Safe and Convenient Use at Ground Level

Laser Scanning for Change Detection

Advances in laser scanning are opening up some interesting new applications in three-dimensional mapping. With recent developments in scanning technology and processing software, new systems are being developed to electronically map and monitor change with greater precision than previously possible. Here we will look at examples in the environmental, mining, construction and education sectors where the technology is addressing important safety, security, commercial and research requirements.

By Graham Hunter

European research project involves tracing the movements of dinosaurs by their footprints.

Anglo American has installed SiteMonitor at a number of platinum and iron ore mines.

This type of ‘stop and go’ laser scanning has all sorts of uses for 3D mapping, from construction site mapping to coastal surveys and research. More unusual uses include a European research project to trace the movements of dinosaurs by their footprints. The University of Manchester and Universitat Autònoma de Barcelona are using a scanner with integrated digital camera and satellite positioning to accurately record and locate individual footprints. In this case a portable Riegl LMS Z420i laser scanner is used that comprises a high performance long range 3D laser scanner, software and an integrated high resolution digital camera. The laser transmits a light pulse, from a known position and at a known angle, which is reflected off a surface or feature and bounced back to a receiver. Using the time taken for each individual pulse to be returned and the known value of the speed of light the system can automatically calculate the distance of the feature from the unit. From this data highly detailed and accurate 3D models can be produced. “This project would simply not have been possible without the laser scanning system,” said Dr David Hodgetts, Lecturer in Reservoir Modelling and Petroleum Geology, School of Earth, Atmospheric and Environmental Sciences at The University of Manchester. “Due to the fragile environment and the sensitivity of the site we were not permitted direct contact and therefore all measurements had to be taken remotely. Laser scanning allowed the rapid, high resolution digital mapping of an otherwise inaccessible site.”

The vehicle mounted WireFinder system measures the position of telecom network assets, such as poles and wires.

Tripod-based systems are fine for one-off mapping but it is a slow and therefore costly process and does not address the requirement for change monitoring. To broaden the scope of laser scanning, recent developments have looked at ways of speeding up data capture and the added portability of devices has led to a number of vehicle and even back-pack mounted systems. Such technology was used in a recent project to map part of the South Coast of England. The project, commissioned by New Forest District Council in partnership with the Channel Coast Observatory, employed laser scanning to monitor changes in coastal defence structures over time. A series of lasers mounted on a specially equipped Quad Bike scanned the coastal terrain capturing millimetre-accurate measurements to create a 3D model of the rock and soil surface. “Laser scanning allows us to record changes in the rock structure that would be difficult and time consuming to detect using our existing surveying techniques,” said Stuart McVey, Coastal Surveyor. “When you also consider the speed at which the data is captured and the fact that we can remotely access unsafe or otherwise inaccessible parts of the rock structures, this technology gives us very valuable data and provides good value for money.”

Laser scanning is being used to monitor slope deformation in open cast mines, improving the safety of personnel and reducing risk in operations.

Even greater portability is offered by an innovative system that can be carried as a back-pack. This has been developed to map overhead infrastructure such as power lines. Major power cuts are becoming a common occurrence both in Europe and North America and one cause is the increased vegetation growth rates, which are perhaps induced by global warming. Power companies have traditionally used airborne LiDAR to survey high voltage power networks however low voltage cables are too small and too close to the ground to be visible. Their size and proximity to both ground and vegetation make them vulnerable to damage therefore increasing the risk of network failure. This system instantly maps the proximity of vegetation to overhead cables. Special software automatically identifies potential conflict between cable and vegetation, determining the level of risk, backed up with images from an integrated digital camera. By maintaining accurate and up to date records of the infrastructure and nearby vegetation proactive maintenance can be scheduled and the risk and liability reduced.

StreetMapper and WireFinder

A similar system has been developed for mapping overhead telecom networks. In this case the vehicle mounted WireFinder system accurately measures the position of telecom network assets, such as poles and wires. The WireFinder laser scanner with its 360 degree field of view can capture 12,000 measurements per second, at distances of up to 300 metres with a repeatability of less than 10 millimetres. The system, which is mounted on the roof of a 4x4 or other suitable vehicle, is used while stationary, making the WireFinder solution significantly safer than existing systems where survey staff have to stand in the road while recording measurements. In other sectors there is an increasing demand for systems that can rapidly map infrastructure such as highways and this has led to some major developments in vehicle-based systems. Mapping in 3D at normal road speeds threw up some serious technical issues and 3D Laser Mapping formed an alliance with IGI mbH. The two companies spent one and a half years tackling these technical issues and successfully developed a system now known as Street­Mapper. Operating at speeds of up to 70 km an hour, laser surveys can be undertaken quickly and safely to create highly detailed picture of the road network and associated assets and features. The accuracy is such that the heights and positions of overhead wires as small as 3mm in diameter can be accurately recorded. StreetMapper can be used for a wide range of applications including road surface and safety inspections, landscape mapping, street asset recording, bridge height surveys and road width mapping for entire routes. Originally developed as a custom-fit system, the system has been further developed as a modular vehicle-mounted system. Suitable for fitting to a standard 4 wheel drive vehicle ‘StreetMapper 2’ allows surveying off road, extending the scope of use beyond the highway. With easy-fit rack mounting and a roof rack suitable for any 4x4, 3D Laser Mapping is able to ship the system to any location allowing StreetMapper technology to be used worldwide for the first time.

The Sishen Mine, an open pit operation with extraction dating back to the 19th Century.

Mining Operations

Although portable laser scanning is proving to be an important innovation for many markets, some of the most important commercial developments for laser scanning have been in the mining sector. Here laser scanning is proving to be a tremendous asset in supporting mining operations through site monitoring and improving site safety. A system called SiteMonitor has been designed to provide accurate and repeatable measurements of surfaces and slopes in hazardous or inaccessible environments. The application was first developed for monitoring slope stability on old coal mine waste tips in South Wales, UK. Now the system is being adopted more widely in the mining industry. SiteMonitor records movements in the slope surface as small as 10mm with a distance range of up to 1000m. It records and analyses up to 8,000 measurements per second to create a detailed, accurate and continuous record of the slope profile. SiteMonitor can deliver real commercial benefits by allowing mining operations to be optimised; allowing greater extraction volumes through steeper slope profiles; something that is only possible with continuous monitoring.

Platinum

Anglo American has installed SiteMonitor at a number of platinum and iron ore mines. Anglo Platinum is the world’s largest primary producer of platinum, with a production target of 2.9 million ounces of refined platinum in 2006. Safety is a primary concern for the company whose operation comprises of 7 mines, 3 smelters, a base metals and a precious metals refinery. SiteMonitor is used at Anglo Platinum’s Potgietersrust Mine in South Africa. “Traditionally we have used conventional survey methods to monitor slope stability of open pit slopes. This limited the size and number of locations we could survey and the frequency of survey,” said Frans Benadé, Section Surveyor. “The combination of highly accurate laser scanning units and software specifically engineered for this application enables us to cover a larger area at more frequent intervals.” Anglo Platinum is currently operating two Riegl LPM-2K Laser Scanners. These units are specifically designed for the automatic and manual long range profiling of surfaces, operating at distances up to 2,500 metres with an accuracy of 50 millimetres. The systems perform continuous, 24/7, remote scanning at locations determined by Anglo Platinum’s Geotechnical Rock Engineering team collecting hundreds of point measurements daily. The point cloud data collected by the laser scanners is automatically analysed using SiteMonitor software from 3D Laser Mapping. By comparing readings against base measurements the software can detect surface movement or slope deformations. “SiteMonitor has significantly reduced the risk of injury to personnel, property and equipment, enabled higher production due to decreased downtime and reduced the resources required for ongoing safety monitoring.” Commented Benadé.

Slope deformation

New laser scanning technology is also helping South Africa’s Kumba Iron Ore to improve the safety of iron ore extraction. Kumba Iron Ore is majority owned by Anglo American and a new Riegl LMS Z420i laser scanner is being used to monitor slope deformation at the Sishen Mine, an open pit operation with extraction dating back to the 19th Century that achieved a record production of 28.5 million tonnes last year. The Riegl LMS Z420i laser scanner is specifically designed for the mining environment. The system comprises of a high performance long range 3D laser scanner, associated operating and processing software and an integrated and calibrated high resolution digital camera. The unit is rugged and fully portable and offers an unrivalled combination of wide field of view, high maximum range and fast data acquisition. “The laser scanning system has a number of features that make it ideal for our environment and application. The scanner covers a broad area so even small failures can be detected and operates at a range of 800m. Laser scanning complements our existing slope monitoring equipment and adds an extra dimension to the monitoring network at Sishen; improving the safety of personnel and reducing risk in our operations” said Glen Mc Gavigan of Kumba Iron Ore’s Geotechnical Services.

Scanning Underground

Safety is a big concern in all mining operations and the use of laser scanning is not restricted to open cast mines. Surveying can be taken underground and one of the latest innovations is a laser scanning robot called 3D-R1. The idea of a Remote Sensing Vehicle (RSV) for mining was first conceived at the UK’s Camborne School of Mines and that technology has been employed in the 3D-R1. Developed by Jobling Purser RSV LLP in conjunction with 3D Laser Mapping, 3D-R1 allows 3D surveying to be carried out in dangerous or hazardous environments. Traditional scanning in hazardous situations often lead to blind spots due to restrictions in access but the RSV is moved by remote control from location to location. It can perform scans and video in areas that are otherwise not safe to enter. Even in safe environments, the RSV is a useful tool that can increase productivity by 75% be eliminating the need to manually set up scanners at each location. Being light and easy to use, 3D-R1 can also be used easily elsewhere and potential applications including tunnel surveys and the surveying of earthquake, fire or blast damaged buildings.

Real-world View

One of the most important aspects of developments in laser mapping is the rapid processing of the vast amounts of data generated from scanning itself. This improved processing is underpinning many of the new applications where traditional methods of data collection are regarded too slow and too inaccurate. The presentation of the data is also improving all the time with advances in visualisation and interpretation using GIS and 3D modelling software. So, the information provided by laser scanning provides an important new perspective, enhancing information systems with an accurate real-world view of both the natural and man-made environment. As long as man requires detailed information about the world that surrounds him technology will continue to develop and innovate in order to meet this demand. We already have laser scanners in aircraft, ground vehicles and even robots, what comes next could be down to you.

Dr Graham Hunter (graham@3dlasermapping.com), Managing Director of 3D Laser Mapping Ltd. For more information visit www.3dlasermapping.com.