A Smartphone 3D Positioning Method using a Spinning Magnet Marker

In recent years, the importance of location information has increased due to the popularization of terminals such as smartphones. Our purpose is to estimate the 3D position of smartphones within several centimeters. This location information can reveal a person's behavior patterns and subject of interest. A method based on dynamic magnetism can estimate the 3D position of a terminal within several centimeters, and it is robust against the environment. However, since the performance of the smartphone's magnetic sensor is limited, this method cannot be used in smartphones. In this research, we propose a smartphone 3D positioning method using a Spinning Magnet Marker (SMM) that spins a powerful neodymium magnet with a motor. Magnetoquasistatic field generated by an SMM is detected by a magnetic sensor mounted on a smartphone, and the 3D position of a smartphone based on the SMM is estimated from the magnetism. We developed an SMM with a stepper motor to improve estimation accuracy. In addition, we studied the magnetism generated by an SMM and derive equations to estimate the 3D position of a smartphone. Furthermore, we improved the estimation accuracy and expanded coverage by introducing a noise reduction method. We evaluate the estimation accuracy of the proposed method. When the azimuth angle is 0°, the elevation angle is 0°, and the distance is 3m, the azimuth angle is estimated with a mean error of 1°, the elevation angle is estimated with a mean error of 4°, and the distance is estimated with a mean error of 9cm.