Exploration of Mesophotic Coral ReefsNovember 18 2015
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I've been working with some telemetry from a test dive, as the ability to record and download ROV telemetry data is a must for any scientific exploration. However, I have found that there are few resources available through the OpenROV support forums that explain how to access and use these data. I have written up a short protocol, which can be found below, but will also be posted on the forums.
1) As you set up the ROV for startup, make sure you orient the nose northward. The compass cannot determine magnetic north, and therefore takes its 0-degree calibration from its position upon startup.
2) During the dive, make sure that telemetry is recording in the cockpit GUI. The Download button should be clickable and the recording light green.
3) Once you have finished recording telemetry data, click Download and a .json file will be downloaded through your browser. If you open this file in a text editor or in Excel, you will see it is a form of a comma separated text file. As is, Excel cannot interpret individual data values for each parameter (pitch, yaw, depth, etc.) and therefore it must be separated.
4) The fastest way I have found to do this is to use an online .json to .csv converter, such as konklone.io/json. This will interpret the code into headers (or columns), with each parameter value separated by a comma.
5) Copy all of your data into an Excel spreadsheet. Only the first column will contain data, which are each of the parameter values at a particular timestep.
6) Highlight the first column, then navigate to Data, Text to Columns. Select Delimited, Next, deselect Tab and select Comma, Next, General, Finish. Each parameter should now have its own column.
7) Next, you need to line up the telemetry data feed with your recorded video. The timestamp in the dataset is in milliseconds from initial startup and matches with the timestamp shown in your full screen video recording. From there, you can convert it to real time or elapsed time based on your computer’s time at ROV startup.
8) From there, you can do any kinds of analyses on your ROV telemetry parameters. I suspect you can create a rough bottom profile of a feature of interest by “mowing the lawn” (parallel linear transects) and then plotting depth over time.
My second update is not as good. I was attempting to test the above protocol on a small ledge just outside of the FAU Harbor Branch channel today. The ledge is almost a meter high, 5-6 meters long, and is a good habitat for local groupers, snappers, and invertebrates. I deployed the ROV right after peak low tide and immediately ran into issues with low visibility. As I was trying to explore the site and get my bearings, the outgoing tide picked up considerably and pushed the ROV off station. The tether got caught on some unknown object and after initially not being able to come two meters off the bottom, I recovered the ROV but not the tether. I had to sever the wire at the ROV to unhitch everything. Upon shutdown and inspection, I also noticed more water in the port battery tube like last time at the lake. The batteries were still functioning, but obviously I am very hesitant to put this back in the water until I can figure out where the leak is happening.
Despite horrible offshore weather due to El Nino (think gusting winds, low visibility, rain, and rough seas), I have gotten a chance to take the OpenROV out for some confined water flying. FAU Harbor Branch occasionally visits "Ditch 5," an affectionately-named former sand quarry now used for SCUBA education. During a recent training dive at the lake, I brought the ROV along to explore the navigation course and monitor the divers.
Visibility at this lake is normally 5-10ft, so I'd consider it pretty lucky we got 5ft after all the recent rain. Navigating the reeds and obstacles (tractors, lines, etc.) proved to be quite challenging, but perhaps the most difficult aspect of the flight was staying off the bottom. As it was ballasted for saltwater, and coupled with poor viz, the ROV had a tendency to ram into the soft sediment, and in some cases, get stuck. Contrary to this expedition's mission of monitoring divers, I in fact had to use their better mobility and situational awareness to recover the ROV twice.
Considering it was my first major flight and without someone to manage the tether, I am still pleased with the results. I have some video to edit and upload as well. One thing I noticed after the dive, however, that I had some water in the port battery tube. It did not cause any power failure during the dive or corrosion, but I am somewhat confused as to what happened. The seals appear fine, but there was some sand around the o-ring. My best theory is that due to the "ramming," some sand may have displaced the o-ring and caused a small leak. A test in deeper water and more careful flying will determine if this is the case.
Once this weather calms down, I'll be out again to dive on some local worm rock reefs and hopefully monitor some diver deployments.
I completed assembly and dry testing of the ROV a little over a week ago now. The next step was a pressure test using FAU Harbor Branch's pressure chamber. We prepped the empty ROV housing and tether for full submergence and slowly cranked up the pressure to the maximum operating depth of 100m. Suddenly, at 85psi, a pressure equivalent of approximately 200ft, we heard a muffled thump and saw a sudden drop in chamber pressure. Knowing something had imploded, we released the chamber pressure and inspected the damage. One of the battery tubes had imploded, but did not crack. The endcaps and o-rings appeared to be intact, but cannot be trusted.
After a quick call to OpenROV HQ, David and JR informed me that the failure was likely the result of the battery tubes being tested empty. The batteries provide structural support, so make sure to always put something in the tubes during testing!
So, with replacement tubes, I rebuilt the ROV and successfully completed an in-water test in FAU Harbor Branch's 40,000 gallon laser test tank. Check out the embedded Youtube video below for a short glimpse of our testing process. Keep following along as we move to field testing next year!
The kit arrived this week, and I have begun building the ROV. So far, I am very impressed by the build quality of the components and the detail included in the photo guides. I am currently finished with the first three guides and will be able to mount to motors when they arrive next week and continue wiring.
In order to be completely transparent throughout the build, I would like to speak on the process of constructing the ROV. I ran into an issue and was not able to find much relevant information on the OpenROV forums that could help me. Cementing acrylic is a new skill for me and I am more or less unfamiliar with using water-thin cements and glues. I watched the provided how-to videos and photo guides provided by OpenROV, but nothing can prepare you for when you actually go to dispense some cement and it drips everywhere and mars the acrylic.
The kit starts you off cementing some frame pieces together at 90 degree angles. Pretty simple. Hold the pieces, use capillary action with the cement syringe, and wait about a minute to set. Once you get to making the endcaps, however, it gets much more challenging as you are gluing several large faces of acrylic together. You use the motor axle to line up all the pieces, but you then have to account for rotational movement to perfectly align cutouts in each slice for later wire routing. Using a syringe here was difficult as you have to dispense a lot of extra cement. Then, when you press the two pieces together, cement gets everywhere and leaves air bubbles between the layers. Since the cement glues acrylic together by softening the surface, any extra will drip and etch the once-smooth outside edges. I have attached a photo to show what happened with my build. The end result is some very unprofessional-looking endcaps that should still function normally. I asked OpenROV HQ if this is usable and they say not to worry.
Nonetheless, I will be testing the endcaps for structural integrity in FAU Harbor Branch's pressure chamber before I add the sensitive electronics. I will post an update of the hopefully-successful test next week.
A note to future builders: I spoke with our machinist who deals with a lot of precise acrylic projects and he recommended when gluing two faces together, dip the smaller face into a shallow pool of cement for 30 seconds, then attach the pieces and apply light pressure. This should result in fewer to no bubbles and a much cleaner appearance. If someone tries this method, please document the process and post photos!
We have just ordered an OpenROV v2.8 kit and accessories. Our plan is to view the live feed through an iPad by modifying the Ethernet signal via this method (bit.ly/1PNQtpQ), and control the ROV with a Bluetooth game controller (amazon.com/gp/product/B00RE6FMD8?psc=1&redirect=true&ref=ohauidetailpageo03_s00). Once we receive our kit, Michael Studivan will begin the build and initial dry testing through December 2015. Starting in 2016, we will do pool checks and eventually, in-water operations at a local coral reef off of Stuart, FL. Check out the embedded video for a description of this local shallow site.
We also have two Trident ROVs on pre-order and expect to begin using that platform starting November 2016.
Advanced technologies are required to observe and explore mesophotic reefs (40-150m), since they are generally found below recreational SCUBA depths. FAU Harbor Branch has addressed this issue with the formation of a technical diving science team and collaborative research with the Flower Garden Banks National Marine Sanctuary Mohawk ROV. Still, both technologies are expensive, gear-intensive, and require extra considerations with research cruise logistics. The OpenROV platform gives us the opportunity to greatly reduce the costs and planning associated with mesophotic reef exploration. An added bonus is the ability to quickly locate a suitable site for additional technology deployment via SCUBA or conventional ROV, and the ability to monitor diver teams during the course of their bottom and decompression times.
In conjunction with ongoing research in the Voss Lab at FAU Harbor Branch, we will use the OpenROV v2.8 and the upcoming Trident ROVs to accomplish four research objectives: (1) to assess the OpenROV platform for assisting scientific diving and data collection, (2) to rapidly locate target sites at 50m, (3) to monitor technical diver teams during bottom time and decompression, and (4) to collect reef survey data.
This project is funded to PhD Candidate Michael Studivan through the FAU Graduate Research and Inquiry Program (GRIP) Grant.