El mundo al instante

Norway proves Russian interference

jammer on truck ministry of defense russia 600x285 PPNorway has electronic proof that Russian forces disrupted GPS signals during recent NATO war games, according to a report in Reuters news service. The Scandinavian country andNorth Atlantic Treaty Organization (NATO) member has demanded an explanation from its neighbor. “We recognize Russia’s right to exercise and train its capacities [but] it is not acceptable that this kind of activity affects security in Norwegian air space,” stated the Norwegian defense ministry.

Finland and Norway published claims in November that Russia may have intentionally disrupted GPS signals before and during NATO military exercises. The radio-frequency interference also affected the navigation of civilian air traffic in the Arctic. Both countries protested to Russia, which dismissed the allegations.

“We gave them the proof,” Norwegian Defence Minister Frank Bakke-Jensen stated publicly. Russia demurred, with Foreign Minister Sergey Lavrov terming the Norwegian allegations “a fantasy,” and said it would conducts its own investigation. “To be a neighbor of Russia you need to be patient,” added Bakke-Jensen.

Could Russia have targeted Norway intentionally? The minister replied: “They were exercising very close to the border and they knew this will affect areas on the other side.”

November saw NATO’s largest exercise in decades, involving forces from 31 countries in an area stretching from the Baltic Sea to Iceland.


Above: Krasukha jammer mounted on a heavy-duty truck, part of the radio electronic warfare unit (EW) of the Western Military District. Photo: Ministry of Defense of the Russian Federation 

http://www.gpsworld.com
Jueves 21 de Marzo del 2019

Surveyors and smart cities — partners in technology

Image: Celebrating200years.noaa.gov

Image: Celebrating200years.noaa.gov

Everywhere we turn today, the term “smart” is attached to an item or to a process. Smartphones, smart cars, smart electricity grids, smart home appliances; you name it, someone is making it a “smart” item or process. Advancement in technology has increased computing power, expanded data storage capability, and has allowed for miniaturization of circuits and processors. This forward progress has led to the creation of these smart item/processes, and together creates the real possibility of making many of life’s tasks and normal operations more automated. This potential automation also brings new systems monitoring conditions of various entities and operations within our daily lives, such as increased efficiency of HVAC systems, utility metering that adjusts to our patterns of consumption and landscape watering that only provides water when needed.

In addition to the personal systems now being controlled with these machines, there is now revitalized interest in the creation of “smart cities.” The concept of this type of a civilized urban metropolis once existed only in science fiction, but technology has brought this concept to life in ways not imagined by the best of those writers. Surveyors have a big role in the development, installation and maintenance of these cities, so let us spend some time digging into the element that go into our future environments.

What is a smart city?

For those old enough to remember, the concept of a smart city only existed on “The Jetsons” cartoon from the early 1960’s, with cities in the sky, flying cars and some technological advancements that do exist today. While Orbit City may not come to fruition in the next several generations, many of the concepts of a smart city are taking shape today.

For the definition of a smart city, we go to the Google search engine and find the following entry from Internetofthingsagenda.techtarget.com:
A smart city is a municipality that uses information and communication technologies to increase operational efficiency, share information with the public and improve both the quality of government services and citizen welfare.

Establishing a smart city requires forward thinking leadership and substantial funding to be created and maintained; however, the real function lies within the computing infrastructure and collection/manipulation of large quantities of data to create an environment of efficiency and conservation. A true comprehensive system combines available historical data, a collection of sensors and data collectors transmitting real-time information, and a powerful computing system containing analytical programming with extensive database functionality.

Is smart cities technology and adoption really that important?

Population trends worldwide continue to show that urban and suburban areas are expanding while rural areas are seeing a large reduction in residence. Several factors are at play, with technology being the central reason for the migration from the farm/small towns to the bigger cities.

Statistics show that in 1960, two billion people worldwide lived in rural areas while one billion lived in urban sections. As the population has increased drastically, the percentages for each category have reversed; in 2007, the two categories were equal and by 2017, the urban sector has jumped to 4.13 billion versus the rural population of 3.4 billion.

Chart: Our World in Data

Chart: Our World in Data

Population experts estimate by 2050, upwards of 70 percent of the world’s population will be living in urban areas. Whether this population shift goes directly to the city centers or the less dense outskirts, municipal facilities and services will need to be upgraded and expanded with the continuing trend. Add to this surge the challenge to create a more sustainable environmental infrastructure and ecosystem, and it becomes a maintenance challenge and logistical nightmare. By using technology to create smarter infrastructure monitoring and management systems, the creation of smart cities with advancing technology will be key to successful and sustainable growth for municipalities and its citizens.

One of the biggest challenges faced by most municipalities is aging infrastructure. Utility systems, including water supplies and stormwater drainage, was installed several generations ago without a plan for replacement and/or expansion. Redevelopment in older urban areas are now taxing these aging systems well beyond their initial capacity, all while these facilities begin to fail simply because of continued use well beyond their original designed life span. Municipalities are forced to spend money on repairing and modernizing the existing infrastructure before entertaining the idea of upgrading new installations to “smart city” specifications. However, many municipalities are mandating that new developments and infrastructure improvements meet these specifications so any future upgrades can include computerized systems.

All these systems, new and future, will require extensive planning and mapping to be effective and efficient to justify their expense. Surveyors, utilizing a variety of tools based around high-accuracy mapping and data collection, can provide the necessary base information for these systems.

Where does surveying fit in?

Just as computers and electronic technology has allowed many industries to evolve, the surveying profession has also advanced with new methods and equipment. Our ability to perform advanced measurements and establish positional location information is critical in providing the base data necessary for smart city services. Previous surveying, mapping and record keeping systems were sufficient for the needs of the time period. However, these historical data points were nearly impossible to place into a single database simply because of one factor: georeferencing.

The surveyor has the unique responsibility of being recognized as expert measurer and locator of physical points on the ground in relation to property and boundary rights. It is because of this distinctive role within the community that the surveyor can provide a significant role in the development of the groundwork of a smart city. The introduction and implementation of newer technology and tools has allowed the surveyor to become a valuable member of the infrastructure mapping team. It always hasn’t been this way and the surveying profession shoulders most of that blame.

Past promises: digital vs. smart

Many surveyors will make the argument that our profession has been ahead of the game for years with our data collection processes having been transformed from notes in a field book to electronic devices. Digital data, however, isn’t necessarily smart data as many factors go into establishing the difference. The physical form of the survey information has no direct correlation to the basis of the data; in this case, the records need to be based upon a spatial reference frame rather than an assumed data system.

Also on the topic of spatial reference systems, we can also address the lack of respect given to geographical information systems (GIS) from surveyors during its initial introduction and implementation. GIS was discounted as a convoluted graphical database not sophisticated enough for the high-accuracy world of surveying. Little did the surveying profession know that GIS would become the spatial basis for many mapping systems and be utilized in millions of locations worldwide. Only now does the surveying community realize that we missed the bandwagon and can help to provide the crucial link between spatial data and actual points on the ground in relation to physical improvements and property ownership.

Another digital platform not initially embraced by the surveying community is building information modeling or BIM. This software is a three-dimensional modeling program used mostly by architects and mechanical engineers for depicting and designing buildings and plumbing systems. One of the advantages of BIM versus traditional CAD is a database information link containing data regarding the entities within the BIM. Among the attributes contained with BIM are documentation, spatial reference, time, cost, operational applications, and related applications (contracts, purchasing, suppliers, procurement solutions, etc.). The existing spatial data necessary for this system can be supplied by surveyors using a variety of methods but not many have implemented the software.

Technology, availability, cost of entry and overall usefulness

Surveying instruments and measuring techniques has turned a significant corner in the past two decades. While conventional measurement methods are still used (including steel tapes, laser-based total stations, and GNSS receivers), more types of sensors are being introduced to enhance the accuracy and expand the volume of data points being collected. Scanners, using phase-based and time-of-flight methodologies, are now more popular than ever as ease of use has increased while the cost of ownership has greatly decreased. Ground-based and mobile LiDAR used to be only available to large firms and the government, but new models are being introduced at price points affordable to many surveyors. Many articles have been written regarding the lightspeed adaptation of surveying, engineering and construction firms with UAV use of photogrammetry methods to quickly map areas that were previously inaccessible and meeting standards not thought possible. We are also seeing more implementation of new scanning methods, including SLAM (simultaneous localization and mapping) using handheld and backpack devices.

The common thread for all these technologies and methods is one thing: georeferencing. What was once nearly impossible is now a reality; data collection from various methods all being located within a common horizontal coordinate and vertical datum systems. The ability to obtain literally millions of data points with high-accuracy horizontal and vertical values is phenomenal with most of the credit going to the United States Department of Defense and their implementation of the GPS. Yes, the technology of scanners and data collection would have been invented without the overall coordinate tie-in but having the ability to reference that same data to a common system is the key.

Also key to the smart city data collection methodology is the surveyor as the expert measurer. A trained and experience surveyor can lead the data collection of significant projects, including location of existing improvements and establishment of future installations. From establishment of parcel/right-of-way lines to integration of point clouds from scanners and photogrammetry, the surveyor can assemble this data together to provide the groundwork for successful analyzation and planning. By combining data from various areas of a municipality, including utility atlases, existing improvements, and future expansion plans, a database can be created in which a smart city will rely upon for oversight and monitoring. The surveyor fills a vital role to determining the accuracy and effectiveness of data like no other profession and should not be overlooked when assembling a team for the creation of a smart city.

Future opportunities

Like all technological discoveries and enhancements before, the future is bright with many possibilities to increase the effectiveness and efficiency of a smart city. More types of sensors are being introduced on a regular basis and in every way imaginable, including wireless communication, RFID tags, and microelectromechanical systems (MEMS) devices.

Image: GetKidsintoSurvey.com & www.elaineball.co.uk

One of the latest buzzwords is the “Internet of Things” (IoT), with many new devices being created to interconnect a network of web-enabled computerized devices using microprocessors, a variety of sensors and wireless communication hardware to gather, transmit and perform actions on information acquired from their environments. IoT presents advantages to users by enabling them to monitor their overall business processes and improve the customer experience. These actions can also precipitate changes to allow the company to save time and money, enhance employee productivity, integrate and adapt business models, make better business decisions, and generate more revenue.

As discussed in previous articles (GPS World March 2018 and GPS World November 2018), the next big technology to look forward to is the telecommunications upgrade to 5G. Once a full 5G network is running with extended coverage, we can look forward to new opportunities for indoor location services with similar accuracy to our existing GNSS capability.get kids into survey burch column W 300x203

What’s next?

The technology sector will continue to push the limits of computing speed, physical size and data capacity looking for the “next big thing.” The surveying profession has enjoyed many of the fruits of that success so one has to imagine that many more advances will be coming soon. Smart cities will continue to evolve as citizens of Earth keep migrating to the urban areas and forcing the existing infrastructure to expand or face failure. Surveyors will continue to help provide a variety of services to those citizens and municipalities, with an eye on the future for more advancing technology. I can’t wait to see what is next.

http://www.gpsworld.com
Jueves 21 de Marzo del 2019

Schriever Air Force Base releases GPS Week Number Rollover guidelines

CoastGuardCGSIC logo 275x170The 50th Space Wing Public Affairs office of the Schriever Air Force Base established and posted guidelines, known as Interface Specification GPS-200 (IS-GPS-200), for receiver manufacturers to ensure continued capability during the GPS Week Number Rollover on Coordinated Universal Time derived from GPS devices.

According to the Schriever Air Force Base, users should be aware of the upcoming GPS Week Number Rollover as it may impact receivers that are not manufactured in compliance with IS-GPS-200 specifications.

The GPS Week Number count began around midnight on Jan. 5, 1980. Since then, the count has been incremented by one each week and years later broadcast as part of the GPS message. One of the GPS week number fields in the legacy navigation message counts from zero to 1,023 weeks. At the completion of every 1,024 GPS weeks, the field rolls from 1,023 to zero and starts counting again. The first occurrence took place the evening of Aug. 21, 1999, and the message field rolled to zero at midnight GPS time. The next similar GPS Week Number Rollover is set to take place April 6.

“We appreciate the 4 billion people around the world who use GPS signals on a daily basis, which is why we are transparent in providing detailed guidance on use for compatibility,” said Lt. Col. Stephen Toth, 2nd Space Operations Squadron commander.

Civil GPS users are encouraged to submit reports of GPS problems to the Coast Guard Navigation Center; civil aviation users are encouraged to report GPS anomalies to the Federal Aviation Administration; and military users should contact the GPS Operations Center.

http://www.gpsworld.com
Viernes 15 de Marzo del 2019

Technologies for the Future: A Lidar Overview

Building the Capability for High-density 3D Data

National topographic databases store data refined from field measurements, imagery and laser scanning data at certain specifications and purposes, but lack the ability to adapt to ever-changing needs and situational awareness. ‘Data on demand’ is a recognized megatrend in the geospatial industry.

Point cloud data can be captured with an ever-increasing number of means – e.g. ground-based, airborne and spaceborne platforms – to understand the surrounding reality, from grain scale to global overview. Different scales and viewpoints can provide comprehensive multimodal data for environmental analysis, assessment of natural resources, development of urban infrastructure, and critical services. Semantic point clouds, temporal coverage, multimodal data sources, and automated processing form the framework for the future topographic data.

Lidar Technologies

Laser scanning is based on the use of optically directed Lidar beams to collect object information in direct 3D measurements. This allows the system trajectory (i.e. position and attitude), to be produced robustly and accurately. Prior to the mid-1990s, GNSS-IMU technology was not affordable for commercial use. Since then, however, the market for devices has exploded, especially with the development of fibre-optic gyroscopes (FOG) and microelectromechanical systems (MEMS) technologies. Also, the buildup of nationwide GNSS base station networks has contributed to the success of Lidar in surveying and mapping in all its variety.

What makes Lidar so effective in topographic mapping is the capability to direct 3D measurements for the target and penetration of the beam through vegetation to collect information from objects and the ground beneath. The light wave front passing through the vegetation produces information on the vegetation as a side product. To yield such information, certain principles of laser ranging have to be deployed. The traditional way to gain long-range measurements is to shoot powerful laser pulses towards the target and collect the backscattering signal. The signal is then processed to detect objects at distinct ranges within the beam illumination area. These systems are the current mainstream and use a selection of spectral wavelengths to convey the data collection.

Dense and geometrically accurate point cloud offers photographic 3D capture of the reality for mapping, modelling and monitoring. Spectral information from Lidar will have significant implications on automated data interpretation.
Dense and geometrically accurate point cloud offers photographic 3D capture of the reality for mapping, modelling and monitoring. Spectral information from Lidar will have significant implications on automated data interpretation.

However, for spaceborne applications, this has proved problematic due to the excessive power needed to reach the Earth’s surface from orbit, because of the havoc heat causes for the optical components. A novel emerging technology is to harvest the energies at the single-photon level, reducing stress on the optics. Some single-photon devices available in the market promise high data-collection efficiency due to the high altitudes permitted by the sensitive detection. On the other hand, cloudiness sets limits for achieving the full potential in practice. The detector does not sample each returning photon but instead at detector-specific probability, and photons from other sources are detected in addition to those emitted by the Lidar source. This stochastic nature of detection forces adaptation of data processing methodology, because data characteristics and implications on data accuracy and processing are not yet fully commonly understood.

There are currently two techniques implemented for single-photon detection. In the Harris Geiger mode system, each detector pixel for a single pulse is occupied with the first photon received and no data beyond that is captured. Detection efficiency is less than 10%. Large-size detectors compensate these two characteristic features, and the data products typically give 8 or 32 points per square metre. However, penetration under vegetation remains somewhat uncertain. In the Leica SPL100 single-photon Lidar sensor, multiple targets are detected for each pulse per pixel after a short dead time of the detector when triggered by a photon. This gives penetration capability similarly to conventional Lidar. However, more analysis is needed to find out the pros and cons of these technologies unambiguously.

Airborne Lidar

Topographic surveys from the air form the firm basis of mapping. Information needs include ground elevation, building and network infrastructural assets and development. Airborne laser scanning is a two-decade old technology used to produce information for national mapping agencies, municipalities, and engineering companies, to fulfil the needs of communities, decision-makers and land-use planners.

Airborne Lidar data iscollected for projects and data needs exhibiting various scales. For maximum detail, the data is collected from low-altitude flights (50-300m) at millimetre-level accuracy for utility mapping and civil engineering (e.g. RIEGL VUX-240, or Optech ORION C300-1). The data densities at this level are at tens or hundreds of points per square metre. For road and urban planning, mid-altitude (400-1,000m) scanning is often used and the data density is typically around a couple of dozen points per square metre. Country-scale mapping flights are conducted using high altitudes (2,000m and up) for efficiency, and data densities are less than ten points per square metre, typically 1-2. The latest instruments for these applications on the market are the Leica Terrain Mapper, Optech ALTM Pegasus and RIEGL VQ-1560i.

Principles of certain Lidar modes. The most complete signal is recorded with full-waveform Lidar. On-the-fly detection and single-photon techniques reproduce discrete sampling. Increasing the scan angle has an effect on the signal as per the changing light path through the canopy.
Principles of certain Lidar modes. The most complete signal is recorded with full-waveform Lidar. On-the-fly detection and single-photon techniques reproduce discrete sampling. Increasing the scan angle has an effect on the signal as per the changing light path through the canopy.

Multi-platform Mobile Laser Scanning

Vehicle-mounted laser scanning systems have proven to be very efficient in measuring road and city environments. Multi-platform systems expand the use cases of MLS to natural environments, industrial installations and urban environments that cannot be easily accessed by a vehicle-mounted system. With the development of algorithms that allow simultaneous localization and mapping (SLAM), mobile laser scanning has also advanced to provide 3D data from global navigation satellite system (GNSS) denied environments, e.g. indoors and industrial sites.

In this field, sensor technology is still experiencing a significant reduction in size and price. Simultaneously, the performance and accuracy has been improved to provide detailed 3D structural information on tunnels, roads, urban scenes and industrial sites. While a few years back certain industrial scanners were not able to be synchronized to an external positioning system, current sensors are usually pretty easy to integrate on multi-sensor platforms. Small sizes and easy integration allow systems to be adapted for diverse 3D measurement needs. We have seen MLS mounted on cars, trains, all-terrain vehicles (ATVs), boats and tractors in the past, and new applications using kinematic data collection will no doubt emerge in the future.

In the future, increasingly detailed models and maps could be generated based on high-resolution airborne laser scanning (ALS) data. Multiple terrain and infrastructure features can be captured in a single flight to save cost. Complementary data can be collected with unmanned aerial vehicles (UAVs or ‘drones’) and ground-based mobile laser scanning (MLS).
In the future, increasingly detailed models and maps could be generated based on high-resolution airborne laser scanning (ALS) data. Multiple terrain and infrastructure features can be captured in a single flight to save cost. Complementary data can be collected with unmanned aerial vehicles (UAVs or ‘drones’) and ground-based mobile laser scanning (MLS).

Drones and Lidar

Unmanned aerial systems (UASs) constitute an increasingly important segment of engineering. Mapping and surveying drones provide an easy-to-deploy platform for aerial views of an area of interest. Currently there are some factors limiting the use of drones regarding operation time and development of regulation in many countries. At best, drones contribute to the production of valuable 3D and image data for needs in various engineering projects, urban planning and scientific tasks. Sensor pools are expanding rapidly, and small sensors are already available for UAS-Lidar applications, depending on the drone scale, such as the RIEGL MiniVUX-1UAV and Velodyne Buck LITE in the conventional category, and the Cepton SORA200 in solid-state implementation. Longer ranges and faster data rates are becoming available for this segment to enhance the data products and broaden the application envelope.

The clear development trends are towards automated systems and real-time data processing. Also, longer operation times for UAVs are achieved with improved avionics, battery life and indigenous ideas, such as the Avartek Boxer Hybrid drone with 2-4 hours’ flight time. Small but high-performance sensors and real-time data are the most relevant needs for drones, and typically limited project areas do not necessitate the presence of a GNSS-IMU; data is processed to a local coordinate system using techniques prevailing within the robotics community. However, ever-smaller and more capable GNSS-IMUs, like the NovAtel CPT7 or SBG Ellipse2-D are available, and with decreasing prices, direct georeferencing reduces the effort for ground control.

SLAM/LOAM Laser Mapping

GNSS-free laser scanning is developing rapidly. Systems typically consist of low-cost laser scanners and inertial measurement units. Lidar data is used, and on some occasions augmented with visual odometry from cameras, to compensate for instantaneous movements of the sensor system, to calibrate low-performance IMU, and to keep track of the sensor and/or platform pose. These mapping solutions provide real-time or near-real-time 3D data for tasks with moderate accuracy needs. The development has been possible due to the miniaturization of sensors and SLAM, Lidar odometry and mapping (LOAM) and related algorithms. Multi-layer scanning in particular has proven to give sufficient information to estimate platform movements from single scans. Algorithms for scan matching with such data perform reasonably well and reliably to give good pose estimations, and are able to detect loop closures for global drift mitigation. A couple of examples are the Gexcel HERON, GeoSLAM Zeb Horizon and Kaarta Stencil systems, all based on Velodyne’s Lidar Puck scanner. Notably, many companies are planning to bring similar sensor products on to the market, among them devices from RoboSense and Ouster.

In the area of terrestrial laser scanning, automated registration of scans has seen an interesting development implemented in the Leica RTC360. The scanner is implemented with image-augmented inertial measurements to compensate for movements between scan stations, thus speeding up the scanning work on site. Beyond that, use of Lidar for measuring submerged structures and objects is of increasing interest in the maritime industry, and kinematics-based localization systems using inertial and data-matching techniques are applied similarly to the counterparts on the ground.

Backpack Lidar mapped spatter cone and adjacent lava field. Such applications permit better understanding of natural processes and mitigation of hazards, but also bring possibilities in exploration and planetary research.
Backpack Lidar mapped spatter cone and adjacent lava field. Such applications permit better understanding of natural processes and mitigation of hazards, but also bring possibilities in exploration and planetary research.

Multimodal Mapping

Affordable but high-performance systems are already changing the ways of producing topographic data. Unmanned drones are an emerging technology that, coupled with advanced systems featuring laser scanning and imaging sensors, allows for rapid aerial data for various purposes. Combining UAV-based airborne sensors and mobile laser scanning with imagery brings together the flexibility of mobile systems and allows for short response times and low mobilization costs. Use of these systems provides data with minimal occlusions enabled by easily accessed viewpoints. This data typically represents the objects of interest at a very high level of detail (LOD) down to a scale of a single railing, cable or sign.

Vehicle-mounted kinematic mapping systems are useful for road and street data capture for mapping and maintenance purposes. Such data provides high-density base map data for autonomous driving – an example of a new kind of mapping for the future. Backpack scanning is a suitable method of collecting 3D data from cultural heritage sites, buildings, streets and terrain.

GNSS-IMU and SLAM-based laser scanning systems can be mounted on virtually any kind of platform to carry out tasks in variable environments, and for variable data requirements and scales.

Autonomous Vehicles and Crowdsourced Mapping

Autonomous vehicles have attracted considerable industrial interest in recent years. Following the DARPA Grand Challenge competition for self-driving cars, several major manufacturers have announced their future goals of providing autonomous vehicles. This requires fitting the vehicles with highly capable 3D mapping systems, much like those encountered in contemporary MLS. For the geospatial information community, these future autonomous vehicles are a potential source of highly detailed and frequently updated 3D mapping data.

In addition to vehicles, 3D mapping capabilities are increasingly carried by consumers in their smart devices – simply put, smartphone camera images and positioning information may contribute to mapping. More capabilities are offered by other sensors such as depth cameras and 3D image interpretation. These technological developments hold the potential to replace the prevailing centralized mapping conventions with decentralized, distributed and frequent crowdsourced mapping.

Mapping and monitoring of power grid facilities and other structures critical to our everyday life and function is a prominent application of airborne and UAS-Lidar.
Mapping and monitoring of power grid facilities and other structures critical to our everyday life and function is a prominent application of airborne and UAS-Lidar.

Multispectral Sensors – Colour Vision with Lasers

Multispectral laser scanning technology is currently in its technological adaptation phase in ALS, promising an increase of active spectral information for mapping and detection. The first example of this was the recording of laser backscatter intensity and the use of the intensity values in the visualization of point clouds and in certain classification tasks. The emerging multispectral laser scanning (e.g. Optech Titan for ALS) increases the amount and quality of spectral information obtainable. However, the current implementation is not optimal for acquiring spectral information due to distinct scan angles and patterns for each channel, and data needs to be interpolated for analysis. Alternatively, the RIEGL 1560i-DW provides a two-wavelength instrument.

Actively sensed radiometric properties of target objects do not suffer from illumination variations and anomalies caused by solar illumination present in passive imaging products. The autonomous driving industry is predicted to explore this opportunity in the future, as well as forecasting the availability of small form-factor sensors.

Classification results with the data from the first multispectral ALS systems have been promising. For example, a very high overall accuracy (96%) of land cover classification results has been achieved in some studies, with six classification categories (building, tree, asphalt, gravel, rocky, low vegetation).

GNSS-free SLAM and LOAM solutions could provide 3D data in almost real-time, which is a desired feature for time-critical applications such as emergency response. Could Lidar systems help firefighters to navigate in smoke and detect victims in limited visibility in the future?
GNSS-free SLAM and LOAM solutions could provide 3D data in almost real-time, which is a desired feature for time-critical applications such as emergency response. Could Lidar systems help firefighters to navigate in smoke and detect victims in limited visibility in the future?

Single-photon Systems

Single-photon technology is an emerging technological breakthrough for airborne laser scanning. Single-photon systems require only one detected photon compared to hundreds or even thousands of photons needed in conventional Lidar. As a result, pulse densities of ten to a hundred times higher can be attained compared with conventional sensors. In addition, the sensitivity of the detector to energies in the single photon range allows the systems to attain higher maximum ranges and remain eye-safe. This has also contributed to the recent launch of ATLAS, a spaceborne Lidar-based sensor for global monitoring aboard ICESat-2. Similarly, the single-photon technology will be used in autonomous driving and drone sensors before long.

Single-photon data are available currently from two sensors: Leica SPL100 and Harris Geiger-mode Lidar. The operational differences, albeit generally similar, can be deciphered in Figure 2 and compared to the conventional one. Both single-photon systems available are implemented to use green light (532nm) that makes them suitable for use in bathymetric mapping as well. There are also single-photon detectors available, both on the market and in research labs, allowing miniaturized systems for UAV scale in the near future. Sensitive detection is expected to improve the depth data, although it will still take some time to perfect the processing methodologies and harness the full potential.

High-density mobile laser scanning data permits cadastre, and urban planning and management. Reflectance data can be used in object interpretation.
High-density mobile laser scanning data permits cadastre, and urban planning and management. Reflectance data can be used in object interpretation.

Implications of High-resolution Lidar

The developments in acquiring point cloud and spectral data significantly increase the data volumes produced. Automation is needed in order to transform the increased measuring frequency and point cloud density into efficiency and a high level of detail in mapping. The emergence of national laser scanning campaigns, such as those in the Netherlands, Sweden and Finland, highlights the need for automated processing methods.

On a more limited scale, multi-temporal point clouds have been applied to change detection both in the urban and natural areas, for management of resources and coping with hazards, effectively showing the potential of multi-temporal 3D data. Combining these methods with automation and periodically repeated country-wide scanning campaigns would allow spectral and geometrical change detection in unseen detail for improved understanding of natural resources and the biosphere.

In addition to change detection, automation is required for various modelling tasks. In urban environments, automated generation of simple building models has become the default approach for 3D city modelling. Several algorithms for detailed building modelling have been introduced, potentially raising the level of detail in automated modelling. In a similar fashion, algorithms have been introduced for modelling road environment objects from dense mobile laser scanning point clouds. In natural environments and forestry, point cloud datasets have been applied both for producing parameter information over larger areas (e.g. for hydraulic modelling and flooding analysis or permafrost processes), and detailed modelling of individual trees for forest resource and biomass assessments.

Ideally, the change detection, mapping and modelling should be combined with periodical 3D data acquisition at intervals of just a few years. Based on multi-temporal data, possible changes can be detected, identified or classified based on spectral and geometric features, and modelling, maintenance or any similar action or effort can be focused based on data-derived signals or early warnings to save costs or avoid indirect damage.

Multispectral Lidar point cloud from Optech Titan representing the urban environment. Combined data at different wavelength regions helps greatly in classification and object recognition. Differing scan patterns for each channel become visible in the raw point cloud data.
Multispectral Lidar point cloud from Optech Titan representing the urban environment. Combined data at different wavelength regions helps greatly in classification and object recognition. Differing scan patterns for each channel become visible in the raw point cloud data.

Summary

Current topographic databases are commonly based on aerial images and maintained by national mapping agencies with a significant amount of manual work. Developments in laser scanning and point cloud processing could provide significant cost savings via automation of mapping processed with improved output and quality of data.

Multimodal Lidar data will increasingly be used in the future thanks to the development and availability of capable sensor technologies. Ever-smaller systems with similar or improved performance will provide applications using virtually any platform to operate Lidar for mapping and surveying. Aircraft, drones, vehicles, backpacks and handheld mapping systems all serve as means to gather complementary data for virtually any task imaginable.

Emerging single-photon technology has the most potential as a sensor solution for providing dense point clouds with low unit costs for country-level data acquisition. Multimodal laser scanning from airborne and terrestrial perspectives can be utilized for obtaining more detailed data from selected areas.

Dense point clouds with multispectral information provide a common starting point for automated modelling workflows and direct visualization applications, forming the future topographic core data. They represent a significant asset for business in improved forestry and infrastructure management, and provide a platform for developing several future applications.

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Leica SPL-100 single-photon elevation data. In the foreground, only data points from the forward part of the scanning cone are shown revealing the scan pattern on the ground.
http://www.GIM-INTERNATIONAL.com
Miércoles 06 de Marzoo del 2019

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