Gozo Underwater Cave Mapping

Today gave us an opportunity to obtain some long-awaited data from a cave in Gozo. At 7am Timmy drove us to Manoel Island Yacht Marina where we met our skipper, Paul. After carrying all of the equipment on the boat, Austin, Tyler, Prof. Clark, Paul and I departed and began our 1.5 hour voyage to Gozo. Apart from some heavy chop in the beginning of the trip, the day was beautiful and the ride presented some incredible views of Malta, Comino, and Gozo.

When we arrived we ran across some tour boats which continued to come to the cave throughout the day, but for the most part we enjoyed uninterrupted access to the cave. In addition to being the first time we had mapped a cave, today was the first time we had ever used the Smart Tether. The Smart Tether is an advanced piece of equipment that contains nodes every couple of meters which use accelerometers, rate-gyro sensors, and magnetic sensors to track the orientation and position of the ROV. The Smart Tether greatly increases the accuracy of our ROV localization which in turn helps us create better maps.

In each of our experiments we took turns piloting the ROV, logging data and sketching maps, recording sonar and Smart Tether data, and working the Smart Tether. We started off using the sonar to take horizontal scans of the underwater cave, but we weren't able to get that far into the cave before running out of tether. We decided to add the 80 meter extension to our 40 meter Smart Tether, which allowed us to venture much deeper into the cave. This time we attached the sonar vertically and got some great scans with well-defined cistern-like walls. We ran across many fish, jellyfish, and even an octopus which grabbed onto the ROV. After backing out of the cave, we deployed one more time with the Smart Tether extension to take horizontal sonar scans. We ultimately got about 60 meters in before turning back. Before leaving, we made sure to shoot some underwater video of the ROV with one of the GoPros we brought along.

If all goes well, we should be able to use this data to create 3D maps of the caves using a combination of the horizontal and vertical sonar scans for mapping and Smart Tether logs for localization.

Quick Technical Update:

I was able to test both the laser and the GoPro setup today with some exciting results. Using the new skid it was possible to position the lasers to line up vertically at just less than 2 feet. This will enable the driver of the ROV to position it appropriately for texture images.
The pictures from the GoPro cameras are amazing! The GoPros are positioned just below the ROV’s center camera and are much better resolution than the ROV's camera. The GoPros also receive much less backscatter than the main camera does due to the fact that the GoPros are further away from the ROV’s lights. Both of these factors lead to crisper cleaner underwater images.