A method of simplifying the arithmetic operation in a global motion compensation process approximates the motion vector field of the whole image without using many parameters. A rear portion of a motorcycle includes a rear cowl covering sides of a vehicle body frame, a grab rail disposed on vehicle body sides of a rear occupant seat of a tandem seat above the rear cowl, a rear lamp assembly in the rear of the rear occupant seat and a rear mudguard under the rear lamp assembly. The rotating drum is hollow and has a plurality of radial separating plates defining a number of niches. The windings of the second group are displaced, relative to the windings of the first group in order to cancel out an n-pole component of the magnetic field. By using the switch to switch the load impedance in and out of the connection with the scattering object a large dynamic range for a fluctuating scattered signal may be achieved. By providing a staking part on the inner periphery of the housing in the vicinity of the annular groove using a staking device, the magnetic collecting ring can be secured in the annular groove through a simple process.