GPS World

Author: Tracy Cozzens

  • Antenna pattern uniformity effects on pseudorange tracking error

    More satellites, more constellations, more multi-frequency receivers — they all drive greater achievable accuracy. But they also raise the requirements on GNSS antennas because of the stronger impact that possible imperfections might have in the overall error budget for multi-frequency combinations. This analysis of antenna-induced errors in pseudorange code measurements for different antenna feed types helps identify the advantages and disadvantages of such technologies for precise positioning.

    By Stefano Caizzone, Mihaela-Simona Circiu, Wahid Elmarissi, Christoph Enneking, Michael Felux and Kazeem A. Yinusa, German Aerospace Center (DLR)

    The combination of signals from two frequencies and multiple constellations leads to dual-frequency multi-constellation (DFMC) capabilities, which currently appear to provide improved performance, due to the increased number of satellites available. This leads to better available satellite geometries, but also to the possibility to strongly mitigate ionosphere-related errors, thanks to dual-frequency combination of the ranging signals.

    In such scenarios, the hardware-related errors (from satellite and even more from receiver side) will gain a much stronger weight in the overall error budget and should be tackled accordingly.

    This article focuses mostly on the receiver antenna contribution, leaving the effects due to the satellite and to the receiver for later work. We will show that the choice of the antenna technology (mostly in terms of the number of feeding points) has a strong impact on the pattern uniformity and therefore on the differential group-delay characteristics over the aspect angle. Optimal performance is demonstrated when using more sophisticated solutions, providing a ground for cost/performance analysis to system engineers of specific applications.

    GROUP DELAY PERFORMANCE

    Antenna performance in GNSS application is mostly evaluated in terms of antenna gain pattern, noise figure and group delay for code measurement or phase center variation for carrier phase measurement. Gain and noise figure impact on the signal level available at the receiver, while the group delay is a measure of the delay introduced by the antenna hardware to the different spectral components of the signal. The differential group delay (DGD) is

      (1)

    with φ, f, Az, El being respectively the antenna phase, frequency, azimuth and elevation.

    The DGD variation with respect to frequency and aspect angle (that is, elevation and azimuth) actually poses a problem in precision applications: as a matter of fact, if the group delay were constant for all frequencies and all angles of arrival of the signal, no additional error would be introduced in the position calculation, because the group delay term common to all satellites would be encapsulated at the receiver into a user clock offset.

    However, group delay can change significantly with respect to aspect angle and frequency, contributing in a different manner for each satellite (due to different angles) and for different signals (due to the different spectral components of each signal), therefore finally producing errors in the pseudorange estimation.

    The influence of the DGD on pseudorange measurement error has already been studied in the past and is also taken into consideration in the antenna Minimum Operational Performance Standards (MOPS) for avionic antennas. Empirical studies on the combined effect of antenna group delay and multipath effect on board commercial airplanes have been published recently. However, to our knowledge, the correlation between the antenna intrinsic characteristics (such as gain and phase patterns and smoothness) and group delay behavior has not yet been properly analyzed, leaving a gap in the full understanding of the antenna design impact on the final GNSS receiver performance.

    GNSS antennas can be divided into families, according to their geometry (and the related radiation mechanisms): for instance, spiral, helix and microstrip (patch) antennas are quite common in GNSS applications.They differ in achievable bandwidth, size and ease of manufacturing.

    Even antennas of the same family can provide different performance, mainly because of the number of feeding points, which are the points where the signal is fed into the antenna.

    In order to analyze the relationship between the group delay performance and the antenna properties, we will take into consideration three GNSS antennas of the same family (microstrip patch), having all about half-effective-wavelength size (with the effective wavelength considering the dielectric properties of the substrate material on which the patch antenna is positioned), but with a different number of feeding points. The antennas will be denominated respectively single-feed, double-feed and four-feed antennas.

    The single-feed antenna is a square patch, with truncated corners to achieve circular polarization. On the other hand, the double- and four-feed antennas are square patches, having feeds positioned along their x- and y-axis. The feeds are fed progressively: that is, with same amplitude and 0°–90° phases for the double feed and 0–90–180–270° phases for the four feed.

    Single-feed antennas are representative of lower cost antennas used in mass-market applications, due to their extreme simplicity allowing for low-cost production. However, their performance exhibits strong cross polarization levels and non-uniform patterns over the azimuth. Dual- and four-feed antennas are more complicated to manufacture and need further hybrid circuits to properly distribute the signal between the different feeding points. However, an increase in the feeding points leads to more uniformity in the radiation pattern and lower-cross polarization and can therefore be expected to improve performance.

    Dual-feed antennas are common in applications where a balance between precision and cost is needed, while four feeds are used in high-end applications, such as geodesy and reference stations.

    The antennas under consideration here have been tuned to obtain optimal behavior at GPS L1/Galileo E1 band and have been simulated in an electromagnetic solver (Ansys HFSS), with an infinite ground plane assumption, to resemble the large metallic body frame of aircraft structures.

    The gain patterns of the different antennas at GPS L1 / Galileo E1 central frequency ( f=1575 MHz) are shown in Figure 1. As discussed earlier, the pattern is not uniform over angle for the single-feed solution. On the other hand, the four-feed antenna shows improved pattern uniformity: the pattern has fewer azimuth and elevation variations, with the two-feed solution providing intermediate results.

    Phase patterns for the three antennas are shown in Figure 2. Here again, the one-feed solution exhibits more angular variation than the multi-feed solutions. It is interesting to notice how strong phase variations occur in the same regions where the gain pattern also varies strongly.

    When considering the DGD, the frequency dependence of the phase pattern will have to be taken into account, according to Equation (1). To show the DGD variability with respect to the aspect angle, the standard deviation of the DGD over a 20-MHz bandwidth has been calculated (for each azimuth and elevation angle) and is shown in Figure 3, confirming the better behavior of the four-feed antenna.

    Figure 4 shows the group delay versus frequency and elevation (with different azimuth values being represented by curves with different colors) for the three typologies of antennas: such typology of figure contains all information about DGD variation versus frequency and angle and is first introduced in this article. For comparison, in the RTCA’s 2006 MOPS document for airborne antennas, for the sake of simplicity, either DGD variation versus angle at central frequency or DGD variation over frequency at zenith were considered, hence not fully covering the complete space {Frequency, Azimuth, Elevation}.

    While the single-feed antenna in Figure 4 shows a big variation of the DGD when moving from zenith (that is, Elevation = 90°) to lower elevations, a substantial decrease in the DGD spread is recorded for the four-feed solution, with the dual-feed one having again intermediate results.

    It is worthwhile noticing that the results obtained for the dual-feed solution are in agreement with the current MOPS for L1 antennas (RTCA DO-301), specifying a maximum value of 2.5 nansoseconds (ns) for the group delay spread at low elevations (normalized to boresight, El = 90°).

    The results show how angular variation of the DGD can be related to non-uniformity along the aspect angle (Az or El) and frequency, hence suggesting to use multiple-feed solution for obtaining optimal performance.

    A useful metric to quantify the uniformity of the group delay can be introduced as the Uniformity Indicator for Group Delay (UIGD):

       ( 2 )

    with  being the sum over frequency (Nf  is the number of frequency steps considered) and DGDzenith,n being the value of the DGD at zenith for frequency n.

    The UIGD expresses the maximum variation of the DGD over elevation and azimuth from a reference condition (the DGD at zenith) in the bandwidth of interest, extending de facto the MOPS requirements by considering the whole bandwidth behavior in the whole upper hemisphere.

    The UIGD for the one-, two- and four-feed antennas is respectively 4.18, 1.03 and 0.05 ns, hence effectively mirroring the better pattern uniformity of the four-feed solution.

    The UIGD is a comprehensive metric to describe the DGD uniformity, but needs accurate phase measurement over the entire bandwidth, which may not be always easily obtainable. As a matter of fact, phase can be challenging to measure: some indication of the areas most likely to deliver increased DGD can be found while considering gain patterns, qualitatively providing an easier metric to compare different antennas. In this case, the Uniformity Indicator for Gain (UIG)can be used:

       (3)

    The UIG expresses the maximum value over all elevation and azimuth angles of the standard deviation of the RHCP gain derivative over frequency (in the band of interest), therefore indicating the roughness of the antenna gain pattern in frequency and angle.

    Such a metric does not relate totally with DGD behavior, but serves as an easier metric of pattern uniformity. The UIG for the one-, two- and four-feed antennas is respectively 68.5, 5.7 and 0.3%.

    REAL-LIFE PERFORMANCE AND IMPACT ON ACCURACY

    To evaluate the performance of actual antennas, three prototypes were measured in a Satimo Starlab anechoic chamber at the German Aerospace Center (DLR).

    The antennas under test were:

    • A badly polarized COTS active antenna, having a behavior similar to that of a single-feed antenna;
    • An in-house developed passive antenna with two feeds;
    • An in-house developed passive four-feed antenna.

    All antennas were properly tuned to obtain optimal gain and minimum reflection losses (input reflection coefficient <–10 dB) at L1 /E1 central frequency.

    The measured RHCP pattern for the various antennas is shown in FiGURE 5. The UIGD for these antennas is 0.9, 0.7 and 0.2 ns respectively, while the UIG is 46.6, 38.5 and 9.0%.

    Differential group delay was calculated from the measured phase values and is shown in Figure 6.

    The results are similar to those obtained from simulation and clearly show the improved flatness of the DGD for the four-feed case.

    Moreover, if the measured phase data are fed into an ideal GNSS receiver, able to provide the tracking biases occurring in the pseudorange code measurement for all elevations and azimuths, antenna-effects-only (as weighted by the signal characteristics) will be visible (as in this case, neither multipath nor receiver or satellite imperfections are included in the ideal receiver). The results are shown in Figure 7.

    A substantial decrease in the antenna-induced error is evident as expected when the four-feed antenna is used.

    The differences in performance among different antenna technologies shown here provide valuable insight in the choice of the antenna technology for a specific application, thanks to the better understanding of the impact of the antenna characteristics on the error at pseudorange level. Moreover, they can support the evaluation and definition of antenna requirements and connect them to the expected GNSS pseudorange error, such as during the process of MOPS definition as currently occurring for DFMC systems.

    CONCLUSIONS

    After investigating the effects of pattern uniformity on antenna-induced errors, group delay behavior over aspect angle and frequency has been shown comprehensively for different antenna feeding technologies for the first time. Minimal error in pseudorange measurements is obtained when the antenna has a smooth pattern, with no abrupt variations or nulls/sidelobes both in aspect angle and frequency. Different antenna feeding technologies currently in use for circularly polarized radiation have been evaluated, and the best performing one has been identified in the multiple-feed solution.

    Both a comprehensive and an easier-to-measure metric for group delay uniformity have been identified, providing useful insight for fast comparison of the performance of multiple antennas in terms of GNSS accuracy.

    STEFANO CAIZZONE received a Ph.D. in geoinformation from the University of Rome, Tor Vergata. He is is responsible for the development of innovative miniaturized antennas in the antenna group of the Institute of Communications and Navigation of the German Aerospace Center (DLR).

    MIHAELA-SIMONA CIRCIU received a master’s degree in computer engineering from Technical University Gheorghe Asachi, Romania, and a master’s in navigation and related applications from Politecnico di Torino, Italy. She works on the development of the multi-frequency multi-constellation Ground Based Augmentation System for DLR.

    WAHID ELMARISSI received a Dipl. Ing. in electrical engineering from the University of Applied Sciences, Kiel, Germany. He is responsible for measurement and manufacturing of antennas and antenna electronics at DLR.

    CHRISTOPH ENNEKING received a MSc. degree in electrical engineering from the Munich University of Technology. He conducts research in GNSS signal design, estimation theory and GNSS intra- and inter-system interference at DLR.

    MICHAEL FELUX is a research associate specializing in GBAS integrity issues for CAT -II/III operations and program manager for the research on GBAS navigation at DLR. He graduated in technical mathematics at Technische Universität München.

    KAZEEM A. YINUSA received MSc. and Dr.-Ing. degrees in electrical engineering from the Technische Universität München. He is a researcher at DLR.

  • Where is that spoofed signal coming from?

    An experiment in an anechoic chamber with a JAVAD GNSS TRIUMPH-LS shows the approximate orientation of the spoofer (at 283° azimuth.)

    Javad GNSS advises that with its equipment it is possible, when a spoofer is detected in the area, to identify the direction from which the spoofing signals are coming.

    Hold the receiver antenna horizontally and rotate it slowly (one rotation in 30 seconds) to determine the angle at which satellite energies become minimum.

    The spoofer’s direction lies behind the null point of the antenna reception pattern.

    An experiment in an anechoic chamber with a Javad GNSS Triumph-LS shows the approximate orientation of the spoofer (at 283 degree azimuth.)

  • The System: China launches BeiDou-3 twins

    China launches BeiDou-3 twins

    China launched two BeiDou-3 navigation satellites into space on Jan. 12 as part of efforts to enable its BeiDou system to provide navigation and positioning services to countries along the Belt and Road by the end of 2018. The Belt and Road Initiative aims to create the world’s largest platform for economic cooperation, encompassing China, Southeast Asia, South Asia, Central and Western Asia, Middle East and Africa, and Central and Eastern Europe.

    The twin satellites are coded MEO-7 and MEO-8, the 26th and 27th satellites in the BeiDou Navigation Satellite System. They are based on a newly developed dedicated satellite bus that features a phased-array antenna for navigation signals and a laser retro-reflector. They each weigh about one metric ton, and both have two deployable solar arrays; their design life is 12 years. This was the first BeiDou launch in 2018, which will see an intensive further launch schedule throughout the year.

    In his December 2017 “Directions” article in GPS World, Changfeng Yang, chief BeiDou system architect, wrote that “Eighteen BD-3 MEO satellites and one BD-3 GEO satellite will be launched by around the end of 2018. Upon the deployment of those 19 satellites, BD-3 will possess the initial operational capability and serve the countries along the Belt and Road.”

    This would bring the constellation to an initial operational capability before the end of this year. China targets completion of the fully operational global system in 2020.

    B1C, B2A Control Document. On the Chinese part of the BeiDou website, there is now an English version of the Test ICD for the B1C and B2a signals. The link to the website item is www.beidou.gov.cn/icdb1cb2abeta.html, and the actual document is at www.beidou.gov.cn/attach/beidou/2333234155.pdf.

    More interference potential from another tower set

    Satellite operator Iridium asked the Federal Communications Commission (FCC) in April 2017 to modify its license to add a new class of ground stations called Certus for expanded terrestrial, maritime and aeronautical operations.

    Iridium’s 66-satellite constellation provides, in addition to mobile communications signals, the Satelles time and location service: microsecond timing accuracy and 20- to 50-meter unaided position accuracy worldwide (see the “Innovation” column, July 2017 GPS World).

    GPSIA. The GPS Innovation Alliance (GPSIA) commented in September, “GPSIA seeks to ensure that radio navigation satellite service (RNSS) receivers operating in the 1559–1610 MHz band are adequately protected from out-of-band emissions (OOBE) generated from the new Certus mobile Earth station (MES) terminals that will operate on the second-generation Iridium satellite system.

    “GPSIA and Iridium are actively engaged in constructive discussions regarding the adequacy of that protection, but no final resolution has yet been reached. [….]

    “In the unlikely event that GPSIA is unable to reach an agreement with Iridium, it asks the commission to impose limitations on the operation of Certus terminal devices to protect GPS/RNSS operations in the 1559–1610 MHz band at a level equivalent to what terrestrial terminals in the same and other frequency ranges provide at –95 dBW/MHz.”

    Hexagon. Hexagon, the parent company of GPS manufacturer NovAtel, commented on Jan. 8, “Certain statements in the modification application regarding output power and amount of terminals to be deployed cause great concern regarding the unimpeded operation of radio navigation satellite service (RNSS) receivers. The application does not include enough information to simulate the impact properly.

    “Hexagon politely requests that the FCC will exercise the same due diligence [as] during previous modification applications close to the RNSS bands (for example docket 11-109) and establish a technical working group or a similar testing process that ensures unimpeded coexistence of the modified Iridium terminals with the established RNSS systems.”

    Documents related to the case can be found here, on the FCC International Bureau website.

    Galileo security center moves to Spain

    The Galileo Security Monitoring Centre (GSMC) for the European Union’s Galileo satellite system will move from the United Kingdom to Madrid, Spain, as a result of Brexit.

    The center, not yet fully operational, is expected to grow to a staff of as many as 30. It controls access to the satellite system and provides around-the-clock monitoring when the main security center near Paris is offline.

    The GSMC is operated by the European GNSS Agency. It is one of a number of EU institutions leaving the UK as a result of the 2016 referendum vote.

    Spain has another of the fundamental centers of the program, the Loyola de Palacio GNSS Service Center, also in Madrid.

  • Esri releases Operations Dashboard for ArcGIS to manage events in real time

    Esri has released a new web browser application, allowing users to create reporting dashboards that use charts, gauges, maps and other visual elements to reflect the status and performance of people, services, assets and events in real time.

    Using dynamic dashboards through Operations Dashboard for ArcGIS, organizations of all types — from emergency operations centers to public utilities — can view crucial activities and key performance indicators that are vital to meeting their objectives.

    “The Chicago Office of Emergency Management and Communication [OEMC] GIS team has been using Operations Dashboard to support various events with access to real-time information,” said Joe Kezon, GIS manager for the Chicago OEMC. “We are looking forward to the enhancements that will further increase our ability to ensure the safety and security of the City of Chicago.”

    With an easily accessible web app, executives can monitor their organizations’ activities to assess what is working well and what needs attention.

    Esri-Operations-Dashboard-ArcGIS-W

    “The Emergency Management division of the Chicago Office of Emergency Management and Communications works very closely with our public safety partners and the city’s infrastructure departments in our comprehensive approach to event and incident management,” said Thomas Sivak, deputy director, Emergency Management, Chicago OEMC. “The Operation Dashboard allows us to effectively coordinate among agencies and adjust resources to make Chicago a safe place to live, work, and play.”

    Having this type of authoritative data allows decision-makers to reduce the risk of costly errors due to inaccurate or outdated information, better control the allocation of resources, maintain real-time awareness of where assets and human resources are located, monitor conditions live such as weather and traffic, and achieve real-time insight to respond to changing conditions.

    “The new Operations Dashboard web app enables, at a glance, decision-making better than ever,” said Jeff Shaner, Esri product manager. “Not only can dashboards be authored online — anywhere, at any time — but the common platform allows greater collaboration among personnel.”

    Operations Dashboard also provides a common interface to monitor progress and identify vulnerabilities that could compromise the success of an organization’s mission. Dashboards can be authored completely in a web browser. There is no need to download and install an app anymore.

    Users can launch Operations Dashboard by using their ArcGIS organizational account. They can also browse and manage dashboards within their ArcGIS organizational content or on the dashboard home page.

    Photo: Esri

  • NavVis improves SLAM precision indoors

    NavVis, a mobile indoor mapping, visualization and navigation company, released new mapping software that significantly improves the accuracy of simultaneous localization and mapping (SLAM) technology in indoor environments, such as long corridors, the company said.

    The software update will be available for users of the NavVis M3 Trolley and will significantly improve the accuracy of the resulting maps and point clouds. NavVis’ mobile mapping system, the M3 Trolley, builds upon SLAM to increase speed and efficiency when scanning buildings.

    The images below demonstrate the impact of NavVis Precision SLAM technology. The left image depicts a long corridor mapped with a conventional SLAM system where the above-mentioned drift error has occurred. The green outline shows how the map deviates from the true structure. The image on the right shows the significantly improved map accuracy obtained when mapping the same area using the M3 Trolley with the new Precision SLAM technology.

    Image: NavVis
    Image: NavVis

    Here is a closer look:

    Image: NavVis
    Image: NavVis

    SLAM is a technique originally developed by the robotics industry that is now increasingly being used in surveying and autonomous driving technologies. It solves a core problem that long plagued robotics engineers by enabling a device to determine its location while simultaneously mapping an unknown environment. This is done by chaining millions of measurements into a trajectory estimate.

    However, even when a device captures highly accurate individual measurements, chaining them will result in an accumulation of noise and tiny measurement uncertainties. Over time, the estimated motion will start to deviate from the true motion (drift error). This can often be observed as a slight bending of long corridors that are actually straight. All available SLAM systems — regardless of whether these use LIDARs or other sensors — are inherently affected by this phenomenon.

    The NavVis Precision SLAM technology significantly reduces drift error and improves the SLAM accuracy. This is particularly evident in cases where complementary techniques such as loop closures cannot be deployed, if, for example, the building’s layout does not allow for it.

    Precision SLAM even improves accuracy when SLAM anchors are used to incorporate ground control points into the mapping process.

    “I am very excited about our new Precision SLAM technology,” said Stefan Romberg, head of mapping and perception at NavVis. “We are always striving for the highest possible map and point-cloud accuracy and improving SLAM is a critical component to being successful. It is widely known among SLAM developers and users that complementary approaches such as loop closures or ground control points are needed to achieve a high accuracy.

    “However, with the Precision SLAM technology we have developed an approach that not only nicely complements the former techniques but is especially evident when these have little effect or cannot be used.”

  • GNSS earthquake early-warning tested in Chile

    Researchers testing a satellite-based earthquake early warning system developed for the U.S. West Coast found that the system performed well in a “replay” of three large earthquakes that occurred in Chile between 2010 and 2015, reports the Seismological Society of America.

    The results, reported in the journal Seismological Research Letters (SRL), suggest that such a system could provide early warnings of ground shaking and tsunamis for Chile’s coastal communities in the future.

    The early warning module, called G-FAST, uses ground motion data measured by GNSS to estimate the magnitude and epicenter for large earthquakes — those magnitude 8 and greater. These great quakes often take place at subducting tectonic plate boundaries, where one plate thrusts beneath another plate, as is the case off the coast of Chile and the U.S. Pacific Northwest.

    Using data collected by Chile’s more than 150 GNSS stations, Brendan Crowell of the University of Washington and his colleagues tested G-FAST’s performance against three large megathrust earthquakes in the country: the 2010 magnitude 8.8 Maule, the 2014 magnitude 8.2 Iquique, and the 2015 magnitude 8.3 Illapel earthquakes.

    G-FAST was able to provide magnitude estimates between 40 to 60 seconds after the origin time of all three quakes, providing magnitude estimates that were within 0.3 units of the known magnitudes. The system also provided estimates of the epicenter and fault slip for each earthquake that agreed with the actual measurements, and were available 60 to 90 seconds after each earthquake’s origin time.

    “We were surprised at how fast G-FAST was able to converge to the correct answers and how accurately we were able to characterize all three earthquakes,” Crowell said.

    Most earthquake early warning systems measure properties of seismic waves to quickly characterize an earthquake. These systems often cannot collect enough information to determine how a large earthquake will grow and as a result may underestimate the earthquake magnitude—a problem that can be avoided with satellite-based systems such as G-FAST.

    It’s difficult to test these types of early warning systems, Crowell noted, because magnitude 8+ earthquakes are relatively rare. “We decided to look at the Chilean earthquakes because they included several greater than magnitude 8 earthquakes, recorded with an excellent and consistent GNSS network. In doing so, we would be able to better categorize the strengths and weaknesses in G-FAST.”

    ShakeAlert

    The Chilean tests will play a part in furthering developing G-FAST for use in the U.S., where Crowell and colleagues have been working to include it in the prototype earthquake early warning system called ShakeAlert, now operating in California, Oregon and Washington. The Chilean earthquakes, Crowell said, represent about half of magnitude 8 events in the recorded catalog of earthquakes that are used to test G-FAST and other geodetic algorithms for inclusion in ShakeAlert.

    Ten magnitude 8 or greater earthquakes have occurred along the Chilean coast in the past 100 years, including the 1960 magnitude 9.5 Valdivia earthquake, which is the largest earthquake recorded by instruments. “The hazard due to these large events is well recognized and understood,” in Chile, wrote Sergio Eduardo Barrientos of the Universidad de Chile, in a second paper published this week in SRL. “Return periods for magnitude 8 and above events are of the order of 80 to 130 years for any given region in Chile, but about a dozen years when the country is considered as a whole.”

    After the 2010 Maule earthquake, the country began installing a network of digital broadband seismic and ground motion stations, GPS stations, and GNSS stations to provide accurate information for tsunami warnings and damage assessment. Since 2012, the Centro Sismológico Nacional at the Universidad de Chile has operated more than 100 stations, and has recently begun to operate almost 300 strong-motion accelerometers that measure ground shaking.

    In a third paper published in SRL, Felipe Leyton of the Universidad de Chile and colleagues analyze data collected from 163 of these strong-motion stations to learn more about the local site conditions of underlying rock and soil in these areas. Site conditions can modify the shaking of large earthquakes and control the damage to buildings and other infrastructure caused by the shaking.

    The new study “gives us a unique opportunity to improve our knowledge of the behavior of soil deposits during earthquakes, especially in urbanized areas,” write Leyton and colleagues, who say the data could be used to help improve building designs and codes.

  • ION announces annual award winners

    The Institute of Navigation (ION) presented its Annual Awards during the ION International Technical Meeting (ITM) and Precise Time and Time Interval Systems and Applications (PTTI) meeting in Reston, Virginia, Jan. 29-Feb. 1.

    The ION Annual Awards Program is sponsored by The Institute of Navigation to recognize individuals making significant contributions or demonstrating outstanding performance relating to the art and science of navigation.

    Zheng Yao received the Early Achievement Award for his pioneering contributions in developing new GNSS signals and multiplexing techniques; and advancing the Chinese BeiDou Navigation Satellite Systems (BDS) signal design. The Early Achievement Award is presented in recognition of outstanding contributions made early in one’s career.

    Captain Gregory DuBose received the Superior Achievement Award for sustained performance in combat operations in Afghanistan, Iraq and Syria; and assistance in the recovery of a downed B-1 crew in Montana. The Superior Achievement Award is presented to an individual demonstrating outstanding accomplishments as a practicing navigator.

    William Bollwerk received the Distinguished PTTI Service Award for service to the Department of Defense and country in promoting the importance of time, and educating policymakers and mission operators to ensure understanding of time in critical operations. The Distinguished PTTI Service Award is presented to recognize outstanding contributions related to the management of PTTI systems.

    Luke B. Winternitz, William A. Bamford, Samuel R. Price, J. Russell Carpenter, Anne C. Long and Mitra Farahmand received the Samuel M. Burka Award for their paper “Global Positioning System Navigation above 76,000 KM for NASA’s Magnetospheric Multiscale Mission” published in the Summer 2017 issue of NAVIGATION, Journal of The Institute of Navigation, Vol. 64, No. 2, pp. 289-300. The Samuel M. Burka Award recognizes outstanding achievement in the preparation of a paper contributing to the advancement of the art and science of positioning, navigation and timing.

    Professor Allison Kealy received the Captain P. V. H. Weems Award for sustained contributions to advancing the art and science of navigation, and promoting and expanding the use of PNT among worldwide science and engineering communities. The Captain P. V. H. Weems Award is presented to individuals for continuing contributions to the art and science of navigation.

    David A. Turner received the Norman P. Hays Award for his role in the formation of the International Committee on GNSS (ICG) and the development of globally recognized principles of GNSS compatibility, interoperability and transparency. The Norman P. Hays Award is given in recognition of outstanding encouragement, inspiration and support contributing to the advancement of navigation.

    Yang Gao received the Thomas L. Thurlow Award for significant contributions and leadership in the development and application of Precise Point Positioning (PPP) and high-precision GNSS technology. The Thomas L. Thurlow Award recognizes outstanding contributions to the science of navigation.

  • Delair offers advanced UAV for aerial surveying and mapping

    Delair offers advanced UAV for aerial surveying and mapping

    Delair, a supplier of drone solutions for commercial industries, has introduced the next-generation of its high-performance DT26X Lidar UAV.

    The DT26X is a long-range fixed-wing drone that combines highly accurate lidar sensing capabilities with an integrated high-resolution RGB (red, green, blue) camera, dramatically increasing the precision, efficiency and cost effectiveness of surveying and 3D mapping.

    The Delair DT26X lidar drone combines lidar sensing with RGB camera data to enable highly accurate and high-resolution 3D representation and measurement over large areas with minimal flights and in challenging environments. (Image: Delair)

    Details of the new model, which builds on Delair’s proven expertise in long distance, beyond visual line of sight UAV operations, were revealed at the International Lidar Mapping Forum in Denver.

    Aerial-based lidar allows for extremely detailed and accurate collection of elevation data of the ground, even in large and vegetated areas, but is typically performed with specialized, single function platforms or expensive manned aircraft surveys with long lead times.

    Camera-enabled drones offer a complementary solution for collecting imagery that can augment the lidar-based models. Most projects therefore require multiple mapping flights and separate UAVs, with initial missions using lidar sensors and subsequent flights equipped with RGB-cameras to enhance the digital rendering.

    The Delair DT26X lidar’s combined payload of a lightweight sensor and integrated camera allows the acquisition of lidar and photogrammetry data in a single flight, which drastically reduces cost and immediately provides an extremely detailed digital model of the inspected assets.

    The lidar sensor is specifically designed for UAV use, adding little weight or bulk to the Delair frame. The fully-integrated smart RGB camera enables real-time camera sensor control and in-flight photo review with automated quality checks.

    The new platform delivers increased accuracy in 3D mapping and modeling of terrain and corridors in challenging physical environments (e.g. mountainous, inaccessible by road or foot, dense vegetation) and with difficult visibility, lighting or weighting conditions.

    Its long range flying capabilities — allowing coverage of up to 2,400 square acres, communication range of 30 kilometers and 100 minutes of flight time — improve the efficiency of aerial mapping operations over large areas. As a result, the Delair DT26X lidar is well suited for uses such as environmental and land surveys, forestry monitoring, infrastructure surveillance, powerline and pipeline inspections, and road and rail construction.

    “The combination of a sophisticated lidar sensor and an industrial grade RGB camera removes the ‘either/or’ decision of choosing between lidar and imagery data acquisition for geospatial professionals,” said Chase Fly, geospatial product manager at Delair. “This is the most versatile and cost-effective UAV solution for large area, long range mapping and surveying where accuracy and detail are required. It provides the precision and visibility required by the most demanding use cases and allows data acquisition and advanced digitization not possible through terrain-based or satellite 3D mapping techniques, or with limited short-range UAVs. With this configuration, users can acquire all the data required for a colorized point cloud from a single flight, which eases the point cloud classification process back in the office, saving significant time and money.”

    New lidar sensor for more accurate mapping. The Delair DT26X lidar fixed-wing UAV incorporates the new RIEGL miniVUX-1DL lidar sensor, a specially designed device for the needs of UAV use.

    The small form factor sensor includes a downward looking and optimized field of view specifically geared for corridor mapping tasks. The wedge prism scanner construction produces a field of view of 46 degrees, and the circular scan pattern provides a very high point density and point distribution.

    It offers a high scan speed of up to 150 scans per second and a measurement rate of up to 100,000 measurements per second. It is effective in penetrating poor lighting conditions or dense foliage. The lidar sensor makes use of RIEGL’s Waveform-lidar technology, allowing echo digitization and online waveform processing. It supports multiple-target resolution of up to five target echoes per laser shot.

    “The new Delair UAV is typically the type of drone RIEGL had in mind when designing the RIEGL miniVUX-1DL, and represents another step toward completing our UAV lidar equipment product portfolio. The scanner’s specific wedge prism scanning mechanism generates a circular scan pattern, resulting in high point densities and therefore is especially well suited when deploying the scanner from fast moving acquisition platforms such as fixed-wing UAVs. The FOV (field of view) of the miniVUX-1DL is 46deg, resulting in optimized efficiency for downward-looking, linear acquisition set-ups like corridor mapping applications, for example. We are pleased to have such an innovative company like Delair as an esteemed OEM integration partner, bringing our sensing technology to key market sectors that require a flexible lidar solution,” commented Michael Mayer, managing director, RiCOPTER UAV GmbH.

    RiCOPTER UAV GmbH is a subsidiary of RIEGL Laser Measurement Systems GmbH, an international provider of technology in airborne, mobile, terrestrial, industrial and unmanned laser-scanning solutions. RiCOPTER UAV GmbH commercializes RIEGL’s turnkey lidar UAV solution and laser-scanning payloads dedicated for UAV integration.

  • Sentera adds elevation maps to AgVault platform

    Elevation variance maps are now available within the Sentera AgVault platform, offering agronomists, crop consultants and growers additional field insights.

    Topography and elevation data helps agriculture professionals increase operating efficiencies when building variable rate prescriptions, creating drainage or land-leveling plans, and designing subsurface drainage.

    Elevation maps are ordered within AgVault and are delivered as both a color-mapped topographic map image and a set of industry-standard shapefiles.

  • Raven grows precision ag facility in South Dakota

    Raven Industries has given South Dakota State University (SDSU) $5 million to establish a precision agriculture facility within the College of Agriculture and Biological Sciences on its main campus in Brookings, South Dakota.

    SDSU is the first U.S. land-grant university in the country to offer both a four-year degree and a minor in precision agriculture.

    The facility will be the nexus for innovation and collaboration across several disciplines, including engineering, agronomy, horticulture, mathematics and the decision sciences, according to SDSU President Barry Dunn.

    It will enhance innovation and the development of educational programs that will deliver applications to enable data-driven decisions in precision farming, ranching and conservation, as well as promote collaboration between faculty, students and industry experts.

  • Trimble acquires e-Builder to expand construction management solutions

    Trimble has acquired privately-held e-Builder, a software-as-a-service (SaaS)-based construction program management solution for capital program owners and program management firms.

    e-Builder extends Trimble’s ability to accelerate industry transformation by providing an integrated project delivery solution for owners, program managers and contractors across the design, construct and operate lifecycle, the company said.

    e-Builder manages more than $300 billion of construction project value and over 200,000 projects from some of the most influential owners in North America. Owners benefit from the e-Builder solution through improved transparency and accountability while contractors benefit from faster payments, increased productivity and improved competitive advantage.

    The e-Builder solution is uniquely designed to measure and manage every step of the capital project delivery process including planning, design, procurement, construction and operations.

    Trimble’s wide range of construction hardware and software solutions significantly improve project cost, schedule and effectiveness — beneficially impacting owners, architects, engineers and contractors. The Trimble presence in construction has two points of focus, one on civil engineering projects and the other on the construction of buildings and structures. Both will benefit from the e-Builder acquisition.

    Trimble solutions leverage constructible building information model (BIM) workflows to integrate processes, improve information fidelity, reduce rework, establish transparency and deliver higher productivity. By using Trimble technologies, contractors and owners are realizing substantial reductions in total project cost.

    The combination of Trimble and e-Builder accelerates value creation for both owners and contractors by combining e-Builder’s best practice solutions for owners with Trimble’s construction lifecycle solutions, access to contractors and global reach.

    The combined solution portfolio will accelerate the integration of field operations with enterprise needs, enabling additional productivity gains. The tangible benefits include more consistent on-time and within-budget project delivery that is enabled by improved visibility, clear accountability for outcomes and the ability to convert large volumes of disparate data into actionable workflows and measurable outcomes.

    “e-Builder has always recognized that owners play a key role in the construction lifecycle and that their influence will be key to the adoption of transformative construction technology,” said Steven Berglund, president and CEO of Trimble. “Trimble will extend its reach into the owner community by leveraging e-Builder’s presence. In turn, we intend to aggressively bring e-Builder solutions to civil and building contractors and the international market. We see a significant opportunity in leveraging data and intelligence gained through design-construct workflows across the full infrastructure lifecycle. e-Builder’s solutions and, more importantly, its organization provide a strong platform for significant growth.”

    “e-Builder’s mission is to improve project execution to make construction faster, less expensive and more reliable,” said Ron Antevy, president and CEO of e-Builder. “The addition of our solutions to Trimble’s broad portfolio extends our collective ability to best support owners and contractors with project delivery and management. e-Builder current and future customers will benefit from Trimble’s construction management expertise, culture of innovation and global reach to take e-Builder solutions to the next level.”

    The e-Builder business will be reported as part of the Buildings and Infrastructure Segment.

    Financial Terms

    The all cash purchase price of $500 million will be financed through a new $300 million credit facility and cash. The new facility has terms and conditions similar to the existing revolver with a 364 day term.

    e-Builder’s reported trailing twelve month revenue is approximately $53 million. In recent years, e-Builder’s revenue growth rate has exceeded 20 percent annually, with greater than 65 percent subscription revenue as a percentage of total revenue. The transaction is expected to be dilutive to Trimble’s first quarter non-GAAP net income per share by $0.01 per share and dilutive to full year 2018 non-GAAP net income per share by $0.02 to $0.03 per share, due to the impact of fair value accounting of e-Builder’s deferred revenue and interest expense. Trimble expects the acquisition to be accretive to 2019 non-GAAP net income per share.

    An overview of e-Builder and the strategic rationale for the acquisition is available on Trimble’s Investor Relations website. For a more detailed description of the acquisition and credit agreements see Trimble’s Form 8-K filed with the U.S. Securities and Exchange Commission (SEC) on Feb. 2, 2018.

    About e-Builder

    Founded in 1995, e-Builder is a provider of integrated, cloud-based construction program management software for top facility owners and the companies that act on their behalf.

    The company’s flagship product, e-Builder Enterprise, improves capital project execution, resulting in increased productivity and quality, reduced cost and faster project delivery.

    Since 1995, e-Builder’s technology leadership and construction industry focus have helped thousands of global companies, government agencies, and health care and educational institutions manage billions of dollars in capital programs with solutions to improve the plan, build and operate lifecycle.

    The company is based in Plantation, Florida.

  • NVIDIA Jetson takes to the sky to improve worksite visualization

    Komatsu plans to introduce NVIDIA graphics processing units (GPUs) to its SmartConstrution jobsites. The GPUs will communicate with drones from Skycatch, a Komatsu partner, which will collect 3D images, generate terrain data and “visualize” site conditions.

    Komatsu is deploying the artifical intelligence (AI) project as an extension of its SmartConstruction initiative in Japan; the drone-assisted, automated equipment service was launched to alleviate the burden of the country’s severe shortage of skilled workers.

    The company has deployed SmartConstruction at than 4,000 jobsites across the country, and the AI extension will be integrated into those sites.

    Working with NVIDIA, OPTiM Corp. — another Komatsu partner and an internet of things management software company — will provide an application to correlate terrain data to jobsite workers and construction machines for visualization.

    Enter Jetson. At the center of this collaboration is the NVIDIA Jetson artificial intelligence platform. When Jetson, which works with NVIDIA’s cloud technology, is installed in construction machines, it will be able to provide 360-degree images, enabling prompt recognition of workers and other machines nearby. The technology could potentially decrease fatalities that result from workers being struck by an object, piece of equipment or vehicle.

    Jetson will also be used with the stereo cameras installed in the cabs of construction equipment, and will recognize continuously changing jobsite conditions on a real-time basis, to better provide accurate instructions to machine operators.

    Future plans call for use not only for automatic control of devices, but also for high-resolution rendering and virtual simulation of construction and quarry jobsite operations.