Read about the advantages that we are providing to the rail industry with our UAV technology. In this month’s edition of Rail Professional Magazine our survey manager Stuart Thomas discusses how the adoption of UAV technology is revolutionising the way surveys and inspections are being conducted in the rail sector.
"The rail sector is traditionally very quick to adopt new technology for surveying and inspection tasks. In recent years the advent of GPS, laser scanning and mobile mapping has given rail surveyors a new range of survey tools to use. More recently developments in land surveying techniques for rail include laser scanning (train-mounted, aerial and terrestrial) and interactive virtual site visits using ground based sensors or sensors mounted on manned aircraft.
In the last few years unmanned aerial vehicles (UAV), also known as drones, ROAV, UAS or RPAS, have become available on the commercial market. This is mainly due to the miniaturisation and reduction in the cost of components such as autopilots, cameras, batteries, etc. The development of software and processes for flight-planning and data manipulation has also been rapid.
The use of UAV by survey professionals is now becoming an accepted technique to provide rapid, cost-effective and high quality survey data. Network Rail recently awarded a framework agreement to 4 companies to provide UAV survey services on the rail network.
Two main types
UAVs come in 2 main types, Fixed-wing – which is essentially a small aeroplane, and Multi-rotor – a small helicopter style craft with 4, 6 or 8 rotors. Both types are fitted with high spec camera and autopilot for autonomous flight. Fixed-wing UAVs are most suited to larger land survey projects, whereas a multi-rotor is best used for smaller survey projects or for visual inspection where its hovering capability comes into its own. This platform also has the advantage of vertical take-off and landing which allows aerial work on confined sites.
All commercial UAV operations in the UK are governed by the Civil Aviation Authority (CAA). Companies with CAA ‘Permission for Aerial Work’ must comply with a number of regulations such as maintaining line-of-sight with the aircraft (within 500m from the ground-based pilot) and flying below a maximum flying height of 120m above ground.
UAV surveys on the rail network
Aerial survey projects using UAVs can be controlled from outside the railway boundary without the need for track possessions. This obviously means a potentially significant in disruption to rail services and removes people from risk.
Typical uses for UAVs on rail survey projects are to provide geo-referenced orthophotos, digital elevation models (topographic data), and aerial oblique and panoramic imagery.
An orthophoto, typically to 3cm/pixel accuracy, provides a high definition and up to date vertical view of the area of interest, allowing distances to be measured and to assist with planning, The creation of a digital elevation model using photogrammetry techniques, typically to an level accuracy of 50mm on a 1m grid, provides accurate topographic data allowing site design and volumetric analysis. The acquisition of aerial oblique and panoramic imagery provides a wider view of the project including its setting within the local environment.
Advantages of UAV surveys
UAV provide a number of benefits to the rail industry, ranging from reduction in cost, increased speed of delivery and improved safety.
Reduction in cost
Acquisition of aerial data from full-size aircraft is an accepted method for larger rail projects. However, it is not always cost-effective on smaller projects due to mobilisation costs. UAVs can be mobilised very rapidly and can survey sites at a fraction of the cost of the full-size alternative.
Additionally, for smaller sites, UAV survey does not require people working track side and so removes the costs of organising track possessions.
Increased speed of delivery
With the ability to cover more than 100 hectares in a day, UAV survey acquisition is significantly more efficient than traditional ground based survey techniques. This means survey data can be captured and delivered faster and allows for more frequent surveys to be provided. For example, Due to the ease of mobilisation and speed of survey it can be cost-effective to carry out multiple aerial survey missions over the course of a construction project. The progress of the project can be effectively tracked by means of repeat aerial imagery and topographic data acquisition. Time stamped aerial imagery assists in tracking progress, providing invaluable information to tendering contractors, reporting to senior management and can be used to complement existing site orientation information for health and safety purposes.
As UAV survey does not require people being trackside, it removes the risks of trackside work.
Disadvantages of UAV surveys
Accuracy (Line Of Sight Limitations)
UAV surveys may not be the best solution for larger linear inspections, for example, to survey the full east coast main line will be more effectively completed by a full size aircraft
UAV surveys will not replace track geometry surveys using total stations and rail gauges, these surveys have very tight accuracy requirements, where a standard UAV topographical survey may be accurate to +/-50mm, more than adequate in many situations but not for detailed track geometry studies. However, the imagery provided by a UAV survey can still be hugely beneficial for this type of work.
UAV inspection on the rail network
As part of the Network Rail frame work agreement, UAVs are also being used for close visual inspection tasks on the rail network.
Current inspection methods for high volume, low height rail infrastructure, is typically ground-based inspection crews working under line possession. The use of UAVs to carry out visual inspection reduces the need for interruption to rail services and also provides detailed imagery from an elevated viewpoint which can identify defects that may not be visible from ground level.
For low volume, high rail infrastructure such as viaducts and bridges, traditionally the inspection access method would be rope access, scaffolding or elevated platform. The use of UAVs to inspect these structures saves time and expense plus removes inspection personnel from the inherent risk in working at height.
Cyberhawk Innovations, one of the professional UAV companies on the Network Rail framework, have developed an end-to-end inspection solution for the inspection of rail infrastructure. Using advanced inspection design and cloud based software, iHawk, Cyberhawk provide powerful asset management information to the client allowing them to review the inspection findings and make decisions in the comfort and safety of the office.
Technology more widely available
Network Rail’s recent framework agreement for UAV survey and inspection work means the technology will be more widely used over the next few years on the rail network, enabling the rail industry to benefit from the cost savings and safety improvements that UAV surveys provide".
Full article available here.