Fig. 1From: A reduction method for magnetic disturbance caused by DC railway systemGeomagnetic data collected at BJI (black line), the processed data with the adaptive Kalman filter (red line) and data at BMT (blue line). a Horizontal component. b Vertical component. The mean values were subtracted to keep the geomagnetic data on the same order of magnitude. The vertical geomagnetic field at BJI are largely affected by the Metro systemBack to article page