Calibration courses and targets

Calibration courses and calibration targets configured for calibrating sensors used in vehicles or mobile robots. A system for calibrating a sensor of a vehicle comprising a processor configured to emit a lidar signal and receive a reflection from a calibration target and use the received response to calibrate the sensor. The target 1000 comprising an irregular asymmetrical 3d shape having a top surface 1002 and at least 4 side surfaces. The calibration target comprises a top surface and at least four side surfaces 1004, the side surfaces having an edge 1006b shared with the top surface and an edge 1006a shared with the bottom 1010 of the target, the angle difference between a horizontal plane and a side surface α is different to the angle between the horizontal plane and an adjacent side surface β. In another embodiment the top surface is angled relative to the horizontal plane, the side surfaces connected to the top surface and each arranged at a different angle relative to a horizontal plane. The side surfaces are preferably planar and the target preferably forms a convex shape.