Technologies & sensors

The 3D imaging of the surface and everything on it has been done for decades from airplanes and satellites. Photogrammetry is the creation of maps from digital aerial photographs which have been made with special high-resolution cameras. More specifically, this is called aerial photogrammetry. Using lightweight cameras, these high resolution 3D aerial photographs can also be made by drones. With special software the photos can be processed and manipulated. This technology can be used for many different purposes. Besides maps and geo-information photogrammetry can be used to generate digital aerial photographs, digital orthophotographs, 3D relief models, high density point clouds and ortho mosaics. These 3D spatial data of (objects on) the earth's surface can be used to calculate distances, surfaces and volumes. The current technology allows us to make elevation models with a resolution and vertical precision of better than a few centimeters.

How does it work?
To create the digital photographs, high resolution digital photocamera's are used making vertical (for stereo photographs at least with an overlap of 30%) or oblique (with an angle of 45° for depth effect) photographs of the earth's surface.

Infrared (IR) thermography is a no-contact technique for measuring the surface temperature of a body or an object. The Infrared camera is equipped with an optic for infrared and a detector which analyses the wavelength of the emitted light. Light has three variables:

  1. luminous intensity, determined by the amplitude,
  2. colour, determined by the frequency or wave length
  3. polarisation, determined by the direction of the vibration.

The frequency or wave length of the light emitted by an object can be used to determine its surface temperature, making it possible to determine the temperature of an object using a colour spectrum (thermography). IR themography is mostly applied in industry, electrical engineering and in the built environment, for example for security purposes, localization of fires, detection of missing persons and the detection of heat losses and overheating on high voltage pylons or power plants, often indicators for damage to or future failure of insulation material.

How does it work?

An IR thermography camera produces a thermogram, a visual representation of the temperatures of the object, with different colours representing different temperature ranges. In most cases low temperatures are represented by dark colours and high temperatures by lighter ones.

Various parameters are linked to a thermogram, some of which strongly influence the results. For example the emission value, reflectivity, humidity and the type of camera used. The camera provides information on the resolution of the detector, IFOV (Instantaneous Field of View) and the temperature range. Other important parameters are linked to the scope of the thermographic measurement. The best results are achieved in cases with temperature differences of at least 10 degrees Celsius between the object and its environment. This makes winter the most suitable season for drone IR thermography in the open air.

By radiating a molecule with infrared (IR) light, a part of the light will be absorbed by the molecule. Which part of the infrared light is being absorbed is dependent on the chemical bonds within the molecule, as it will absorb those frequencies of infrared ligt that match the frequencies of the various vibrations within the molecule. This infrared absorbtion can be measured with an infrared spectometer. Possible applications of drone IR spectrometry are mainly in E&P, mining, environmental surveys aimed at determining the chemical composition of ore bodies, reservoir rocks and pollutants. In agriculture this technology can be applied for the early detection of crop diseases.

How does it work?
By determining which frequencies of the infrared light have been absorbed, the chemical bonds in the object can be identified. An infrared spectrometer consists of a source and a detector. The light of the infrared source is devided by several mirrors in two identical beams. One of those, the reference beam, reaches the detector without obstructions. The other beam is aimed at the object. The detector now compares the light in the reference beam with the beam reflected by the object. The difference between these two beams shows which frequencies of the infrared light have been absorbed by the object. Consequently,  the percentage of light reflected by the object is represented in a graphic, called an infrared spectrum (IR-spectrum). An IR-spectrum is a representation of the frequencies of the absorbed infra red light. The spectrum can be used to analyse which chemical bonds are present in the analysed object.

The Laser imaging Detecting And Ranging (LiDAR) technology uses laser pulses to determine the distance to an object. The technology is comparable to radar, but where radar uses radar waves, LiDAR uses light waves. Since the wavelength of laser light is much shorter than radar waves, LiDAR is able to detect much smaller object. Also, its short wave length makes LiDAR relatively insensitive to surface vegetation. Because a part of the laser light will always be able to penetrate the vegetation and reach the surface, it can be used to calculate vegetation density, CO2 storage in rainforests and to detect overgrown ruins in densely forrested or barren areas. Other applications are 3D elevation models of areas with dense vegetation, velocity measurement and the periodic measurement of the polar ice cap and glaciers.

How does it work?
LiDAR works according to the same prinicples as radar: a transmitted laser beam is reflected by an object and after a while returns to receiver. The speed of the laser beam and the time span between transmission and reception determine the distance to te object. Since the laser beam stays strongly bundled, it's possible to make a surface or relief scan of an object or area by gathering data from different angles. The velocity is determined with the Doppler effect.

The Height Technologies (HT) G3 LiDAR/RGB packet offers a drone with integrated LiDAR technology  Find out more.

A Corona camera shows the corona discharge caused by damaged insulation materials protecting for example high voltage switches or wires. Corona is the cause of high energy losses of up to 200 kW per kilometer of high voltage wiring. Failure of insulation materials can lead to discharge failures causing damage to the implant, a break down of the power supply and possibly even fires and explosions. Drone inspections with a Corona cameras can be done without shutting down the power line, which has considerable advantages in terms of costs, risk and time compared to inspections performed by people.

How does it work?
A corona camera  shows the UV light generated when nitrogen comes into contact with a power leak. As "normal" ultra violet light is filtered out, corona can be visualised even in broad daylight. During the measurements a normal video image and the UV source are shown simultaneously, making it easy to locate the corona accurately.

Natural gas is composed of more than 75% methane. There is a high demand for an easy and cost-efficient method for the detection of methane in all sectors of the natural gas industry. The measurement principle of the drone methane detector uses the characteristics of methane, which absorbs laser beam (infrared rays) of a specific wavelength, called infrared absorption technology.

How does it work?
The laser beam directed at targets such as the ground or gas piping, will reflect back a diffused beam from the target. The device will receive the reflected beam and will measure the absorption of the beam, which will then be calculated into methane column density (ppm-m). Due to the fast spreading of methane outside the leak, the best results are obtained in calm weather.

Magnetometer and Gradiometer make it possible to dectect ferrous objects and layers from the air. This geophysical technique is applied mainly to detect metal objects, like UXO, in undisturbed rural areas, in mining and for mapping ore bodies. The gradiometer is a magnetometer which measures the changes in the magnetic field (the gradient of the field). Compared to the magnetometer, a gradiometer increases the accuracy of the measurements and decreases the sensitivity for regional changes of the earth's magnetic field. Both technologies can also be applied for water bottom research.

The drone magnetometer system has been used in many UXO detection projects and has proven to be very efficient and accurate. Possible applications are UXO detection, geophysical exploration, archaeology and the detection of underground infrastructure or landfills.

How does it work?
Magnetometer and gradiometer measure the earth's magnetic field. This field consists of the the so-called main field, which slowly varies and causes variations due to local deviations such as the presence of ore or ferrous objects in the underground. By measuring these local deviations of the total magnetic field, the location of ferromagnetic objects and layers can be determined. The dimension of the deviation is proportional to the amount of ferromagnetic material in the underground. To detect metallic objects, peak values in the registered data are analysed according to their horizontal and vertical position, approximate dimensions and the ferrous mass of the metal object.

*Drone magnetometer is currently under development.

Ground Penetrating Radar (GPR) is an electromagnetic reflection technique. It is able to quickly, accurately map the first few meters of the underground from the surface or just above. GPR has high accuracy and is mainly used to locate objects or layers. There are various tools for both deep and shallow research.

The GPR systems used in combination with drones have an antenna frequency of 500 MHz or higher. For optimal results the equipment needs to be moved as close to the surface as possible. The maximum penetration, depending on the soil composition, is approximately 1.5 m.

How does it work?
GPR uses electromagnetic waves sent into the ground or object by a transmitter antenna. The waves are being reflected if there is a change in material properties of the ground or construction. The reflected waves are registered by a receiver antenna. The measurement results are analysed to determine the horizontal and vertical position and the dimensions of objects and/or layers.

* Drone GPR is currently under development.

EM (Electro Magnetic) induction or Radio EM is a technique which determines the electrical conductivity of the underground in a non-destructive way. Metal objects like UXO (ferrous and non-ferrous), cables and pipelines, conductive soil layers and fracture zones in the underground can be detected with this geophysical technique.

How does it work?
The electromagnetic (EM) field is sent into the ground by a transmission coil. This primary EM-field inducts a secondary EM-field. In conductive objects or layers this inducted EM-field is larger and of longer duration compared to the less conductive surrounding material. The longer response of the conductive object is received by the reception coil. To detect conductive objects, peak values in the registered data are analysed according to their horizontal and vertical position, approximate dimensions of the conductive object and signal strength.