AgJunction Inc., a provider of innovative hardware and software solutions for precision agriculture, has signed a new strategic agreement with Hemisphere GNSS, a provider of GNSS technology.
For an undisclosed, one-time payment and a new long-term supply agreement, AgJunction has agreed to release Hemisphere from a license restriction that prevented them from selling their GNSS products directly into the global agricultural market. Supply and market restriction agreements previously created between AgJunction and Hemisphere ended in 2016 while the market restriction agreements continued indefinitely.
Both were originally one company. In 2013, Hemisphere GPS split with its precision agriculture division, which then named itself AgJunction, while the GNSS part of the business was purchased by UniStrong Science & Technology Co. and renamed Hemisphere GNSS.
The agreement is expected to provide customers a more direct relationship with their GNSS supplier, creating better efficiencies for original equipment manufacturers, value-added resellers and growers alike. This agreement is also consistent with AgJunction’s desire to provide its steering customers the ability to choose among several possible GNSS options.
“AgJunction is pleased with the signing of this agreement as it will insure our customers, who have chosen Hemisphere’s GNSS receivers and antenna technology, direct access and an uninterrupted supply,” said Dave Vaughn, CEO of AgJunction. “As a leader in the precision steering machine control business, it is incumbent upon us to provide the GNSS solution our customers prefer, and this agreement does just that.”
This agreement does not affect AgJunction’s exclusive right to sell certain steering and machine control technology covered by the company’s extensive IP portfolio into the agriculture market.
“Hemisphere is excited to work more directly with our OEM agriculture partners,” said Hemisphere President and CEO Farlin Halsey. “This new supply agreement will forge a deeper relationship, providing faster response to sales and support requests and increased customer feedback, resulting in stronger innovation and solutions. We would also like to thank AgJunction, and look forward to both companies’ future success.”
Specific terms of the transaction were not disclosed.
Esterline CMC Electronics showcased advanced displays and CMC Electronics-brand integrated helicopter avionics at the Hai Heli-Expo, held Feb. 26-March 1 in Las Vegas.
Esterline’s new helicopter demonstrator featured the CMA-6024 GNSS landing system. While introduced last fall, the CMA-6024 has been customized for rotorcraft operations to allow operators to achieve precision approaches to CAT II and CAT III minimums at helipads.
The CMA-6024 GNSS module for aircraft.
The CMA-6024 GPS sensor that delivers a high-reliability satellite-based augmentation system and ground-based augmentation system (SBAS/GBAS) CAT-l/ll/lll precision approach solution for all aircraft.
“Our CMA-6024 is the result of over 35 years of experience in the design and manufacture of certified airborne GPS products for the air transport, business aviation and helicopter markets,” said Jim Palmer, vice president, Navigation Solutions. “It is a collaborative effort with NovAtel Inc. and its patented Narrow Correlator signal tracking technology.”
The CMA-6024 aviation GPS/SBAS/GBAS sensor, featuring an embedded VHF Data Broadcast (VDB) receiver, is a complete, self-contained, fully certified precision approach and navigation solution, certified to Design Assurance Level A (DAL-A). Designed as an easy-to-integrate solution for all aircraft, the plug-and-play tandalone unit requires no specialized installation or integration support.
The CMA-6024 provides a navigation solution that is fully compliant with Automatic Dependent Surveillance-Broadcast (ADS-B) and Required Navigation Performance (RNP). The CMA-6024 includes SBAS Localizer Performance/Localizer Performance with Vertical Guidance (LP/LPV) and GBAS GNSS Landing System (GLS) GAST-C/D Precision Approach guidance for all aircraft. The CMA-6024 meets or exceeds the most stringent environmental requirements set out in RTCA/DO-160G and goes further to meet additional requirements for specific aircraft.
Built on the successes of the CMA-5024, the CMA-6024 is the next evolutionary step forward that adds a complete GBAS/GLS solution. All CMA-5024 receivers can be upgraded to a CMA-6024. All of the benefits of the CMA-5024 are retained and a new self-contained GBAS/GLS functionality has been added to produce the CMA-6024.
CMC’s family of GPS products includes the CMA-5024 GPS Landing System Sensor that meets the requirements for an Instrument Flight Rules, civil certified Global Navigation Satellite System (GNSS). The European Geostationary Navigation Overlay Service (EGNOS), a component of SBAS, augments GPS to provide an extremely accurate navigation solution that will support all flight operations from en route through Localizer Performance with Vertical Guidance (LPV) CAT-l equivalent approach. The CMA-5024 is compliant with and completely supports EGNOS/SBAS, from departure, en-route navigation, and all EGNOS/SBAS LPV Precision Approaches, and complies with published Communication Navigation Surveillance/Air Traffic Management (CNS/ATM) navigational mandates.
CMC is a wholly owned subsidiary of Esterline Corporation, a specialized aerospace and defense company headquartered in Bellevue, Washington, that employs over 13,000 people worldwide.
As government agencies expand their use of cell-site simulators or “stingrays” and other digital tracking technology, Sen. Ron Wyden, D-Ore., Rep. Jason Chaffetz, R-Utah, and Rep. John Conyers, Jr., D-Mich., introduced the Geolocation Privacy and Surveillance Act (known as the GPS act) to create clear rules for when agencies can access and track an individual’s geolocation information.
Chaffetz introduced the House version of the bill on March 6, with four Republican and three Democratic cosponsors. Wyden introduced the Senate bill Feb. 15.
Courts have issued conflicting opinions about whether the government needs a warrant to track Americans through their cell phones and other GPS devices. The Supreme Court unanimously ruled in 2012’s U.S. vs. Jones case that attaching a GPS tracking device to a vehicle requires a warrant, but it did not address other digital location tracking, including through cell phones, OnStar systems and consumer electronics devices.
The GPS Act applies to all domestic law enforcement acquisitions of the geolocation information of individual Americans without their knowledge, including acquisitions from private companies and direct acquisitions through the use of cell-site technology. It would also combat high-tech stalking by creating criminal penalties for surreptitiously using an electronic device to track a person’s movements, and it would prohibit commercial service providers from sharing customers’ geolocation information with outside entities without customer consent.
Wyden and Chaffitiz have now introduced versions of the GPS Act four times since 2011. Though hearings have been held, the Act has yet to make it out of committee for a vote.
“Outdated laws shouldn’t be an excuse for open season on tracking Americans, and owning a smartphone or fitness tracker shouldn’t give the government a blank check to track your movements,” Wyden said. “Law enforcement should be able to use GPS data, but they need to get a warrant. This bill sets out clear rules to make sure our laws keep up with the times.”
“Congress has an obligation to act quickly to protect Americans from violations of their privacy made possible by emerging technologies,” Chaffetz said. “As we welcome innovative technologies that help fight crime, we must be mindful of the potential for abuse. This bill will build a framework governing the use of geolocation and cell site simulator technologies.”
“We must enact the Geolocation Privacy and Surveillance Act to require the government to obtain a warrant based on probable cause to compel companies such as cell phone service providers to disclose the geolocation information of their customers,” said Rep. John Conyers, Jr. (MI-13). “Geolocation tracking, whether information about where we have been or where we are going, strikes at the heart of personal privacy interests. The pattern of our movements reveals much about ourselves. When individuals are tracked in this way, the government is able to generate a profile of a person’s public movements that includes details about a person’s familial, political, professional, religious, and other intimate associations. That is why we need this legislation to provide a strong and clear legal standard to protect this information.”
Support for the Act
Technology and civil rights organizations praised the bill’s introduction.
Neema Singh Guliani, legislative counsel at the American Civil Liberties Union: “In today’s world, most Americans use cell phones or other electronic devices that are capable of tracking their every move, including visits to a mosque, doctor’s office, domestic violence shelter, or political rally. This information that the government should not be able to get without a warrant – yet law enforcement routinely fails to meet this standard. Congress should swiftly pass the GPS Act to protect this sensitive information.”
Gabe Rottman, deputy director of the Freedom, Technology & Security Project at the Center for Democracy and Technology: “As we move into the world of connected devices, and as the sheer number of these devices grow, location tracking becomes more accurate, and more revealing. Basic notions of American privacy necessitate passage of this important reform to require a warrant for location tracking.”
Amie Stepanovich, U.S. policy manager at Access Now: “Computer scientists have proven that even a few location points can be used to reveal incredibly broad and personal information about an individual. At the same time, ever more devices are collecting our location data. Law enforcement agencies are using an increasingly sophisticated array of technology to obtain that information without proper legal protections. What you don’t know can hurt you. Access Now applauds the GPS Act for protecting this sensitive information and mandating a warrant requirement for law enforcement access.”
Lee Tien, senior staff attorney at the Electronic Frontier Foundation: “Geolocation data paints a detailed portrait of our daily lives that reveals sensitive information about us and our families — whether a visit to a children’s cancer specialist or to a church, synagogue or mosque. The government shouldn’t be able to track us without a warrant just because we use cellphones. The GPS Act ensures all Americans have strong legal protections for their geolocation data.”
All across Europe, the number of smart cities is multiplying. To tackle their growing needs and to guarantee efficient city planning and maintenance, many cities are engaged in massive investments in such key areas as street lighting, road maintenance, traffic and waste management.
In parallel, public transportation is continuously evolving in terms of coverage, comfort and technology.
Within this context, the exploitation of Galileo and its integration with other sensors is key to developing concrete solutions for current and future smart-city planning. Along these lines, the Horizon 2020-funded GHOST (Galileo Enhancement as Booster of the Smart Cities) project is designing, developing and validating an intelligent system for vehicles that equips existing public transport fleets with a Galileo-enabled camera and connects these vehicles to a web portal.
The GHOST system equips existing public transport fleets with a Galileo-enabled camera and connects these vehicles to a web portal. (Photo: GSA)
The system automatically takes pictures of predefined points of interest (POI) based on the accurate position of the vehicle — provided by Galileo. All images are sent to a processing server capable of detecting such anomalies as potholes or a burnt-out street light. The system then uses the web portal to report these findings to the relevant authorities.
“At this point, GHOST is designed primarily for reporting street lighting anomalies and road deteriorations, monitoring public garbage collection and detecting double parking infractions or disabled parking spots occupied by unauthorized vehicles,” said Project Coordinator Claudia Maltoni. “In addition to these basic functions, we have also identified more advanced services, such as spotting bus-lane and congestion-charging-area violations, which will be implemented at a later date.”
A user-focused system
The GHOST system’s key differentiator is its use of Galileo positioning, which gives it the capability to take autonomous snapshots with an error range of 1 to 10 meters (depending on the size of the POI). In densely populated urban environments, such a level of service is only possible with the combined use of Galileo, inertial sensors and Kalman filters.
The GHOST system’s key services:
reporting street lighting anomalies and road deteriorations
monitoring public garbage collection levels
detecting double parking infractions or disabled parking spaces occupied by unauthorized vehicles
monitoring timely collection of garbage.
Another unique feature is a free smartphone application that citizens can use to collect geo-localized snapshots. “Whenever an individual user sees an anomaly within a city’s infrastructure, all they have to do is snap a picture with their smartphone,” explained Maltoni. “This level of engagement not only enhances the overall system, but also empowers individual users to play a key role in urban upkeep.”
Improving urban efficiency
By taking advantage of the many vehicle movements happening in cities every day, GHOST proposes a competitive way to improve the efficiency of monitoring a city’s operations and infrastructure. Once finalized, the system will enable faster detection of double parking or road deterioration and help reduce traffic, accidents and pollution.
“Thanks to our field tests and favourable lab results, we are already setting up the next phase of the project, with the aim of taking the system’s technology to the next level,” concluded Maltoni. “This includes providing real-time, onboard image processing so that the system can handle such dynamic scenarios as bus-lane infractions and congestion-charging enforcement.”
The project is working to bring GHOST technology to market. Coordinators are busy making key contacts with interested public administrations, garbage collection companies and traffic police departments. It is also working to ensure that the system complies with all European regulatory standards, such as those related to circulation or privacy.
On March 20, PRN 123 (now in test) will be introduced in the operational platform, and on March 21, PRN 136 will be moved from the operational platform to the test platform.
Users equipped with non-(E)TSO-certified SBAS receivers (such as those used in agriculture, surveying, mapping and maritime, but not in aviation), it is recommended that users reassess the equipment configuration after the change, to ensure that both operational EGNOS GEO satellites (PRN 120 and PRN 123) are configured in the equipment.
More details on this change are available in the official Service Notice #15.
Depending on the receiver, users can check equipment manuals or contact product manufacturer/dealer. Guidance is provided on the EGNOS website on how to configure an EGNOS receiver for some of the most common equipment used in agriculture.
A SpaceX Falcon 9 stands ready for launch from Cape Canaveral Air Force Station, Fla. The Air Force awarded a second contract for GPS III Launch Services to SpaceX.
SpaceX has won a second contract from the U.S. Air Force for launch services to deliver a GPS III satellite to its intended orbit.
SpaceX was awarded the $96,500,490 firm-fixed-price contract over the United Launch Alliance. ULA — a joint venture of Lockheed Martin Space Systems and Boeing Defense, Space & Security — did not compete for the first GPS III launch contract. That contract, worth $82.7 million, is expected to orbit a GPS satellite aboard a Falcon 9 rocket in May 2018.
According to the contract announcement, SpaceX will provide launch vehicle production, mission integration, launch operations, spaceflight worthiness and mission unique activities for a GPS III mission. The contract is being overseen by the Air Force’s Space and Missile Systems Center (SMC), Los Angeles Air Force Base, California.
Work will be performed at Hawthorne, California; Cape Canaveral Air Force Station, Florida; and McGregor, Texas. It is expected to be complete by April 30, 2019.
“The competitive award of the GPS III Launch Services contract to SpaceX directly supports SMC’s mission of delivering resilient and affordable space capabilities to our nation,” said Lt. Gen. Samuel Greaves, leader of SMC.
Telit, a global enabler of the Internet of Things (IoT), has introduced advanced positioning modules in the SE868xx-Ax family featuring multi-constellation GNSS receivers with 9 square millimeter patch antennas.
Telit’s SE868Kx-Ax series offers high performance for space-constrained applications such as wearables, tracking, telematics and security. The new integrated antenna modules include advanced features that significantly increase RF sensitivity, allowing for a much simpler integration without external components.
The SE868K3-A/AL is a multi-constellation GNSS variant with flash memory and a GNSS core.
The SE868K7-A/AL is a GPS variant with ROM memory and a GPS core.
The new module variants are designed with the same, ultra-compact 11 square millimeter cavity PCB package as the other modules in the series, with the bonus of a second low noise amplifier (LNA) and surface acoustic wave (SAW) filter. Footprint compatible with other modules in the family, the SE868Kx-Ax series includes variants with multiple interfaces and a combination of features including:
Ultra-compact 11 x 11 mm “cavity” PCB package
Standard variant with integrated 9 millimeter by 9 millimeter by 4 millimeter SMT antenna
Low-profile variant with 9 millimeter by 9 millimeter by 2 millimeter antenna
Additional LNA and SAW filter
Real time clock (RTC) and temperature compensated crystal oscillator (TCXO)
Jamming rejection
Pin-to-pin compatibility with other modules in the series
Ephemeris file injection (A-GPS)
Satellite-Based Augmentation System (SBAS) compliant
With the different options available in the SE868Kx-Ax series, customers can design once and interchangeably mount the solution most appropriate for the environment, Telit said. This enables developers to select the right technology for their use case without having to redesign the entire application when it comes time to transition.
“The SE868Kx-Ax series is an exciting enhancement to our positioning product portfolio,” said Felix Marchal, EVP GNSS and short range, Telit. “Our commitment to excellence is reflected in the years of experience releasing breakthrough positioning modules and solutions. This latest release specifically addresses the integration challenges that IoT developers face today. Leveraging the low-profile and SMT mounting options that do not compromise the host PCB, developers can take advantage of the most important and advanced features available in positioning technology tangibly booting the efficiency of global design efforts, schedules and budgets.”
The Telit IoT Know How program assists customers to accelerate the deployment of cost-effective and future-proof solutions integrated with GNSS from idea to market, the company said.
The variants will be available in the second quarter of 2017. Telit is exhibiting them at Embedded World 2017, Nuremberg, Germany, March 14-16, located at hall 3, booth 3-518.
The agricultural robots market is expected to grow from $2.75 billion in 2016 and is expected to reach $12.8 billion by 2022, at a compound annual growth rate of 20.71 percent between 2017 and 2022, according to a new report by MarketsandMarkets.
The increasing focus on farm efficiency and productivity and increasing global demand for food are some of the significant drivers for the growth of the agricultural robots market.
Hardware. The hardware component is expected to hold the largest share of the agricultural robots market between 2017 and 2022. The hardware components include automation and control systems, and sensing and monitoring systems. Automation and control systems such as global positioning system (GPS) receivers, guidance and steering devices, and variable rate technology devices form a major part of the agricultural robots market. These hardware components have the largest share of the overall agricultural robots market owing to their extensive use in field farming technologies.
Weather forecasting. Weather tracking is one of the important parameters in agriculture as this application facilitates up-to-date information on prevailing climatic conditions, such as temperature, rain, wind speed and direction, and solar radiation. There are various kinds of devices used for this application, which include handheld instruments and on-field weather stations. Weather tracking helps in taking decisions before severe and potentially dangerous climatic conditions occur, thereby protecting a farmer’s family or business.
North and South America. The Americas held the largest share of the agriculture robot market in 2016. This growth is attributed to the increased industrialization of farming equipment with the need for improved efficiency and productivity to meet the global demand for food. Efficient farming requirements, high production accuracy and increased use of farm management software are some of the factors for the growth of the agricultural robots market in the Americas.
Major players in the agricultural robots market mentioned in the report include Deere & Company (U.S.), Trimble Inc. (U.S.), AgJunction Inc. (U.S.) and AGCO Corporation (U.S.).
The report is titled “Agricultural Robots Market by Type (UAVs, Milking Robots, Harvesting Systems, Driverless Tractors), Offering (Hardware-Automation & Control System, Sensor & Monitoring Device; Software; Services), Application, and Geography — Global Forecast to 2022.”
The report includes 203 pages, including 79 market data tables and 79 figures, with an in-depth table of contents.
British aerial mapping innovator Bluesky International is expanding its business into North America following the acquisition of Col-East Inc., a Massachusetts-based aerial survey company. Col-East has been mapping the Northeast United States for 65 years and will continue as Col-East International Ltd., forming the U.S. arm of Bluesky.
Founded in 1952, Col-East has a long-established reputation for high-quality topographic mapping with particular expertise in specialized aerial surveys, such as high-precision aeronautical mapping requiring skilled analysis. Bluesky has seen an increase in the demand for specialized large-scale mapping, 3D modeling and feature extraction in recent years in the European market, and the company intends to apply these skills to the expanding U.S. market.
Bluesky has improved on aerial mapping techniques in the UK in recent years, backed by the latest digital cameras and 3D laser mapping technology. The Leicestershire-based company will not only be equipping Col-East aircraft with the latest digital aerial surveying equipment, including cameras and sensors for laser (lidar), thermal and infrared capture, but will also be building on the existing technical and experienced Col-East skill base by introducing new workflows and image-processing techniques honed in the competitive U.K. and European markets.
“Britain has a long tradition as a pioneer in mapping techniques, and the Bluesky team was behind the creation of what was the world’s first nationwide high-resolution aerial photo map, created back in 1998,” said Rachel Tidmarsh, managing director of Bluesky International Ltd. “Since then, we have developed new systems and techniques that are underpinning advances in environmental and 3D mapping, and we will be introducing these advancements to the U.S. market with the acquisition of Col-East.”
As well as topographical mapping and aeronautical work, Col-East offers a range of aerial imaging services such as the production of terrain models, orthophotos and volumetrics, providing cost-effective mapping solutions from estates to development sites and complex transportation corridors.
Col-East owns a huge archive of aerial photography that has been captured over many years and dates, back to 1946. Col-East will gain immediate access to Bluesky’s proprietary technology used in the development of some ground-breaking derived products, including 3D building modeling, tree mapping, air quality mapping and state-wide solar power potential mapping. Products will also be available to purchase through the new Col-East online Mapshop, which will be launched soon.
“It’s a very exciting time for Col-East,” said Mark Thaisz owner and general manager at Col-East. “Bluesky is bringing significant investment, new technology and added resources that will allow the business to expand freely. Already we’ve equipped our aircraft with a new Vexcel UltraCam Eagle survey camera which offers high accuracy and unsurpassed clarity to bring a whole new edge to the aerial survey market in New England.”
A technique developed by researchers at the University of Illinois at Urbana-Champaign distinguishes a reflected non-line-of-sight (NLOS) signal of a particular satellite from the LOS signal and characterizes the NLOS signal as coming from a virtual mirror-image satellite in the direction of the signal reflection point. By using information on the position and orientation of the reflector, the NLOS signal can be treated as an additional LOS signal.
By Yuting Ng and Grace Xingxin Gao
INNOVATION INSIGHTS with Richard Langley
THIS ARTICLE IS ABOUT VIRTUAL SATELLITES. No, we don’t mean physical objects that are almost satellites. That’s the common everyday meaning of the word virtual. We mean it in the sense used in computing to describe something that is not physically present but made to appear so by software (and perhaps aided by hardware). The word was first used in this sense by computer scientists in the 1950s in the term virtual memory to describe a memory management technique. It is now widely used in computing, most commonly as virtual reality. But what is a virtual satellite then?
As we all know, GPS satellite signals are quite weak. The antenna of a standard GPS receiver needs to have a clear line-of-sight (LOS) view to the satellites for successful signal tracking and position determination. Buildings and other structures will block signals coming from certain directions. In built-up areas, this can result in fewer LOS signals than the minimum of four needed for unaided positioning. Even with four or more LOS signals, the receiver-satellite geometry may be poor resulting in a large dilution of precision and poor positioning accuracy as a result. It is true that augmentations such as wheel sensors and inertial measurement units coupled with dead reckoning may permit an acceptable level of positioning accuracy for some kinematic applications, but the accuracy will degrade over time if satellite blockage continues unabated. And yes, multi-GNSS can help in these situations with receivers availing themselves of additional LOS signals from the GLONASS, Galileo, and BeiDou systems and in Japan, QZSS. But Galileo, BeiDou and QZSS are still in development with a variable number of satellites available at a given location during the day. Is there anything else that can be done to improve the availability of GPS signals?
In fact, there are often more GPS signals arriving at a receiver’s antenna than just the LOS signals. These are non-line-of-sight (NLOS) signals that bounce off nearby structures before arriving at the antenna. We call the phenomenon multipath and, as we have discussed before in this column, multipath typically reduces positioning performance when the NLOS signals from a particular satellite combine with the LOS signal to distort a receiver’s standard correlator outputs thereby biasing pseudorange and carrier-phase measurements. Various techniques have been developed to reject multipath signals at the antenna or in the receiver while others have been developed to lessen the effect of these signals and so minimize their impact on position solutions. On the other hand, non-positioning GPS applications have been developed to use reflections from the Earth’s surface to measure snow depth, ground moisture content, and ocean-surface roughness. But could we somehow use multipath signals to improve positioning applications rather than degrade them?
In this month’s column, we look at a technique developed by researchers at the University of Illinois at Urbana-Champaign that distinguishes a reflected NLOS signal of a particular satellite from the LOS signal and characterizes the NLOS signal as coming from a virtual mirror-image satellite in the direction of the signal reflection point. By using information on the position and orientation of the reflector, the NLOS signal can be treated as an additional LOS signal, albeit from a ghost satellite. The authors have demonstrated that the technique works well in practice and in one difficult positioning environment, obtained an improvement in horizontal position accuracy of 40 meters — a reflected blessing indeed.
Building obstructions and reflections present serious challenges to GPS receivers operating in urban environments. In such environments, buildings may obstruct GPS signals, leading to reduced GPS signal availability. In addition, buildings may reflect GPS signals, resulting in reception of non-line-of-sight (NLOS) signals. NLOS GPS signals are delayed versions of the line-of-sight (LOS) signals. As such, they lead to pseudorange errors, resulting in positioning errors. Conventional approaches treat NLOS GPS signals as unwanted interference to be rejected or mitigated.
Conventional approaches reject NLOS GPS signals at multiple stages of GPS signal processing. Antenna-based approaches include the use of right-hand-circularly-polarized (RHCP) antennas and controlled reception pattern antennas (CRPA). Correlator-based approaches include the use of the narrow correlator, the double-delta correlator, the multipath estimating delay lock loop (MEDLL) and the vision correlator by various receiver manufacturers. In addition, receiver autonomous integrity monitoring (RAIM) approaches reject pseudoranges with inconsistent positioning residuals.
Besides rejecting NLOS GPS signals, conventional approaches also make use of robust filtering and joint signal tracking techniques to mitigate the effects of these signals. Robust filtering techniques include the use of Bayesian filters such as Kalman filters and particle filters. Joint signal tracking techniques include vector tracking and direct position estimation (DPE). A list of existing approaches addressing NLOS GPS signals is provided in TABLE 1.
TABLE 1. Approaches for rejecting and mitigating NLOS GPS signals.
In contrast to conventional approaches that reject or mitigate the effects of NLOS GPS signals, we propose transforming NLOS GPS signals from being unwanted interference to becoming additional useful navigation signals. In addition, we provide a navigation solution under reduced GPS signal availability.
RELATED WORK
In our approach to using NLOS GPS signals, we make use of DPE and 3D map-aided positioning. The following sections provide an overview of these techniques.
Direct Position Estimation. DPE is an unconventional joint signal tracking and navigation technique that directly estimates the GPS receiver’s navigation parameters from the GPS raw signal. It does so by directly comparing the expected signal reception of multiple potential navigation candidates against the actual received signal. The navigation solution is then estimated as the navigation candidate with the highest overall correlation between the expected and the actual received signal. This overall correlation is an accumulation of signal correlations across all available satellites, with replica signal parameters aligned to the candidate navigation parameters. In this manner, DPE jointly uses signal correlations from all available satellites to produce a robust navigation solution.
3D Map-Aided Positioning Techniques. State-of-the-art approaches use available 3D maps to predict NLOS signal reception. Apart from rejecting and/or mitigating the effects of NLOS pseudoranges, state-of-the-art approaches leverage the benefits of NLOS pseudoranges, constructively using the affected pseudorange measurements through special treatment of NLOS paths during trilateration. Using 3D building models, they model NLOS paths as LOS paths from satellites to virtual receivers located at receiver mirror-image positions. However, these approaches are limited by the issue of reduced signal availability due to multipath fading in addition to building obstruction. Under reduced signal availability, the navigation solution obtained via trilateration is degraded. With further reduction in signal availability — the number of available pseudorange measurements reduced to fewer than four — conventional calculation of the GPS navigation solution via trilateration with four unknowns is not possible.
In contrast to state-of-the-art approaches addressing NLOS signal reception at the GPS pseudorange measurement level, we directly address and constructively use NLOS signals at the GPS signal level via DPE using NLOS signals.
OUR APPROACH: DPE USING NLOS SIGNALS
We first model NLOS signals as LOS signals to virtual satellites at satellite mirror-image positions, as shown in FIGURE 1. This approach is similar to using virtual transmitters for multipath-assisted wireless indoor positioning. We calculate these satellite mirror-image positions and velocities using knowledge of building reflection surfaces estimated from available 3D maps.
FIGURE 1. NLOS signal transformed from being (top) an unwanted interference to becoming (bottom) an additional LOS signal to a virtual satellite at the satellite mirror-image position.
We then integrate these NLOS signals into GPS positioning via DPE. We modify the expected signal reception used in DPE to include NLOS signal information, as shown in FIGURE 2. Our approach deeply integrates this information and accurately describes the actual received signal.
FIGURE 2. Overall correlation in DPE, with the NLOS signal treated as an additional LOS signal to a virtual satellite at the satellite mirror-image position.
In addition, our approach provides a navigation solution under reduced signal availability. FIGURE 3 shows a block diagram of our approach.
FIGURE 3. Block diagram of DPE using NLOS signals and involving calculation of satellite position, velocity and time (PVT) and batch correlation using a fast Fourier transform (FFT).
IMPLEMENTATION AND EXPERIMENT RESULTS
We implemented DPE using NLOS signals with commercial front-end components and our software platform, PyGNSS. We conducted an experiment in front of the 53 meters by 40 meters wind tunnel located at NASA’s Ames Research Center, Mountain View, California (see FIGURE 4).
FIGURE 4. Experiment setup in front of the 53 meters by 40 meters wind tunnel located at NASA’s Ames Research Center, Mountain View, California. (a) data collection equipment; (b) wide-angle photograph of the wind tunnel’s air-intake port.
The material of the vertical surface of the wind tunnel’s air-intake port is a metal wire mesh with a grid spacing of 1.8 centimeters by 1.8 centimeters, as shown in FIGURE 5. This grid spacing is approximately one tenth of the carrier wavelength of the GPS L1 signal; the mesh wire radius is much less than the grid spacing. Thus, the vertical surface of the air-intake port acts as a reflector of GPS L1 signals.
FIGURE 5. Metal wire mesh on the vertical surface of the wind tunnel’s air-intake port. (Left) close-up photograph showing the grid spacing of 1.8 centimeters by 1.8 centimeters; (right) photograph from another perspective showing wire mesh covering the entire vertical surface of the air-intake port.
We estimated the normal vector and a point on the wind tunnel’s reflection surface using a geo-referenced 3D point cloud available on line through the National Oceanic and Atmospheric Administration’s (NOAA’s) Data Access Viewer tool. We refined the estimate using iterative closest point map-matching with a lidar scan (FIGURE 6).
FIGURE 6. Building reflection surface estimated from NOAA Data Access Viewer (DAV) point cloud, refined using map-matching with a lidar scan.
We then determined possible LOS and NLOS paths from satellite elevation-azimuth plots. Plotted in FIGURE 7 are the satellite positions, the satellite mirror-image positions and the building reflection surface. An NLOS path to a satellite exists if the corresponding LOS path to the satellite mirror-image intersects the building reflection surface. In our experiment, LOS paths exist to satellite PRNs 5, 7, 27 and 28 and an NLOS path exists to satellite PRN 5. Thus, both LOS and NLOS signals from satellite PRN 5 are present. This is verified by examining the amplitude of the in-phase prompt correlations over time. Only the in-phase prompt correlations of satellite PRN 5 exhibit a sinusoidal behavior characteristic of having both LOS and NLOS signals, as shown in FIGURE 8.
FIGURE 7. Elevation-azimuth plot with satellites highlighted using green boxes and satellite mirror-images highlighted using red boxes. The 3D point cloud of the wind tunnel’s air-intake port is plotted using grey dots. The path to the mirror-image of satellite PRN 5 passes through the surface of the wind tunnel. Thus, an NLOS path to satellite PRN 5 exists. In addition, LOS paths exist to satellite PRNs 5, 7, 27 and 28.FIGURE 8. Only the in-phase prompt correlation of satellite PRN 5 exhibits a sinusoidal behavior characteristic of having both LOS and NLOS signal components.
We then performed DPE, including the signal correlation contribution from the NLOS path to satellite PRN 5, where the NLOS path is represented as a LOS path to the satellite mirror-image. The overall correlation result, including the signal correlation from the NLOS path to satellite PRN 5, is shown in FIGURE 9. The color of the position markers, plotted using Google Maps, represents the overall correlation amplitude. Red indicates a high overall correlation amplitude and blue indicates a low overall correlation amplitude. The navigation solution is directly estimated as a correlation-weighted mean of the navigation candidates.
FIGURE 9. Normalized overall correlation with contributions from all satellites, including the satellite mirror-image of PRN 5.
The result, as compared to that estimated using pseudoranges from scalar tracking followed by trilateration, is shown in FIGURE 10. DPE using NLOS GPS signals demonstrated improved horizontal positioning accuracy by 40 meters.
FIGURE 10. DPE using NLOS GPS signals demonstrates improved horizontal positioning accuracy by 40 meters. This is in comparison to the navigation result obtained using pseudoranges estimated from conventional scalar tracking followed by trilateration.
CONCLUSION
In summary, we proposed DPE using NLOS signals to mitigate the issues of NLOS GPS signal reception and reduced GPS signal availability in urban navigation. We modeled NLOS signals as LOS signals to virtual satellites at satellite mirror-image positions. In this manner, NLOS signals are transformed from being unwanted interference to becoming additional useful navigation signals. We then created expected signal receptions to include NLOS GPS signal information at multiple potential navigation candidates and use DPE for positioning. Finally, we experimentally demonstrated a reduction in horizontal positioning error by 40 meters. This is in comparison to the navigation result obtained using pseudoranges estimated from conventional scalar tracking followed by trilateration.
ACKNOWLEDGMENTS
The authors thank the Safe Autonomous Flight Environment (SAFE50) and the Unmanned Aircraft System Traffic Management teams at NASA’s Ames Research Center, where the lead author was hosted for the summer of 2016, for their equipment support. The authors also thank Akshay Shetty for collecting and map-matching the lidar scan to the geo-referenced 3D point cloud.
This article is based on the paper “Direct Position Estimation Utilizing Non-Line-of-Sight (NLOS) GPS Signals” presented at ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, held Sept. 12–16, 2016, in Portland, Oregon.
YUTING NG received her B.S. degree in electrical engineering and her M.S. degree in aerospace engineering from the University of Illinois at Urbana-Champaign (UIUC) in 2014 and 2016, respectively. Her research interests are advanced signal processing, satellite navigation systems and radar.
GRACE XINGXIN GAO is an assistant professor in the Aerospace Engineering Department at UIUC. She obtained her Ph.D. degree in electrical engineering from the GPS Laboratory at Stanford University in 2008. Before joining UIUC in 2012, she was a research associate at Stanford University.
FURTHER READING
• Authors’ Conference Paper
“Direct Position Estimation Utilizing Non-Line-of-Sight (NLOS) GPS Signals” by Y. Ng and G.X. Gao in Proceedings of ION GNSS+ 2016, the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, Sept. 12–16, 2016, pp. 1279–1284.
“Mitigating Jamming and Meaconing Attacks Using Direct GPS Positioning” by Y. Ng and G.X. Gao in Proceedings of IEEE/ION PLANS 2016, the Position, Location, and Navigation Symposium, Savannah, Georgia, April 11–14, 2016, pp. 1021–1026, doi: 10.1109/PLANS.2016.7479804.
“Evaluation of GNSS Direct Position Estimation in Realistic Multipath Channels” by P. Closas, C. Fernández-Prades, J. Fernández-Rubio, M. Wis, G. Vecchione, F. Zanier, J.A. Garcia-Molina and M. Crisci in Proceedings of ION GNSS+ 2015, the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation, Tampa, Florida, Sept. 14–18, 2015, pp. 3693–3701.
“On the Maximum Likelihood Estimation of Position” by P. Closas, C. Fernández-Prades and J. Fernández-Rubio in Proceedings of ION GNSS 2006, the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation, Fort Worth, Texas, Sept. 26–29, 2006, pp. 1800–1810.
“NLOS Correction/Exclusion for GNSS Measurement Using RAIM and City Building Models” by L.-T. Hsu, Y. Gu and S. Kamijo in Sensors, Vol. 15, No. 7, 2015, pp. 17329–17349, doi: 10.3390/s150717329.
“GPS Multipath Detection and Rectification Using 3D Maps” by S. Miura, S. Hisaka and S. Kamijo in Proceedings of ITSC 2013, the 16th International IEEE Conference on Intelligent Transportation Systems, The Hague, The Netherlands, Oct. 6–9, 2013, pp. 1528–1534, doi: 10.1109/ITSC.2013.6728447.
“Urban Multipath Detection and Mitigation with Dynamic 3D Maps for Reliable Land Vehicle Localization” by M. Obst, S. Bauer and G. Wanielik in Proceedings of IEEE/ION PLANS 2012, the Position, Location, and Navigation Symposium, Myrtle Beach, South Carolina, April 23–26, 2012, pp. 685–691, doi: 10.1109/PLANS.2012.6236944.
• Virtual Transmitters
“Simultaneous Localization and Mapping in Multipath Environments” by C. Gentner, B. Ma, M. Ulmschneider, T. Jost and A. Dammann in Proceedings of IEEE/ION PLANS 2016, the Position, Location, and Navigation Symposium, Savannah, Georgia, April 11–14, 2016, pp. 807–815, doi: 10.1109/PLANS.2016.7479776.
Canadian UAVs and Lockheed Martin CDL Systems have completed their first Beyond Visual Line Of Sight (BVLOS) inspections for pipelines, well sites and power lines using unmanned aerial vehicles (UAVs).
The inspections were completed using the Transport Canada Compliant Lockheed Martin Indago 2 at the Foremost Testing Range.
Wellhead inspected Beyond Visual Line of Sight. (Photo: CNW Group/Canadian UAVs)
Canadian UAVs seeks to provide its customers with innovative technology to ensure safe and economic data acquisition for oil and gas and other industrial assets.
At the UAV Testing Facility in Foremost, Alberta, Canadian UAVs successfully performed multiple BVLOS operations to inspect several pipelines, wellheads and powerlines. This demonstration leverages Canadian UAVs’ solutions to provide BVLOS operations for its customers while maintaining strict manned aviation safety best practices.
“It’s a milestone our team has been working towards for years,” said Sean Greenwood, president of Canadian UAVs Inc. “Going BVLOS has technically been solved for some time with regards to powerful communications links and autopilot hardware. Canadian UAVs has been focused on creating an end-to-end paradigm in coordination with Transport Canada to conduct these operations outside of Restricted Military Airspace where our customers have a substantial regulatory and logistical needs to acquire actionable data. Due to our in-house combined military and commercial, manned and unmanned aviation backgrounds, the most advanced Lockheed Martin unmanned aircraft systems and a constant drive to evolve our aerial solutions, we have been able to demonstrate today the most logical operating structure for BVLOS on the market.”
Indago 2 UAV from Lockheed Martin.
“We are pleased that Canadian UAVs has selected our Indago 2 aircraft system with mobile ground control station as a solution for their commercial enterprise,” said John Molberg, business development lead for Lockheed Martin CDL Systems. “Our systems routinely fly beyond line of sight for our military customers, and that has allowed us to gain compliance status with Transport Canada for use in commercial airspace.
“This flight achievement is a bellwether for Canadian UAVs, Lockheed Martin and Foremost Test Range, while also showcasing the leadership provided by Unmanned Systems Canada and Transport Canada for the safe use of unmanned systems in Canadian airspace,” Molberg said.
“The ability to use BVLOS for UAV inspection and survey purposes would considerably increase safety, economic, and environmental considerations,” saidBeau Chaitan, environmental and regulatory engineer at MEG Energy. “As many of the assets and areas we are interested in surveying are located in regions of dense muskeg and access is significantly limited. Using traditional techniques on the ground for performing integrity inspections on remote sites or conducting reclamation monitoring would require the construction of either winter ice roads, or extensive summer access.
Wellhead inspected Beyond Visual Line of Sight. (Photo: CNW Group/Canadian UAVs)
“This is not only an expensive exercise, but it’s also environmentally disruptive, as it creates numerous linear disturbances that potentially affect wildlife. BVLOS with a UAV is an improvement over performing inspections and monitoring with a manned helicopter, as it is safer from a worker exposure point-of-view.
“Additionally, helicopter use has been known to scare off wildlife, which is counterproductive to the activity of conducting wildlife monitoring in remote areas. As oil sands operators continue to collaborate on regional initiatives, the ability to employ BLVOS with a UAV further enhances the possibilities to cooperate on environmental and regulatory activities.”
For more information, visit our website: canadianuavs.ca.
Researchers at the University of Bath, U.K., have gained new insights into the mechanisms of the Northern Lights, providing an opportunity to develop better satellite technology that can negate outages caused by the natural phenomenon.
Previous research has shown that the natural lights of the Northern Lights — also known as Aurora Borealis — interfere with GNSS signals. Plasma turbulence within the Northern Lights has been deemed responsible for causing GNSS inaccuracies. However, the latest research found that turbulence doesn’t exist, suggesting new, unknown mechanisms are actually responsible for outages on GNSS signals.
This is the first time it has been shown that turbulence does not take place within the Northern Lights. The findings will enable new technological solutions to overcome these outages.
The research team from the University of Bath’s Department of Electronic & Electrical Engineering, in collaboration with the European Incoherent Scatter Scientific Association (EISCAT), observed the Northern Lights in Tromsø, Norway, where they observed and analyzed the Northern Lights simultaneously using radar and a co-located GNSS receiver.
GNSS signals were used to identify how the Northern Lights interfere with GPS signals. Radar analysis provided a visual snapshot of the make-up of the phenomenon.
The researchers believe this heightened understanding of the Northern Lights will inform the creation of new types of GNSS technology that are robust against the disturbances of the Northern Lights, and help influence GNSS regulations used in industries such as civil aviation, land management, drone technology, mobile communications, transport and autonomous vehicles.
“With increasing dependency upon GNSS with the planned introduction of 5G networks and autonomous vehicles which rely heavily on GNSS, the need for accurate and reliable satellite navigation systems everywhere in the world has never been more critical,” said university lead researcher and lecturer Biagio Forte.
“The potential impact of inaccurate GNSS signals could be severe. Whilst outages in mobile phones may not be life threatening, unreliability in satellite navigations systems in autonomous vehicles or drones delivering payloads could result in serious harm to both humans and the environment,” Forte said. “This new understanding of the mechanisms which affect GNSS outages will lead to new technology that will enable safe and reliable satellite navigation.”
The Northern Lights occur at North and South magnetic Poles, and are the result of collisions between gaseous particles in the Earth’s atmosphere with charged particles released from the sun’s atmosphere.
