Beneath the Waves — Using Professional Survey UAVs to Map the Ocean

Tellus4D 2

Tellus4D Geoimaging is an Australian company that uses survey UAVs to collect land and shallow water imagery.

Waypoint recently sat down with Tellus4D’s CEO, Dr. Geoffrey Gearheart, to learn more about his company, how he uses survey UAVs, such as senseFly’s eBee Plus fixed-wing drone, to capture all this data and much more.

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Thanks so much for taking the time to chat with Waypoint today, Geoff. Can you give us some background on Tellus4D?

Absolutely. At Tellus4D, we work with governments, private industry and individuals to provide scientific-grade aerial imagery and data interpretation, with a focus on answering questions related to coastal processes, such as geology, ecology and oceanography.  To do all that, we use unmanned aerial systems (UAVs) to collect data, such as RGB, multispectral and LiDAR, and process it all using a suite of specialised software such as Fledermaus, Agisoft and ArcGIS. Our clients, so far, have been government and private sector companies whom we team up with to generate comprehensive datasets, combining acoustic and optical imaging products.

What would you say differentiates Tellus4D from other companies in your space?

We see ourselves more as a data company than just a drone operator. Here in Australia, there are lots and lots of drone service operators, and they all do very similar work. They’ll do videography and map mining pits, even do some agricultural mapping. We are different in that we are scientists that try to do more challenging work where we map the coastline. Our data is acquired using survey-grade georeferencing, and our ultimate goal is to map below the shallow water surface using drones.

Draping high-resolution orthomosaics (Top) on DEMs (Bottom) provides valuable insight and makes visual and quantifiable linkages between onshore and offshore surveys. It’s also an excellent method to survey habitat recolonisation, macroalgae habitats and suspended sediment transport patterns.

The fact that we know what’s behind the data we generate is important; we’re not just making pretty images. Because of our background, we hold PhDs in oceanography, we provide more than just plain imagery, as we understand the processes that underlie the data. We’re able to explain what processes cause the features that we’re seeing, and so by understanding that, we’re also able to give advice regarding certain processes.

What are some of the main projects you work on?

Our main work right now is a partnership that we have with a multinational company called iXblue, which is a large, vertically structured engineering company that has a survey branch with different offices around the world. So, we work with the Australian survey branch—and what they do is seafloor mapping, mainly for nautical charting.

…There are areas that they just can’t reach with a boat, either because it’s too shallow or too dangerous. That’s where we come in with the drones.

We also advise our clients on mitigation and management measures, such as the location of breakwaters and beach nourishment, provide government clients with updated nautical charts and create “seamless datasets” that connect bathymetry—measured by sonar—and topography, which is measured using drone-based sensors. All our products are certified by SSSI, Australia’s surveying institute.

How do you use the drones?

iXBlue, for example, uses acoustic sonars to make high-resolution maps of the seafloor. They actually go out in a boat and map. But there are areas that they just can’t reach with a boat, either because it’s too shallow or too dangerous. That’s where we come in with the drones.

To map the near-shore zone, Tellus4D used an eBee Plus fixed-wing drone. The coastal area, covered in grassland, was well suited for take-off and landing.

The drones we use can fly safely over obstacles and exposed rocks, where the hydrographic vessels can’t go; and we can image through shallow water—down to two meters in clear waters. We plan on using additional sensors in the future, to measure water depths even further down.

How was this work accomplished before using drones?

The coastal mapping work was done using ship-based LiDAR, which isn’t ideal for complex coastlines and only provides a profile view of the landscape above the waterline.

And why did you choose to go with a senseFly drone?

Honestly, it was the cost/benefit and flight efficiency of the eBee Plus that convinced us. We were interested in other platforms, but they were too expensive. We also really like the eMotion 3 flight-planning software and the user-friendliness of the eBee.

We’ve heard of professionals using senseFly drones to map things like coastal erosion, but you seem to be using drones in a very unique way.

Exactly! We see this as a pretty novel application of the eBee. I’ve visited the senseFly website and the YouTube page and it’s all agricultural, mining, inspections and stuff like that, and I thought maybe it would be interesting to share how we’re using the eBee. I’m not sure if mapping the ocean was ever an intended use when the eBee was being developed.

You mentioned bathymetry earlier—why is it so important to get frequent and accurate bathymetry data? Is there a public safety element to the work your company is doing?

The main reason we need good bathymetry data is to update nautical charts for maritime safety. Nautical charts are used by many industries from large commercial ships and small fisherman ships to tour operators and whale-watching vessels. They’re very important for navigational safety. So essentially, we need to have good nautical charts to know where dangerous obstructions are located and how deep [the water] is to keep people and ships safe.

The drones we use can fly safely over obstacles and exposed rocks, where the hydrographic vessels can’t go; and we can image through shallow water—down to two meters in clear waters.

It’s also worth noting that accurate nautical charts are becoming increasingly important due to changing geostrategic and economic shifts, which are occurring now in Asia. Drones can map the very narrow band of coastal areas that are inaccessible by survey boats. This is very relevant because that’s where most of the people are concentrated—over 80 percent of Australia’s population lives within 50 km from the coast—so there’s a lot of people using these shallow waters and a lot of the nautical charts are extremely outdated! So, there is a demand for good, updated bathymetry data.

Can you give our readers a real-world example of the work Tellus4D has done with a client?

Yes. The video [below] shows how we teamed up with iXBlue in New Zealand because in Kaikoura, on New Zealand’ South Island, there was a massive earthquake in 2016 which drastically altered the coastline. After the earthquake, the coastline uplifted, so large rocks that were at depths for boating shifted upward, becoming hazards for mariners in an area that vitally depends on marine industries. Accurate marine charts are a must for economic success in this region.

You mentioned how rocky shorelines create potential hazards for ships. What other hazards did you face before using drones?

The weather, well, a combination of weather, waves and the rocks would make it even more dangerous. Small survey vessels face dangerous conditions when mapping rocky coastlines. By using drones, we are able to remove the risk of having humans operate in these dangerous conditions.

It seems like you’re enjoying several benefits from flying the eBee. What’s your favourite feature and how has it helped you accomplish your goals?

Well, I use the eBee Plus with eMotion, and so far, I’ve never had one glitch with eMotion 3. For me, that’s a really big deal because I also use less specialised drones like the DJI Matrice 210, which is a good drone, but it’s not designed specifically for surveying.

…It was the cost/benefit and flight efficiency of the eBee Plus that convinced us. We were interested in other platforms, but they were too expensive. We also really like the eMotion 3 flight-planning software and the user-friendliness of the eBee.

For that drone, you have to source an app—it’s a third-party app—that does the mission planning and the flight planning that eMotion 3 does so well, and that the eBee includes out-of-the-box. Those [third-party] apps are very glitchy and I’ve heard of peoples’ drones coming out of the sky. So, I’m very happy that eMotion 3 works so well.

Flightpath of one example flight over coastal zone. Note the change in altitude based on flight-planning with elevation set as “Above Elevation Data” (AED) allowing Tellus4D to maintain uniform ground-sampling distance.

I also think a key feature that is difficult to find in third-party mission-planning apps is a reliable “terrain hugging” feature such as the one eMotion has. What it does, basically, is that it allows you to fly AED—which is Above Elevation Data—meaning you download a map of the area which will serve as the base of your survey. Based on that data, the elevation data in that Google Earth image, the flight planning software will adjust the flight elevation of the drone based on the terrain. That’s very important because it lets you get a pretty stable ground sampling distance (GSD), which is the resolution of your imagery. Resolution is a function of the characteristics of your sensor (which you can’t change) and the distance from the object you are measuring. So, the higher you fly your eBee, the lesser your resolution, and you want to try to keep that resolution stable throughout your survey.

Digital elevation model (DEM) created from photogrammetry mosaic using structure from motion (SfM) techniques. Note some seafloor structure is imaged in areas where water was clear.

Most of the third-party apps don’t have that fancy feature like the eBee. I don’t know about other fixed-wing specialised survey drones, but I really appreciate the fact that it’s so stable. It just doesn’t disappoint.

What has your ROI been since using UAVs?

I haven’t made the calculations for the ROI yet, but we’ve been using a rental from a local company here, so we want to buy our own platform. I think once we have our own platform, we’ll be able to have a better idea on the ROI. But so far, we’ve been able to pay off our rental fees, the lease fees we have… at least each project several times over.

Thanks for talking with us today, Geoff.

My pleasure.

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[…] Información extraída del blog Oficial de senseFly “Waypoint” y traducida por Tecnitop. Puede ver el artículo original en inglés aquí. […]

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