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.

Scanning in Sicily

Today we had the opportunity to perform our first scans in the coastal town of Carini (in the province of Palermo, Sicily). The local archaeologists led us to an old building in the nearby countryside where a small rock column opened up into the cistern down below. The building was once a basilica from the 17th century, and was fascinating in itself. We successfully deployed the ROV and gathered a solid set of data from the site. Once we finished collection, we took a short walk up the street to a second, smaller cistern outside of another old building. Once back at home, we settled down in the hotel lobby and spent a few hours working on our visualizations. Everything is coming along nicely; today was an excellent field day!

Back at home, I made some more progress on my projective texture system. I am now able to load Jeff's maps in and project a single texture using shaders. My next goal is to add shader support for multitexturing and blending. The picture here shows a map from our hotel room projected into the main room of Jeff's keyhole cistern.

Technical Update - Mapping and Image Processing

Departure is nearly upon us! We have been doing a great deal of work the last few weeks getting everything ready. Erik and I had an opportunity recently to drive the ROV in the pool and perform a full mapping run. We positioned the ROV in strategic locations throughout the pool and captured a series of sonar scans. These were fed through Billy's mapping program to generate a map of the pool.

It was an excellent opportunity for us to practice the teamwork and processes necessary for a full deployment, including setup, un-boxing, deployment, scanning, assembly, and take-down. After the session I feel a great deal more comfortable with the equipment and software we will be using in Malta.

In addition, I have been doing further research on the topic of image processing. In particular, I need to smooth the back-scatter out of the cistern photos, then sharpen the images and equalize their appearance for texturing. Smoothing will be done using a median filter, as shown below. Notice how an increasing filter size greatly reduces the noise in the picture. However, it also blurs the subject of the image. This effect may be reversed using a laplacian mask to re-sharpen the transitions of the image. Once this process is complete, I hope to have a clear, sharp picture ready for texturing. The final step will be to equalize the gamma across all images so they blend smoothly together on the final mesh.

Tim is also doing some image processing work with his 3D imaging project. I am hoping that the research I have done for texture smoothing will also be able to help him in generating his bump and disparity maps.