In many environments, it is useful to have a surface which is level regardless of the orientation of the structure supporting the surface. For example, helicopters or other vehicles including fixed-wing Unmanned Aerial Vehicles (UAVs) and rotary-wing Vertical Take-off Unmanned Aerial Vehicles (VTUAVs) often need a level surface from which they can take off and land in a wide range of sea conditions. Providing such a surface is not a problem on land-based facilities or other structures that are secured to a solid surface such as oil drilling platforms that are anchored to a sea bed, etc. However, providing such a surface can be difficult when the object on which the aircraft is to land can move. For example, helicopters attempting to take off and land on ships are currently limited to a relatively narrow range of sea conditions in order to avoid injuring the aircraft and/or crew.
Given these problems, there is a need for a mechanism that can be operated to maintain a surface in a desired orientation regardless of the fact that the support for such a surface is not level and/or is moving.