Hyperspectral imaging

February 27, 2019 5:12 pm Published by

drone with advanced sensors

Hyperspectral sensors, thermal imaging cameras and other advanced instruments can now be easily mounted to UAVs to see the unseeable and produce spectral analyses that can increase the effectiveness and reduce the cost of a site investigation.

The electromagnetic spectrum is a complex beast. From high energy, dangerous gamma rays on the left, it stretches all the way across to low energy, everyday radio waves on the right passing all other types of electromagnetic radiation on the way.

Of course, we are most familiar with the part of the spectrum that we can see: visible light.

And, for a few years now here at T&P, we’ve been able to attach a camera to a UAV and, as part of an investigation, fly it over a site to capture a series of images which can be stitched together digitally to make a detailed 3D topographical map of the site’s surface features.

With a typical Ground Sampling Distance* of just 5 cm, the results of these aerial surveys have been impressive, and our models have shown levels of accuracy comparable with traditional surveying techniques which often take longer and are more expensive.

So far so good, but what of the potentially valuable information about a site in the other parts of the spectrum that are not captured by a camera and are invisible to the human eye?

This is why I’m excited about the growing number of sensors that can now be mounted to UAVs to capture information from a far wider range of the electromagnetic spectrum.

Thermal imaging cameras have been around for a long time and can be attached to a UAV to enable a temperature map of a site to be produced by capturing infrared radiation.

The real advance though is hyperspectral sensors.

Hyperspectral sensors are special as they can capture a large number – sometimes 100s – of narrow and contiguous wavelength bands that collectively cover far more of the electromagnetic spectrum than is covered by a traditional or thermal imaging camera.

The easiest way to understand them is in terms of their output: a hyperspectral cube. This sounds complex, but it can be thought of as simply a series of pictures of a single location stacked on top of each other with each corresponding to a different wavelength band.

Basically, hyperspectral sensors capture a full spectrum for each and every pixel – you are genuinely getting every single possible piece of information out there.

So what’s the benefit?

Well, it all goes back to the fact that every object has its own spectral profile, and while this may not differ from another profile in the visible light band, it will differ in one of more other bands of the electromagnetic spectrum.

In layman’s terms, you can take a picture of a site with a camera and just see grass, but take the picture with a camera that operates at the right spectral wavelength and you might be able to detect and quantify specific materials such as lead and copper on the surface.

Does this mean we should now always be looking to do an aerial survey using a drone with a full, modern sensor array?

No.

But it does mean that there are now more options out available there when it comes to investigating more challenging sites such as the locations of former mines

The key point is that now this is all possible it should definitely be considered at the planning stage to see whether it offers an opportunity to improve the effectiveness and reduce the cost of a site investigation.

Need a hand understanding more about drones and aerial surveying? We’d be happy to give you a demonstration or to talk you through it just give us a bell on 01179 277 756 or email us at info@tp-regen.co.uk. We’d love to hear from you

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This post was written by Mike Nicholas

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