Place the checkerboard at roughly 3 m - 10 m from the camera. For the closest position, the closer, the better, but it should be far enough so that all the edges of the board are visible from the camera and radar. For radar that can detect elevation, the height of the calibration target should be varied above/below the radar level. Otherwise, keep the calibration target at a levelled ground. The checkerboard should not be occluded in the camera or radar view.