ROVworld Subsea Information

Harbour approach survey in the Caspian Sea using a commercial man-portable AUV c
Date: Wednesday, January 23, 2008 @ 12:00:00 EST
Topic: AUV NEWS


Harbour approach survey in the Caspian Sea using a commercial man-portable AUV carrying a wide swath bathymetric sonarIn 2007 the Gavia Autonomous Underwater Vehicle (from Hafmynd, Iceland) and the GeoSwath wide swath bathymetric sonar (GeoAcoustics, UK) were used for the first time to perform a post-dredge survey of a port approach. This was part of an investigation of grounding of an oil company's supply vessels. The survey found sandbars in the harbour approach which had been missed by previous single-beam surveys.

The Gavia was in the Caspian Sea to perform a pre-lay trench survey for the engineering and construction contractor Acergy. For this job it was hand-launched from a beach; the Gavia is 2.6m long and weighs 80kg in air when configured for hydrographic survey. After the mission was complete the operating company requested a survey of the depths in a local port approach channel. The oil company's captains were reporting groundings, but no swath survey vessels were available and a previous single beam survey had found no high spots.

 

Survey of the Port Approaches
Picture top: Survey of the Port Approaches

Picture right: GeoSwath on Gavia AUV

  GeoSwath on Gavia AUV  


The Gavia AUV was launched from a vessel holding station outside the port area. For the first mission it was programmed to run several meters below the surface and fully map the harbour approach channel using six 500m survey lines at 40m line spacing. This took less than an hour, and the Gavia then returned to the mother vessel and surfaced. The Gavia's short-range wireless communications link was used to download the survey data from the GeoSwath unit. After a check of the data quality a second mission was uploaded, this time to survey the harbour approach inside the breakwater.

The GeoSwath data was processed within an hour of the Gavia's return. The bathymetric map revealed several sandbars extending into the shipping channel, still showing the keel marks from the reported groundings. This map was supplied to the port authorities who carried out the required remedial dredge works.






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