The Art of Sonar Mosaics

Hand-Mapping a cistern using sonar scans can be quite a tedious but rewarding task. After the many hours spent in the field collecting data there is still the sometimes overwhelming task of analyzing 10's of sonar scans for each cistern. To make this job a bit easier, I like to think of each sonar scan as a piece of a puzzle. At first, I am given a number of pieces in the form of sonar scan data for each cistern and it is my job to put them together. Each scan gives a limited visibility of the cistern but with all of the pieces properly placed, a relatively accurate 2D representation of the cistern can be achieved.

Here is a general overview of one of the map-making processes:

First, I open one of the sonar scans and take a screen shot of the entire scan.

A black and white representation of the scan is used to clearly indicate what is a wall, shown in black, and what is water/data that cannot be collected, shown in white.

Next, I crop the screen shot to only show the sonar data and alter the transparency to allow multiple sonar scans to overlap. For this example I have changed the color of the walls to blue to show where this particular scan overlaps in the final map. The image is then rotated to best-fit the current map.

Finally, each useful piece of sonar data is pieced together to form a sonar mosaic of the cistern. This particular mosaic is one of the more recent cisterns we visited in the Wignacourt Museum.

Timmy wins every game of Connect Four in 3 moves.

The Cave

Today (Wednesday) we began exploring a cave at St. George's Bay in St. Julian's. It was huge! It is this large, deep pool of water contained completely in this cave. We had a bit of a trek to get to the entrance, and when we got there, we had to walk down a staircase which led to the water. We set up our equipment up near the entrance so we had some light to work in, and Andy and Brig practiced their driving skills for the first time since we've been here in Malta.

Unfortunately, like yesterday, we had a lot of technical problems with the sonar communication (a relatively new problem since Chris showed up...impeccable timing). We ended up deciding to not dedicate too much time initially to troubleshooting the problem, and get on with exploring the cave. We took a lot of video and really just wanted to get a feel for the size and environment of the cave. With 3 days to explore, we wanted the first day to be dedicated to getting a grasp on the cave as a whole.

Around lunchtime, we decided to pull the ROV out, and attempt to do some debugging on the sonar connection. We narrowed the problem down to the actual connection between the ROV and the tether, but were not able to come up with a solution on site.

Deciding to continue with just video, we put the ROV back in the water and I took control of the control box for awhile. My goal was to get as deep into the cave as possible, given the limited amount of cable we had.

After exploring for awhile, I hit a maximum depth of about 35 meters (114 feet!). I went into the cave as far as I could, and when I was pretty sure I had run out of cable, we decided to turn around. Upon trying to surface, I realized that there was a bit of a problem: I had created some significant snags in the tether while driving around. This was probably one of the worst tangles that the ROV had experienced thus far, according Chris, so as one could guess, there was a bit of stress around the cave site. Half of the team was down in the cave, waiting to wrap up the cable as it became untangled, while the other half watched the video feed and attempted to strategize a plan to untangle the ROV. Chris ran back and forth between the computer and the cave to try and quickly solve the problem so we didn't end up becoming completely stuck in this massive cave. It took quite awhile to remedy, but after some careful driving, we were free and to the surface. Getting stuck allowed us to more closely see some of the natural formations of the lower parts of the cave, which were super interesting!

With the significant technical problems of today, we have decided that it would be best to stay home and troubleshoot tomorrow instead of trying to explore the cave with non-functioning equipment. We hope that by Friday, we will be able to have the sonar connected so we can create some maps of the cave (not an easy task), and maybe even connect our second tether so we can explore even deeper!

The Legend of the Pygmy Hippo

A long, long time ago time ago a magnificent species walked the earth. It was found only on a small island in the Mediterranean, the island of Malta. Long separated from its mainland parents these animals evolved having a unique trait, they were 1/3 the size of their parents. These were in fact, pygmy hippos. Known as Hippopotamus melitensis, they stood only 80 cm high. Plagued by the incidence of insular dwarfism, evolution of a smaller species due to land restriction, their isolation has made them unique. Having first arrived on the land we now Malta by crossing the land bridge during the ice age, they became isolated once this disappeared. These hippos existed during the Pleistocene (2,588,000 to 12,000 years BC), long before the building of the oldest stone structure in the world, the Ggantija Temples, found on the island of Gozo.

We were privileged enough to explore these temples on Tues, March 8th. The temples themselves had something in common with the hippos - they were much smaller in person than they appeared in pictures. Constructed to represent the earth mother, the two temples consist of multiple round open rooms. The pictures of these temples show these multiple circular rooms for worship - an intriguing pattern when viewed from above. This construction is an incredible feat as some of the larger stones weigh many tons, and were assembled to their present position through human strength and early innovation.

I was most impressed with how well these structures have held up considering they were built 5,800 years ago. Despite the wearing of the stone, and age the of evidence (and removal to museum sites), the unique features were still visible even to my untrained eyes. I could see how the location was a place of peace, offering a beautiful view overlooking the island, tall green grass all around, and an amazingly beautiful structure to offer up worship. I would have loved to find a small area of the temple to curl up and read a good book, enjoying the clean air and sunshine.

It is unfortunate that the people who built the Ggantija Temples did not have a chance to interact with the pygmy hippos as they became extinct long before evidence of any human life on Malta. However, these magnificently small animals were companioned on the island by another small creature - the pygmy elephant, Elephas falconeri, whose story is similar to that of the hippo, and stood only 90 cm high.

We were first told about these unique creatures during Timmy's visit to San Luis Obispo, CA. He warned us, "Watch out! You might see them roaming the land." Little did I know, it is only Timmy who has the power to awaken the ancient species. As I began to visualize these two species, a vision of epic hippo and elephant battles danced in my head. Now, I'm not going to lie - even though I knew it was never possible - I had high hopes for seeing these elephants and hippos roaming through the streets of Valletta, or tromping through the countryside. And to my disappointment - I have yet to see any hippos or elephants.

Pressure Problems

Calibrating the ROV depth sensor has been a continuous event throughout our trip. Our excursion to the Mdina cisterns began with an investigation of the local gas station air compressors. Before getting there we were discussing all the different units of pressure that we might run into to preempt converting units if we had limited access to the air compressors. It turns out the common units were lbf/in^2 and Bar. The first gas station had a free air compressor to use but the pressure was no more than ~20 psi but there was no pressure gage to know for sure so we moved on. We found another gas station nearby with an adequate air compressor and the gas attendant was very excited to help us when he saw our robot. The pressure from the air compressor was not high enough and after briefly explaining the problem to the gas attendant he began brainstorming with us on how to solve the problem given the limited equipment we had to work with. After clarifying the problem, he left and came back shortly with a small plastic cap and he began using a knife to take out some of the plastic so it would fit better on the air compressor nozzle. Billy and I fastened the make-shift pressure adapter onto the nozzle and we were able to get the correct pressure to calibrate the ROV. We never knew how exciting it would be to calibrate the ROV (again) and gain so much knowledge about engineering and culture in Malta. Learn by doing at its best!

Chuck Norris jokes are good but Timmy jokes are better simply because Timmy is the subject.

The Most Interesting Man in the World

Timmy Gambin - "The Most Interesting Man in the World"

From the start we all loved Timmy. Tyler said "from the moment I laid eyes on him I knew he was amazing." We have all continued to be amazed by this incredible man. From his seemingly endless knowledge to his striking resemblance to "the most interesting man in the world" in the Dos Equis commercials often seen in CA, Timmy Gambin may actually BE the most interesting man in the world.

Today we went to the hardware store a few blocks up from the street we are staying on, Howard's Hardware Shop looking for more plug converters (we have been battling over the handful we have - we are trying to avoid resorting to violence), an extension cord (sometimes 20 meters isn't enough), a surge protector (we blew up the one we brought from the US - our power learning curve has been slow), a large trashcan (to help test the depth sensors for the ROV), a hair dryer (apparently it is more expensive to buy a transformer than a new hairdryer), and an exacto knife (to avoid toxic fumes from melting apoxy).

It was at this hardware store we discovered Timmy's expansive amazingness - the two men in the hardware store both knew him well. An even more amazing discovery: one of the men in the hardware store was the original author of the first paper published about the cave we will be exploring next week. Timmy really must be incredible to have these connections everywhere we go.

It didn't take long for the complements to start:
"Timmy created Chuck Norris jokes for the attention to be takin off of him"
"Timmy doesn't need a bow-flex, so he gave it to Chuck Norris"
"Timmy touched me today and my spider bite was instantly healed - he is that amazing"
"Timmy doesn't need to do laundry - he just blows on his clothes and they are instantly sterile"
"Timmy doesn't need to trim his perfect beard because he efficiently re-directs the proteins to other parts of himself"
"Timmy knows everything"
"Timmy didn't just write down history - he IS history"

As you can see, we are very impressed with our archeological and spiritual guide here in Malta. He has been wonderfully accommodating, providing guidance, history, and insight into the culture of Malta. We are looking forward to spending more time with him over the course of the next 3 weeks. We love you Timmy!

Research Project Discussion at Backstage - 2/15/11

So I got one picture...

Hopefully it's an okay summary of our meeting with Timmy Gambin and the awesome insights he was able to give into our individual research projects and also just some useful general knowledge about Malta.

Can't wait to talk with him more!