From coastal landslide modelling to mapping geological hazards, monitoring active lava domes and biodiversity management, Lee Jones explains how drone-based and terrestrial LiDAR scanning has transformed image capture for environmental research.
Over the last two decades, advances in technology have meant that the applications and use of terrestrial Light Detection And Ranging – more commonly known as LiDAR – have expanded dramatically, transforming our ability to better measure, monitor and model the Earth.
A type of remote sensing, LiDAR relies on pulses of light directed at a target to measure vertical distances with high accuracy, greatly advancing our ability to produce high-quality 3D maps with greater speed and precision. In fact, geodetics continues to be one of the fastest expanding global markets, driven by technology. Combining both science and technology, it integrates the more specific disciplines and technologies of geodesy, surveying, mapping, positioning, navigation, cartography, remote sensing, photogrammetry, and geographic information systems (GIS).
[3D attributed s-Grid generated from VOM. RGB coloured LiDAR scans were used to create DTMs and virtual outcrop models (VOMs), which in turn were used to create 3D S0Grid facies models (in SKUA-GOCAD) to be used for CO2 flow modelling, as part of research into carbon capture and storage in sandstone reservoirs. Source: Remote Sens. 2021, 13, 395]
Surveying and geomatics professionals can now use a range of software, satellite, sonar 3D scanning and drone technology, and although LiDAR is just one tool in our armoury, it is a fast-growing and exciting example of how the methods and technologies used to collect, distribute, and store geographic data, is rapidly changing; even changing the way we process and present data.
3D mapping with LiDAR
In the past, LiDAR has typically been used for security, police, and military applications. But its exceptional ability to map and provide data on large areas quickly means it has more recently found applications in studying coastlines, forestry, glaciers, and cities which, due to their density and varying heights, are often very challenging to navigate and map by foot and too complicated to measure by satellite.
The ability to produce a 3D, highly detailed map with relative ease and speed, can provide scientists, conservationists, and public servants the information they need to understand an area's biodiversity, geologic history, unexpected terrain differences, and changes over time. High accuracy landcover and shoreline maps are particularly important in fields such as flood and coastal management, ecosystem monitoring and biodiversity management.
Mobile Mapping Solution (MMS)-based research
The British Geological Survey (BGS) is currently at the forefront of Terrestrial LiDAR Scanning (TLS) and Mobile Mapping Solution (MMS)-based research for geohazard mapping, monitoring, and modelling, with over 400 surveys from over 200 sites, both in the UK and overseas, carried out over a 20-year period. During this time, it has used these technologies for widespread applications in earth sciences, engineering geology, geohazards, and climate change, including terrain modelling of inland and coastal landslides, eroding coastlines, actively growing volcanic lava domes, retreating glaciers, rock stability and subsidence features, soil erosion, and geo-conservation.
In 2000, BGS became the first organisation outside the mining industry to use TLS as a tool for measuring change. Paired with a Global Navigation Satellite System (GNSS), we were able to measure, monitor, and model geomorphological features of landslides in the UK, digitally. Most commonly, our approach combines airborne LiDAR scanning with a mobile mapping solution (MMS) that can be worn on your back.
The MMS can capture and collect data indoors, outdoors, and underground, and when paired with a GNSS, allows scientists to obtain a terrestrial equivalent of an airborne LiDAR survey and create a 3D model. It combines five cameras offering 360 degrees view and two LiDAR profilers with an ultra-light carbon fibre chassis. With the addition of an external light source, precise scanning of tunnels and cave systems is also possible (see Nottingham Caves Survey). The system can also be vehicle-mounted, for mobile mapping of large areas, or polemounted, for lowering into voids or sinkholes.
The power of combined technologies
Importantly, an MMS enables disaster responders to capture data in 3D, on foot, in danger zone areas; and, in combination with SLAM (Simultaneous Localisation and Mapping), that uses features captured in the scans to orientate the final point cloud, and its high precision IMU (Inertial Measurement Unit), that tracks the 3D movement of the unit, to achieve accurate positioning even during GNSS outages. This ability to combine different technologies (LiDAR, GNSS, UAV, InSAR) to create a system greater than the sum of its parts, has resulted in a powerful tool for research and industry.
[Image below: 3D models of the retreating cliff line at Aldborough, 2001 to 2017, benefit from improved quality and resolution of scans since 2012 (orange to blue). Source: Remote Sens. 2021, 13, 395]
Current GNSS units operate to subcentimetre accuracy and can be used to acquire precise surveys of non-linear features, including watercourses where the depth to the bed cannot be recorded as easily as other features. The BGS is also in the process of developing a low-cost GNSS system as a rugged ‘disposable’ solution for monitoring the movement of a landslide, the flow velocity of a glacier, volcanic deformation, coastal evolution, or differential ground subsidence. In addition, UAVs can now be fitted with digital cameras, thermal detectors, multispectral cameras, and LiDAR scanners to provide highly accurate data, with full coverage 2D and 3D models.
Thanks to huge technological advances in the field of geodetics and geomatics, it’s now possible to believe that a map can transform what we know about the Earth, our impact upon it, and our ability to adapt and build resilience to our rapidly changing environment.