Félix Pinto

Combining BIM and GIS for a Sustainable Society

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Community-scale Assessment of Energy Performance

Nikken Sekkei Research Institute in Tokyo, Japan, has developed a vision for cities to help them choose an energy optimisation strategy for neighbourhoods comprising a variety of building types. The optimisation of energy consumption is approached from an area-wide standpoint. The added value of the method for city renewal programmes has been demonstrated based on a central district in the Japanese capital.

Japan has low energy resources and a high population density. That provides extra stimulation to develop ecofriendly urban planning. City and environmental designs use low carbon footprint solutions as their starting point, and planners, urban designers, architects, engineers and landscape specialists work together to provide integrated solutions. Urban energy supply and demand is an important item in this context of smart city management. It is a far more complex system than a single building since there are synergies between various elements like transport and the city infrastructure. Especially in Japan’s largest cities, that infrastructure is becoming more and more compact.

Transit-oriented development

According to the latest forecasts, more than a quarter of Japan’s citizens will be aged over 65 in 2055. By then, the population will also have shrunk from the current 127 million to 90 million. In Tokyo (13 million people), one in four elderly citizens live alone with no family to take care of them. The predicted population growth in the 65-and-over group is one of the reasons that, for the past two decades, city planning has been based on compact, multifunctional neighbourhoods concentrated around the public transport system. Japan has no choice but to invest in developing such infrastructure rather than controlling road traffic.

Tokyo Metropolitan City is huge, but the scale has remained human in its neighbourhoods since Tokyo opted for the transit-oriented development (TOD) concept. Most people live no more than 1,000 metres from a train station. In these communities, everything is within walking distance: shops, offices, public facilities, parks and green spaces, and of course transport. “It helps people of all ages to live independently in their own homes and communities. It also saves emissions by vehicles and contributes to mitigating the production of greenhouse gases,” elucidates Mr Shinji Yamamura, executive officer at the Nikken Sekkei Research Institute. Reducing CO2 is very important for Tokyo. The city is a typical example of an urban heat island; the annual mean temperature has increased by about 3ºC (5.4ºF) over the past century. The municipality wants to reduce greenhouse gas emissions by 25% by 2020 compared with the level in 2000. Therefore, the city has not only created a thousand hectares of new green space over the last decade, but there is also a pressing need to reduce energy consumption, both in transport and in buildings.

Low-energy buildings

Tokyo’s urban infrastructure evolved during the city’s period of rapid economic growth, and now requires renewal. Of course, energy saving is part of the plan. Mr Yamamura explains: “New buildings will be recommended, but net zero-energy buildings (ZEB) are not always possible. That is especially so in renovation. Much larger investments are needed than when one aims at the more common level of low-energy buildings. And even for that level, owners of very large commercially exploited buildings can perhaps generate enough budget, but it is still very difficult for the owners of small to medium-sized buildings.” Nevertheless, it is necessary. In 2014, the average annual energy consumption in Japan’s commercial buildings was around 2,140 to 2,450MJ/m2, in office buildings it was 1,457MJ/m2, in hospitals it was 2,952MJ/m2 and in residential buildings it was 778MJ/m2.

Figure 2, Structure of the energy assessment tool.

These elements – community infrastructure, renovation needs, energy reduction policies –inspired the researchers to develop a flexible strategy to renovate all the buildings in a neighbourhood as energy-efficiently and as pragmatically as possible, instead of each building on its own. It is the overall result for Tokyo that counts. Minimising the range of the infrastructure to be renewed would also reduce the initial costs.

The researchers developed three variations of pragmatic renovation policies and studied the effects of them in different areas of Tokyo. “In this process, BIM-GIS integration is essential to combine data in an efficient and holistic, user-friendly way,” states Shinji Yamamura. Building information modelling (BIM) is essential for the energy consultants and urban planners to prepare the building-related data, which can be combined with simulation software to predict the effect of every measure within or amongst buildings. The urban infrastructure data for this energy simulation comes from the local geographic information system (GIS) databases. The result is returned to the 3D city model on the GIS platform to check its effect at city or community level. The platform developed by Yamamura and his colleagues enables energy management operators or local government staff to visualise the energy consumption of the city, district or building. After inputting the location of a target area for city renewal, the planner obtains not only the urban plan information and the community features, but also the energy technology package that is likely to be most effective and needs further simulation and analysis.

Three package variations

Along one train line (East Japan Railway Company) in Tokyo, the researchers picked 12 communities which each have a train station at their centre. The GIS analysis combined with BIM databases from the urban planning department showed that there are a total of 150,000 buildings in those communities, 72% of which are small to medium-sized buildings. Only one community is made up of approximately 50% large buildings (over 50,000m2). In three of the 12 communities, buildings are in use for commercial or business purposes; the other nine are more residential areas.

The first option is to check whether the community has buildings with more than 50,000m2 of floor space. The owners of these large buildings would be in a better position to raise the budget for low-energy renovation work than the owners of small and medium-sized buildings. Rigorously renovating the large buildings only in such a way that they consume over 60% less energy and leaving the small and medium-sized buildings as they are would produce around 18% energy savings across the whole community, concluded Nikken Sekkei Research Institute. “By using advanced technologies such as ZEB-ready methodologies, the large buildings can achieve that 60% reduction,” claims Yamamura. But it is expensive.

As the second alternative, the government should still stimulate renovation of all the large buildings, but more simply. The aim is for them to use 20% less energy. That is feasible with today’s more common technologies to reduce energy consumption in the field of isolation, lighting, cooling and heating. Simultaneously, all the small and medium- sized buildings should implement rather small and easy measures to reduce their energy consumption by only 10%: change to LED lighting, use slightly more efficient air-conditioning systems, etc. In this case, the community achieves 20% energy savings overall.

The third option is that half of the large buildings implement measures to save 20% and all the small and medium-sized buildings likewise save 20%. In that case, energy consumption is reduced by more than 27% for the whole area. To reach that goal, the same reduction steps as in the second renovation policy have to be taken and an area energy management system also has to be implemented. Using the cluster of computer-aided tools, the electricity grid operator optimises the performance of the energy generation and transmission systems.

Looking to the near future, Shinji Yamamura reveals: “The software platform we developed suggests the best-performing strategy, depending on the input from the BIM and GIS databases. Artificial intelligence (AI) can automatically design the optimised energy consumption communities; I am now developing such an AI-oriented tool.”

Figure 3, Osaki Station West Exit Area, Tokyo – microclimate plans with thermal environment simulation support the municipality in creating breeze corridors.

Heat island

BIM-GIS integration is useful in all kind of 3D simulations; Yamamura also uses it a lot for 3D-environment thermal simulations. Although only the energy-oriented issues are highlighted for the purpose of this article, this energy management technology can be part of a comprehensive system that includes the transportation system and urban design measures for heat island mitigation. Yamamura explains his vision: “It is part of a smart city concept with the aim to develop solutions simultaneously and widely at different levels. I believe that prevention of global warming and pursuit of comfortable living conditions are both realisable at the same time.”

When a government decides to invest in BIM-GIS integration, it has a multipurpose functionality in environmentally friendly design. Yamamura, who is also an expert on urban thermal environment planning, has advised on many‘cool city’ design projects that mitigate heat island phenomena in Japan and elsewhere in Asia. Microclimate plans with thermal environment simulations support municipalities in creating breeze corridors in city centres to alleviate the heat problem. The starting point is the same as with area energy management: neighbourhoods or districts must be seen as part of the whole system to achieve success at city level.

Shinji Yamamura and Nikken

Shinji Yamamura is executive officer and principal consultant with Nikken Sekkei Research Institute in Tokyo. He has a PhD in engineering and is a registered building mechanical and electrical engineer. Nikken Sekkei Research Institute was founded in 2006 and is one of the companies in the Nikken Sekkei Group (1950), providing a large variety of city planning, design and redevelopment services (2,600 employees). Its award-winning urban services can be seen throughout Japan, Russia, Asia and the Middle East.

http://www.GIM-INTERNACIONAL.com
Viernes 19 de Enero del 2018

Surveying in the Mining Sector

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An Overview of Geospatial Methods in Mining Engineering

Wim van Wegen

Geospatial data forms the foundation of mining. The rapidly evolving innovations in the geomatics sector are bringing previously unforeseen opportunities that will provide a major boost, both to mining surveyors and the mining industry as a whole. Read on for an article which starts with some history – after all, we should never forget where we came from. It then goes on to present a general outline of surveying in the mining industry, with a focus on the survey equipment and the technologies that are being used today.

Surveyors in the mining industry fulfil an essential function since they provide indispensable information to all the other mining disciplines. Mining surveyors are responsible for the accurate measurement of areas and volumes mined, plus the precise representation of the surface and underground situation on mining plans.

History

The disciplines of surveying and mining both date back to ancient times. The ancient Greeks not only developed the science of geometry, but they also developed the first surveying tool: the diopter, an astronomical and surveying instrument dating from the third century BCE. The diopter can be regarded as the ancient predecessor of the theodolite. The first land surveys can be traced back even further in time, to approximately 3,000 years ago when Egyptian surveyors divided up the fertile land around the mighty River Nile. Likewise, mining engineering is a field with a long history. Archaeological studies have revealed that mining played an important role in prehistoric times, as evidenced by the flint mines in the countries we today call England and France.

The Romans were renowned for their innovations in mining engineering. The copper mines in Rio Tinto in Spain – the best-known ancient mining complex in the world – are a striking example of this. While surface mining was the most common approach, the Romans also used more advanced methods and techniques. Tunnels were dug in order to extract valuable minerals such as gold and silver; this required great planning and advanced knowledge of surveying, mathematics and geometry. However, it was not until the 18th century, when the industrial revolution in the UK was well underway, that the role of the mining surveyor became a widespread and recognised profession.

One of the instruments used back then was the dial: a compass made especially for underground purposes. This method was often inaccurate; iron tools or iron ore deposits in the mine tended to interfere with the needle of the compass. But by the middle of the 19th century more sophisticated devices were being produced. These theodolites were equipped with telescopes, spirit levels and vertical quadrants, enabling the measurement of vertical angles. Theodolites made surveying more accurate by traversing, i.e. measuring fixed points in the mine, so it was no longer necessary to rely on the compass. A short time later, the theodolite had replaced the dial as the main tool of the mine surveyor.

Today, mine surveying is an exact science. Modern theodolites (which in fact are incorporated in total stations, the state-of-the-art surveying instrument that integrates an electronic theodolite with an electronic distance meter) – using laser sighting and electronic data storage – coupled with a global navigation satellite system (GNSS) offer an accuracy that is probably beyond the wildest dreams of the early surveyor armed only with his simple dial and measuring chain.

Mine Surveying Today

Mining surveying can be summarised as ‘the digging of mine shafts and galleries and the calculation of volume of rock’, although it entails much more than this in practice. Geometric constraints – e.g. vertical shafts and narrow passages – demand the use of specific survey techniques. While the basic principles of surveying may have remained largely unchanged throughout the ages, the instruments used have not. Common technologies in mine surveying today include terrestrial laser scanning, airborne laser scanning (further referred to as ‘Lidar’), airborne photogrammetry, unmanned aerial systems (UASs), satellite imagery. Besides this, software forms an essential part of the mining surveying profession nowadays. After all, the captured data needs to be processed in order for it to be of any use.

Terrestrial Laser Scanning

Surveying in the mining industry, both in open-pit and underground mines, often goes hand in hand with terrestrial laser scanning (TLS), which is deployed to verify the spatial changes of mining works. Thanks to its high point density and high accuracy, TLS is a very suitable surveying technique for monitoring movements and deformations.

By obtaining a highly detailed set or ‘point cloud’ of three-dimensional vectors to target points relative to the scanner location, TLS technology collects a large amount of valuable geospatial information in an automated manner. By combining Lidar with GNSS, it is possible to obtain a fully geospatially referenced dataset, which opens up opportunities for changes to be directly measured and monitored over time. In mining specifically, TLS has the potential to be used for a wide range of applications: monitoring and documenting the progress of underground mining works, assessing the stability and hence worker health & safety at mining sites, monitoring deformation and convergence, calculating volumes, providing supplementary evidence (e.g. in the case of accidents or damage), aiding security and protection of mining sites, etc. Hence, laser scanning in the mining industry represents a significant growth market. The technology is already used for the documentation of corridors and infrastructure by room-and-pillar mining methods, although it has not yet gained a substantial foothold in the case of long-wall mining, for example: a form of underground coal mining whereby a long wall of coal is mined in a single ‘slice’. Manufacturers of laser scanners – such as RIEGL and Maptek – often not only produce the hardware, but also offer a software solution with a streamlined survey workflow. With the purchase price of the device and the corresponding software amounting to roughly EUR100,000, the required level of investment is a key factor affecting the adoption of this technology in the mining industry.

Airborne Laser Scanning

Another method of capturing the mining environment is airborne laser scanning, also known as ‘airborne Lidar’. Utilising high-end manned or unmanned airborne platforms makes it possible to obtain data in challenging circumstances. Airborne Lidar offers great opportunities for the mining sector, as it is able to acquire millions of points per square kilometre. This density creates a robust dataset in the form of a digital terrain model (DTM) or digital elevation model (DEM) that can be used for mining applications such as volume calculations, geomorphology and structural geology, slope analysis and surface run-off modelling for feasibility studies and environmental impact studies. Volumetric mapping or time-sequenced topographic modelling to facilitate subsidence monitoring is also a service that can be provided when using airborne Lidar.

Portable Laser Scanning

A more recent trend is the use of portable laser scanners, which are particularly suitable for the challenging mining environment. Handheld laser scanning is an ideal solution thanks to its ease of use, and some lightweight and compact scanners can also be mounted on mobile platforms. Portable scanners are an excellent tool for surveying mining tunnels as well as tasks such as stockpile volume measurements or advanced tracking and change management.

Apart from the favourable mobility aspect, some portable scanner systems utilise simultaneous localisation and mapping (SLAM) algorithms – a robotic technology which enables them to accurately register the scanned data by using the surrounding geometry.

The ever-growing number of portable laser scanning solutions offer an effective alternative to the more traditional GNSS-based survey technologies which do not perform well in underground and covered areas. It seems safe to say that laser scanning will be the preferred method for capturing survey data in the mining industry for the coming years, and handheld or portable scanners add a new dimension to the opportunities for geospatial data acquisition. One important advantage in terms of the application of portable laser scanners is their reasonable price range.

Aerial Photogrammetry

Over the past few decades, aerial surveying has changed the overall face of mining operations and has revolutionised exploration. The application of aerial photogrammetry is a proven method of pit mapping and stockpile volume measurement, with a particular emphasis on 3D modelling and monitoring. The spatial data acquired in this way is used, for example, to create digital terrain models, orthorectified georeferenced imagery and topographic maps. The imagery derived from an aerial survey can also be used in automated processing for the production of DEMs.

Nowadays, aerial photogrammetry is often combined with Lidar technology and is increasingly being obtained using UAVs. The successful use of aerial photogrammetry is dependent on factors such as the expertise and delivery speed of the aerial survey company, the level of ground support from mine site survey staff and, not unimportantly, favourable weather conditions.

Unmanned Aerial Vehicles

Reflecting the trend in the entire geospatial profession over the past five years, a growing number of mining companies are working with UAVs. These are equipped with digital cameras to provide high-resolution aerial imagery, which is then further processed to produce highly precise orthophotos, point clouds and 3D models. This data can be used for forecasting the development of the mine, monitoring changes and calculating volumes. UAVs can also play a role in improving the safety of workers underground by providing information about the above-ground situation.

A new disruptive technology in the broader geospatial industry that can bring benefits for the mining sector too is the combination of UAV and Lidar. This may have the potential to replace many existing options. Several companies, such as YellowScan, have launched ultra-compact and lightweight unmanned Lidar systems. The demanding environmental circumstances and sometimes dangerous conditions make UAV surveying the ideal solution in terms of producing GIS data for DEMs and DTMs.

Satellite Imagery

A lot of powerful information for the mining industry is obtained from space. Satellite imagery is an essential tool in support of mineral exploration projects, for example. Thanks to the detail-rich satellite imagery, the presence and patterns of pathfinding minerals can be mapped, providing valuable insights for mining companies before they decide whether to invest in field deployments. Due to its global coverage, satellite-derived imagery is a safe and cost-effective method for obtaining information regardless of local constraints, even in remote regions. Satellite imagery also makes it possible to monitor elevation changes in an open-pit mine. Image processing, orthorectification, georeferencing, feature extraction, and mosaicking are all techniques that guarantee tailor-made image data for numerous different mining and geological applications. One technique especially worth mentioning is short-wave infrared (SWIR) wavelength bands which offer unique remote sensing capabilities, such as material detection, which are often impossible with other technologies. The SPOT satellites (SPOT 4 and 5) are equipped with SWIR, for example, while DigitalGlobe is an experienced provider of high-resolution SWIR imagery.

Processing Software

Over recent years a broad variety of innovative software solutions for mine planning and surveying have emerged. Bentley’s mine surveying solution brings together mine site survey data, surface terrain models, digital images and point clouds. The solution enables mining engineers to develop a comprehensive 3D model of the mining site compliant with company standards. One company that offers the whole geospatial workflow associated with mining is Maptek. This Australian-based company bridges the gaps between the geological, spatial design, execution and measurement details of a mining operation. Other renowned companies in the geomatics industry such as Leica Geosystems (integrated with Hexagon Mining), Topconand Trimble (Trimble Connected Mine) also offer a complete product suite for mining engineers. Their solutions include aerial, terrestrial and underground scanning and imaging, positioning infrastructure, planning software, visualisation software, GIS and more. In fact, they comprise all the tools a mining surveyor needs.

The Future of Mine Surveying

In view of such completeness of the surveying solutions for mining professionals that are now available, one could be inclined to rest on one’s laurels. What else is left to wish for, when so many state-of-the-art solutions are making surveying relatively easy? Nevertheless, a couple of exciting broader technological developments deserve a mention here as being set to make mining even more productive: virtual reality (VR) and augmented reality (AR). In fact, the global mining industry has been an early adopter of both of these technologies. One of the industry’s pioneers when it comes to VR is Brazil-based Vale, the world’s largest producer of iron ore and nickel. Since 2000, Vale has been assembling geographic databases of its fields, by investing in very-high-resolution images. The company conducts 3D aerial surveys with laser geotechnology and assembles 3D digital models. In 2013, Vale entered into a partnership with the British Geological Survey, which has played a major role in the use of virtual reality in mining. Vale now uses VR to aid decision-making in several aspects of its operations and projects: from defining the mining area to environmental licensing scenarios and even closure of a mining site. Geological, geotechnical and environmental studies are carried out with VR

Likewise AR – which superimposes a layer of interactive digital information over images of the physical world – offers significant opportunities for the mining industry in terms of improved productivity, reduced equipment maintenance costs and employee safety. Microsoft’s HoloLens AR headset is already transforming businesses in architecture, the automotive industry, engineering and education, to name but a few, and the potential of ‘mixed-reality’ technology to revolutionise the mining industry is already being widely recognised.

So ‘complete’ solutions are already being supplied by the leading companies in the field, but the definition of ‘complete’ seems likely to expand further in the near future. If our own minds sometimes boggle at these science-fiction-like advancements, just what would a Roman surveyor of the ancient Rio Tinto mine make of such innovations?

http://www.GIM-INTERNACIONAL.com
Viernes 19 de Enero del 2018

BlackBerry and Baidu partner on connected car technology

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Blackberry QNX car O

BlackBerry Limited and Baidu Inc. are collaborating to accelerate the deployment of connected and autonomous vehicle technology for automotive OEMs and suppliers worldwide.

The companies have signed a statement of intent to make BlackBerry QNX‘s ISO26262 ASIL-D certified safety operating system (OS) the foundation for Baidu’s Apolloautonomous driving open platform.

Also, BlackBerry and Baidu will work together to integrate Baidu’s CarLife, the leading smartphone integration software for connected cars in China, as well as its conversational artificial intelligence system DuerOS, and high-definition maps to run on the BlackBerry QNX Car (Infotainment) Platform.

Blackberry QNX will host demonstrations of its foundational software for autonomous and connected vehicles at the Consumer Electronics Show (CES) 2018, at North Hall Booth 7523. The show takes place Jan. 9-12 in Las Vegas.

“BlackBerry QNX has established itself as the OS platform for safety-certified production-based systems,” said Li Zhenyu, general manager of Intelligent Driving Group, Baidu. “We aim to provide automakers with a clear and fast path to fully autonomous vehicle production, with safety and security as top priorities. By integrating the BlackBerry QNX OS with the Apollo platform, we will enable carmakers to leap from prototype to production systems. Together, we will work toward a technological and commercial ecosystem for autonomous driving, intelligent connectivity and intelligent traffic systems.”

“Joining forces with Baidu will enable us to explore integration opportunities for multiple vehicle subsystems including ADAS, infotainment, gateways and cloud services,” said John Wall, senior vice president and GM of BlackBerry QNX. “Baidu has made tremendous strides in artificial intelligence and deep learning. These advancements paired with their high-definition maps and BlackBerry’s safety-critical embedded software and expertise in security will be crucial ingredients for autonomous vehicles.”

Announced by Baidu in April 2017, Apollo is an open platform that provides a comprehensive, secure, and reliable solution that consists of cloud services, an open software stack and reference hardware and vehicle platforms. It supports all major features and functions of an autonomous vehicle.

More than 70 global partners are involved with Apollo, including OEMs, Tier 1 suppliers, developer platforms and technology start-ups. The project was named after the historic lunar landing program to illustrate its scale and complexity. BlackBerry provides OEMs with cybersecurity technology to protect and mitigate, including hardware, software, applications and end-to-end systems from cyberattacks.

BlackBerry’s pedigree in security and continued innovation has led to recent automotive design wins with Delphi, Denso, Qualcomm, Visteon and others.

www.http://gpsworld.com - 09 de Enero del 2018

Research Online: Urban positioning accuracy enhancement using 3D buildings model

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gps1217 research online constructed 3D model

Above: The constructed 3D model for 26 buildings; below: illustration of the direction of recording of surfaces. Click to enlarge.

By Nesreen I. Ziedan, Zagazig University, Egypt / Presented at ION GNSS+ 2017, September 2017

Multipath is a major source of positioning accuracy degradation in urban areas. Advances in 3D mapping and the availability of 3D city models have encouraged a set of new techniques for multipath mitigation.

This paper presents three algorithms to enhance the accuracy of urban positioning using all the available line-of-sight, multipath and non-line-of-sight signals:

■ An accelerated ray tracing technique that first eliminates the 3D surfaces that are invisible with respect to a position, and then analyzes the visible surfaces to predict the existence and path lengths of reflected signals. The ray tracing algorithm is applied on the possible range of positions.

■ A Markov Chain Monte Carlo-based algorithm that applies both the Gibbs sampler and the Metropolis-Hastings technique to analyze the received correlated signals to estimate the delays of reflected signals for all the received signals.

■ A Van Rossum-based technique that measures the discrepancy between the estimated delays and the predicted ones at a range of possible positions, where the position that generates the minimum discrepancy is taken as the estimated position. Test results indicate the ability of the algorithms to successfully utilize reflected signals to enhance urban positioning accuracy.

www.http://gpsworld.com - 09 de Enero del 2018

UAS-borne Lidar for Mapping Complex Terrain and Vegetation Structure

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New Lightweight Laser Scanners for Very-high-resolution Point Clouds

Gottfried Mandlburger, Philipp Glira, Norbert Pfeifer

The development of lightweight, survey-grade Lidar sensors has made it possible to equip unmanned aerial systems (UASs) with very precise laser scanners, thus opening up new possibilities in the domain of close-range 3D mapping. To test the capabilities of UAS-borne laser scanning, a flight experiment was conducted using the RIEGL VUX full-waveform scanner mounted on a RIEGL RiCOPTER UAS platform. In the experiment, both the topography and the vegetation structure of an alluvial forest along the River Pielach in Lower Austria were captured. The resulting point cloud has a density of more than 1,500 points/m2 and an accuracy of better than 2cm.

The Neubacher Au is a Natura2000 conservation area near the confluence of the Pielach and Danube rivers (Figure 1). It is a highly dynamic landscape due to periodical inundation during flood peaks. The fluvial topography includes pristine channels, side channels and oxbow lakes. This topography is perpetually changing, as is the vegetation structure. As a retreat area for aquatic and terrestrial habitats, alluvial forests are of high ecological value. Mapping these sensitive areas with traditional terrestrial or airborne techniques is challenging due to the high complexity of the terrain and the vegetation.

The recent advance of survey-grade Lidar sensors with a weight of less than 10kg offers new perspectives for 3D mapping of complex natural landscapes in high resolution. To test the potential of UAS-borne laser scanning, a flight experiment was conducted using the RIEGL VUX sensor mounted on a RIEGL RiCOPTER UAS.

Figure 1, The study area of Neubacher Au: DEM shading superimposed with point density map and flight trajectories.

Sensor System

The carrier platform is a RIEGL RiCOPTER, which is an X-8 array octocopter. Four foldable carrier arms, each carrying a coaxial array of two propellers, are attached to the carbon-fibre main frame. A shock-absorbing undercarriage enables safe landings. The maximum payload including batteries and all sensor components is 16kg. At the maximum take-off mass (MTOM) of 25kg, the RiCOPTER achieves a flying time of 30 minutes. The maximum flight altitude is 150m, but nationally regulated limits for civil unmanned aircraft need to be considered.

The VUX sensor system is mechanically and electrically integrated into the RiCOPTER aircraft fuselage. It consists of a global navigation satellite system (GNSS), an inertial measurement unit (IMU) for capturing the flight trajectory, the VUX-1 time-of-flight laser scanner, a control unit and a camera for video downstream. Furthermore, two Sony Alpha 6000 RGB cameras can be mounted on the UAS. The scanner features an effective measurement rate of 350kHz with a total field of view (FOV) of 230°. The large FOV is beneficial for vegetation mapping as trees can be captured from both above the canopy and from the side. The ranging accuracy is 10mm according to the vendor’s datasheet. Figure 2 shows a photograph of the UAS and the sensor system just after take-off, with the alluvial forest visible in the background.

Figure 2, Photograph of RiCOPTER UAS platform and VUX sensor system during take-off in front of alluvial forest.

Data acquisition

Data was captured on 26 February 2015 under leaf-off conditions. The flight crew consisted of the pilot remotely controlling the UAS and the sensor based on either a line-of-sight view or video images. An additional operator was present at the ground-station computer for flight mission guidance. The acquisition of the area of interest was based on a standard airborne laser scanning (ALS) flight plan with longitudinal and cross strips. The regular strip distance was 40m and the flying altitude was 50m above ground level, which was about 15m above the highest trees. Depending on the sensor-to-target range, the resulting laser footprint diameter was between 1 and 2.5cm enabling detection of small vegetation objects. Take-off and initialisation of the navigation system were performed manually. The GNSS/IMU system was initially aligned on the ground and after take-off by backward movements of the UAS. After finishing the initialisation procedure the autopilot took over control and the RiCOPTER subsequently flew the programmed path autonomously at a speed of 8m/s. The mission parameters and the large scanner FOV resulted in a mean laser pulse density of 1,500 points/m2 and in multiple strip overlaps so that the vegetation was captured from all sides.

The high strip overlap was additionally used for a thorough calibration of the entire sensor system in post processing by a strip adjustment. This was done by simultaneously minimising the point-to-plane distances of more than 100,000 correspondences. Within the strip adjustment, the acquisition system was fully recalibrated. This includes the estimation of scanner calibration parameters (e.g. rangefinder scale error), mounting calibration parameters (i.e. misalignment and lever arm), and strip-dependent trajectory errors (i.e. GNSS and IMU errors). The adjustment led to a substantial quality improvement of the acquired point clouds, resulting in a final relative accuracy of 1.7cm (Figure 3).

Figure 3, Colour-coded height differences within smooth strip overlap areas. Background: DTM shading.

Results and applications

While thorough processing of the flight data is still work in progress, the first preliminary results are presented in Figure 4. A perspective view of the dense 3D point cloud coloured by reflectance is illustrated in Figure 4a, whereby the trunk, stem and thicker branches appear in red colour tones indicating high target reflectance and lower values (green to blue) are observed for the thinner twigs and their tips. Figure 4b shows a small section of the near-ground 5cm–resolution digital elevation model (DEM), which demonstrates that topographic features and dead wood can be mapped with remarkable sharpness. Furthermore, the density and spatial coherence of the point clouds fuel hopes that these point clouds can also be used for characterisation of terrain roughness with an accuracy better than 10cm. A potential field of application is flood modelling where, besides geometry, roughness (flow resistance) is an important input parameter.

Figures 4a and 4b both show the potential of the ultra-high-density 3D point cloud for detailed single-tree modelling. Whereas complete coverage of individual trees with points on all sides and from the trunk to the canopy is hard to achieve with terrestrial laser scanning (TLS), unmanned laser scanning (ULS) makes it possible thanks to the flexible flight path. ULS point clouds thus combine the advantages of TLS (short sensor-to-target range) and ALS (regular planimetric point spacing, bird’s-eye perspective). Compared to TLS, there is less scan shadow in ULS as the laser beam first traverses the rather sparse canopy area before hitting the thicker branches and tree trunks near the ground. Due to the high scan rate and the resulting ultra-high point density, many last echoes hit the ground surface. This enables the derivation of a very-high-resolution digital terrain model (DTM) with grid spacing in the 10cm range.

Figure 4a, Perspective view of 3D point cloud coloured by target reflectance.

The diameter at breast height (DBH) is an important parameter in forestry since, in combination with the tree height, it allows the estimation of biomass. Whereas obtaining tree heights from ALS is already state-of-the-art, DBH estimation based on Lidar remote sensing is currently only feasible via TLS, which is both time-consuming and labour-intensive in forest environments. Figure 4c shows a horizontal section of the ULS point cloud including all points 1.20-1.40m above the terrain. In this dataset the stem diameters can directly be measured with centimetre precision. Individual colours are used in Figure 4c for the points of each flight strip, underlining the remarkable georeferencing quality.

Concluding remarks

The field experiment employing the RIEGL VUX sensor system mounted on the RiCOPTER UAS provided a homogeneous, ultra-high-resolution 3D point cloud of a complex alluvial area comprising both topography and vegetation. With a point density of more than 1,500 points/m2, a vertical strip-fitting precision of less than 2cm and a comprehensive 3D capturing of the terrain shape and vegetation structure, the experiment demonstrated the high potential of UAS-borne laser scanning for different environmental sciences and applications.