The camera outputs live video of each dive, which can be recorded if required, and sends high quality digital images to the surface within a couple of seconds. The digital still images can be saved to flash memory in the camera and simultaneously saved to hard disk in the survey vessel so data are always secure. Still images have a resolution equating to 23 million pixels per square metre of seabed with a frame size of 400mm by 320mm. Remote control of all functions, live video feed and still image viewing at full resolution are all available with the tool deployed.

Obtaining good underwater images in poor visibility is only possible if the survey vessel can hold station properly.  'Aquadynamic' was designed for this role and can keep position indefinitely using her forward and aft water jets. Control of each jet is linked to a 3D joystick in manual mode and to a DGPS-referenced dynamic positioning system in DP mode. This degree of vessel control enables the capture of closely grouped images around a station to emulate a replicate sampling technique. With the aid of specialised software, Aquadynamic can recover a sediment sample from within 2m of any image site if required. This combined technique is used in sensitive areas where ‘blind’ sampling is unacceptable.

The new camera, combined with benthic sampling and/or sonar data, has produced very encouraging results on two recent studies for Marine Ecological Surveys Ltd. Dr L. J. Seiderer of MESL said, ‘In a recent survey carried out to assess the geographical extent of nearshore Sabellaria reefs using high resolution side scan sonar, the Weasel was deployed in order to ground-truth the sonar results. Despite the ubiquitous nearshore hindrance of extremely poor water visibility, the Weasel obtained excellent digital images of the seabed. We were therefore able to construct a GIS biotope map. The work was highly commended by both CEFAS and JNCC.’ A second generation ‘Weasel II’ camera is now under construction with a larger frame size, a smaller housing and an increased resolution of 53 million pixels per square metre.

MJ Information No: 22714