Technological advancements onboard recently launched satellites, such as those which form the European Space Agency (ESA) Copernicus program, have improved the quality and quantity of remote sensing data available for environmental monitoring. Data obtained by the ESA is not just optical but includes Synthetic Aperture Radar Missions (SAR) and altimetry. Applications are varied but common geoscience applications have included soil moisture, and natural hazards such as earthquakes, landslips and flooding. Universities known to be undertaking remote sensing natural hazards research projects include Newcastle, Portsmouth and Surrey.
The National Centre for Earth Observation (NCEO) commissioned by NERC is based out of the University of Leicester with other Directors from the University of Reading, Imperial College, King’s College and the University of Edinburgh. NCEO publish over 150 papers every year and recently included a paper demonstrating that remote sensing can have geo-environmental applications too. Similarly, hyperspectral imagery has been used to identify asbestos roofing in urban areas.
It is noted in this report produced by London school of Economics and commissioned by Innovate UK in 2018 that ‘Satellite-derived EO is potentially a huge market but is, to date, still relatively immature’ and ‘from the nine use cases examined, the predominant use of EO is in Meteorology – accounting for more than 90% of the current derived value.’ It is noted within the report that ‘Satellite-derived EO has also been widely used to support ground monitoring for specific infrastructure projects, including the construction of Critical National Infrastructure (CNI). Examples of actual use include HS2 and the Jubilee Line extension, while areas of potential use include fracking and mining infrastructure projects.’ Consequently, it is anticipated the applications within site investigation and construction will continue to grow.
Drones and sensors
Technological advances in Unmanned Aerial Vehicles (UAV) / Drones and sensors have widened the possibilities for terranean, sub-terranean, atmospheric and water-based data capture from a hobbyist birth place to new vantage points and commercial scales.
Capability developments resulting from increased popularity are fast leading to specialisation and enhanced functionality in the range of UAV and emerging sensors; all of which is set to benefit asset management to the tune of £42 billion by 2030 –‘Skies without limits’.
Innovations in data capturing sensors ‘sky-hooked’ onto UAV of most interest to the site investigation and construction industry are gathering pace. Visible imaging sensors, capturing what is visible to the naked eye and from a vantage point which would otherwise be dangerous or unaffordable, are amongst the most commonly applied. Images captured using photographic devices are processed using photogrammetry to generate highly detailed 3D point cloud data for true scale and georeferenced asset/site mapping and modelling, rivalling traditional surveying approaches (providing those who gather the data are appropriately qualified), but most importantly bringing assets to life through creation of a digital twin.
It is understood that this is providing incredible visual advantage to investigation/construction project teams and an array of technical disciplines. Proposed management of such exciting advances are documented in the Centre for Digital Built Britain - Gemini Principles Paper 2018.
Light Detection and Ranging (LiDAR)
LiDAR is a long-standing proven technology, also effective in capturing terrain (often alongside RGB imagery), amongst other data (surface characteristics, chemical and velocity). Drone mounted LiDAR has advantages over visible imaging when sites are densely vegetated due to the intensive volume of laser scans emitted from the sensor. It also is of benefit when capturing linear features and mines.
Infrared (thermography) and Optical Gas Imaging (OGI) sensors
Thermography and OGI sensors are gaining value and recognition within the utilities industries. Heat mapping has been effective in the detection of subterranean leaks for targeted investigation. OGI has applications in industry where gases must be monitored, including landfill emission management.
The evolution of multispectral to hyperspectral imaging is opening doors for site investigation applications, albeit very specific questions about the information requirements must be clear to harness its potential. Site conditions and information demands must be suitable, but this technology and new spatial operation can be used to identify minerals, contaminants, invasive vegetation, ecological habitats, etc. on the basis that unique spectral ‘fingerprints’ can be identified from known records or distinguished within an image. This technology is anticipated to advance, through further demands for data gathered in this way, to provide full spectral imaging.
Radiation sensors navigated by UAV's are also proving an invaluable aid in better understanding the radioactive landscape where conventional methods have not been safe or far reaching enough.
The detection of near surface UXO via magnetometer and other structural sub-surface features is a field of technology that is currently very active with pilot studies, innovation and market testing, with some interesting developments documented in recent articles
Ultraviolet (UV) photography
UV photography is still in its infancy due to limitations in commercial hardware. However, highly specific applications to date include the detection of small amounts of surface contamination or small surface features. ‘Reflected’ UV imaging has also been employed to locate corona discharge
from high voltage power lines, where insulation has broken down and the electrical field strength is increased.
Many examples of the innovative status quo and future developments in UAV sensors are captured in CIRIA publication Unmanned aerial vehicles for managing assets C783
Developments for future sensors are underway in the improvement of payloads
, and in the collection of weather data, radar, sonar, acoustic and gravimetric parameters. Whilst these, along with already established applications must be carefully tempered with careful appreciation of the professional skills needed to design, execute and assess the various data sets, UAV in their various emerging forms provide an extraordinary tool going forward for the investigation industry. Watch this space!
Structure -from-Motion (SfM)
SfM is the process of reconstructing 3D structures from a series of 2D overlapping images taken from different viewpoints. As a result, it has been used as an effective low-cost topographical tool and has potential in geoscience applications. Currently, Newcastle University has research underway to develop low cost, on-site investigation and near real-time landslide monitoring using a mobile device.
- On-site monitoring and telemetry
On-site monitoring may include periodic monitoring, high-frequency monitoring and/or continuous monitoring varying as BS 8576:2013 says from a number of monitoring events to multitudinous. Increasingly for parameters that are affected by seasonal and weather related changes there has been interest in the value that can be added to site investigation by continuous monitoring through reducing overall monitoring periods and uncertainties in data sets.
Whilst continuous permanent ground gas monitoring equipment has been around for a few years it has continued to be improved to now include other environmental parameters such as gas flow. It has been adapted to measure the actual ground gas at the. Further information on the use of continuous ground gas monitoring of both sources and receptors can be found in the CL:AIRE Technical Bulletin TB18.
- On-site chemical testing
Technology in this area has struggled due partly to the difficulty of acquiring UKAS accreditation for on-site tests, and also because of the ever increasing requirements for lower detection limits, which are often more problematic with on-site instrumentation. There are some areas where on-site testing is preferable, particularly for groundwaters or gas monitoring. For gases, there are various meters for measuring oxygen, carbon dioxide, methane, plus other hydrocarbon gases, and also for measuring total (unspeciated) VOCs. With vapour monitoring, there may be issues to be addressed due to uncertainty regarding the precise composition of the total VOCs measured, and in relation to limits of detection relative to (higher than) the concentrations at which some compounds have the potential to cause harm.
For soils, there are not as many options although X ray fluorescence (XRF) has had some success with metals, despite level of detection (LoD) issues, and for hydrocarbons there are methods using solvent extraction and spectrophotometers.
- Direct Push Technologies
Direct push tools are driven, rather than drilled into the ground, using a set of pushing rams, and can be used for rapid screening of a range of geotechnical and geo-environmental parameters. The principles of this technology have been around for several decades however technological advances are allowing a new generation of tools to be used to greater effect. Ever increasing demand for more data points at a reduced cost, time frame and impact on site means that Direct Push Testing is a useful addition to the range of tools we have to offer. Rapid screening of parameters, and instant data allows for investigations to be directed on-the-fly and ground models to be produced quickly and accurately. Upwards of 150m per day per tool is possible. The linear nature of these tools often allows tool combinations to be used, collecting multiple data streams in a single push – i.e Cone Penetrometer Test Membrane Interface Probe (CPT-MIP) , or Seismic CPT cones.