#4 – Brad Barker and Derek Wheeler

Recently, the Thomas Jefferson Foundation commissioned Surdex Corporation to fly high-density lidar over the 5000-acre Monticello estate in Charlottesville, Virginia. In this episode, we speak with Brad Barker, Director of 3D Mapping at Surdex, and Derek Wheeler, research archaeologist at the Thomas Jefferson Foundation, to discuss how lidar has brought Monticello into focus.

Episode Transcript:

#4 – Brad Barker and Derek Wheeler


March 26th, 2024


Announcer:           Welcome to the LIDAR Magazine Podcast, bringing measurement, positioning and imaging technologies to light. This event was made possible thanks to the generous support of rapidlasso, producer of the LAStools software suite.


Stewart Walker:          Welcome to the LIDAR Magazine podcasts. My name is Stewart Walker and I’m the Managing Editor of LIDAR Magazine.


I’m absolutely delighted to welcome two guests today: Brad Barker is Director of 3D mapping at Surdex Corporation in Chesterfield, Missouri. Derek Wheeler is Research Archaeologist at the Thomas Jefferson Foundation, Charlottesville, Virginia.


The context of today’s podcast is a forthcoming article in the magazine. Brad is the author of that article and the title is, “Lidar brings Monticello into Focus.” And Derek represents the Thomas Jefferson Foundation, Inc., a nonprofit founded in 1923 that owns and operates the Monticello site.


Before we go on, LIDAR Magazine also wishes to express thanks to Mark Zeman, Marketing Manager at Surdex who did a great deal of the grunt work behind both the article and the podcast and he facilitated communications between the various organizations.


And interestingly, Mark is an author and his book “Historic Tales of St. Louis” is available on Amazon.


So, to cut to the chase, the Thomas Jefferson Foundation commissioned Surdex to fly high-density lidar over the 5,000-acre Monticello estate that Jefferson inherited when his father died in 1757.


Listeners and, of course, our guests know far more about Jefferson than I do, so I’ll just say three sentences: he was born in 1743 and I’m happy to say that in 1752 he studied in a school run by a Scottish minister who proudly referred to himself using the old Scots’ word dominie. Jefferson was third President of the US from 1801 to 1809 and it’s intriguing that his Vice President from 1805 was George Clinton, no relation. And Jefferson died in 1826.


Now, let’s bring this closer to our own geospatial world. George Washington wasn’t the only President to work as a surveyor. Thomas Jefferson was appointed to work as the Albemarle County surveyor in Virginia in 1773. He also promoted surveying by sending Lewis and Clark on their expedition to explore the land gained through the Louisiana Purchase.


So, Derek, would you like to say a little bit about yourself and then introduce us to the Thomas Jefferson Foundation and the Monticello site?


Derek Wheeler:           Sure thing. Thank you, Stewart. I’ve been with the Thomas Jefferson Foundation for a quarter of a century now. So, I’d like to say the majority of my adult life I’ve been here at Monticello. However, what my main goal is—which aligns perfectly with this topic—is to try and understand what that 5,000-acre plantation looked like during Jefferson’s lifetime.


As you know, it’s a large chunk of land, it saddles both sides of the Rivanna River which runs right through the middle. And Jefferson, like most of his contemporaries in Virginia, broke up that large land holding into what was called the quarter farm system.


So, he had four quarter farms, no relation between quarter and four; it just happened that this was four quarter farms and Monticello was where he lived and that was about 500 acres. And then he had three additional quarter farms: Tufton, Lego and where he was born, a placed called Shadwell which was about two miles from where he eventually built his mansion house.


So, my job is, yes, just try to understand what the plantation looked like, where were the people situated, where were the buildings, where were the agricultural fields, the roads and everything else.


Stewart Walker:          Of course, as many listeners know, lidar has a rich history in the world of archaeology; probably best known for several very dramatic examples of Inca, Mayan and other sites in Latin America. But, obviously, Monticello is different from those.


Could you explain why you decided to commission a lidar survey? What did you do before the modern lidar age? So, what were the objectives of the new survey?


Derek Wheeler:           The objectives were to try and systematically record all topographic features that may relate to not only Jefferson’s lifetime but also before and after so that we could, in a nutshell, understand the landscape history of the plantation, of the 5000 acres.


And before lidar was available to us at the foundation, we, as a part of our archaeological survey of looking for where people were living by excavating shovel test bits, these are small holes about a foot in diameter and usually about a foot deep, you screen the soil for artifacts.


And we used Total Station to map in the location of all these test bits and that helped us figure out where people were living and we were able to see large landscape features, obvious landscape features, the larger erosional gulleys hold some of the more prominent road traces.


However, we realized that since our primary goal was to do the shovel test bit survey, we weren’t adequately recording all of the landscape features as well as we had hoped. This is during Jefferson’s lifetime roughly 1,000 acres was cleared fields with surrounding forest; today it’s almost completely forested, reforested land.


So, we just were unable to see these landscape traces. And so, that’s the genesis for wanting to get the lidar data, help us see what we were missing.


Stewart Walker:          So, Brad, please, first of all, tell us a little bit about yourself and about Surdex. I noticed on your website the firm was founded in 1954 by Earl Hoffman, a former US Navy pilot. And I know that you’re headquartered in Chesterfield, Missouri—which is near St. Louis—on an airfield with your own large hangar. And I was interested that Surdex stands for survey design exploration.


Brad Barker:               Yes, thanks, Stewart. My name is Brad Parker, I’m the Director of 3D mapping here at Surdex and I’ve been here for – this is my 26th year. And as Stewart was saying, Surdex is located in Chesterfield, Missouri which is in the St. Louis region and it was founded by Earl Hoffman after he got out of the military. He was a pilot and he wanted to find a way to turn his passion into a business.


So, he started flying aerial photography for the Corp of Engineers and then got into photogrammetry and so that sprung board us into where we are now as a full photogrammetric shop that offers orthophotography, lidar and planned metric mapping.


And as Stewart alluded to, we have our own hangar and we have currently 11 aircrafts that we utilize for all of our own acquisition and process.


Stewart Walker:          Thank you. Now, I have to say I remember vividly a morning I spent at your headquarters many years ago with the late great Molander and with Scott Merritt who is now your VP of R&D. And I came away enormously impressed by the company’s focus on optimizing that investment in those large modern aircraft and sensors through efforts on business development, project management and especially IT.


And I think I also came away with the impression that you had very special expertise in pursuing the large US government programs like the National Aerial Photography Program, the National Agriculture Imaging Program and now 3DEP.


And, indeed, in 2021 we published an article in the magazine of a joint venture between Surdex and Merrick to acquire 3DEP data over part of Arizona. Were those impressions correct, do you think?


Brad Barker:               Yes, those are correct impressions. We are always looking to be on the cutting edge as far as sensor capability and acquisition. We realize that if we can control our fleet and our assets, we’re able to help our customers achieve their goals whether that’s through scheduling and through pricing as well.


And we are in a joint venture with Merrick and we do a considerable amount of work for the USGS. So, that’s really where our specialty is is in wide-area collect for QL2 all the way down to QL0 lidar datasets.


Stewart Walker:          Now, as we’ve said, most of your operations are out of Chesterfield, Missouri. Does the company have any other offices?


Brad Barker:               No, we have – all the headquarters is here. We have some remote staff, both sales and some operational staff that are outside of St. Louis but everything else here is located in Chesterfield.


Stewart Walker:          Okay, thank you. And now for a word from our sponsor, rapidlasso.


Host:                     The LIDAR Magazine Podcast is brought to you by rapidlasso. Our LAStools software suite offers the fastest and most memory efficient solution for batch-scripted multi-core lidar processing. Watch as we turn billions of lidar points into useful products at blazing speeds with impossibly low memory requirements. For seamless processing of the largest datasets, we also offer our BLAST extension. Visit rapidlasso.de for details.


Stewart Walker:         Now, Brad, tell us how the Monticello project came in the door and how you determined customer requirements and designed your response. What were the particular challenges, what equipment did you decide to use and what were your thoughts with respect to the mission planning?


Brad Barker:               The way this project came about was that we had a statewide contract with Virginia and I believe that the Monticello team got in contact with somebody there and found out that Surdex was providing lidar to them.


So, they got ahold of our sales team and we had a meeting and just had a discussion of what they were looking for. And that was the starting point was understanding what the client’s expectations were, what the area looked like so we could then choose our equipment and start our planning for acquisition.


And what we determined was that the area like Derek had alluded to was a rugged landscape and it had been reforested. So, we chose our Optech Galaxy (sounds like: Prime) for our sensor and that was in a Cessna 206.


And what we did was acquired 23 flightlines over the area and we were looking to achieve QL0 accuracies and this was achieved with the 23 flightlines with 60% overlap.


And this overlap allowed us multiple look angles so we could get down and penetrate through that canopy and actually capture the features that were on the ground that was going to help Derek and his team look for landscape features.


Stewart Walker:          The flightlines must have been pretty close together?


Brad Barker:               Yes, they were. We were flying at a height of about 1,350 feet so they were very tight and condensed but that allowed us the ability to get different angles, look angles as we were acquiring the area so we’d have more points to work with. And we had planned this for about a 30 points per meter point density so that way we were able to provide a really high-resolution digital elevation model.


Stewart Walker:          Now, would it be fair to say that 5,000 acres is rather a small project for one of your aircraft but it’s also too big for using a UAV?


Brad Barker:               That’s correct. Most of our projects are hundreds if not thousands of square miles in size and this – it was just too big for a UAV. We were able to get onsite and get the data acquired in one day. So, we were able to get down there, get it acquired and back to the office without having to worry about any kind of temporal differences or changes in the weather effects.


Stewart Walker:          Now, did you use ground control? What about the datum coordinate system, units, all the normal questions that listeners are interested in?


Brad Barker:               Sure. We sent our surveyor down onsite and we captured about 41 points that we used for both control and we had some NVA and VVA which is non-vegetated and vegetated points. And we were achieving four-centimeter accuracies for vertical and sub-four-centimeter accuracies for relative accuracy and we produced the entire project in a (sounds like: UTL).


Stewart Walker:          And do you do some kind of system calibration? Do you fly in a special pattern at the beginning of a mission like that?


Brad Barker:               We do. We like to set up a small calibration site that’s either onsite or with the settings that are going to be used during the acquisition and we fly this calibration site and that will be postprocessed and allows us to get all of our angles and bore site information that we will utilize on the project.


Then during the acquisition, of course, we will fly a line and then we will turn and come back and do the line the opposing direction and then we also always have a start and stop and make sure that we’ve allowed the GPS to get calibrated before we’re online and making sure that our turns aren’t too steep and that we’re maintaining good GPS contact.


Stewart Walker:          One of the other interesting aspects, I think, of any modern lidar project is the point classification. How much of that was automatic and how much of that was done by your staff looking at the lidar point clouds on screens?


Brad Barker:               The initial classification we have several macros that we’ve developed over time and we use those as a starting point and that’s like our seed file. And then my senior analyst on my team will jump in, check a few of the areas, make any adjustments they feel necessary to the macro and then we will run that across the entire project.


And we’re seeing results between that 75% to 80% as far as the initial classification and then we have – our technicians and analysts will jump in and do a manual reclassification of the points and that’s utilizing many tools as far as profiles, different elevations with the DEM and the DSM to make all the final small adjustments to the data that the macro was just not able to handle.


Stewart Walker:          Yes, I think that’s important in this age where AI is in the news every day I think it is important to remember that on many of these projects there’s a great deal of hard work has to be done by experienced people before the process data is good enough.


Brad Barker:               And that was one of the things that we learned when we met with Derek and the Monticello team was they were very interested in features on the ground. So, we had to be very cognizant of that when we were doing the manual cleanup because some things it might like small anomalies may be something, in fact, that they’re interested in looking at. So, you have to be careful not to overgeneralize your ground surface.


Stewart Walker:          Yes, I can see that. So, would you like to describe what the deliverables were? What did you have to supply to the Jefferson Foundation?


Brad Barker:               So, what we supplied to the Jefferson Foundation was the classified point cloud and these were all tiled up into a size that would be – make it easy for them to utilize them. We provided a digital elevation model and a digital surface model both with a one-foot GSD and along with that we also provided an intensity image at one-foot GSD and so those were our primary deliverables to the Monticello team.


Stewart Walker:          Now, the way that we’ve discussed that, it sounds a little bit as if the process was entirely linear. There was an initial site meeting with Derek and his colleagues. But, in fact, after that there was interaction, presumably, when they first saw the deliverables. So, was there any sort of pilot process, any refinement of the specifications after the first products were seen?


Brad Barker:               Yes, there were. We provided the pilots to Derek and his team and they looked at it and then that’s when they started providing more information about what they could see in the digital elevation models.


And Derek had actually built a hill shape from that as well and he was showing us the type of features they want and that’s when we adjusted our level of manual classification on the files to ensure that we weren’t taking away any feature that would be useful for them to look at landscape features on the ground.


So, it was an iterative process. We’d make some changes and then provide the data back to them for review.


Stewart Walker:          So, Derek, you’re quoted in Brad’s article as exclaiming when you saw the data on the screen: “The level of detail that the lidar data provides is outstanding; it’s like waking up in the morning and putting on my glasses. The world goes from fuzzy and indistinct to clear.” Would you like to say more about that, your reactions?


Derek Wheeler:           Yes, it was truly amazing. From the 1990’s we had a two-foot contour map of the property that was produced from aerial photographs and at the time I thought it was great and that it provided lots of detail.


But when we received the lidar data back, it made me realize just how much we were missing. Once again, these are things that Brad was talking about, these small landscape features. By small they could be long, linear landscape features but not very much change in elevation.


And one example that I immediately shared with Brad was the fact that we could see what were remnants of an old orchard and a completely reforested area; an area that I’d walked over a half dozen times and walked by on a yearly basis and yet I had no idea that these low, linear berms were sitting right next to the path that I was walking on.


That’s what I mean by that I was shocked at the clarity that was provided by the lidar data. And also, these are areas that during our archaeological survey, I was a part of it for a good number of years and I walked over these landscape features and didn’t know they were there.


And so, that’s, I guess, the shock of the initial just looking at it and just going, “Whoa, there’s a lot more out there than we realized” even from walking over the property multiple times and walking over it systematically, not just haphazardly.


Stewart Walker:          And I think it’s worth repeating that much of this area is densely forested so there were enough lidar shots got through to the ground to provide you with this incredible detail that you were looking for.


Derek Wheeler:           Indeed, yes. At Monticello Mountain I mentioned the quarter farms earlier, the 500-acre Monticello Mountain that was the home of Thomas Jefferson, the home of his mansion house, probably 95+% of that is now thick forest; a hundred years ago not so much, but today it’s completely reforested.


And the lidar data was able to strip at least the bare earth that was provided to us by Brad and his folks. They stripped away all the forest, the canopy, the trees, the buildings and they just gave us the bare earth which was for us in the archaeology program the most important part of it to help us understand the landscape history.


Stewart Walker:          Yes, I think that’s the incredibly exciting aspect and that’s what we’ve also read about many times with respect to those many investigations in Latin America that, of course, I’m sure you’re familiar with too.


Derek Wheeler:           We’re not quite the same level of forest jungle as in Central America, but, yes, that is truly amazing to see what they can provide, the type of data that the lidar can show and expose.


But we do have areas that it’s hard to even walk through in a straight line, never mind see the ground surface, yet the lidar data here was able to penetrate the canopy and the bushes and everything else and really provide excellent detail.


Stewart Walker:          How will this affect what goes on at Monticello? I’m thinking of a number of things. It presumably will make a big difference to how you conduct archaeological investigations on the ground in the months and the years to come, presumably it will lead to publications, further investigations and maybe an enhancement of the tourist experience.


Derek Wheeler:           Indeed. We are already starting to incorporate the lidar data into all of our internal maps that we share with other departments here at Monticello. They will soon start being used as the base map for all publications.


And from the archaeological perspective, by allowing us to see the bare earth it is giving us insights into where to excavate in the future and I mentioned the archaeological survey showed us where the people were living, but interestingly for us and as part of the landscape history, we want to know how did the environment change over the last 200 years.


And one of the great things about the lidar data is it’s showing us areas where you can imagine during Jefferson’s lifetime these were hillsides that were farmed by the enslaved laborers and these agricultural fields on hillsides caused a great amount of erosion and we can see areas where these erosional deposits would accumulate.


And it will provide us a place to go and look and dig to then sample these layers in these sediment catchment areas to get not only dates as to when the deposits were laid down, but also things like pollen and phytoliths which can tell us a great deal about the environment was at different times.


And this will not only work for the Jefferson era but precolonial times as well so we can see what the effects were when this was a working plantation, then what happened in the 19th century and early 20th century as well.


Stewart Walker:          And some of that work is done by setting out quadrants on the ground and going in and kneeling down and digging and investigating?


Derek Wheeler:           Yes, that’s the one thing as you mentioned about AI. AI, as far as I know, can’t dig yet and the thing we need to do is go physically investigate these areas and without that on the ground kneeling with shovels, with trowels, screening, putting all the sediment that we dig up through a screen looking for artifacts, that’s what needs to be done. The lidar data provides us with an avenue to pinpoint where we should do that so that we do it in not only a systematic way put in a smart way.


Stewart Walker:          So, Brad, is archaeology a new business segment for Surdex or was the company already active in this area?


Brad Barker:               No, this is something new for us. We are usually providing data for people to do planning or hydrography analysis, so this was a new avenue, if you will, and something that was very interesting for us. From the on-start we definitely wanted to part of this project because the ability to help Derek and his team what they were trying to uncover and just because of it’s such a well-known historical area.


Stewart Walker:          And has there been any discussion of using other sensors such as ground-penetrating radar that would complement the airborne lidar?


Derek Wheeler:           I’ll go ahead and jump in there. We try to employ that in areas that it would be helpful to use it. Unfortunately, the soils that make up Monticello is part of the (Inaudible) Formation that’s hundreds of millions of years old and so it’s a very dense or high proportion of clay and these small clay particles are great for preserving pollen to help us figure out the environment, but conversely they pack so tightly they hide the features that are underground using ground-penetrating radar.


It’s an ongoing mystery as to coming up with the right techniques to find what’s under the ground without having to dig here at Monticello.


Stewart Walker:          So, maybe, Brad, you’ve now got some new things to say about Surdex’s skills and you can slightly change the angle of your marketing to certain communities.


Brad Barker:               Yes, it is always something that’s interesting when we’re looking to expand our services. This gives us another idea to go after a specific vertical, if you will. So, we were able to say, “Here’s what we did at Monticello.” If somebody was looking for something similar we can provide examples of how we did that.


And it gives us a good starting point of maybe some of the different people or organizations that we would want to target.


Stewart Walker:          Well, let’s close with maybe a question that I can put to both of you. I was reflecting on the article and putting together my thoughts for this podcast and it occurred to me both of you are extremely experienced in your own fields, one in archaeology and one in geospatial project management, and you’ve come together on this project.


Would you say that as a result of your interactions with each other you made the project more successful, it became possible to get more out of it? And therefore, do you think that this is an exemplar or the customer-supplier partnership at its very best?


Brad Barker:               From my standpoint, the collaboration was absolutely critical to get the most out of this project. I feel like we could provide Derek and the Monticello team some of the characteristics of what the lidar might present, how to use it in some different settings.


But they were unbelievable in providing the background information that we wouldn’t even know about when we were going through and trying to look at the lidar and determine what would be on the ground.


Derek Wheeler:           And I would add that having Brad coming to an onsite visit, it’s hard to explain archaeology over a phone call; it’s a lot easier when you’re out in the field and with Brad’s willingness to come out and meet with us onsite and walk the property and do those conversations we were able to more effectively tell them what we wanted and they were able to tell us what was possible. And that was a great interaction from our point of view and one of the best selling points was, yes, onsite visits.


Stewart Walker:          I think that’s marvelous. I think there’s a lot of excellent advice there for people involved in similar projects in the future and hopefully we will hear and read more about lidar being brought to bear in this kind of work.


So, I want to thank both of you once again, Brad and Derek, for spending so much time with us. I think listeners will have enjoyed the insights that you’ve given us today and I hope that we’ll be able to have further guests and projects from Surdex Corporation and the Thomas Jefferson Foundation on future podcasts.


I also want to underline our gratitude to our sponsor, rapidlasso GmbH, the German software company founded by the late Dr. Martin Isenburg. We hope you will join us for future podcasts. We are expecting some guests whom we believe you’ll want to hear. Thank you very much for listening and good day.


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