Tuesday, July 1, 2008

Robots into the Abyss II

Brought to you by Alexander Forrest, Environmental Engineer

One of the challenges for the team working with UBC-Gavia, the autonomous underwater vehicle (AUV), is designing missions that play to the strengths of the vehicle. Additionally, the team is optimizing the collected data in order that be used directly by the Deepworker team for flight plan development. A unique application of this is the exploration of the abyssal plain of the central basin of Pavilion Lake. This part of the lake is the deepest part of the lake (~ 55 - 60 m deep) that is generally characterized by a very flat, muddy bottom and low microbialite coverage. Due to the fact that there are few targets of interest in this region, Deepworker pilots find this a tedious area to explore and so prefer to autonomous robots to explore the deep.

The main instrument onboard UBC-Gavia was the sidescan sonar. This device operates on either high or low frequency to render a relief image on either side of the AUV. A common analogy used is that it is like shining a flashlight away from the vehicle and anything that is obstructs the light is bright on one side and casts a shadow on the other. The missions that were run yesterday were being run at high frequency (better quality images) and the reduced range of 30 m (compared to 100 m at low frequency). Making sure there was sufficient overlap between each of the AUV missions, runs were conducted that covered the north half of the central basin.

It was discovered that there was very little of interest in this section of the lake (as was previously expected) but several interesting areas were identified on one edge of the runs. Odd ridging appeared in the images running perpendicular to shore that is currently unexplained (shown in the picture). This has been now identified as a potential mission priority for the Deepworkers if there is sufficient time available. Further exploration of the abyssal plain continues today in those regions that weren't previously surveyed with the boat sonar.
Sample of sidescan sonar data with the centerline representing the path of the AUV, the wavy, vertical line representing the bottom surface with the range away from the vehicle shown on the bottom axis and the obvious ridging shown in the upper right hand corner (~ 20 m off the port side of the AUV).

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