Multi-spectral sensors are able to capture image data within specific wavelength ranges across the electromagnetic spectrum. Measuring these wavelengths can be very interesting when you want to measure vegetation or soil, but also things like nutrient deficiencies, identifying pest damage, or assess water quality. Multispectral sensors capture data on the reflection of light energy that bounces off objects in the environment, which can be compared to data of other nearby objects. Humans, for example, can only see between 0.4 and 0.7µm. For reference: seeing dust or smoke fits in band 1, between 0.43 and 0.45µm. Measuring can be done by satellite, but also by drone.
Thermal sensors measure objects’ surface temperature, through the use of a thermal imaging camera. These cameras form an image using infrared radiation and identify different temperatures through colour palettes, like a heat map. Thermal images are used for for example through drone-based observation, inspecting infrastructures, water sources, livestock detection, and heat signature detection. Heathrow airport started a trial in May to detect the body temperature of its passengers in the rise of the spread of COVID-19, using thermal imaging facial recognition cameras.
Synthetic Aperture Radar (SAR) is an active radar system that sends wavelengths and collects these again after reverberation. This is used to create 3D or 3D imagery of an environment. A more advanced radar system is interferometric synthetic aperture radar (InSAR), which uses two or more SAR images to create a digital elevation map, making it possible to measure with high precision deformation over time. Earth Watchin (ESA), a service which helps local authorities during emergencies with remote sensing data, shows in this article how they used SAR technology in mapping deforestation over 20 years in Cameroon. “The image shows in red (2008) a rainforest area where deforestation is still ongoing, while the areas in green and blue are the areas where deforestation started in 1994.” SAR is also able to select different frequencies to avoid weather-caused signal change. Using this technology will help with environmental monitoring, like oil spills, urban growth, deforestation, or biomass, but also for monitoring civil infrastructure stability, like bridges.
LiDAR (Light Detection and Ranging) is a technology used for mapping the height contours of an object or building. The technology uses lasers to determine the distance between objects and the sensor. Based on the perspective of the sensor, the outcome can either be a heightmap or a complete 3D model. The technology is being used in autonomous vehicles for auto parking. Luminar has developed a sensor that is more affordable than any other sensor out there. LiDAR technology can be combined with different carriers – land-born, air-born, UAV-born and satellite-borne – which define the accuracy and remoteness of the sensor. LiDAR technology produces point clouds, which can be transformed into a Digital Surface Model (DSM) to create 3D models of buildings or objects. Even though LiDAR technology has been around for a long time, it has gained new attraction in recent years as lighter sensors now allow UAV-borne sensing. Besides, Coming years we expect the technology to become more affordable and therefore also easier to deploy. Besides, we expect development in the field of algorithms to analyse the collected data.
Even though remote sensing technologies are still mainly being used for scientific purposes, we are noticing a growing interest in these technologies in a broader commercial spectrum. The main reason for these developments is that these technologies are increasingly becoming cheaper and smaller and therefore more adaptable. Not only helps remote sensing us seeing things from a distance, these technologies also help us measure things we have never been able to measure before. Wider implementation of these technologies will therefore basically shape a completely new view of the world. At Bit, we explore together with our clients how these technologies might be useful for an innovative future and at what point it would be feasible to adopt. This is how we stay ahead of the curve together!