The Real Tech Behind The Tomb of the Primal Dragon: Interview with a Drone Software Expert

Are drones the future of archaeology?

The thing I love most about writing fiction is using my novel as an excuse to interview people in tech, business, and academia. I arrive at a coffee shop via Lyft after explaining the premise of my novel to the driver: “A young historian gets invited to help chronicle the excavation of an ancient tomb using today’s cutting edge technology.” He says he’ll pick it up, and he pulls it open on Amazon when he drops me off at the door. He likes the idea for the story.

I walk into the coffee shop, and look at the menu. Jackson, a drone software expert, agreed to meet with me to discuss the real technology featured in The Tomb of the Primal Dragon. Jackson is one of the first people to fly a drone underground. He arrives within a few minutes, and we get coffee. I ordered one of those chocolate mocha things that reminds me it’s almost that time of year for Christmas shopping and James Bond films.

Where it all begins

Time to talk shop. I’d written about drones in the original manuscript for The Tomb of the Primal Dragon, but I had no knowledge of the real technology, and I didn’t know how to do the research back then.

This November, during Mediatech Week in Austin, Jackson was speaking, and I had the time to stop by, and get familiar with drones-as-a-service from a software perspective. It seemed like all the technology was there, and that there are companies that might be able to pull off this drone-powered excavation soon. We agreed to have a deeper conversation about it later, which is why we’re sitting in this coffee shop now.

In the story, a software developer turned aerial drone raconteur is working with Tsinghua University, and the Terracotta Warrior Museum to develop a prototype drone that could conceivably go inside the first emperor of China’s tomb, and take enough data to build the entire environment in virtual reality.

Why haven’t they gone inside the tomb?

The last time I checked, the museum is still reticent to go inside because they don’t believe the technology’s there, but there’s also dangers lurking inside the tomb. If you can avoid the supposed mechanically triggered bows and arrows rigged throughout the tomb, and you can make it beyond the rivers of mercury to the emperor’s sarcophagus without severe nervous system failure—volatilized mercury is highly toxic—you might get a chance to see the wonderful treasures buried inside.

And the structure is supposedly vast. It’s only one part of a grand complex built to protect the emperor, Qin Shi Huang, in the afterlife. I’m starting to believe it was meant to be lost to history forever. That seems more plausible than anything.

Drones are more commonly used for construction projects than archaeology, but in my conversation with Jackson, I became convinced that the technology for a reality data capture project as outlined in the novel is right around the corner. It might even be here now. So, what does that look like?

How can drones be used to run an excavation?

We talked about the idea of this being conceivable in fiction without going so far as to say, “this is exactly how we do this.” The reality is that, as a novelist, and not a trained archaeologist, or V.R. developer, I have no idea how to gather enough reality capture data to create a precise 1:1 replica of the tomb. Jackson certainly knew what tools you might fit to the drone for data capture, and showed me examples of what that would look like.

Here’s my conversation with Jackson:

The legend behind this tomb… the Grand Historian of China wrote about this site. It’s basically booby trapped with mechanically triggered bows and arrows, there are rivers of mercury, they dug out trenches to represent the rivers… They have a scale map of China about the size of two football fields… This is at the Terracotta Warrior Museum, and they’re never going in there. They don’t want to desecrate the tomb, or destroy anything, and they’ve said nobody has the technology to go inside and excavate.

So, in this novel, Westerners become obsessed with the history behind the tomb, and they build a prototype drone to run the excavation autonomously. The first part of this project in the book is using aerial drones. How would they come into play?

Jackson: The drone’s first job would be to run a mission to capture reference points to assist with mission planning, and then execute a second mission, very carefully planned of course, to capture precision data.

Right, and so the characters explore the possibility of what it would require to go inside, but the tomb is dangerous. The bows and arrows, and volatilized mercury… Ideally, they want to recreate the inside of this in V.R., and they want it to be highly accurate. How would drones be used on an archaeological project like this?

Jackson: Drones are basically robotics platforms designed to deploy sensors that record data… but they also need sensors to inform them how to operate relative to their environment in the first place… In addition to motors and batteries and all that, most come equipped with pixel-based image sensors (a camera), inertial measurement units (like an accelerometer in a cell phone), a compass, and GPS chip…using US or Russian satellites or both. At any given time you could be connected to 12+ satellites. The more you’re connected to the more accurate the position…. Then all of these sensors feed data to some centralized flight controller that makes sense of it all in addition to the orders you give it, to stabilize flight and perform its mission….

Then to run it autonomously—you need that data to be very accurate.. Each sensor has its own margin of error, especially GPS systems when trying to operate underground…. That’s the real challenge…

Funny kind of heads-up here, I have written a lot of that in there, and I don’t know any of this… Like, I have no knowledge about how this stuff works, but I figured maybe 100 ft. under the ground that wouldn’t work… Internet connectivity is not gonna be a thing. Remote operating it with even a tablet is not a thing…

Jackson: You can do that. Drones use radio signals at certain frequencies to connect the image feed for the video and the images it generates. It actually stores them on the SD card that’s on the drone, so you can have a 64gb micro SD on the drone… Here’s the projection mapping project (he pulls open a video). It’s 26 ft. wide actually. I was able to control this with radio signal, but it didn’t have any stabilization or… spatial correction from the satellite system whatsoever. It was just all me manually flying it. You can program it if you have a powerful enough autonomous flight engine.

This (he points at my phone) has got a lot of processing power, right?

More than what it took to land on the moon.

Jackson: Right. So the processing power in here transmitted over a radio signal can inform the drone what to do, but it doesn’t have any spatial correction from satellites…

How far away can you operate that with a radio signal?

Jackson: depends on a lot of factors… maybe two miles away with the DJI Lightbridge system. Anyway, you can use this (the phone) to transmit radio signal to the drone, but you would have to have a schematic, a drawing, or a map of the inside of the space. Then you can program the drone to do whatever you want, you just can’t guarantee that it’ll be accurate in that space.

You can say exactly where you want to go, and where not to go, so you can give it x, y, and z coordinates, but if your map is here, and your drone starts here, and it thinks the map is here, say it thinks it’s gone 5 feet, but it’s really gone 5.3 feet… In addition to being off by a few inches on the coordinate plane, there’s all kinds of costly errors that can happen.

Computation at the edge and micro-location can help achieve real-time positioning gains for drones, but there are all kinds of engineering issues that need to be solved…

So would you have the ability to have this drone autonomously say “here’s what I expected to find, but here’s what I actually found, and I’m going to reconcile these, and keep moving…”

Jackson: Yeah, that’s the theory and logic behind it. It’s possible. So, here’s photogrammetry. If you zoom in, each one of these is a point taken from an image. We took thousands of images, and then we’d have a billion points for those images. And then we used an algorithmic process and special software to stitch them together. You just need two overlapping points, and you can get a three-dimensional image. It’s just trigonometry, right? If you know sohcahtoa, if you know two points, you can get the third. If you know the hypotenuse, you can get the adjacent.

So, you can build these very highly accurate models.

Now, if I’m a V.R. company, I could potentially use that to create a model, right? This is my base point, now I don’t have to guess what the tomb looks like. How accurate would you say it is?

Jackson: I would need to think about it in more detail…. If you have a good system for positioning and real-time communication of that position then it is definitely feasible. There are geo-registered control points and things like RTK systems that use carrier-measurements and a base station to improve positioning accuracy relative to a well-known fixed point…You can also use LiDAR (which is what all the autonomous vehicles are using) to create “3D maps” and detect even the smallest changes in your environment… Right now these can be expensive and the payload is considerable, meaning you need a bigger drone. Affordable solid state LiDAR is coming though…

When you say payload, do you mean the actual data?

Jackson: No, not the data, the weight. The actual weight of the instrument. The payload you’re hauling on the aircraft is considerable.

Okay, so they’re heavy, but they’re not something you can’t fix to a drone, it’s just gonna make it clunky, it’s just gonna make it more difficult…

Jackson: You can fix it to a drone, it just adds weight, and that means less flight time. Every ounce you add to your drone restricts your flight time… So, what was 30 minutes of flight, now becomes 12 minutes, and you get a lot less data because you covered a lot less ground… It’s an engineering problem with a bunch of parameters. The bigger the battery, the more the weight. The more weight, the less battery life you have anyway. You have this law of diminishing return with the carrying capacity of the drone. It’s the aerodynamics of the drone that you have to worry about here. Lift becomes an issue, and the aerodynamics break down.

Let me show you the map of this tomb and everything that we’re talking about right now… If I wanted to do this, what kind of budget do I need for something like that?

Jackson: This would definitely be a custom job. You might be able to do it for a few thousand dollars if you have the right equipment. If you have fifty grand, you can get state of the art LiDar, drones, software to process the data. For photogrammetry, you don’t get this stuff in real time, you’d have to go back and process the data after the fact. So you go capture data, and then you catch the drone again, and take all that data through some third party software that allows you to transform the data into a three-dimensional model.

Theoretically, can you send that data over radio signals? Let’s say the drone records all this information, and you’re expecting it might get captured or destroyed, so you want to send it to a separate device as a backup.

Jackson: Yeah. You could stream it over radio signals. Video’s the heaviest file. With LiDar, I’m not sure which equipment would allow you to do this. It’s such a new thing, that I haven’t had the chance to blow fifty thousand dollars to learn all this stuff… But yeah, you could stream it, and it would stay here. And you could store it on the phone, or you could have a computer connected to this. There’s no problem with that. It would be streaming over two radio frequencies, and writing directly to this storage.

To give you an idea of the scope of what we’re talking about recreating here, I mean, everyone of these guys is about six feet tall. There’s about 6,000 of them here. This is actually the Terracotta Warrior Museum here. This is public, you can go inside there, you can buy tickets… It’s incredible. This is about the size of Cowboys Stadium or whatever. You get a sense of the scope there. Now recreating all this accurately with all these individual soldiers, that sounds like it would be more difficult.

Jackson: You’d have to find a way to make it more accurate.

How long would it take to get the entire site?

Jackson: How many acres?

At this point, my voice recorder shut off, and being that this was my first interview, I didn’t think to check that it was still on. We estimated that the site was about 560 acres based on the map, and we figured 15-20 painstakingly complex missions of around 23 minutes each based on the battery life, and the size of the complex. That means in very little time, you could create a virtual map of the Qin Emperor’s grave site.

The proper equipment for a digital excavation inside the tomb

For this theoretical drone that goes inside the tomb, and operates on its own—should they decide to go in, here’s the starter list of what you’d want given the scenario:

  • Autonomous flight engine and drone
  • Photogrammetry (imaging)
  • LiDar (laser imaging)
  • Microlocation services (GPS / Radio frequency)
  • 20 megapixel cmos (low light)
  • Flood lights
  • Obstacle avoidance, and collision tolerant housing
  • Computer Vision processing
  • Data streaming over radio frequency
  • Remote control over radio frequency

The next question is whether anyone would have an interest in recreating this historical, and immersive experience as a game? The premise of my novel is that virtual reality is the future of journalism, and that this type of story, a forbidden tomb, is the perfect one to showcase what the medium can do. But, are there any V.R. production companies out there who would want to give it a go?

Recreating the deadly tomb the right way

In the next article, I’ll set out to find some of the top V.R. experiences out there, and I’ll engage some of the developers directly to find out what type of experiences are leading the industry.

To be continued…

The Tomb of the Primal Dragon is Will Ruff’s debut novel, and it follows the excavation of the first emperor China’s unopened tomb using cutting edge drone technology. You can order a copy on Amazon Kindle here.

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