# Design of OCC Indoor Positioning System Based on Flat Panel Light and Angle Sensor Assistance
## 5 Experimental Results and Analysis
### Precise Positioning Experimental Results  
The coordinates of the LED center O point are (90, 90, 200), the A point coordinates are (120, 75, 200), and the spacing is a fixed value of 33.54 cm. The vertical distance h changes between the receiving end and the ground. Considering the height of most users and the height of the ceiling in the conventional building, this experiment will set h to 40 cm, 60 cm, 80 cm, 100 cm, respectively, for 16 test points The experiment is conducted, and Figure 15 shows the comparison between the calculated estimated coordinates results and the real location coordinates. Figure 14: Decoding success rate of images from four angles at different heights. As can be seen from the figure, the distance between the true location coordinates and the estimated location coordinates is relatively close, and as h increases, the estimated location is closer to the true location coordinates; the points that are further away from the flat light have a larger error compared to the center of the point. Commonly used metrics to evaluate the performance of indoor positioning techniques are accuracy, precision, complexity, and scalability. In this paper, accuracy is used as a performance metric for analysis. Accuracy refers to the degree of conformity between the estimated position coordinates and the true position coordinates under certain experimental conditions, and the Euclidean distance between the true coordinates and the estimated coordinates is usually used to express the magnitude of the systematic error. Let the true position coordinates be (x,y) and the estimated position coordinates be (x\({}_{0}\),y\({}_{0}\)), then the localization error can be expressed as Equation (9). \[e\ =\ \sqrt{\left(x-x_{0}\right)^{2}+\left(y-y_{0}\right)^{2}} \tag{9}\]  
In order to analyze the positioning results more clearly, the positioning error of each test point at different h values was calculated, and the results are shown in Figure 16a. From the figure, it can be seen that the maximum positioning error of 10.59 cm and the minimum can reach 2.97 cm for h = 100 cm, which was obtained at the point (120, 120). When h = 40 cm, the maximum positioning error of 23.14 cm was obtained at the point (0, 180). As h decreases, the distance between the mobile terminal and the flat lamp  
Figure 15: Coordinate plot of the calculated estimated value of the precise positioning algorithm against the true value for different values of h: (a) h = 40 cm; (b) h = 60 cm; (c) h = 80 cm; (d) h = 100 cm. increases, the accuracy may decrease when the corner point is identified, and the azimuth angle of the receiving end changes significantly, so the accuracy of the estimated position coordinates decreases. The average error \(e_{R}\) is calculated at each point when the value of h is changed, where n is the number of measurements, and \(n=16\) in this experiment. The calculation formula is Equation (10):  
\[e_{R}\ =\ \frac{\sqrt{\sum_{i=1}^{n}\varepsilon_{i}^{2}}}{n}\ =\ \frac{\sqrt{\sum_{i=1}^{n}\left[\left(x-x_{0}\right)^{2}+ \left(y-y_{0}\right)^{2}\right]}}{n} \tag{10}\]  
Figure 16b shows that the average error decreases as the distance between the transmitter and receiver decreases with increasing h, and the average error is negatively correlated with the value of h. The minimum value of the average error is 6.5 cm. We have made some comparisons between the method proposed in this paper and existing single lamp VLP localization algorithms, as shown in Table 3. Refs. [26, 27, 28] all use a single circular lamp as the transmitting light source, and the processing at the transmitting end is very similar, relying on the flashing of the lamp to transmit information, which requires a large circuit laying cost. However, their processing at the receiving end is different; improvements have been made, and the positioning accuracy has been improved (both are 3D positioning). The innovation of the method proposed in this paper is that no large-scale circuit modification is required, and the stability of the system is improved.