# A Novel Indoor Localization Method Based on Image Retrieval and Dead Reckoning
## 5 Experiments and Results
### V-PDR Testing Result  
We performed our V-PDR experiments, which were divided into two parts. One was to show the ability of V-PDR to correct PDR cumulative errors, and the other was to test the ability of V-PDR to work in a three-dimensional environment. Experiments were conducted in our laboratory building and the ground truth was obtained by laboratory engineering drawings and high-precision measurement tools. The accuracy comparison test was conducted on the third floor and the total length of the route was about 64 m. The three-dimensional localization ability test of V-PDR was executed from the first floor to the third floor and the total length of this test route was about 120 m, not including the climbing  
Figure 11: The test result of VPR. process. The experiments were performed on an Android phone. We wrote a software application on a mobile phone for VPR and PDR. Every step, we took a photo with the mobile phone, the photo was transported to the cloud server for VPR localization and the software processed the data of PDR and VPR our algorithm. The first experiment was performed on the third floor of our laboratory. We tested PDR and V-PPR with the same phone. We randomly specified a location as the starting point, and then randomly moved. After walking for a period of time, we obtained the relative motion path of the PDR. The V-PDR was tested through the same path to obtain the absolute position path of the V-PDR at the same time. Then, the paths were compared with the high-precision measurement path to analyze the results of our algorithm. The comparison results include maximum error, mean error, and 95% situation error. Maximum is the maximum location error distance in the experiment and the mean error is the average error for the path. The 95% situation error is the least 95% error in the experiment, which shows the effect for most locations. The results of the first experiment conducted in the third floor are shown in Figure 12. The red curve is our ground truth. The blue and green curves represent the PDR trajectory and the V-PDR trajectory, respectively. The pedestrian departs from the start point and circles clockwise along the corridor to the end point. Obviously, the trajectory of PDR is quite far away from the ground truth, especially when the pedestrian turns corners. This bias denotes the accumulative localization errors of PDR, which is mainly caused by three reasons: step detection errors, stride length estimation errors and heading calculation errors. By contrast, in the V-PDR test, the results of PDR are successfully corrected by VPR at the turns, which makes the estimated pedestrian trajectory closer to the ground truth. The improvement of localization performance can be proved more intuitively from the estimated end positions of PDR and V-PDR. The end point of PDR is 1.43 m away from the actual end point, while the distance in V-PDR method is 0.35 m. The statistics of calculated errors of PDR and V-PDR are listed in Table 2. Due to the small scale of the neural network, it is fast to generate a vector and to find the similarity through matrix operations. Figure 12: Estimated trajectories of PDR and V-PDR. From the mean error column, we know that a 51.2% improvement in localization accuracy was achieved by V-PDR compared with PDR. Through this experiment, it can be seen that our method is effective in reducing cumulative errors of PDR and improving localization accuracy. The second experiment was carried out on the first floor to the third floor. The experimental setting was similar to the first experiment. The difference was that there were up and down movements in the elevator in the second experiment. The other settings were the same. The results of the cross-floor experiment are shown in Figure 13. Again, the blue curve represents the trajectory of PDR, the green curve represents the trajectory of V-PDR and the red curve is the ground truth. The pedestrian walks along the ground truth shown in Figure 9 and goes upstairs from the first floor to the third floor.