Back in September at the Institute of Navigation GNSS+ convention in Tampa, Florida, one of the papers went a long way to explaining why and how more GNSS satellites in more constellations is better. The natural assumption is that because there are more satellites, a multi-constellation receiver can choose which ones have the best signal and which provide the best solution — and it’s not always the same satellites.
Best geometry together with best signal strength obviously provide the best solution, but this might change in, for instance, a downtown urban setting for a car using a satellite navigation system. While most Western car-nav systems use only GPS, the study by Martin Escher, Mirko Stanisak, and Ulf Bestmann at the Institute of Flight Guidance, Technical University in Braunschweig, Germany, clearly shows that there is an advantage to embedding multi-constellation receivers in these systems.
Skyplot of GPS, GLONASS, Galileo and BeiDou satellites at Braunschweig.
The above skyplot shows a perfect reception of all GNSS satellites during a period of 14 hours — 30 usable satellites — obtained with a high-quality antenna without any obstacles. Car driving downtown will almost never encounter such good GNSS reception.
The Technical University put two different receivers in a car under static, representative, urban conditions, and went about evaluating reception against that predicted by an in-house simulation. The high-precision survey-grade receiver receiver tracked signals from all four constellations, while a lower cost receiver used in some car-nav systems was configured to only track GPS and Beidou. In this scenario, valid signals were obscured by surrounding buildings and the total number of visible satellites was reduced from 23-30 to 11-18.
The measurements validated the university simulation model and demonstrated how the high-precision receiver was able to remove multipath and other diffracted or reflected signals, while the lower cost receiver collected all available signals and therefore suffered some accuracy degradation.
Braunschweig urban scenario.Predicted satellites reception with an elevation of up to 65 degrees often obstructed by buildings.
The area chosen for this demonstration is dominated by narrow roads with multi-story buildings on both sides of the road. To begin, only GPS positioning was used on the test route — representing the current state-of-the-art for most production car-nav systems. For large portions of the test drive, no GPS-only position solution was achieved because of insufficient GPS measurements.
While there was some improvement in tracking using a multi-constellation receiver, when GNSS differential corrections over a mobile telecom link were incorporated, tracking performance was significantly improved. But when inertial and wheel sensors were also added into the solution, almost perfect positioning was achieved over the whole route.
Multi-constellation with differential corrections and sensor aiding.
Given that commercial GPS/GLONASS corrections are now available almost everywhere over a large portion of the globe and some assisted GNSS services are beginning to add both Galileo and Beidou corrections, it’s possible that downtown loss of signal for car drivers may soon be a thing of the past. And, of course, many car-nav systems currently incorporate wheel sensor inputs for dead-reckoning when GNSS is lost.
Drone use in difficult locations
Another interesting ION GNSS 2015 paper from Adam Schultz, Russell Gilabert, and Maarten Uijt de Haag of The Ohio University details the way a couple of students and their professor set out to fly a drone down corridors and within the halls of the Engineering Department. They are hoping to soon get access to the extensive maintenance tunnel system at Ohio University for more autonomous flights using newer, smaller drones.
The objective is to investigate the requirements and use of drones for missions in remote or difficult locations for applications such as large building maintenance, search and rescue, and indoor mapping.
But watch out, people in the Engineering building, if you see an unmanned hex-copter heading toward you on your way to class! Sounds like great fun as the UAV research students see the shots of the scattering inhabitants via the onboard Point Grey FireFly MV color camera!
The UAV/drone is equipped with a navigation and mapping system for both outdoor and indoor environments, using multiple laser scanners, an inertial measurement unit (IMU), barometric height and GNSS, whenever its available.
The UAV is a 3DRobotics hex-copter with a payload that includes an onboard processor, two short-range and one long-range laser range scanners, autopilot, Xsense MTI IMU, GPS receiver and a standard Wi-Fi link to relay real-time maps, trajectories and video to the remote operator.
Ohio U Hex-copter with similar payload as flown through indoor environment (speed ~2m/s).
Guidance, navigation and control (GNC) of the unmanned hex-copter is accomplished by tactical and strategic modules. In known environments, the strategic GNC keeps track of the planned and actual flight trajectories and provides the next waypoints for the mission.
In unknown environments, the strategic GNC maintains a rough estimate of trajectory and the current map of the UAV’s location. The UAV can be flown either manually by the student managing the flight controller or, when in autonomous mode, by the internal UAV flight control computer. Laser scanners provide horizontal position estimation and altitude estimation, while also collecting mapping data.
The mission manager is programmed with a simple rule-based system that uses the system’s 2D and 3D maps to control the route. The drone flies autonomously through the corridors and rooms, while the UAS operator monitors progress on a laptop. The operator can manually take control of the UAV guidance at any time.
The autopilot provides magnetometer and inertial measurements that are used to loosely maintain heading when moving from outdoors to indoors. When indoors, the lidar, inertial and optical (LION) mission controller continuously outputs position and orientation and generates short 10-30 second trajectories for the flight controller — providing a series of waypoints and required velocities for the UAV to follow.
Map generated by the UAV mission controller (red) versus truth reference map (blue).
Should this research ultimately lead to a commercial UAV implementation, it sure would help solve the huge problem we have now for generating indoor maps. The current simultaneous localization and mapping (SLAM) method for generating these indoor maps usually means somebody walks throughout a mall or office building carrying one of several indoor location systems or even taking physical measurements. If a very small UAV were to be flown safely throughout such an indoor location, data would be collected quickly, hopefully with a lot less effort than current methods allow. There’s still a lot of research and development required, but this sure does look promising.
Tony Murfin
GNSS Aerospace
References
“Future Automotive GNSS Positioning in Urban Scenarios,” Martin Escher, Mirko Stanisak, Ulf Bestmann, ION GNSS+ 2015.
“Indoor Flight Demonstration Results of an Autonomous Multi-copter using Multiple Laser Inertial Navigation,” Adam Schultz, Russell Gilabert, and Maarten Uijt de Haag, ION GNSS+ 2015.
Averna has acquired 100 percent of Europe-based Test & Measurement Solutions for an undisclosed amount. Averna is a developer of test solutions and services for communications and electronics device-makers worldwide.
Averna’s main shareholders, Tandem Expansion and Caisse de dépôt et placement du Québec (CDPQ), both helped finance the acquisition. For CDPQ, the investment is consistent with its objective to further the international expansion of high-performing Quebec companies.
T&M Solutions develops multidisciplinary solutions to test, measure, inspect, assemble and validate products in nearly all segments of the production industry. Headquartered in Belgium and with offices in the Netherlands and Poland, T&M Solutions is a National Instruments Gold Alliance Partner and has 100 employees, including 70 engineers with almost 50 NI certifications.
The acquisition increases Averna’s global reach as well as provides a strong local presence in Europe, according to an Averna press release. It will enable Averna to enter the market with a well-established and respected solution provider while giving it a springboard for further European deployments. In addition, T&M Solutions brings unique expertise in semiconductor testing, vision inspection systems and precision assembly.
T&M Solutions’ management, including current owners Roel Geraerts and Kurt Hensen, will continue to play key roles in operations and expansion plans for the European market.
“This major expansion into Europe signals Averna’s strategic positioning to accelerate growth and become a truly global Test Engineering powerhouse. Test & Measurement Solutions and Averna share complementary solution portfolios, clients and partners, so this is a real win-win arrangement for everyone,” said François Rainville, vice president of sales and marketing for Averna. “We are proud to welcome T&M Solutions’ customers and employees while providing all our customers with additional expertise and increased worldwide presence.”
André Gareau, Averna’s president and CEO, added “We’re building a strong track record of successful acquisitions and are motivated by our robust pipeline of opportunities in Europe and around the world. These are exciting times for Averna and the industry as our leading test expertise, rapid processes and global support continue to demonstrate that we are a strategic-value partner for our clients’ ongoing product quality and market goals.”
“We are very excited to become part of Averna, a leading player in our field. This transaction creates a unique strategic opportunity as we combine T&M Solutions’ mature European presence and respected expertise with Averna’s expansive global footprint and renowned products and solution delivery capabilities,” said Kurt Hensen, CEO of Test & Measurement Solutions. “As part of Averna, our portfolio will deliver even greater value as we remain focused on our strengths and customers.”
In February, I hit the 10-year mark with GPS World magazine. That milestone caused me to stop and reflect on all the changes in my work over the past decade.
In 2006, our web presence was mostly taking the print magazine and replicating it on the website, complete with a Table of Contents for the current issue. We had dozens of categories and subcategories, slicing and dicing the industry into micro-segments. I found it increasingly difficult to decide which category to place stories into, because so much research and so many products have multiple applications.
We’ve now greatly simplified the categories, but they still overlap. A Mobile story will touch on Transportation and OEM. A Survey story is also a Mapping story. A UAV story has applications for Defense or Mapping. Because of this, I invite you to see our categories as a jumping off point, not as independent silos. Peruse all the pages of our magazine — you may be surprised at what you find.
Another massive change over the past decade is our way of thinking. GPS World is no longer just a monthly print magazine with a now-and-then web story or editorial. We are the major industry web presence, with almost 1.5 million page views annually.
In 2006, I spent perhaps 20 percent of my time on the website. Today it’s closer to 80 percent.
In many ways, I have gone back to the early days of my career as a daily newspaper journalist to post news every day on both gpsworld.com and our sister Geospatial Solutions website. You can easily tap into these news streams through Twitter (which, coincidentally, is celebrating its 10th anniversary this month.)
I’m looking forward to another 10 years with GPS World, and I hope you come along for the ride.
D-COAX Inc. has introduced a reconfigurable probe station (Model W4.0 x L6.5) for design engineers and technicians. It’s used to test a chip or small circuit board for the project that cannot wait for local lab probe station availability. The probe station has a small footprint (X = 22 in, Y = 9 in, Z = 8 inch) and can be used at the desk or a lab. It is transportable at 9 pounds.
The probe station is fully manual with the following features:
4.0 inch x 6.5 inch test plate with vacuum holes
wide probe holder plates on each positioner with multiple holes for probe mounting
both positioners can slide back and forth in the X and Y directions and can be moved toward the DUT at the angle
the height positioning is accomplished via digital micrometers
each positioner can be locked independently.
Magnetic plates attach to the normal probe mounting holes to allow additional magnetic XYZ positioners with fine adjustment
probe arms are adjustable in the X, Y, Z, and theta.
The probe station is compatible with all standard wafer probes and many DC needle set-ups. See a video at the company’s website. All D-COAX products are made in the USA.
Trimble has introduced its latest smart antenna with an integrated multi-GNSS receiver for high accuracy and precise timing applications. The Acutime 360 smart antenna provides a pulse-per-second (PPS) output synchronized to UTC within 15 nanoseconds (one sigma).
The Acutime 360 is the latest in the Acutime line of products, which have been deployed in the field for more than 20 years. With a user friendly interface for communication, the GNSS smart antenna is light weight and easy to integrate with a host system. It is suitable for critical infrastructure including wireless networks and utilities.
The Acutime 360 GNSS smart antenna is built using the Trimble 360 technology platform for multi-GNSS systems, which includes support for GPS, GLONASS, BeiDou and is Galileo-ready. The Acutime 360 has tracking sensitivity of -160 dBm and an acquisition sensitivity of -148 dBm. The increased sensitivity translates into greater reliability and accuracy.
The Acutime 360 smart antenna uses a standard 12-pin connector and is footprint-compatible with previous generations of Acutime antennas. The Acutime 360 antenna is an ideal solution for precise timing and frequency synchronization for a wide range of applications including:
sync reference for wireless and small cell networks
utilities – smart grid
Supervisory Control and Data Acquisition (SCADA) systems
critical infrastructure
Designed for long-term reliability, the IP67 compliant Acutime 360 is corrosion-resistant and waterproof and has a rounded top that facilitates run-off from the elements. It weighs less than 6 ounces and offers an extremely cost-effective solution for adding GNSS reference to any application where ease of installation and long-term reliability is critical.
Once powered, the Acutime 360 automatically tracks satellites and surveys its position to within meters. It then switches to over-determined time mode and generates a PPS, outputting a time tag for each pulse. The smart antenna’s Time-Receiver Autonomous Integrity Monitor (T-RAIM) algorithm maintains PPS integrity.
The GNSS smart antenna can operate in extreme temperatures (-40°C to +85°C) and hostile RF environments typically encountered at wireless network transmitter sites. It requires less than 1 watt of power to operate and outputs the Trimble Standard Interface Protocol (TSIP) or industry-standard NMEA messages.
The Acutime 360 smart timing antenna is expected to be available in the second quarter of 2016 through Trimble’s Time and Frequency sales network.
Exploiting terrestrial signals of opportunity (SOPs) can significantly reduce the vertical dilution of precision (VDOP) of a GNSS navigation solution. Simulation and experimental results show that adding cellular SOP observables is more effective in reducing VDOP than adding GNSS space vehicle (SV) observables.
By Joshua J. Morales, Joe J. Khalife and Zaher M. Kassas
GNSS position solutions can in many cases suffer from a high vertical dilution of precision (VDOP) due to lack of space vehicle (SV) angle diversity. Signals of opportunity (SOPs) have been recently considered to enable navigation whenever GNSS signals become inaccessible or untrustworthy. Terrestrial SOPs are abundant and are available at varying geometric configurations, making them an attractive supplement to GNSS for reducing VDOP.
Common metrics used to assess the quality of the spatial geometry of GNSS SVs are the parameters of the geometric dilution of precision (GDOP); namely, horizontal dilution of precision (HDOP), time dilution of precision (TDOP), and VDOP. Several methods have been investigated for selecting the best GNSS SV configuration to improve the navigation solution by minimizing the GDOP. While the navigation solution is always improved by additional observables from GNSS SVs, the solution’s VDOP generally remains of lesser quality than the HDOP. GPS augmentation with terrestrial transmitters that transmit GPS-like signals have been shown to reduce VDOP. However, this requires installation of additional proprietary infrastructure.
This article studies VDOP reduction by exploiting terrestrial SOPs, particularly cellular code division multiple access (CDMA) signals, which have inherently low elevation angles and are free to use.
In GNSS-based navigation, the states of the SVs are readily available. For SOPs, however, even though the position states may be known a priori, the clock-error states are dynamic; hence, they must be continuously estimated. The states of SOPs can be made available through one or more receivers in the navigating receiver’s vicinity. Here, the estimates of such SOPs are exploited and the VDOP reduction is evaluated.
PROBLEM FORMULATION
Consider an environment comprising a receiver, M GNSS SVs, and N terrestrial SOPs. Each SOP will be assumed to emanate from a spatially stationary transmitter, and its state vector, xsop(n), will consist of its three-dimensional (3-D) position rsop(n) and clock bias cδtsop(n), where n=1,…,N and c is the speed of light. The receiver draws pseudorange observations from the GNSS SVs and from the SOPs. The observations are fused through an estimator whose role is to estimate the state vector of the receiver xr=[rrT, cδtr] T, where rr and cδtr are the 3D position and clock bias of the receiver, respectively. To simplify the discussion, assume that the pseudorange observation noise is independent and identically distributed across all channels with variance σ2. The estimator produces an estimate of the receiver’s state vector and associated estimation error covariance P =σ2(HTH)-1.
Without loss of generality, assume an East-North-Up (ENU) coordinate frame to be centered at . In this frame, the dilution of precision matrix G≡(HTH)-1 is completely determined by the azimuth and elevation angles from the receiver to each SV, denoted azsv(m) and elsv(m), respectively, and the receiver to each SOP, denoted azsop(n) and elsop(n), respectively, where m=1,…,M. Hence, the quality of the estimate depends on these angles and the pseudorange observation noise variance σ2. The diagonal elements of G, denoted gii, are the parameters of the dilution of precision (DOP) factors:
Therefore, the DOP values are directly related to the estimation error covariance; hence, the more favorable the azimuth and elevation angles, the lower the DOP values. If the observation noise was not independent and identically distributed, the weighted DOP factors must be used.
VDOP REDUCTION VIA SOPs
With the exception of GNSS receivers mounted on high-flying and space vehicles, all GNSS SVs are typically above the receiver, that is, the receiver-to-SV elevation angles are theoretically limited between 0°≤elsv(m)≤90°. GNSS receivers typically restrict the lowest elevation angle to some elevation mask, elsv,min, so to ignore GNSS SV signals that are heavily degraded due to the ionosphere, troposphere and multipath.
As a consequence, GNSS SV observables lack elevation angle diversity, and the VDOP of a GNSS-based navigation solution is degraded. For ground vehicles, elsv,min is typically between 5° and 20°. These elevation angle masks also apply to low-flying aircraft, such as small unmanned aerial vehicles (UAVs), whose flight altitudes are limited to 500 feet (approximately 152 meters) by the Federal Aviation Administration (FAA).
In GNSS + SOP-based navigation, the elevation angle span may effectively double, specifically –90°≤elsop(n)≤90°. For ground vehicles, useful observations can be made on terrestrial SOPs that reside at elevation angles of elsop(n)=0°. For aerial vehicles, terrestrial SOPs can reside at elevation angles as low as elsop(n)=–90°, for example, if the vehicle is flying directly above the SOP transmitter.
To illustrate the VDOP reduction by incorporating additional GNSS SV observations versus additional SOP observations, an additional observation at elnew is introduced, and the resulting VDOP(elnew) is evaluated. To this end, M SV azimuth and elevation angles were computed using GPS ephemeris files accessed from the Yucaipa, California, station from Garner GPS Archive, which are tabulated in Table 1.
Table 1. SV azimuth and elevation angle (degrees).
For each set of GPS SVs, the azimuth angle of an additional observation was chosen as a random sample from a uniform distribution between 0° and 360°, that is, aznew~U(0°,360°). The corresponding VDOP for introducing an additional measurement at a sweeping elevation angle –90°≤elnew≤90° are plotted in Figure 1 (a)–(d) for M=4,…,7, respectively.
Figure 1. A receiver has access to M GPS SVs from Table 1. Plots (a)- (d) show the VDOP for each GPS SV configuration before adding an additional measurement (red dotted line) and the resulting VDOP(elnew) for adding an additional measurement (blue curve) at an elevation angle –90°≤elnew≤90° for M=4,…,7, respectively.
The following can be concluded from these plots. First, while the VDOP is always improved by introducing an additional measurement, the improvement of adding an SOP measurement is much more significant than adding an additional GPS SV measurement. Second, for elevation angles inherent only to terrestrial SOPs, that is, –90°≤elsop(n)≤0°, the VDOP is monotonically decreasing for decreasing elevation angles.
SIMULATION RESULTS
To compare the VDOP of a GNSS-only navigation solution with a GNSS + SOP navigation solution, simulations were conducted using receivers mounted on ground and aerial vehicles.
Ground Receiver. The position of a receiver mounted on a ground vehicle was set to rr ≡(106 )•[– 2.431171,– 4.696750, 3.553778]T expressed in an Earth-Centered-Earth-Fixed (ECEF) coordinate frame. The elevation and azimuth angles of the GPS SV constellation above the receiver over a 24-hour period was computed using GPS SV ephemeris files from the Garner GPS Archive. The elevation mask was set to elsv,min≡20°. The azimuth and elevation angles of three SOPs, which were calculated from surveyed terrestrial cellular CDMA tower positions in the navigating receiver’s vicinity, were set to azsop≡[42.4°,113.4°,230.3° ]T and elsop ≡[3.53°,1.98°,0.95°]T, respectively. The resulting VDOP, HDOP, GDOP and associated number of available GPS SVs for a 24-hour period starting from midnight, Sept. 1, 2015, are plotted in Figure 2.
Figure 2. Fig. (a) represents the number of SVs with an elevation angle >20° as a function of time. Fig. (b)-(d) correspond to the resulting VDOP, HDOP, and GDOP, respectively, of the navigation solution using GPS only, GPS + 1 SOP, GPS + 2 SOPs, and GPS + 3 SOPs.
The following can be concluded from these plots. First, the resulting VDOP using GPS + N SOPs for N≥1 is always less than the resulting VDOP using GPS alone. Second, using GPS + N SOPs for N≥1 prevents large spikes in VDOP when the number of GPS SVs drops. Third, using GPS + N SOPs for N≥1 also reduces both HDOP and GDOP.
Unmanned Aerial Vehicle. The initial position of a receiver mounted on a UAV was set to rr ≡(106 )•[–2.504728, –4.65991, 3.551203]T. The receiver’s true trajectory evolved according to velocity random walk dynamics. Pseudorange observations on all available GPS SVs above an elevation mask set to elsv,min≡20° and three terrestrial SOPs were generated using a MATLAB-based simulator. The simulator used SV trajectories which were computed using GPS SV ephemeris files from Sept. 1, 2015, 10:00 to 10:03 a.m.
The positions of the SOPs were set to rsop(1)≡(106)•[– 2.504953,– 4.659550, 3.551292]T, rsop(2)≡(106)•[– 2.503655, –4.659645, 3.552050]T, and rsop(3)≡(106)•[– 2.504124,– 4.660430, 3.550646]T, which are the locations of surveyed cellular towers in the UAV’s vicinity. The UAV’s true trajectory, navigation solution from using only GPS SV pseudoranges, and navigation solution from using GPS and SOP pseudoranges are illustrated in Figure 3 (top). The corresponding 95th-percentile uncertainty ellipsoids for a sample set of navigation solutions are illustrated in Figure 3 (bottom).
Figure 3 . Simulation results for a UAV flying over downtown Los Angeles. Top: Illustration of the true trajectory (red curve), navigation solution from using pseudoranges from six GPS SVs (yellow curve), and navigation solution from using pseudoranges from six GPS SVs and three cellular CDMA SOPs (blue curve). Bottom: Illustration of uncertainty ellipsoid (yellow) of GPS only navigation solution and uncertainty ellipsoid (blue) of GPS + SOP navigation solution.
The following can be noted from these plots. First, the accuracy of the vertical component of the GPS-only navigation solution is worse than that of the GPS + SOP navigation solution. Second, the uncertainty in the vertical component of the GPS-only navigation solution is larger than that of the GPS + SOP navigation solution, which is captured by the yellow and blue uncertainty ellipsoids, respectively. Third, the accuracy of the horizontal component of the navigation solution is also improved by incorporating cellular SOP pseudorange observations alongside GPS SV pseudorange observations.
EXPERIMENTAL RESULTS
A field experiment was conducted using software-defined receivers (SDRs) to demonstrate the reduction of VDOP obtained from including SOP pseudoranges alongside GPS pseudoranges for estimating the states of a receiver. To this end, two antennas were mounted on a vehicle to acquire and track multiple GPS signals and three cellular base transceiver stations (BTSs) whose signals were modulated through CDMA. The GPS and cellular signals were simultaneously downmixed and synchronously sampled via two universal software radio peripherals (USRPs). These front-ends fed their data to the Multichannel Adaptive TRansceiver Information eXtractor (MATRIX) SDR, developed at the Autonomous Systems Perception, Intelligence and Navigation (ASPIN) Laboratory at the University of California, Riverside. The LabVIEW-based MATRIX SDR produced pseudorange observables from five GPS L1 C/A signals in view and the three cellular BTSs.
Figure 4 depicts the experimental hardware setup.
Figure 4. Experiment hardware setup.
The pseudoranges were drawn from a receiver located at rr≡(106)•[– 2.430701,– 4.697498, 3.553099]T, expressed in an ECEF frame, which was surveyed using a carrier-phase differential GPS receiver. The corresponding SOP state estimates were collaboratively estimated by receivers in the navigating receiver’s vicinity. The pseudoranges and SOP estimates were fed to a least-squares estimator, producing x^r and associated P from which the VDOP, HDOP, and GDOP were calculated and tabulated in Table 2 for M GPS SVs and N cellular CDMA SOPs. A sky plot of the GPS SVs used is shown in Figure 5.
Figure 5. Left: Sky plot of GPS SVs: 14, 21, 22, and 27 used for the four SV scenarios. Right: Sky plot of GPS SVs: 14, 18, 21, 22, and 27 used for the five SV scenarios. The elevation mask, elsv,min, was set to 20° (dashed circle).
The tower locations, receiver location and a comparison of the resulting 95th-percentile estimation uncertainty ellipsoids of for {M,N}={5,0} and {5,3} are illustrated in Figure 6.
Figure 6. Top: Cellular CDMA SOP tower locations and receiver location. Bottom: Uncertainty ellipsoid (yellow) of navigation solution from using pseudoranges from five GPS SVs and uncertainty ellipsoid (blue) of navigation solution from using pseudoranges from five GPS SVs and three cellular CDMA SOPs.
The corresponding vertical error was 1.82 meters and 0.65 meters respectively. Hence, adding three SOPs to the navigation solution that used five GPS SVs reduced the vertical error by 64.3 percent. Although this is a significant improvement over using GPS observables alone, improvements for aerial vehicles are expected to be even more significant, since they can exploit a full span of observable elevation angles as demonstrated in the simulation section.
Table 2. DOP values for M SVs + N SOPs.
CONCLUSION
This article studied the VDOP reduction of a GNSS-based navigation solution by exploiting terrestrial SOPs. It was demonstrated that the VDOP of a GNSS solution can be reduced by exploiting the inherently small elevation angles of terrestrial SOPs. Experimental results using ground vehicles equipped with SDRs demonstrated VDOP reduction of a GNSS navigation solution by exploiting a varying number of cellular CDMA SOPs. Incorporating terrestrial SOP observables alongside GNSS SV observables for VDOP reduction is particularly attractive for aerial systems, since a full span of observable elevation angles becomes available.
MANUFACTURERS
Two National Instruments universal software radio peripherals were used in the experiment. A Trimble 5700 receiver surveyed the experimental receiver location.
JOSHUA J. MORALES is pursuing a Ph.D. in electrical and computer engineering at the University of California, Riverside.
JOE J. KHALIFEH is a Ph.D. student at the University of California, Riverside.
ZAHER (ZAK) M. KASSAS is an assistant professor at the University of California, Riverside. He received a Ph.D. in electrical and computer engineering from the University of Texas at Austin. Previously, he was a research and development engineer with the LabVIEW Control Design and Dynamical Systems Simulation Group at National Instruments Corp.
This article is based on a technical paper presented at the 2016 ION ITM conference in Monterey, California.
VectorNav Technologies has introduced the VN-360 GPS-Compass heading and position sensor. The VN-360 is an OEM GPS-Compass module that provides an accurate, True North heading solution for systems integrators seeking a reliable alternative to magnetic-based sensors.
Many systems currently available on the market depend on digital magnetometers for providing heading measurements of a manned or unmanned platform. However, the majority of these platforms (such as multi-rotor UAVs, ground robots or satellite antennas) also include ferrous materials, motors, batteries or electrical components that drastically limit the ability of a magnetometer to provide an accurate or reliable heading solution. VectorNav’s VN-360 provides a miniature, cost-effective GPS-based alternative that is unaffected by these magnetic disturbances and changes to the magnetic environment.
Incorporating two onboard GNSS receivers, the VN-360 calculates the relative position between its two GNSS antennas to derive a heading solution that is an order of magnitude more accurate than a magnetic compass. It supports a variety of GNSS antennas that can be mounted on the host platform with a separation distance anywhere from a few centimeters out to several meters. This distance can be configured to provide optimal start-up time, outputting an accurate heading solution typically under two minutes.
“The VN-360 is like no other product on the market in that it provides a cost-effective solution for the difficult challenge of obtaining an accurate and reliable heading solution,” said VectorNav President John Brashear. “VectorNav’s GPS-Compass technology marks a turning point in the way we approach heading measurement and will improve the capabilities and performance of a variety of next-generation manned and unmanned systems.”
The VN-360 is ideal for applications such as antenna pointing, multi-rotor UAVs and aerostats, automated agriculture, heavy machinery, ground robots, weapons training and warfare simulation, and direct surveying among others.
The VN-360 joins VectorNav’s line of inertial sensor systems, which includes the VN-100 IMU/AHRS, VN-200 GPS/INS and VN-300 Dual Antenna GPS/INS, and will be on display at VectorNav’s booth #347 at Satellite 2016 in National Harbor, Maryland, March 7-10. For information on pricing or to schedule a meeting time during the Satellite 2016 event, contact VectorNav at the following: email: [email protected]; tel: +1-512-772-3615; fax: +1-512-772-3086.
SBG Systems has released the Apogee-M and the Apogee-U, two inertial sensors, to complete the Apogee product line.
The Apogee-M is a motion reference unit (MRU), and the Apogee-U is an inertial navigation system (INS). Both are made of titanium with a depth rating of 200 meters.
Apogee Series is an accurate INS based on robust micro-electro-mechanical systems (MEMS) technology. One year after the successful release of Apogee surface sensors (IP68 enclosure), SBG Systems completes the product line with the two inertial sensors, which have titanium subsea enclosures (200-meter depth rating).
Accuracy. Apogee integrates the latest generation of MEMS sensors to reach a high degree of precision — 0.008 degrees in roll and pitch in real-time — while delivering a robust and accurate heading from the continuous fusion of GNSS and IMU data. Made of titanium, Apogee-M and Apogee-U are designed to mount close to the sonar head for hydrographic tasks from shallow to deep water.
Heave computation. The Apogee provides a real-time heave accurate to 5 centimeters, which automatically detects the wave frequency and constantly adjusts to it. When wave frequency is erratic or in case of long period swell, the delayed heave feature can save the day by allowing survey in rough conditions. This algorithm allows a more extensive calculation, resulting in a heave accurate to 2 cm displayed in real-time with a short delay.
Connects to survey-grade GNSS receivers. Apogee sensors can be paired with any type of survey-grade GNSS receiver or with the one offered by SBG Systems. The SplitBox GNSS integrates the latest tri-frequency GNSS receiver to offer several positioning features such as RTK, Marinestar, OmniSTAR, Veripos and TerraStar corrections.
Configuration is acomplished throughout the intuitive, embedded web interface where all parameters can be quickly displayed and adjusted. The new 3D View helps the user check the mechanical installation, especially sensor and antennas position, alignments and lever arms. The user can then connect the Apogee to the main hydrographic software such as Hypack, QINSy or Teledyne PDS2000, thanks to available drivers.
The MEMS technology is renowned for being highly robust and low-maintenance, while the subsea enclosure is made in titanium. SBG SYSTEMS continuously make its systems evolve with new firmware upgrades that are available during the whole life of the product without extra cost.
GNSS module maker OriginGPS has launched the new Multi Micro Spider, which has a fully integrated and highly sensitive multi-GNSS module, with support for GPS, Glonass, BeiDou and Galileo.
The Multi Micro Spider is designed for applications that require quick movement, minimal power consumption and ultra-small form factors, such as wearables and drones.
Like its predecessor, the Multi Micro Hornet (ORG1510-MK), the Multi Micro Spider’s (ORG4033) module utilizes MediaTek’s MT3333 chip and its onboard flash memory to achieve a rapid update rate and positioning speed of up to 10 Hz.
“With the Multi Micro Spider, we’re breaking new ground in what’s possible with GNSS footprints,” said Gal Jacobi, CEO of OriginGPS. “It’s a plug-and-play solution that will enable developers to easily improve performance of products while shortening time to market. Because of its size, low power consumption and high performance, the Multi Micro Spider is the perfect GPS and GNSS solution to power the location services for a wearable out on the go to a UAV tracking action sports.”
Key features include:
Peak performance with ultra-small size — At just 5.6 mm x 5.6 mm, with a height of 2.65 mm, the Multi Micro Spider packs in a sub-one second Time To First Fix (TTFF) and sensitivity of -165 dBm for two simultaneous constellations. All of this achieved using less than 9 mW of power.
OriginGPS’ Noise Free Zone (NFZ) — The ORG4033 utilizes OriginGPS’ patented and proprietary NFZ technology for continued noise immunity and razor-sharp sensitivity even in poor signal conditions.
Onboard flash for market-leading update rate — With an onboard flash memory and an update rate of up to 10Hz, the Multi Micro Spider breaks the market’s standard update rate benchmark of 5 Hz for positioning, accurate to within 2.5 meters.
Intuitive design that facilitates shorter time to market — The Multi Micro Spider makes use of a developer-friendly design that allows for seamless migration from GPS to GNSS pin-to-pin compatibility. This both reduces overall development costs for new products and shortens their time to market.
Easy integration with OriginGPS’ miniature GNSS antenna solutions — The Multi Micro Spider can be easily integrated with the ORG12-4T-GNSS miniature patch antenna to get the best performance out of a compact form-factor.
u-blox has launched a receiver module that brings real-time kinematic accuracy to the mass market. The NEO-M8P GNSS receiver module delivers high performance down to centimeter-level accuracy.
RTK technologies have been used for some time in low-volume niche markets, such as surveying and construction. Because of high costs and complexity, this enhanced positioning technology has been inaccessible for most other uses.
Emerging high volume markets, such as unmanned vehicles, require high-precision performance that is low cost and energy efficient. Other application areas include agriculture and robotic guidance systems, such as tractors or robotic lawnmowers. The u-blox NEO-M8P answers these demands for a small-sized, highly cost-effective, and very precise RTK-based module solution.
The RTK algorithms are pre-integrated into the module. As a result, the size and weight are significantly reduced, and power consumption is five times lower than existing solutions, cutting costs and improving usability dramatically, u-blox said.
Measuring 12.2 x 16 x 2.4 millimeters, NEO-M8P is a small, high-precision GNSS RTK module based on GPS and GLONASS satellite-based navigation systems.
The module is available in two variants. The NEO-M8P-0 has rover functionality, and the NEO-M8P-2 has rover and base-station functionality. The rover with the u-blox NEO-M8P-0 receives corrections from the u-blox base receiver NEO-M8P-2 via a communication link that uses the RTCM (Radio Technical Commission for Maritime Services) protocol, enabling centimeter-level positioning accuracy.
By using the NEO-M8P module, customers can reduce their research and development efforts, because they do not have to spend significant resources and time to develop an in-house RTK solution on a separate microprocessor system.
“NEO-M8P lowers the barriers for innovative companies looking to develop equipment that needs centimeter-level accuracy in many markets and applications, such as UAVs,” said Daniel Ammann, Executive Director Positioning and Co-Founder of u-blox. “Today, most solutions are based on board-level receiver products. NEO-M8P delivers performance that is simply a level above competitive offerings in terms of size and low-power consumption, thereby providing easy integration into customers’ existing product platforms, as well as a significant saving in their cost of goods.”
u-blox NEO-M8P is available for sampling now and will be shipping in volumes in the third quarter of 2016.
Tallysman, a manufacturer of economical high-performance GNSS antennas and related products, is offering a new wideband 28-dB inline amplifier covering the full GNSS spectrum from 1 to 2 GHz.
The TW125B is a low cost, rugged, waterproof, low noise, low current/low voltage, 1 to 2 GHz band, 28dB gain in-line amplifier, specially designed to amplify all GNSS frequency signals, from GPS L5 (1164 MHz) to GLONASS G1 (1610 MHz) and beyond.
The TW125B provides for much longer cable runs from antenna to receiver, for applications such as mast-mount, large vehicle and timing systems, without degradation of system sensitivity.
Its low loading allows for both the antenna and the TW125B in-line amplifier to be powered by the GNSS receiver. The amplifier adds just 12mA of load on the circuit, well within the capabilities of most GNSS receivers on the market.
The TW125B passes DC supply to the antenna, therefore not requiring additional hardware such as bias-T, power cable and power supply.
The amplifier is available with TNC, N-Type, or SMA connectors, and is REACH and ROHS compliant.
Antenna maker Taoglas USA has opened a facility in San Diego for its North American customers.
In the midst of explosive wireless device growth in the Internet of Things (IoT) market, the company has quadrupled the original size of its local facility — now more than 16,000 square feet.
The new Taoglas IoTx Center offers a fully equipped design and test location that supports companies seeking a competitive, time-to-market advantage for machine to machine (M2M) and IoT applications.
According to Taoglas, the location offers support for customers at all stages of their product design cycle — from concept to certification readiness.
“This kind of open-door policy is rare in the antenna and wireless device testing business,” explained Dermot O’Shea, president of Taoglas USA. “We have expanded our engineering team, added more test equipment, and now have two chambers here to increase design and test capacity. As well as being able to prototype antennas and PCBs, we can test the antenna and devices in operation on site to ensure they work reliably in the real world.
“We have also now added an antenna and cable assembly operation so we can quickly produce antenna and custom RF cable orders here in San Diego,” O’Shea said. “Quite often customers require products in a few days rather than weeks and we have now facilitated that demand with this new move.”
Taoglas has dedicated the facility to support it’s North American customer base. San Diego was chosen due to the strong, experienced talent pool in the areas of antenna and hardware design.
In addition to the site’s two CTIA calibrated anechoic chambers, the campus includes a custom antenna and RF cable assembly facility, expanded development and office space as well as a well-equipped, sound-proofed customer lounge area with workspaces and other features to accommodate customers while testing and product development are in process. Taoglas will increase its San Diego staff by 50 percent this year and expects to double that in the next three years.
“Our enlarged San Diego facility reflects our growth rate last year of almost 100%,” explained O’Shea. “We’re bullish about the potential in the Internet of Things (IoT) market, which is key for us. The vendors in this space who we support not only need the off-the-shelf or custom antennas we offer, they need design services and assistance. All our services have clear explanations and fast deliverables, all available on our website. You just select your service code, or call our sales, and we will book you in for work on your device immediately. No waiting around or complicated contractual discussions.
“First time certification is also critical so wireless OEMs can avoid the hardware failures that are so common in the IoT sector. Having two anechoic testing chambers means we can work on multiple devices in real time, helping customers get successful products into the market first time and on time.”
According to International Data Corp., the IoT market will grow to $1.7 trillion by 2020, with a compound annual growth rate of 16.9 percent. “We’re currently shipping millions of antennas per month into the IoT market,” O’Shea said. “Our larger campus here will be well utilized.” Taoglas also has offices in Minneapolis, Ireland, Taiwan and Germany.
According to Rory Moore, a prominent San Diego technology company founder and investor, in addition to being CEO of Southern California startup incubator EvoNexus, “The enlarged Taoglas campus is another sign of success in the local innovation economy. San Diego already has a strong base in IoT growth and this large new Taoglas IoTx facility cements San Diego as an IoT hub in a very hot sector. I also like the fact that Taoglas has been collaborating with SDSU (San Diego State University), building useful bridges between the business and educational communities.”
By Tracy Cozzens, Managing Editor
