A method and an installation for loading and unloading compressed natural gas on ships, said ships being suitable for sea navigation and the ships having receivers. The flagpole includes a plurality of segments including a bottom segment, at least one intermediate segment, and a top segment; a plurality of sleeve assemblies each positioned between an associated pairing of a relatively lower segment and a relatively higher segment; and a plurality of biasing members each urging an associate one of the segments toward an extended position. The joint free spectral range provided by the multiple wavelength reference elements results in a joint transmission peak that is centered at a unique wavelength, and maximum optical power detectable from the beam by the detector occurs at the center wavelength of the joint transmission peak. The image quality degradation unit processes image quality degradation for object data which is frame data corresponding to one frame either before the switching between the left eye video image data and the right eye video image data and one frame after the switching, or two frames before and after the switching. The apparatuses including a door clamp having a stop, a base attached to the stop, a jamb bracket attached to the stop, and a fastener coupled to the jamb bracket. The display apparatus also includes at least one spiral spring having an elasticity enough to support weight of the main body to extend and contract in response to a movement of the slider.