Ocean News & Technology
By Jesse Rodocker, Seabotix, and Joe Burch, Sound Metrics
Living in a three dimensional world (3D) has taught our brains to see images in three dimensions, even though the observations that pass through our eyes are only two dimensional (2D). It's the slightly differing information contained in multiple 2D perspectives that allows us to extrapolate 3D images. The same concept is now being realized in underwater robotic work in zero optical visibility water using high-definition sonar.
Expanding on the vLBV's mechanical capabilities are built-in high resolution sensors, including pitch, roll, heading, depth, and temperature. This onboard data are accessible at the surface for interfacing with thirdparty software to further enhance captured data. Additionally, the vLBV's use of dual vertical thrusters offers the ability to incorporate active roll compensation, resulting in improved stability. Taking the degree of automation and stability to a higher level is auto altitude.
In the past, vectored platforms have predominately been available only as much larger systems. DIDSON, being a larger sonar, has required a larger ROV platform to be a viable option of a multi-beam imaging sensor. With the introduction of the ARIS in a smaller, lighter package than its predecessor, integration onto smaller ROV systems like the vLBV is now possible.
Combining their strengths, SeaBotix and Sound Metrics have set out to augment ROV-based sonar applications. The vLBV provides the stable, capable platform and the ARIS delivers clear, high-definition sonar imagery.
Now getting back to three dimensional thoughts as they pertain to the observer of ROV-captured data. All the sonars mentioned above produce data in two dimensions; range and cross range. Range is the radial distance away from the ROV, and cross-range is measured left and right of the center axis in front of the ROV. The challenge is to quickly perceive vertical information about a target (the third dimension). This provides differing perspectives of an object, allowing the brain to do what it does naturally - interpret the visual information into 3D imagery. Rolling the sonar 90 degrees slowly about the forward axis of the vehicle is how the observer is provided with differing two dimension perspectives. Rolling the sensor exchanges horizontal left right target information for images showing vertical target information. This gradually transitions from the usual apparent top down perspective through a 90 degree roll into an apparent side perspective of the object, which yields the depth perception. The observerÆs brain has just integrated the varying 2D sonar views into a natural 3D perspective of the imaged object without any conscious effort.
An operator can now stand off a target and with confidence, capture real-time, high-quality imagery in black water conditions. This roll capability enables measurements of objects in all three dimensions from accurate sonar data. This roll capability also provides the operator with the ability to match sonar orientation to the slope of the terrain. By rolling the sonar to become parallel with the terrain, the sonar image quality can be maximized. Rolling the sonar allows for terrain matching of the image to surfaces in any orientation, from horizontal to vertical.
Incorporating a variety of technologies and sensors into a single system presents a variety of opportunities. The vLBV fitted with a scanning sonar, ARIS imaging sonar, acoustic positioning, optical camera, grabber, and lighting is a formidable tool for a diverse range of missions. A scanning sonar provides the longer range, 360 degree coverage to locate and navigate to targets where the ARIS provides high-definition imagery and accurate dimensional information. The optical camera and lighting provides real-time visual data where conditions permit and the grabber offers possible object recovery.
The possible applications are vast in number. Operators can use the system to search for objects such as mines, where the added height (Z-axis) information can be used to more accurately identify and classify the target. There is also broad area search capability coupled to ultra-fine image detail on a stable platform that can operate in demanding environmental conditions.
For more information on the vLBV visit www.seabotix.com/products/vlbv300.htm.
Original Article at: http://virtual.ocean-news.com/publication/?i=99313
Subscribe to Ocean News & Technology: http://ocean-news.com/subscribe