LiDAR and Drone Uses

When it comes to UAV payloads, thermal and Red Green Blue (RGB) cameras get a great deal of attention.

With low price points, the technology is easily accessible to just about everyone. Several standard drone missions, such as three-dimensional mapping, are effortlessly carried out using it. There are, however, limitations to using only these two types of payloads on drones.

Thermal cameras are ideally suited for inspections where temperature variations are the primary data points. Beyond this function they are, by design, limited.

RGB cameras are excellent tools for photogrammetry. While this survey method is accurate and useful in a wide range of applications, it is also not without its limitations. For example, drones with RGB cameras can survey vacant land in preparation for development. In most cases, the images collected can produce precise three-dimensional models and topographic maps that planners will find useful.

However, if this same land were covered in thick, dense vegetation, the RGB camera would fail to give planners any information on the actual earth’s surface. For this type of analysis, RGB and thermal cameras are not the best tools for the job.

What is LiDAR and how does it work?

Invented in 1961 by the Hughes Aircraft Company, LiDAR (Light Detection and Ranging) is ideal for the type of analysis mentioned above. LiDAR systems consist primarily of three components: a laser, scanner, and a specialized GPS receiver.

LiDAR works by accurately measuring the distance from the drone to the ground. A laser is fired millions of times from the LiDAR scanner towards the ground as the drone flies a predetermined pattern. As each pulse of light is emitted, the exact time the light is fired is recorded. As the light pulse is reflected, the scanner detects the return and again marks the exact time the light returned.

The specialized GPS receiver records the exact position of the sensor throughout this process. An equation that utilizes the constant speed of light generates a slant range for each beam of light fired. When all the data is compiled, millions of points on the ground produce an accurate representation of the earth’s surface and features above it.

The data points are so numerous and so precise that layers of vegetation or other obstacles can be removed to show the topography of the region. One light pulse can generate multiple returns and thus, layer the area being surveyed. The technology has seen successful use in many fields such as disaster response, high precision infrastructure monitoring, and topographic/hydrographic survey.

 

Types of LiDAR for UAS, and the industries that benefit

UAVs use two types of lidar.

For measuring the earth’s surface, topographic LiDAR is ideal. It utilizes a near-infrared laser for mapping land.

The second type — bathymetric LiDAR — is designed for surveying the seafloor and riverbeds. It uses a green laser to penetrate water, but operates on the same principles as described above.

LiDAR systems on UAS provide professionals across many industries the ability to map the earth’s most challenging environments. The level of accuracy spread across millions of data points is particularly beneficial to construction planners, as well as those monitoring utility infrastructures. Hard-to-see features, such as powerlines, are easily identified by LiDAR. These features can also be isolated from other features, aiding in in-depth analysis.

There is perhaps a no better example of the power of LiDAR than in archeology. The incredibly dense jungles of Central America were home to one of the ancient world’s greatest civilizations, the Mayan. The Mayans built vast cities with massive structures. 

After a mysterious decline and disappearance in 900 A. D., many of their cities were swallowed up by the jungle. Dense jungle canopies all but erased many locations. Traditional investigation methods, such as aerial surveys in aircraft, see only vast expanses of the jungle.

However, LiDAR systems on crewed aircraft and drones are revolutionizing what researchers know about the Mayans. LiDAR can remove the vegetation and show what lies underneath. In some cases, its identified previously unknown locations with tens of thousands of structures. LiDAR is helping to expand this ancient civilization’s study in ways that seemed unimaginable just a few years ago.

Bringing it all together

Drones carrying LiDAR payloads are a power tool.

With only a few years of UAV technology and lidar working together, impossible topographic challenges are becoming increasingly simple tasks. For decision makers in construction, utilities, survey, and research, the advantages of UAVs carrying LiDAR are worth further investigation.

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David Daly - Contributing Author

David Daly - Contributing Author

David Daly, is an award-winning photographer/writer and licensed (FAA) Commercial sUAS pilot. A graduate of the United States Naval Academy, David is a former Marine Corps officer with a BS in Oceanography and has earned his MBA from the University of Redlands. David has worked for Fortune 100 companies and has a background in aerospace, construction, military/defense, real estate, and technology.

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Thermal Imaging: A Colorful Introduction

Lessons Learned – Part 1 of 4

A series of insights brought to you by the Consortiq team

To understand thermal imaging and its applicability in our world, we need to start with the key question:  What is a thermal sensor?  

To understand this, we need to look at some basic – but quantum – physics. 

In essence, we can see because light reflects off an object. That light then enters the eye where rods and cones (receptors) on the back of the eye collect the inputs, and send them to the brain to be processed via the visual pathway. 

Therefore, we can ‘see’ this light, as it becomes visible.

However, “visible” light makes up a small part of the much broader electromagnetic spectrum illustrated here: 

Thermal Imaging Spectrum - Consortiq

Thermal imaging image courtesy of wikipedia on a Creative Commons Attribution-Share Alike 3.0 Unported license

All of these differing wavelengths — from very long waves, such as radio, to very short waves, such as gamma radiation (the shorter the wavelength the more frequently they arrive, hence low to high frequency) — make up the entire spectrum range.   

The key fact in all of this is that, of the entire electromagnetic spectrum, only 0.0035% is the light we actually see – “visible” light.

Thermal Sensors

So, back to thermal sensors. 

They’re capable of ‘seeing’ electromagnetic radiation in the infrared band of the spectrum. Infrared radiation is closely linked to the temperature of the object, so there is a correlation between the object’s temperature and the electromagnetic radiation it emits. 

As that object’s heat increases, it emits higher frequencies on the spectrum until it enters the visible light band and glows red hot.

To get technical, everything has a natural ‘emissivity’ level. In other words, objects have varying levels of effectiveness as it pertains to emitting thermal energy as thermal radiation. 

A thermal sensor uses those levels of emissivity to create a picture. By assigning colors or shades to different thermal radiation values, you get the familiar thermal image.

Drone inspection thermal imaging

Photo By Passivhaus Institute | Image used with permission under the GFDL.

It’s not true to say that a thermal camera can measure the temperature of an object, per se. It’s possible, but only if the camera is set up and calibrated correctly. Additionally, the emissivity values for the substance being measured must be known. 

Simply put, if you know that steel has an emissivity value of “X” at a given temperature, then you can calibrate your system so that, when it ‘sees’ that emissivity value on a steel object, it displays that temperature value. However, if you use the sensor on something other than steel without recalibrating it, the system will display an incorrect temperature reading.

Now, thermal sensors are very good at displaying temperature differentials… not necessarily by amount, but they do show that there is a difference. 

By adjusting the scale — or gain — you can make these differences even more evident, which is particularly useful for certain types of surveys. 

Recent: Drones in Oil and Gas: Safe, Fast, Effective

For example, electrical components that are heating differently to the same component under the same load elsewhere may be indicative of a fault. Moisture leakage may give an artificially cooler result than would be expected.

The proper use of thermal sensors can provide greater insight into a survey area than just a visual inspection, but interpreting the resulting data is crucial. Unlike a visual inspection, there is much analysis that can be done with thermal imagery if captured in a radiometric format.

In effect, this is capturing the thermal data in what a photographer may refer to as “raw footage.”  The ‘picture’ is therefore not just an image, but an accumulation of data. That data can then be manipulated and analyzed to produce a detailed analysis of the properties of the area, item or, indeed, building which has been surveyed.  

Andy Huggett - EMEA Training Manager - Consortiq

Andy Huggett - EMEA Training Manager - Consortiq

Andy served in the British Army prior to becoming a law enforcement officer with Sussex Police for 30 years. Always on the operations side of policing (traffic, firearms, dogs, helicopter unit, etc.), he was also part of a General Aviation Team countering terrorism.

As an emergency response drone pilot for Sussex and Surrey Police, he undertook many differing roles piloting the police drones. He founded his own drone services company prior to leaving the police and, upon retirement, worked full time in this role.

Consortiq contracted Andy to deliver the UK-based Unmanned Aircraft Qualification as a freelance instructor. Subsequently, he moved into a full-time role at Consortiq as the Training Manager with responsibility for Europe, Middle East and Africa. Andy holds both CAA and FAA qualifications for fixed wing and multi-rotor aircraft.

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