It All Comes Down to Data

The system designers from the Extreme Attitude Team discuss data from some of the many maneuvers conducted by the high-speed acrobatic airplane. 

Once the jet-fighter fumes dispersed, the Florida dust settled, and the engineers returned to Hexagon| NovAtel headquarters in Calgary, go time may have finished but crunch time was just getting underway. What would the data show after being run through the company’s many iterations of post-processing software? What would they learn, how would they learn it, and most importantly, how would it inform product road mapping and other developments? How could it benefit customers in a wide range of user communities?

We posed these questions to an Extreme Attitude triumvirate of Gordon Heidinger, segment manager, automotive and safety-critical systems; Sam Kiley-Kubik, geomatics engineer; and Kurt Bahan, manager, sensor fusion. Kiley-Kubik had actually ridden in one of the Aero L-39 Albatros test flights and was eager to share what he’d found in the earliest data runs through post processing.

“The first thing we did with this data,” he said, “once we got it back in the office is select one of the higher-grade IMUs, and that changes based on which of the flights we selected, since we had different equipment on different ones. Those all get run through our post-processing software, which is the commercially available Inertial Explorer that can do processing forward and backward in time. And because you’re doing this after the fact, it can get a much better trajectory out of it than the real time receivers could ever hope to.”

Running the data forward and backward through the software can help cope with GNSS outages, such as those that occur when the plane rolls over in the air and the GNSS antenna is obscured from the sky. During this outage, errors in the inertial solution will start accumulating over time, with an exponential upward growth; this is seen running the data forward. If the same procedure is conducted in reverse in post processing, starting at the back and moving to the front of the file, one again encounters the accumulating error. Taking the two trajectories and combining them, one can in effect meet in the middle of the outage and essentially average the two runs out to obtain a position error that is much lower than it would have been in real time.

“Using that forward-looking ability,” Kiley-Kubik continued, “we generate truths in position velocity and attitude for all that and then we take it back and compare it to all of the test units for each flight. So we’re mostly looking at position-velocity-attitude differences.”

Although still in the early stages of what could become months of data crunching, the team reported interesting findings but nothing particularly surprising. All of the units on all the flights (see Figures 1 and 2 for one example) performed well. Turning to a methodical maneuver-by-maneuver, Kiley-Kubik and colleagues found a few curiosities they want to look at more closely, particularly in the extreme attitude positions where the plane pitched up or down, close to 90 degrees. 

“The other thing we’re doing with this data,” he added, “is passing it through several different firmware versions [of Inertial Explorer]. We have the ability to take the recorded data and process it again, through sort of different revisions of the code, and see how the changes have affected it. The code we flew was a release from this past summer. 

“We were very curious also to test it out on sort of our main development branches and see if those changes are in fact helping. And it looks like they are.”

As to how that improvement is measured, that’s primarily done with the position, velocity and attitude error statistics. Especially as the plane rolls and turns over during its maneuvers, it’s obstructing GNSS antennas. “So you get a lot of error growth and it’s just how you best constrain that. Particularly with the way our installation is done in the aircraft, the antennas, with the exception of the SPAN Passenger mount, are fairly obstructed by the aircraft’s seats and body around them. So they don’t have the greatest view of the sky either.”

The error is constrained using tightly coupled INS and GNSS. The instruments are taking singular observations from GNSS satellites, in addition to the position as a whole, and using those through the Kalman filter updates to estimate the error in the initial solution. 

Although the team’s equipment and software afford them the ability to perform various degrees of coupling, so far they have not experimented with comparing loosely versus tightly coupled sensors. It’s in their plans, but in the offing. The SPAN set-up is closer to a deeply coupled system.

Software Revisions

“With our post-process control,” Bahan said, “we’re able to get continuous absolute error estimates for position in three dimensions, velocity in three dimensions and attitude in three dimensions. Bahan also mentioned that typically for ground vehicles the most interesting maneuvers are in 2D, with the third z-axis dimension pretty stable and uninteresting. Not the case on the L-39; the third dimension is just as dynamic as the 2D.

“We focus in on those particular areas, and then compare performance across the [software] revision it was run on and future development branches that we have and we were testing. We’ll hyper-focus on certain areas to see if there’s performance improvements. We can make further firmware changes and run it again and see if we can improve it. And that can be done basically across all the dynamics of the test flight that we have collected over the four flights.”

By hyper-focus he means zoom in on it to examine the beginning of the airplane rolling or the line-of-sight to the satellites slowly rolling out of sight. That would be one case to study closely, perform a data crop and do the error analysis.

Inertial Explorer software can overlay the satellite usage to visualize how many satellites are actually being used in the positioning algorithms at that point, and track it through the maneuver. That gives a better idea as to the expectation of the error growth and if the IMU’s performance is worse than expected or desired—or, as it turned out in some instances, better than its spec figure.

This type of data isn’t easy to obtain—customers who use such vehicles aren’t able to share information—and will be used for continual future development, Bahan said, making it important to have multiple sensors with different layers of performance. That’s why the team chose IMUs across the company’s portfolio in different price/performance grades. 

The more aviation-minded members of the Extreme Attitude Team designed the test flights (see Figures 3 and 4) to give as large a variability in dynamics and maneuvers as possible. That way, they add the collected data to their regression or continuous monitoring system, which runs on all the firmware changes that NovAtel makes.

In the process of continued product improvement, they can make a small algorithm change, run it before and after, and see the impacts and effects that change has on particular use cases or applications. This adds to their understanding of performance from an iterative level as they develop their code. Future feature development benefits as well.

Truth Talk

“What we’re sharing here is just raw trajectories: how the aircraft flew,” Bahan said. “It doesn’t really give anything away in terms of performance unless we overlaid them and one of them diverged and blew up. What we really look at is comparing latitude, longitude, height; North, East, up; velocity; and roll, pitch, azimuth. The full spectrum of positioning, which is what our customers expect.

“Different customers want better performance in the position domain. They may be less concerned about attitude or they may be less concerned about velocity. But we have requirements and specifications for all of our IMUs, that they should be performing within. Now, that is going to depend on the dynamics and the environment that you’re testing. 

The statistics on NovAtel spec sheets come from land-vehicle dynamic environments, which don’t necessarily translate to an aircraft, which lose potential updates. For example, a vehicle can stop and the positioning unit can perform a zero velocity update to help constrain error growth during a GNSS outage. That’s not possible in an aircraft. 

“So it becomes a more challenging environment,” Bahan said, “and that usually relates to some level of worst performance. What that is, is harder to say because we’ve never had this data with an IMU alongside of it at the quality level to perform a proper truth analysis. 

“So, we will be looking at all of these trajectories in individual three-axes-per-PVA situations and ensuring that our solution is meeting expectations.”

NovAtel continually evolves its SPAN firmware, with developers working every day with micro changes, trying to tweak and improve, adding new features all the time, new constellations, new signals, all of which have downstream impacts into position. The company must be capable of evaluating all those changes at an individual level, ensuring specific algorithm changes don’t cause a degradation in performance. 

“Having this data gives us an incredible value of being able to do that at an individual changeless level. Every time any developer, not just one within my team but one of the upstream teams, puts some type of change in, that would flow down through our system. On top of just the individual micro-change level, we also do bigger feature development. There’s potential there to make specific improvements to particular use cases. 

Right Down to the Real Nitty Gritty

Kiley-Kubik began putting up plots on a shared display screen and zoomed into one section of the Immelmann-Split S-dynamic weaves section of flight, keying in on the Immelmann (Figures 5 and 6). This maneuver, also known as a roll-off-the-top, was traditionally used to re-engage in combat, transitioning from one attack vector to another. The pilot climbs steeply into a backward half-roll, emerging in an inverted position flying level at a higher altitude in the opposite direction; then the pilot rotates the aircraft to fly right side up. 

“One of the things that happens there is your 3D Euler angles that we’re used to using for reporting pitch, roll and yaw sort of loses a lot of meaning. Your azimuth axis and your roll axis are essentially the same. And so if you look at it in terms of the roll and azimuth error, the two thick lines here, azimuth in cyan and roll in the deeper blue. As you go through that, the very top of that maneuver [just before second 251600], you get what shows up, at least on these plots, as an error. 

“It’s really to do with the way this attitude is being represented. When you’re in this condition, what actually matters is the difference of these two parameters rather than their raw numbers by themselves. But all of the IMUs through this area show that behavior like this where it looks like the error’s getting away.”

He then moved the cursor one hundred seconds later, just prior to the 251700 mark on the plot, where the same thing occurs on a different maneuver, the Split S (Figure 7). In the Split S, essentially the opposite of an Immelmann and used to disengage from combat, the pilot inverts the plane, dives steeply backward and downward in a half-loop, and emerges in level flight in the opposite direction.

“You felt that personally too, right?” Heidinger interjected. “So you know.”

“Yeah, well, I thought we did a Split S,” Kiley-Kubik replied. “After watching the video, I think my brain is lying to me.”

“This is why you need our equipment, right?” Heidinger said. “That’s the story right there: don’t trust your brain, trust the GNSS receivers.”

All laughed, then Kiley-Kubik continued. “The other thing would be that if you look at the flight as a whole, once we start doing these super high-rate maneuvers or once the plane starts inverting, you can see an almost immediate decrease in your GNSS position accuracy. Which is both a symptom of losing your GNSS observations (blue in Figure 8) as you go over the top and the fact that we’re losing the TerraStar corrections (green). Where we had fairly low and consistent error estimates before, now all of a sudden we’re sort of falling back to a single-point type position which has a lot more noise in it. Then once the maneuvering calms down here toward the end again, we return to consistent estimates.”

To round out the data and maneuver sampling, he turned next to the Stall maneuver (Figure 9).

“You’re pitching up through 50–60 degrees and the aircraft is losing all of its horizontal speed. It’s essentially down to 27 meters per second, that’s like highway speed: Less than 100 kilometers an hour (60 mph). That’s his sort of horizontal velocity. And then you see, if you look at the altitude plot as vertical velocity, you’re just doing like a full freefall here, coasting on almost zero G, which is just a complete hoot to do when you’re in the aircraft. That’s probably the most roller coaster type maneuver.

“If you watch the video, I’m busy looking at the instruments watching what’s happening and then the pilot tells me to look out the window, and I look off to the left side. And we’re pitching up at that 60-degree angle. And I had no idea, my body had not processed that we were into that turn.”

Kiley-Kubik isn’t sure if he lost consciousness, but he knows he came close during the Immelmann toward the end of the flight. 

Data, Specs and Applications

We came back to Earth, so to speak, talking about performance specifications. How do people analyze the quality or the appropriateness of one type of positioning solution versus another? What insight does this newly gained data bring to standard IMU specs?

Bahan took up the conversation to answer, “Every customer has a different use case with different potential requirements. Certain applications require a very accurate attitude solution. You’re doing LiDAR, photogrammetry, small angles in your attitude error are going to translate to big position errors in the solutions. Whereas other customers just want to navigate a car in a road. It’s less important. 

“Every IMU that we support has a different smattering of performance. In general, they all fall in line from a cost and overarching performance point of view. As the price increases, you get better attitude performance, better outage performance, better velocity performance, less noise and more reliability in your outages. 

“We want to understand the position errors [of each grade of IMU]. We can post process that in RTK, PPP, single point so we can get all that information continually offline. We want to know velocity error, because that’s important in this type of application. We want to know the attitude error. We had vibration sensors on the aircraft that allow us a separate type of control on high vibration potentials that might be going on in the aircraft. We can look at the individual IMU raw data and cross-compare what vibration and frequencies of motion it’s observing compared to the separate higher bandwidth sensor.

With this data, NovAtel customers, current and future, can understand the spec, the performance characteristics, and the capabilities that are enabled by SPAN and the various SPAN solutions. 

The L-39 data provides the ability to run it through incremental algorithm changes and to compare trajectories, compare specific position-velocity-attitude, down to just looking at only the roll if necessary, to ensure new algorithm changes are making the work better. 

Kiley-Kubik: “The biggest long-term benefit is having this in our library of datasets. It’s a flight or a trajectory and sort of attitude configuration we don’t see very much. It’s very useful to have that library to evaluate future changes against and to see if there’s any improvements we need to drive based on that, although I haven’t seen any particular yet.”

“I get excited,” Heidinger said, “when I know what we’ve done—especially being on the ground and observing the data. I really look forward to future customer discussions. Our confidence from a sales and business development point of view has literally been elevated. Our solutions have proven they can handle extreme conditions like this, and we know they’ll work on a multitude of other applications.” 

Not such an extreme attitude afterall.

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A Culture of Innovation

Michael Ritter isn’t afraid to take risks in the name of innovation. And flying a fighter jet with your sensors, employees and a reporter onboard certainly qualifies as risky. 

There’s a culture of innovation at Hexagon| NovAtel, so when the marketing department formulated the idea for the extreme flights, there wasn’t any hesitation. It took time and resources to make these tests happen, and so much could have gone wrong. But that risk of failure was part of the draw. 

“Trying things without knowing what the outcome is,” said Ritter, who’s president of Hexagon’s Autonomy & Positioning division, “that’s a teachable moment for engineers. If you know what the outcome is, that’s not really innovating.”

The data collected will not only be used to develop better products for customers, it will help employees truly understand their needs. 

“Everybody likes to innovate,” Ritter said. “But you can innovate better if you actually know the real customer experience.” 

The two employees who rode in the L-39’s jump seat now have a better understanding of customer requirements and what their equipment goes through. They know what 4-g and 5-g thresholds really mean because they’ve now experienced them. 

It’s no longer something they’ve only read about in a textbook or simulated in a lab. And there’s real value in that. 

Then there’s the verification piece. It’s critical to test sensors in high dynamic environments—and what’s more high dynamic than a high-performance fighter jet? 

“It validates our simulation models,” Ritter said, “which is really important because it means we can test a lot of different operational modalities on new products and in simulation.” 

This isn’t the first time Hexagon| NovAtel has gone to extremes for product development, and it won’t be the last. These types of experiments create an intersection of innovation and motivation that drives team members to excel, and to talk about the unique opportunities they have at work to family and friends. 

“It’s part of recruitment,” Ritter said. “People reading this article will say ‘wow, they do that?’” 

Yes, they do that.

Testing the Limits: Plotting a Course into the Wild Blue Yonder

PART 1: Planning Phase

To determine the limits their equipment could perform to, Hexagon | NovAtel engineers developed a plan to put the company’s sensors to the ultimate test: fly them aboard a Aero L-39 Albatros.

When Hexagon | NovAtel product design engineers set out to architect the kit that would endure extremes of high-dynamic operations on board the Aero L-39 Albatros, they began with a high-end concept. 

“We know we’re always looking for extreme tests and crazy corner cases, for our SPAN products, particularly,” explained Gordon Heidinger, segment manager, automotive and safety-critical systems. He referred to the company’s well-known integration of GNSS and inertial technologies, a deep coupling recognized for continuous 3D position, velocity and attitude. 

“And our other products, too,” he added. “Any of our positioning solutions for that matter. These extreme tests are always exciting and fun to do.”

“The best of our best [SPAN systems] is probably going to perform really well. I don’t expect any issues with the top-end stuff. But how good is the other stuff? And is it good enough for these dynamic conditions? If we can survive a fighter jet, I can sure as heck put it on a car or some UAV that’s delivering pizzas. 

“We’re looking at high Gs, we’re looking at inverted flight,” Heidinger said in Calgary, when the testing, which took place last December in Florida, was still in its planning phase. “This is really going to highlight the sensor fusion elements of our SPAN solutions.” 

The architecture of the equipment under test brought together high-level, mid-level and low-level inertial measurement unit (IMU) solutions side-by-side in one bolted-together piece of equipment. An important control aspect of the tests was data capturing a radio frequency (RF) recording of everything going on.

“That’s for development of future products that I can’t talk about yet,” Heidinger said. 

Three IMUs, High-Dynamics Testing 

Chosen for the side-by-side testing were a well-known navigation grade IMU at the high end of the range, another widely used IMU in the mid range of accuracy, performance and cost, and then on the lower end, a popular MEMS IMU. 

The tests weren’t developed to compare performance among the three IMUs, even though they performed in parallel, side-by-side. It was about taking the equipment to the limit, taking it past its limits and then being able to look back and say, “that’s where it stopped performing at the level I need it to perform.” 

Ultimately, the goal was to answer the customer question: What product is good enough for my application?

As drones and other technologies become more dynamic, it’s important to know how good good actually is, and how far sensors can be pushed for applications with high dynamics. 

“It also introduces more people on our teams to some of the experiences closer to what a customer would experience,” added Stephen Dwyer, systems engineer, Hexagon | NovAtel, “as compared to living in the relative luxury of a lab type test setup. Those situations where you have every instrument at your disposal, all the bandwidth in the world to collect data that you need, that’s a luxury that a customer doesn’t necessarily get, or need, frankly. And so being able to empathize with a customer when they’re trying to do a complex setup, I think that’s pretty important for driving easy-to-use products in the future.”

One of the challenges NovAtel faces is being able to test outside of typical land-vehicle dynamics situations. “We don’t get access to those high dynamics that you see in a fighter jet,” Heidinger said. “So, the high speeds in hundreds of miles per hour, that may not coincide with what our customers are using them for in small UAVs, this provides us with at least a similar dynamics environment.”

While NovAtel has a lot of equipment riding aboard many aerial applications like this, the company’s customers, many from the defense branch, cannot share the classified performance data. “So here’s an opportunity we made for ourselves to be able to access and use that data freely, because we paid for it,” Heidinger added. 

“Another thing about being able to control the data collection,” Dwyer said, “as opposed to getting data from customers, is we get to more tightly control some of our data that we’re collecting, the rate of that data, and some additional debug data that we might not necessarily get from a customer application. And it’s going to be very interesting to see some of that higher fidelity information that we get back from the test, compared to what we normally see.”

The L-39 can customarily pull 4.5 to five Gs of gravitational force during its most demanding maneuvers. That kind of stress reveals what measuring instruments are capable of. NovAtel has done previous comprehensive testing that has been necessarily restricted to the lower G area. Getting double or triple that G loading will definitely be informative.

“If what we predict is going to be met in terms of performance at these key levels, then it definitely gives us much more confidence when we’re moving into even those higher performance specifications or higher dynamic range conditions,” Dwyer said. 

Test System Design

The fighter jet was booked for three 60-minute flights over two days of testing. All three IMUs simultaneously experienced the same flight, three times over. One of the complicating factors was the limited space inside the cabin of the and not being able to modify the aircraft by bolting equipment to its chassis or fuselage. The experiment designers had to fashion a human-resembling apparatus that could be securely strapped into a passenger seat. This presented some cushioning issues with the seat, and additional movement between the seat and the fuselage.

However, all of the IMUs and other sensors were rigidly attached to each other in the seat-form apparatus, so it provided a good platform for comparison between units. 

What the engineers were most interested in was the positioning, velocity and attitude performance under the high G loading, and under the potential partial or full GNSS outages that would occur as the plane’s two GNSS antennas were obscured from the sky with inverted flight at high speeds. 

They were also interested in the vibration, temperature and bias performance of the IMUs under these conditions, even though they weren’t extreme environmentally for those parameters. The vibration in particular would not be that extreme in the cockpit; it would be relatively smooth compared to running on a UAV, for example, one of many other applications on which the SPAN units perform. 

“We also want to make sure we have the RF recorder there,” Dwyer said. “So, we’re going to be able to reproduce some of our data collection offline, which we can use to simulate different GNSS operating parameters, which we’re pretty excited to do.” Indeed, NovAtel engineers back at headquarters in Calgary, Canada, had extensive plans for post-collection processing and simulation using the data. 

“There’s a lot of people’s post processing capabilities that we’re going to get out of this dataset as well, right?” Heidinger assented. “Running with different signals, different signal profiles, different channel configurations, things like that.”

In terms of using external corrections in real time, that was was not the focus of this experiment. But NovAtel engineers plan to do at least some post processing with RTK to compare it with their single-point solution, collecting PPP data as well. That will be post processed as needed with the live data.

Crunching the datasets was an intensive, time-consuming process, with various teams interested in seeing the data for different purposes. 

Experimental Challenges

The biggest challenge, Dwyer said, is the fact there’s no feedback to the tester or the user when the system is being run. That requires a solid configuration ahead of time. “And even though it’s relatively compact,” he said, “there’s still a lot of both hardware and software pieces at work here. We’re testing a few different versions of the firmware, depending on what IMU we’re using, things like that. With that many moving pieces, or that many fixed pieces, I guess, there’s a chance something’s going to fail, whether it’s an antenna connector or a power connector or something like that.” 

The engineers were all on their toes and everything was checked and rechecked before the L-39 taxied out of the hangar to the runway.

“We’re trying to mitigate all risks,” Heidinger said before the flights, “and I can’t guarantee there’ll be no failures; we’ll view them only as setbacks. We’ll work through those setbacks until we succeed, even flying again, or returning to Florida if we need to.” 

Fortunately, and due to the extreme care with which the experiments were designed and conducted, no mishap occurred and there was no need for fallback measures.

Valuable Insights

It can be difficult to know if the entire specific use case for the system is working well with all the different features and sub features, Dwyer said, including dual-antenna GNSS position and heading, and different inertial measurement units mounted in a nonstandard orientation. There’s also managing PPP correction stream and understanding how that is performing in specific dynamics. The team was able to put all these features together during these flights, which isn’t something they get to do in their regular verification and validation testing. 

“That’s true from a simple product management point of view as well, Heidinger added. “We’re going to have a flavor of antennas on there. Some are more automotive, let’s say, and other ones are not, they are more true R&D systems. There’s a mix of systems here, a different range of IMUs so we can really characterize our full product line up.” 

Not the Last Time

As excited as they were about the imminent airborne reckoning aboard the L-39, active minds at NovAtel were already planning and discussing the next applications to come under scrutiny. 

NovAtel engineers always talk about the need for this kind of adventurous testing, this extending the boundaries—into the wide blue yonder, literally—when the discussion turns to simulators and the extensive data runs in that realm. Simulation is absolutely necessary, they readily acknowledge. So is the live testing to go hand-in-hand; one verifies the other, it doesn’t replace the other.

There is an absolute need to verify the models in real-world conditions, and to push them aggressively to discover where their limits may be. To be able to say at the conclusion, yes, we did perform as expected, that’s the ultimate delivery to the customer.

“My hope is that we meet our public performance specs as closely as we can measure them in this situation,” Dwyer concluded. “Obviously, it’s a little tough to measure when you don’t have a real truth system in place here. But with relative comparisons and some offline processing, we’re hoping to hit what our published performance specs are, even though we’re operating far, far outside of the intended range.”

“I’d love to see some of the lower grade IMUs perform beyond expectations,” Heidinger said. “Itwould be great to find out how that cost-effective equipment works and, you know, be like, Wow! This actually did really well on an inverted flight, for example, or a high G and it performed quite well, surprisingly well. We’ll see how that plays out.”

Continue reading (Part Two)…

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The post PNT Fulfills Autonomy Promise for Military appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

The Army intends to develop this payload to support the concept of a rapidly deployable smallsat constellation to provide more effective sensor-to-soldier data transmission when in the field. The development of this new payload is based on Iridium Burst technology, a service that can transmit data to millions of enabled devices at a time from space.

“This program can help add to warfighter readiness to conduct a full range of military operations at a tactical level,” said Scott Scheimreif, executive vice president, government programs, Iridium. “This includes the ability to enhance effectiveness of military units, weapons and equipment during combat against near-peer adversaries.”

The research and development project was enabled through an “Other Transaction Agreement” (OTA) in support of the Army and was entered into between Advanced Technology International (ATI) and Iridium under the authority of the Aviation and Missile Technology Consortium (AMTC). The OTA was developed through the authority of the Department of Defense to carry out these types of prototype projects and to further streamline the process for adopting new technology solutions from various industries.

Image courtesy Iridium.

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Position, Navigation, and Timing Technologies in the 21st Century: Integrated Satellite Navigation, Sensor Systems, and Civil Applications, Volumes 1 and 2 has appeared from John Wiley & Sons (Wiley-IEEE Press). Its 64 chapters in 2,000 pages neatly fall into 6 divisions:

• Satellite Navigation Systems
• SatNav Technologies
• SatNav for Engineering and Scientific Applications
• Position, Navigation, and Timing Using Radio Signals-of-Opportunity
• PNT Using Non-Radio Signals-of-Opportunity
• PNT for Consumer and Commercial Applications

The four lead editors are Y. Jade Morton, University of Colorado at Boulder and past president of the Institute of Navigation; Frank van Diggelen, Google and current president of ION; James J. Spilker, formerly of Stanford; and Bradford W. Parkinson, Stanford, chief architect for GPS and the first Director of the GPS Joint Program Office. Assistant editors are Sherman Lo and Grace Gao, both of Stanford.

The post A Book for our 21st Century Times appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

And who isn’t a smartphone user?

L5 signals are more accurate, more reliable, and are currently available in sufficient numbers, between 16 GPS satellites plus Galileo and BeiDou, to support all user segments.

L5 has several advantages over L1: signal structure, wide bandwidth, pilot codes, other GNSS signals with a common structure, stronger transmission, lower bit error rate and cross correlation, and a cleaner band.

“The use of L5 signals provides the capability of delivering 10x higher precision than a legacy L1 GNSS receiver in an open environment, as well as very noticeable benefits in multipath environments,” said Charlie Abraham, Broadcom Senior Director of Engineering for the Wireless Communications and Connectivity Division.

“Broadcom’s 2nd generation dual-frequency GNSS BCM47765 chip utilizes every available L5 signal in space, which totals over 80 signals, including the 30 new BeiDou3 B2a signals. When BCM47765 is combined with the 3D Building Model correction service from Google, the solution provides pedestrian users with sidewalk-level accuracy in urban canyons.”

That’s the magic. As cogently explained in our cover story, L5 and 3D mapping-aided GNSS go together “like bread and butter.” We leave it to Google, as we leave so much these days, to explain this further, on page 42.

“Google’s 3D mapping aided corrections are a major advancement in personal location accuracy for smartphone users when walking in urban environments,” said DeMarco Chou of MediaTek. “Our Dimensity 5G family enables 3D mapping aided corrections in addition to its highly accurate dual-band GNSS and dead reckoning performance to give the most accurate global positioning ever for 5G smartphone users.”

A second technical feature in this issue, “Catching a Ride: Improvements to Position Accuracy for eMobility Applications,” demonstrates why Lyft intends to build L5 capability into the rental scooters and e-bikes on which we can soon flutter around downtowns. So green, so green.

Chip manufacturers and telecomm companies are well out in front of the trends on this. They have to be.

“Qualcomm Technologies is leading the charge to improve consumer experiences with its newest Qualcomm Location Suite technology featuring support for dual L1/L5 frequencies, sensor-assisted positioning towards lane level and sidewalk accurate navigation—all of which we make available in our flagship portfolio of Snapdragon Mobile Platforms,” said Francesco Grilli, vice president of product management at Qualcomm Technologies, Inc.

To be sure, modern smartphones and mobile devices use a lot more than GNSS to achieve lane-level vehicular or sidewalk pedestrian accuracy. They employ network-based location and assistance, sensor assistance including dead-reckoning, and correction services that bring precision similar to that of RTK, which is not practical to implement in phones.

Finally, at a company devoted singlemindedly to that select new band, Greg Turetzky, VP Product at OneNav, volunteers “We are excited to see the performance improvement from our PureL5 GNSS System, which uses the entire 50MHz bandwidth of all the signals in the L5 band to produce rich measurement data. When combined with Google’s 3D building models, this will provide near meter-level accuracy in the urban canyons for mobile phones users and improve user experience in multiple applications.”

Although the L1 signal structure could be characterized as “outdated,” vulnerable to cross correlation, jamming and spoofing, it won’t go away anytime soon. Its installed base is too large, its use paths so well known and well worn. On the other hand, L1 could come to resemble, one of these days, black and white TV. Still around, still employed by some in some situations, but not, as they say, the leading brand.

The post The Time and the Place: The Power and the Magic of L5 appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

Position, Navigation, and Timing Technologies in the 21st Century: Integrated Satellite Navigation, Sensor Systems, and Civil Applications, Set, Volumes 1 and 2 has appeared from John Wiley & Sons, alternately Wiley-IEEE Press. Altogether it encompasses, as mentioned, 64 chapters over 1970 pages, plus glossary, neatly compartmented into 6 divisions:

• Satellite Navigation Systems
• Satellite Navigation Technologies
• Satellite Navigation for Engineering and Scientific Applications (volume 1 wraps up here)

• Position, Navigation and Timing Using Radio Signals-of-Opportunity
• Position, Navigation and Timing Using Non-Radio Signals-of-Opportunity
• Position, Navigation and Timing for Consumer and Commercial Applications

The four primary editors are Y. Jade Morton, University of Colorado at Boulder and current president of the Institute of Navigation; Frank van Diggelen, Google and executive Vice President of ION; James J. Spilker, formerly of Stanford; and Bradford W. Parkinson, Stanford, chief architect for GPS and the first Director of the GPS Joint Program Office.

Assistant editors are Sherman Lo and Grace Gao, both of Stanford.

The book was the brainchild of James Spilker, according to his co-editors. “He remained a fervent supporter until his passing in October 2019. A pioneer of GPS civil signal structure and receiver technologies, Dr. Spilker was truly the inspiration behind this effort.”

In recounting the early history of GPS, Brad Parkinson recalled the most important early studies aimed at selecting the best passive ranging technique for the navigation signal. Experts including Dr. Fran Natali, Dr. Jim Spilker and Dr. Charles Cahn concluded that the best technique was a variation of a new (in the late 1960s) communications modulation known as code division multiple access (CDMA). Cahn advocated a C/A code length of 2047 chips, while Spilker wanted 511. Parkinson split the difference, yielding the code length of 1023 that the world enjoys today.

A lengthier article on this stunning assembly of erudition will appear in the May/June issue of Inside GNSS, with personal perspectives from some of the editors.

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Characterizing GNSS Interference from Low-Earth Orbit. The results of a two-year study of terrestrial GNSS interference as observed through a software-defined GNSS receiver operating since February 2017 on the International Space Station (ISS).

Low-cost GNSS/INS Integration Conquers Harsh Environments. A software-driven navigation engine makes consistent, reliable navigation possible in tunnels, garages and urban canyons.

GNSS Compare: Real-time Algorithms with Raw GNSS Measurement on Android Smartphones. An Android mobile application, GNSS Compare can provide a real-time position using Galileo and GPS dual frequencies. It directly logs data from the real-time algorithms, and the retrieved files are used for analysis.

Accuracy for the Masses. A new methodology targets sub-meter GNSS accuracies in the consumer realm for applications such as augmented reality and visually impaired navigation. Recent Android RTK smartphone services in a real-time environment achieve accuracies below 50 cm. Can these be matched with PPP?

MIMO-GNSS Signal Processing for Precise Indoor Timing. Future telecom, finance and energy sector applications may require time synchronization of tens or hundreds of nanoseconds. A joint time and composite MIMO channel estimation method for indoor receivers can meet these stringent requirements.

Galileo’s High Accuracy Service: Field Experimentation of Data Dissemination Schemes. Galileo will provide a High Accuracy Service (HAS) with positioning performance in the 20-cm range, disseminating Precise Point Positioning (PPP) corrections through the Galileo E6-B signal. Test results of a data encoding and dissemination scheme in different user environments demonstrate a reception time of the corrections in a few seconds in good channel conditions, and less than half a minute with severe channel impairments.

Way, Way Out in Front – Navigation Technology Satellite-3: The Vanguard for Space-Based PNT. This advanced geosynchronous satellite from the Air Force Research Laboratory will mature next-generation technologies across space, ground control, and user equipment segments. NTS-3 will experiment with multiple integrated technologies. {Image shown above, courtesy AFRL.]

Nobody’s Fool: Spoofing Detection in a High-Precision Receiver. An on-board spoofing detection unit collects metrics from the GNSS signal processing chain and provides a real-time indication if the receiver is under spoofing attack. Test results from several spoofing scenarios are based on GNSS hardware simulations, repeaters and software-defined radios.

Under Attack – Receiver Response to Spoofing: Robustness vs. Resilience. Laboratory tests explore how commercially available receivers respond to meaconing and spoofing, with the goal of developing useful test methodologies and metrics to assess receiver robustness and resilience to real-world spoofing threats.

A Pure L5 Mobile Receiver. A new GNSS receiver for mobile consumer products uses only the modernized, wideband signals at L5, with an acquisition engine to acquire the signals directly and a navigation engine employing artificial intelligence techniques to fully exploit all the signals in L5’s 50MHz-wide band.

TRANSIT on Steroids: Doppler-Based GNSS Meets Large LEO Constellations. The advent of large LEO constellations is a game-changer for navigation. A key feature of these constellations is their potential to allow simultaneous measurement of Doppler shifts from a large number of satellites.

Across the Lunar Landscape: Towards a Dedicated Lunar PNT System. The second of a two-part article explains how an initial system using existing Earth-GNSS constellations may be augmented with dedicated lunar orbiting satellites as well as lunar beacon ranging sources. A gradual deployment leads to a full autonomous lunar navigation system.

The post Top Twelve GNSS Technology Stories of 2020 appeared first on Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design.

The Federal Aviation Administration has released its final Remote Identification (RID) Rule for unmanned aircraft (UA). While GPS/GNSS has been used to advantage aboard many UAVs, this means that a satnav receiver will be mandated aboard all UAVs governed by the Rule that wish to fly in U.S. airspace. Thus a promising potential market opens up into a virtually “guaranteed” — and very significant — market for the GNSS industry.

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We see several dawns cresting the horizon at this moment. If I may interrupt your morning reverie over coffee or tea, gazing at the solar dawn in your part of the world, let’s view together the various GNSS dawns a-coming.

A NEW GPS. The fourth GPS III satellite just launched in early November. While obviously not the first of its generation to rise, the number four holds magic status in satnav credo, being the number of satellites necessary for an accurate position fix. Now, these first four may never be simultaneously visible, thus an exclusively III fix may have to wait for more followers to rise, but still. The number. Magic four.

While we’re counting our new dawns, recycling enlightenment has come to the GPS program. The first-stage SpaceX Falcon 9 boosters from the last two GPS III launches settled gently back to Earth after fulfilling their missions and will return to the Cape Canaveral pad for a second life in 2021. This will be the way of things going forward; further, the multi-million dollar boosters with their nine engines can be recovered again that second time, for additional re-use.

A NEW GLONASS. Similarly, the GLONASS K satellite that began orbiting on October 25 is not the first of Russia’s new generation, but it is the first to rise in several years, five years in fact. Next year, a newer new generation, the K2, is scheduled to launch, and once that constellation is full, it will bring a guaranteed accuracy under 30 centimeters, according to the system’s general designer.

Rising higher in the rosy-fingered sky of the future, an even newer segment of GLONASS will come into existence in 2020. A high-orbit set, with its debut launch schediogh-orbit GLONASS will increase accuracy in the Eastern Hemisphere by 25%. The effort is aimed at improving navigation in urban centers by providing more satellites above a 25-degree masking angle.

A NEW SYSTEM OF SYSTEMS. Galileo’s Full Operational Capability was at one time expected to be declared in 2020, but that new day has yet to arrive. With 21 satellites, the system is oh so close; very soon. BeiDou reached that status by mid-year. We do effectively have an interoperable system of GNSSs; on some recent morning we passed from the rosy fingers into a Golden Age.

A NEW GNSS. And yet, and yet. Just as mid-Earth orbit systems attain their maturity, here come upstarts. Low-Earth orbit megaconstellations may be adapted or even designed from the board to provide a satellite-based PNT service of as yet indeterminate kind, but with many possibilities.

A LUNAR NAVIGATION SERVICE. Authors from the European Space Agency explain how an initial system on our very own friendly orbiting planet, using existing Earth-GNSS constellations, may be augmented with dedicated lunar orbiting satellites and lunar beacon ranging sources. Gradual deployment could lead to a full autonomous lunar navigation system.

DAWN TREADER FOR THE STARS. A few months ago, this column recounted how GNSS signals, now in use by spacecraft flying at 150,000 kilometers altitude, foretell a use of this technology to “enable untold space missions that will extend humanity’s reach for the stars.” (James J. Miller and several ICG co-authors, writing for Inside GNSS in 2019). 

JUST FOR TODAY. People all over the world feel it’s a new dawn, it’s a new day. That’s fully as it should be. Hope springs eternal, and sometimes hope, and faith, and hard work, very hard work by many people joining shoulders and collaborating together, can bring forth a new dawn. Savor it, put its glow to good use, push out the frontiers of knowledge and fulfillment.

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