In harbours and ports where manoeuvring areas are confined and shallow,
there are many navigational restrictions. Therefore ship operators are
required to manoeuver their vessels in accordance with the environmental
situation. Additionally, when the entering and leaving the ports also
involve berthing and unberthing operations, ship handling without
assistance is not easy. This difficulty is due to the problem of
directional control and coursekeeping, a direct result of poor
steerability at low speed and the influence of wind and current.