Visible light positioning (VLP) has been studied widely due to its high accuracy and low cost in the field of location-based services (LBS). However, many existing VLP systems have the requirements that the receiver should be placed horizontally and more than three LED lamps should be used, which are difficult to meet in practical scenarios. Therefore, it is necessary to develop a novel VLP algorithm for tilted conditions. An effective and simple VLP system while the receiver is tilted based on double-LED lamps is proposed in this paper. The vertical position can be determined by combining the information from angle sensors with geometric information. Through analyzing the imaging characteristics of the tilted state, we can utilize the relationship of similarity to calculate the location of the mobile receiver. Experimental results show that the positioning accuracy of our proposed algorithm can reach 5.48 cm.

Nowadays, indoor visible light positioning (VLP) is one of the hottest technologies in the field of positioning; as a result, a number of algorithms for VLP have been proposed. However, unfortunately, few algorithms can be applied to the case that the receiver is tilted. In order to solve this problem, we developed a three-dimensional indoor VLP algorithm which can work effectively and accurately when the lens is tilted. When the lens is far away from the LED, the image of the LED is approximately regarded as an ellipse, and the distance between the two is obtained through the geometric relationship, and we finally achieve the positioning of the camera by the triangulation algorithm. The quantitative results show an average error of 6.74 cm when the tilt angle is estimated to be within 30°. At the same time, we propose an ID allocation scheme, which can effectively reduce the demand for ID.