Field test of a practical test model of maintenance examination system for mooring facilities and additional installation of chain grasping frame in the vehicle

The program of GPS wave gauge deployment by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), for offshore wave monitoring to improve port and harbor facilities, includes inspections essential for sound mid- to long-term instrument operation but does not yet include mooring-line inspection, in part because of design allowances. For the GPS wave gauge buoys, in addition, severe weather and sea conditions tend to hamper diving operations and the size of the buoys and mooring lines render their removal to land impracticable. In this light, the authors are engaged in development of a system for unmanned underwater inspection of the mooring lines of deployed GPS wave gauges, to enable in situ inspection and thus obviate the need for removal to land. In March 2010 we performed in situ trials with a first practical test model (Test Model 1). Here we report on the development and water-tank testing of a new version (Test Model 2) designed for enhanced operational and measurement integrity with newly developed component systems, including a four-arm clinch assembly for steadying movement on the mooring chain during image measurement and an automatic image-measurement mode incorporating automatic chain-edge detection.