing range were analyzed in detail. The relevant results are summarized in Table 8.  
In terms of the minimum sensing height, the sensing range was between 30.5 and 31.1 m, with an average of approximately 30.6 m, which was about 2% higher than the actual height of the base station. Considering the slight deviation between the actual mechanical installation angle of the base station and the theoretical normal direction, as well as the impact of positioning accuracy errors, it can be concluded that the results aligned with the theoretical model expectations. This validates the lower coverage limit of the base station antenna in the vertical direction. Regarding the maximum sensing height, the measured results were consistent with the theoretical value, with a maximum error of 2.1 m and an overall error range of 0-1.53%. The highest sensing heights during vertical flights at all test points were slightly greater than the corresponding theoretical vertical sensing boundary heights. This discrepancy was related to the antenna installation angle errors and sensing accuracy limitations. It can be concluded that the results were generally consistent with the theoretical expectations, verifying the coverage blind spots caused by the vertical FOV.