The USS Monitor, Part 2: Underwater 3D Mapping

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HOST: This is the NOAA Ocean Podcast. I’m your host, Allison Burrell. Off the coast of North Carolina lies the remnants of the USS Monitor, now a protected National Marine Sanctuary. From its sinking in 1862 until now, it has developed into a bustling artificial reef. We are joined in the studio by Maritime Archaeologist, Tane Casserley, from the Office of National Marine Sanctuaries, whose specialties include 19th-century warships and deep-water archaeology. In this episode we discuss a new 3D imaging technology that’s virtually bringing the USS Monitor back to shore.

Now let’s dive in…

I am here again with Tane Casserley, who works with the Office of National Marine Sanctuaries. And today we're going to talk about the Monitor shipwreck again, but the next new thing that is happening, or that has happened, is this new imaging technology by Northrop Grumman. And I'm so interested in this underwater imaging. Has the Monitor been imaged before?

TANE CASSERLEY: Yeah, well, that's a good question. So the Monitor, you know, over the years, we have looked at it with different types of sonar. You know, and sonar is a piece of equipment that really uses sound to image things on the seafloor. It's all different types of technologies. But what makes working with Northrop Grumman unique is the fine-scale resolution that they're able to bring to what we're doing. So I've been, you know, had the pleasure of working with our NOAA ships in the past, and they have multi-beam sonars that are hull mounted. They do a great job. But those are designed to do a very particular thing, right? They're imaging the seafloor. You know, we can get some pretty good images of shipwrecks and things, but they have a very particular mission. The mission of the Northrop Grumman equipment is really to look at much smaller, compact sites, where the NOAA mission is really, with the ships, large scale, right? They're looking at big swaths of the seafloor, as they should be. This Northrop Grumman microsynthetic aperture sonar they have is just phenomenal. So we were so lucky to partner with them and their technology for the conservation team to bring this to us. And this is the first time that technology has been used outside of the defense or aerospace industries. We're so excited to almost be unveiling it publicly for the first time. It's just incredible what we can see with it.

HOST: So how does this new imaging technology work?

TANE CASSERLEY: So the sonar that Northrop Grumman brought out to the Monitor is actually installed within an AUV, an autonomous underwater vehicle. This one happened to be one called a Remus 300, you know, sort of a smaller AUV. You know, you have four or five people actually to be able to recover it and put it in the water, deploy it. So it's mounted within this AUV. And what makes AUVs so unique is that you program them on the surface and then literally let them go on the side and they go off by themselves without a tether, without any of those kinds of things that would encumber it. And it goes off and does a survey and then pops back up and says, hey, I'm here. I finished the survey and you can download it. So you can do much more targeted surveys with an AUV. It could be smaller in scale. You don't have to have all the cables and all those kinds of things. So we were just very lucky to be able to work with this technology.

HOST: So it's collecting information by itself, swimming around down there near the shipwreck. But are you getting anything real time?

TANE CASSERLEY: Not real time. I think they could ping back and forth to it once it's on the surface. I think it can tell us if it accomplished the mission or what it had to do. And they can give it a new mission. So it really is pretty phenomenal.

HOST: How long did it take from it entering the water to do the survey?

TANE CASSERLEY: Oh, Lord. So we tried to go out for multiple days, but we did run into weather. So we got one really good day with it. We might have put it down maybe four or five times perhaps. And each time it went down was maybe for just over an hour. It was really incredible. And we have to remember, too, the Monitor site is quite small. The ship as built was only 173 feet long. So now it's a bit shorter, but it is a very small site. But yeah, and that's what made it so perfect is that we could do these little targeted surveys and get this phenomenal data.

HOST: So what's the difference between an AUV and an ROV?

TANE CASSERLEY: Right, well, an autonomous underwater vehicle, an AUV, and the difference between that and ROV, a remotely operated vehicle, is that the ROV has a tether. So think of it almost like a dog on a leash, right? So you're running out with your dog and it's got the leash on and the dog's running around a tree and then you both get bonked, right? Well, it's kind of analogous to what happens with an ROV is that you have to be very careful with that tether management. In a wreck, it can be challenging, especially North Carolina with the currents, that that tether can get pulled onto things, pulled in different directions. It could wrap around delicate artifacts or structure on the wreck. So if you can take that out of the equation, so you have something that's free swimming and you don't have to worry about the actual sensor itself and a tether, it's just that sensor, it really simplifies things in some ways. In other ways, it makes it more complicated, but I believe it's a bit safer way to work in these delicate sites.

HOST: So that's why an ROV wouldn't work in the environment where the Monitor lies because of the high tides?

TANE CASSERLEY: The current, we have used ROVs at Monitor, but really I think I feel the most effective way that an ROV works on a shipwreck is feeding you real-time video. You can put other sensors on it too, but you get that real-time feedback. But you can also, you can only actually move a certain distance from the ship. So if you want to move to a different part of the shipwreck, the entire ship has to move above it along with the tether, and that can be very complicated. So it can give you great real-time interactions, but it also has limitations.

HOST: Once the AUV is deployed, how does it know where to go? Is there a program, like does it follow a grid pattern?

TANE CASSERLEY: Yeah, so the engineers, they program the AUV, and traditionally, as we would do a sonar survey on the surface, a grid pattern is done. You call it mowing the lawn, and that gives what you hope to be is 100% or 120, 150% coverage of what you're looking at on the seafloor. And it basically goes up, a little bit over, and down, and then up and down, just like you're mowing the lawn, and that covers an area. So it gives you good data, but what can be limiting with it is that it's really just a downward view at different angles. But what's unique about the Northrop Grumman sensors and technology is that they do that, as well as circular surveys around the object at different levels. So now you're getting those different perspectives of the object you're imaging on the seafloor. So you get even a better picture, a resolution of that object. And that's what makes them so unique.

HOST: Maybe we should start mowing our lawns in concentric circles.

TANE CASSERLEY: It could be fun.

HOST: Could be fun. So, your crew had to sail out to this shipwreck to release this AUV. And I know we have video documenting this trip, and it's shared on the Monitor website, which we'll link in our podcast episode page. Did you anchor nearby to stay close to the shipwreck?

TANE CASSERLEY: No, no. And so it's almost the same techniques we use as scuba diving out there. Again, the currents are so strong, there's no sense in anchoring, because it can be difficult to recover, the anchor, you know, you can move out of the way, but you also need to respond quickly. So just like scuba diving out there, we would sort of free drift and free float, and we would just hover in the area on the surface around the wreck. And really, working in those kinds of conditions out there is probably the most effective way and the safest way to do it. But it is unique to the strong currents of North Carolina.

HOST: And then you also had a videographer that came out there with you.

TANE CASSERLEY: We did. We did from NOAA. So we are very pleased to have him out there. And he shot, you know, aerial shots with a drone. So we've got these beautiful shots of the AUV being deployed. So, you know, we can really demonstrate from start to finish what's it like to work with this type of equipment. And maybe we inspire some young kids that they want to follow in our footsteps.

HOST: Was there any video taken with the AUV or was it just sonar?

TANE CASSERLEY: We did experiment by putting a GoPro small camera on the AUV, but we did experiment. We didn't see anything other than some fish. But, you know, again, let's try. You never know what you might find by not just experimenting and theorizing.

HOST: Has this technology been used before?

TANE CASSERLEY: So this is a proven technology at Northrop Grumman. It's one of their newer technologies. But again, it's really only used in that defense or aerospace realm. So we were just so lucky that they brought it onto our project, which makes it a lot more public-facing. And I believe this is really the first time it's been used in this more public project where everybody can benefit from it.

HOST: Do you suppose this new imaging technology will be used on more shipwrecks? Like saltwater and freshwater?

TANE CASSERLEY: Yeah, I hope by basically using Monitor as a testbed, and that's one of the wonderful things about Monitor, that where it's always been pushing technology innovation from 1862 to today, bringing all those new technologies to bear. That, you know, people would look at the example of what we achieved on Monitor with Northrop Grumman using this technology and how it can now be used and applied to other sites as well. You know, whether that be shipwrecks, maybe it's sunken aircraft. You know, maybe there's sunken indigenous sites. You know, just the technology and the resolution we can see for these things is mind-blowing. And the fact that we can collect that so quickly with the AUV, too, is very special.

HOST: So what's exciting about this is it's novelty, and you're able to share the imagery with the public. So someone could visit the wreck virtually. So what kind of products are able to be produced with all of this data that the AUV is collecting?

TANE CASSERLEY: Yeah, well, that's a great question about what, you know, what does this data mean that we're going out with Northrop Grumman and collecting? Like, what does it do? What does it mean to me? Right? So for the sanctuary, it's wonderful because it gives us this hyper-accurate view of the Monitor. So I can see structurally, is it changing? Is it staying the same over time? What's happening? You know, this is really the first time we've collected with that much accuracy and precision. But for the public, you know, what a great way to interact with something in three dimensions. So you see that, and now you get a true sense of, like, what's the Monitor doing down there? What does it look like? What hull remains are there? We're working with Northrop Grumman to identify those different features on the wreck so you can see that in the sonar image and start understanding the wreck site. But what's also wonderful is that data has now been transformed into a three-dimensional model that you can see and manipulate and spin around to get an idea. And also, we're going to be getting a printed model of that, too, the 3D print. And so it just gives us an extra layer of interpretation to say, hey, this is Monitor today. So that incredible, you know, prototype of the pre-battleship and all the technology to that, now we're using the latest technology to see what that wreck looks like today.

HOST: What scale is the 3D printed model going to be at?

TANE CASSERLEY: Ha! I wish it was life-size, but it's about two feet long, two, three feet long.

HOST: That'll still be really detailed.

TANE CASSERLEY: Oh, yeah. The detail is phenomenal. Again, what another great tool that we have to share this heritage. I mean, we all are part of this heritage. Part of the, you know, living in the United States, being citizens, we own this heritage. So to be able to get it out there for folks to interact in different ways is what we should be doing.

HOST: So with the data that's being collected with the AUV, scientifically, what are you doing with that?

TANE CASSERLEY: Well, so Monitor, it is, you know, in some ways we image it, you know, with the photography of the video, but you only get a certain like 2D sense of what the wreck looks like. So you can look at it on video and be like, okay, it looks pretty good. But without having divers down there, which we have done and still do, but it can just be really difficult to get a sense of how is that wreck and the hull changing? What are the variations? You know, because if you're dropping measurements down to the seafloor, but the seafloor depth keeps changing because of the currents moving sediments, what do you use as a baseline to document change? How do you do that? So, by using this technology where now I can look at it in three dimensions and it is so hyper-accurate, but now going back and doing future surveys, I can say, hey, the hull is doing great right now. But maybe in 10 years' time, we've seen flexings and movements, but because this particular product created a baseline, I can track that. But before that, we didn't have that data. It was really just some of those visual datas or the, you know, the very quick measurements we got with our dive teams.

HOST: Who went out on this ship with you to release the Northrop Grumman AUV? What types of jobs were involved in this project? Is this, is it an expedition?

TANE CASSERLEY: Yeah, well, I like to call them all expeditions. Yeah.

HOST: Expedition, this is an expedition. Yeah.

TANE CASSERLEY: Yeah, absolutely. So we went out with Northrop Grumman and their team on their research vessel Discovery. Really, it was the engineering team, the engineering and their field teams. You know, they're the experts. They're the ones who work with this equipment day in, day out. So I was there representing NOAA and the archaeologists, but we also had biologists out there. So a group called Stantec, which is a partner with us, with Northrop Grumman, and they went out there as well. And, you know, we experimented with what happens if we try to sample for eDNA material out at Monitor. So it's pretty innovative.

HOST: Environmental DNA.

TANE CASSERLEY: Yeah. So we look at it as, you know, Monitor is always going to be a test bed. Let's experiment and try. We're already doing this sort of revolutionary sonar. If we experiment by attaching these sort of perforated balls that have a sponge-like substrate inside that will collect the seawater. So we tried that. You know, I wouldn't say we found anything unique, but, you know, we did, you know, the results showed us that it found species that are known to be up in North Carolina. And I think that's just a great start in a way as a foundation to build upon, that how sometimes you compare these different technologies to collect data. You know, it's the start, but, you know, Lord knows without some refinement what else it might be able to detect around different sites.

HOST: So recently you premiered the results of the AUV imaging with an event at the USS Monitor Center. What are the next steps for the Monitor? Will there be more analysis of the imaging collected? Will you go out, like you had said, oh, we were going to do two days and we only did one. Are you going to go out and collect more data?

TANE CASSERLEY: Well, for this particular project, it's at a close. But the next part of the mission is let's get it out to the public, right? Let's start integrating this new imagery and technology into our educational programs. Let's get it on the website. We do, you know, several programs working with the local schools. Well, now let's integrate this new technology into that so now we can start inspiring that next generation of marine scientists to come out. So that's what I look at now is our mission is we have this wonderful data which cannot live just in a filing cabinet. It's upon us now to get it out there and make it meaningful. And it really is incredible. So that's the mission that I see next. We're always open for new ideas at the shipwreck site. But for this particular project, let's get it out. Let's make it meaningful. Let's get it in school kids' hands.

HOST: There is a website associated with this expedition. What are some of the most exciting things that's coming out of that website?

TANE CASSERLEY: Yeah, well, Northrop Grumman have built a web portal for us so you can click these buttons and you can explore what we did in 2025 with the AUV in the survey and see all that incredible data, right? And learn about it. You know, maybe you want to be, it inspires you to be an engineer or some other part of the technical aspects of surveys. But the other part they built on that website was they looked back at Monitor in 1862, which I'm particularly excited by. So, you know, the Northrop Grumman has so much capability, all these different facets of things they can do. So one of them was building 3D models. So I asked them, Monitor’s deck layout changed three times in 1862 as they learned more and did improvements. Can you build us three different models to demonstrate that? And they said, yeah, we can absolutely do that. So one of the things on the website people are going to see now are these three separate and unique Monitor 3D models they can manipulate, move, and learn how Monitor changed over time, which is incredible. We've never had that before. The other exciting part is, you know, when we talk about the ship sinking and what that was like, what that went through, the storm and the incredible heroism of the men that were saved by the sailors of the Rhode Island. And that incredible night, they also created an animation of that sinking event for us. So we can work with the conservation team here at the Mariners Museum and Park, and we can look at what the artifacts told us about some of the damage and things we saw, these recovered items, like part of the Monitor skeg, the prop. You know, the damage that we see at the stern of the shipwreck. So how we believe the vessel sank by coming down by the stern, turning slightly to starboard, crashing into the seafloor, which crushes the stern of the vessel, which is the end of the vessel. And the right-hand side, it crushes that, and then everything flips upside down and lands on top. And I believe we've recaptured that in this animation, how NOAA thinks the vessel actually went down that night, December 31st of 1862.

HOST: So you've collected all of these artifacts from the Monitor and brought them up. How do you conserve them and make sure that they don't just disintegrate when they come up to the surface?

TANE CASSERLEY: Yeah, well, it's a great question. You know, people often think that, you know, you go out to a shipwreck or another site, you've recovered something, you bring it back to the surface, and everybody's celebrating, and that's the end of the story. So that is not the end of the story, right? So before we do anything like that with the national marine sanctuaries, is anybody who's really a responsible archaeologist that, okay, that's one part of the story, but now you're going to need to have funding in place to pay for this thing. Where is it going to go? Who's going to conserve it? This is its own expertise and discipline, right? You need to have the right people doing this. So we are so lucky to have partnered with the Mariners Museum and Park here in Newport News, Virginia. So their conservation team is incredible, dealing with all of this government-owned archaeological assemblage, right? So it's the science that goes into it is incredible. But what I find most exciting by watching these experts here is that they're not only saving our heritage, right, for all of us, but they're pioneering brand-new techniques. Because, as I mentioned, something at this scale has never been done for. So it's known how to conserve metals and things, but to this scale, it's never been done. So they're pioneering new ways and influencing the entire field of marine metal conservation for the better, all because of Monitor. How to do it safer? How to do it cheaper? You know, what can we do to accelerate the process but still ensure the safety of those artifacts, these incredible one-of-a-kind pieces? It is incredible what they've achieved here. And, again, it's all due to the Monitor.

HOST: And is there a virtual way to visit the wreck?

TANE CASSERLEY: Absolutely. So the final part that Northrop Grumman built for us was what we call the wreck-to-reef model. So this is the story we've been telling since the end of the large artifact recovery. So from 2003 till today, we're looking at the wreck historically, archaeologically, but as a thriving reef as well, which is important. So, we worked with the Northrop Grumman team, and we said we would love to see a model of the shipwreck on the seafloor, but let's put that marine life on it. The marine life, the species we know that we've documented on that site, can we put it on there? And they did. So we've got this gorgeous 3D model interaction of the wreck on the seafloor that you can zoom in on and spin around, and you'll see lionfish, you know, the invasive lionfish. You'll see sand tiger sharks. You'll see Atlantic spadefish. You'll see so much more. So, what an incredible way to also now add in that sort of marine biology ecological component, which is so much of what Monitor is today for the public.

HOST: I love that the Monitor is still making history.

TANE CASSERLEY: Yeah, it really is. You know, it sounds like, you know, we're all excited about saying that, but it absolutely is true. I mean, the way it influences things, and we look at, you know, what does the Monitor mean to us as a people? Why does it inspire people? Those same things that inspired people, you know, 100-plus years ago, 163 years ago, the same aesthetics of this little ship that rallied us as a nation, I think is still there today. You know, we have a lot we can learn from that.

HOST: Well, and we’ve got so many firsts. The first iron clad. The first national marine sanctuary. The first public-facing Northrop Grumman AUV imagery. And who knows what the next first will be for this ship.

TANE CASSERLEY: Yeah, exactly, that is what Monitor is known for. And we are open for that. Monitor is a test-bed. And we’re open to talking to new partners, to do new things, and bring in new technologies.

HOST: And I'm also looking forward to seeing the future of this AUV technology and how it can help protect our coasts, our oceans, and our coasts.

TANE CASSERLEY: Yeah, exactly. You know, it can't be so difficult to document and research and visit these deeper areas of the ocean. So technologies like this are bringing it to light. I can't wait to see what happens in the next five or ten years.

HOST: Well, I am looking forward to hearing more from your investigation of the Monitor and unearthing interesting historical facts. This has been an absolutely fabulous conversation. Thank you so much, Tane.

TANE CASSERLEY: Oh, I'm so happy to be here, and, you know, I'm so proud just to be able to talk about Monitor and all the ways it's affected us from 1862 to 2026. I mean, it really is an incredible story, and I hope the story keeps inspiring all of us, you know, as we move forward.

HOST: This has been Allison Burrell with the NOAA Ocean Podcast. Thanks to our deep-water archaeology expert, Tane Casserley, whose stories and work on the USS Monitor have brought it back to life. Explore the new 3D images of this shipwreck through the National Marine Sanctuary website linked on the podcast page. Be sure to check out all our episodes through the National Ocean Service website or wherever you get your podcasts. Thanks for listening. Let’s keep making waves.