Zhoushan, Zhejiang: 'Unmanned fleet' makes maiden voyage, solving intertidal submarine-cable inspection challenge
China's first near-shore twin-hulled unmanned surface vehicle (USV) has officially begun intertidal cable-inspection operations off Gouqi Island, Zhoushan, Zhejiang province. Teamed with an aeromagnetic unmanned aerial vehicle (UAV) and an underwater polarized-optics camera robot, the USV forms part of an "unmanned fleet" that creates an air-sea integrated inspection regime — ending the era of intertidal cable patrols that were weather-dependent, high-risk gambles, and delivering round-the-clock, full-coverage, transparent protection.
[Photo provided to chinadaily.com.cn]
The intertidal zone — alternately submerged at high tide and exposed as mud-flat at low tide — is the critical "choke point" where submarine cables come ashore. Its amphibious nature has long made it an inspection no-go: conventional survey vessels cannot enter because of draft limits, while personnel must wait for the handful of low-tide windows each month and then wade through turbid water hiding sharp shells and quicksand. The work is slow, dangerous and prone to positional error in both cable route and burial depth.
The unmanned fleet targets each pain-point: Air-sea magnetometer UAV — the fleet's pathfinder — carries a high-precision magnetometer and magnetic-fusion algorithm. Unaffected by tide or terrain, it flies above exposed flats or knee-deep water, penetrates the sediment layer and captures the cable's magnetic signature, pinpointing route and depth within hours instead of days.
[Photo provided to chinadaily.com.cn]
When the cable runs into deeper water, the 0.5-meter-draft near-shore USV takes over. Equipped with the same tide gauges and sub-bottom profilers found on conventional survey ships, it enters shallows that traditional vessels cannot reach. Operating in "mother-daughter" mode with the support ship ZhouDian-15, it streams data to the backend in real time, raising daily productivity by 30 percent.
The underwater polarized-optics robot weaves through rock-strewn seabed terrain. Its polarizing lens eliminates refractive distortion, delivering clear images of cable abrasion and sheath integrity almost independent of weather or tide, removing the need to wait for spring tides.
[Photo provided to chinadaily.com.cn]
"When water is shallow we use UAV and USV; when depth and visibility permit we add the underwater robot — achieving seamless, all-time detection," explained He Xutao, level-5 specialist at the State Grid Zhoushan Power Supply Marine Transmission Technology Center. By mixing and matching platforms to suit local conditions, the fleet has compressed the inspection cycle for Zhoushan's 47 intertidal cable sections from six months to two, reduced high-risk man-hours to zero and extended coverage — offering a replicable "Zhoushan solution" for intelligent island-grid operation and maintenance.
