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.

Princeton's First Cistern

Now that the Princeton students are here in Malta, the four of us finally have our chance to actually work with the ROV at a cistern. We went to Mdina today to visit a couple of cisterns at private residences there. Despite some confusion about where exactly we were supposed to go, we manged to get access to a pretty interesting cistern. We also got to explore the fortress at Mdina for a while which was pretty fun since none of us had been to anything like it before.

For this deployment, Drew ran the data collection, I piloted, and Anna and Yingxue managed the ROV. After lowering the ROV down the shaft, we found a rather interesting cistern that consisted of a main bell-shaped room with three circular chambers off to the sides. All of them were at slightly different depths but all were about one meter deep. We took 14 scans in all, and Billy says he should be able to make a pretty nice map out of the data we got.

The owner of the house we were working in was very excited to watch us work and see the images of his cistern. He was particularly interested to see just how much water it could hold.

Goals and Progress

Over the break I've worked on integrating the data from Smart Tether into the FastSLAM algorithm for better localization of the ROV in the underwater caves of Malta. The algorithm will match up several Smart Tether measurements with the times of the sonar scans and use an average of those measurements to calculate a weight for a given particle's estimated position of the ROV. I've also started to make sample Smart Tether data based on the data we collected at the pool to use for testing.

Having worked on localization with the x80 ground robot and a known map in Prof. Clark's Autonomous Robot Navigation class, I am interested in the technical challenges presented by underwater localization and with having no map initially. I've studied Latin for four years and Italian for two, so I'm very interested in the history of Malta as it dates back to Greek and Roman times as well as the culture of Malta and the Mediterranean region.

Hello!

Hey everyone!

My name is Drew Boik and I'm a junior at Princeton studying computer science. I'll be working with Austin Walker on the software for cave mapping. I am from Winter Springs, Florida (near Orlando), and in my spare time I like to sing, play piano, and play trumpet in the Princeton University Orchestra. When I'm in Florida I also work seasonally at Disney World in the Magic Kingdom. I'm really excited to work with the ICEX team and can't wait to go to Malta!