Investigation and Compensation of the Magnetic Deviation on a Magnetometer of a Smartphone Caused by a Vehicle

The built-in magnetometer sensor of a smartphone is an attractive sensor suitable for detecting the direction of pedestrians' movements. This detection can be used to enable collision avoidance between cars and pedestrians, particularly if the pedestrian is not visible from inside the moving car. However, surrounding metallic materials have undesired effects and this influences the accuracy of the magnetometer. This paper investigates the amount of magnetic deviation caused by surrounding metallic material, such as a car, when the magnetometer sensor of a smartphone is used to determine the orientation. A set of experiments were conducted to investigate the effects of magnetic deviation. The experimental setup includes both parked and moving cars. Based on the results of the experiments, we show that the magnetic deviation can influence the efficiency of distinguishing the endangered or secure pedestrians in a car to pedestrian collision avoidance scenario. If we intend to use the magnetometer to detect the pedestrians' movement directions, the magnetic deviation needs to be compensated in order to detect the accurate movement direction of pedestrians. Therefore, in this paper we present a compensation algorithm, which successfully compensates the possible amount of magnetic deviation in the magnetometer of a smartphone.