Using the Eye in the Sky for Mineral Exploration

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This article first appeared in the 2022 Minerals Business Report and Buyers Directory. 

Remote sensing imagery acquired by satellites has opened new frontiers in exploration. Historically, the data have provided information to government entities to measure land use and predict weather and other benefits to society, but natural resource companies are also finding satellite imagery useful for mineral exploration.

Exploration Mapping Group Inc., based in Las Vegas, is among the few providers supplying these industries with geological remote sensing services and interpretation. Managing director Dan Taranik conducts the bulk of this work with Maxar’s WorldView-3 satellite, which offers industrial-grade superspecteral instruments, including 15 or more high-resolution spectral bands to capture imagery.

“WorldView-3 spins around the globe once every 90 minutes, so as it rotates across the globe, we can be over the same site of the Earth once every five days,” he said. “Each one of those spectral bands is designed to measure some mineral or environmental phenomenon, so we can measure a variety of clays, irons [and] silica. And that’s what our geologists want to see before they go in the field so they can plan their time wisely to make the most out of really expensive field time, and it also keeps them safer.”

Exploration geologists prefer WorldView-3 as it is among a small group of satellites with the technical quality, ground resolution and spectral range to create quality images and maps.

“There are other technologies like drones and other airborne technologies that do similar things, but they have a big entourage of pilots, technicians and permitting issues,” he said. “With this satellite, we can jump over all of that and just acquire data without any mobilization and provide results to our clients pretty quickly.”

With more than 30 years of experience in mining and petroleum exploration, Taranik shared his insights with Hart Energy on leveraging remote sensing technology for mineral exploration.

Hart Energy: What is your approach to helping a new client that is looking to explore the potential of new minerals in a certain area?

Taranik: Normally, all we need to start is a polygon on the ground like a shapefile, or what is called the Google Earth KML [keyhole markup language] or KMZ [a zipped file containing one or compressed KML files], and that shows us an area on the ground. We’ll take that polygon and we'll search the archive, and we'll report back to the client what we see in the archived data. We have a collection planning team that are global experts in certain regions of the world with weather.

If we don't have data or if the client wants new data that capture the current state of drilling or infrastructure development, the collection planning team will tell us when the next opportunity will be to collect data again. Once we set a tasking date with the client, the satellite will start passing overhead, and we normally shoot for less than 5% cloud cover because there’s nothing worse than trying to map geology with a big puff of cloud in the way that screws up all the statistics. So we try to collect without clouds if possible. Then we do some custom work on the data that has to do with atmospheric corrections, radiometric corrections and the geometric corrections before we can do our mineral mapping procedures.

Hart Energy: What is the key differentiator of this satellite compared to the imaging technology that was used before to map out mineral assets?

Taranik: I would say the number of spectral bands, the quality of the sensors and its detector elements. It's an extremely high-resolution grade signal-to-noise [ratio], and the geometric accuracy is better because every pixel in the scene—roughly 90% of the pixels—are plus or minus three meters in terms of real-world ground distance.

It’s an industrial grade satellite, which is important to distinguish these days because there are some really great satellites like the Planet Dove satellites about the size of a shoebox, which is good for red, green, blue natural color images, but it doesn't have the spectral depth and the signal-to-noise or geometric accuracy characteristics for mineral mapping.

With remote sensing geological satellites, we can cover large areas of ground very quickly in an objective and unbiased way. We could try to do this on the ground with an army of botanists or geologists walking across an area, but that wouldn't be very efficient. But with remote sensing and very high resolution, we can see individual plant canopies, and we can measure the health of each one of those plants. In a similar way, we can measure the mineral response of every outcrop.

You can’t just drive around and assume that you’ve seen everything. The roads are very limited, and it doesn't show you what’s over the horizon. So remote sensing is really the only technology that can consistently map an area across large swaths.

“WorldView-3 spins around the globe once every 90 minutes, so as it rotates across the globe, we can be over the same site of the Earth once every five days.”

—DAN TARANIK, Exploration Mapping Group Inc.

Hart Energy: How does the imaging process work in this technology, and how has it evolved over time?

Taranik: The image processing used to be very simple back in the ’60s and ’70s, where people would use just band ratios, like band five over seven, which was once used to detect clays. Gradually, as we got more spectral bands, the processing became more sophisticated. It has evolved, and now we have so many bands. There can be up to hundreds of bands, and we use techniques like linear regression, and we have spectral libraries that can sort the spectral signatures that are present in any given scene.

We match against spectral libraries, which will tell us what minerals the pixel most resembles, and we can identify geological materials from that. The processing has gotten more sophisticated over the years as we have more spectral bands, but spectral libraries and spectral mixing have made it easier.

Hart Energy: How does the software distinguish between the different deposit minerals it captures?

Taranik: Every scene is a combination of geology with some degree of organic soil, vegetation, urban infrastructure, maybe oceans, lakes, glaciers, so we do quite a lot to mask out the things that are not geology so that we’re just looking at rocks and soils.

With our image processing and our knowledge of how to combine those bands, we assign colors to the different bands. That way we can determine silica, which we normally color red, from the clays that are a mix of yellow and green. It makes for a consistent product for our clients, so when they do another project a few months later, they'll know what those colors mean and how to interpret it.

Hart Energy: What opportunities do you see for the oil and gas industry to leverage this technology for new mineral leasing and other opportunities?

Taranik: Usually, there are two approaches we see with petroleum and mineral clients. One is that they’re going into a new remote area that requires either long ground transport or expensive helicopter airborne work, so they want to stake ground with mineral leases for the purpose of exploration or drilling. The other scenario is that they have a large land holding, and it’s expensive to hold that every year. Governments around the world charge money for those claims, and they need to drop ground. So they want to know what’s the best ground to hang on to and what they can let go of.