Jan Van Hees, Septentrio’s Business Development Manager, and R&D Director Bruno Bougard

Click here for the truncated version of this interview that appeared in the February 2016 print issue of xyHt. 

Septentrio was started as a spin-off of IMEC and attracts talent from KULeuven University as well as from around the world. What is the current mix of scientific, technical, and commercial backgrounds of your staff?

JVH: We are about 100 people in total, including the groups in Torrance and Hong Kong. The main body of the company is in Belgium. Our office in Torrance is largely, but not exclusively, composed by what used to be Altus Positioning Systems and we started an office in Hong Kong at the beginning of 2015. Roughly 50 percent of the people are in engineering and almost everybody in engineering has a college degree, with a number of PhDs and at that level. So, pretty high. As you can imagine, for people designing GPS receivers, that’s pretty heavy stuff. The other 50 percent is divided between sales, production, and general services, like HR, finance, and so on. Production is largely logistic; we do not do board stuffing ourselves, so we have subcontractors for boards and all we do here is some final assembly and configuration, test, maintenance type of activities. For that reason, the production part, if you want, is a rather small part of the company. The interesting thing to know is that among those 100 people there are about 20 or so different nationalities, so it gives you a good impression of how global our company is, even though it is only a team of 100.

We are a spin-off of IMEC but we are not a part of IMEC. We have a good working relationship with IMEC, of course, being in a cluster of a lot of technology companies around it. Structurally, IMEC is one of a number of Septentrio shareholders, due to our history, but we are a completely independent company. All IPR that was developed when we were still starting from IMEC was transferred into Septentrio and is 100 percent owned by Septentrio. IMEC is a very important technological resource that we are, of course, working with and drawing resources from and stuff like that, but that is all it is. Historically, the work that resulted in Septentrio started at IMEC in the 90s as part of research work for the European Space Agency. It is that work that led a group to develop a high-quality, high-precision GPS and Glonass technology. IMEC is a long-term fundamental research company, so the technology developed for the European Space Agency and for potential use in space, originally was much more applicable than the sort of long-term research goal that IMEC typically has, which is why IMEC was spun out into a commercial company to commercialize, at the beginning of 2000.

What is special about your boards?

BB: If you look at what we have done in recent years, you can see that we are differentiating significantly with the lowest power consumption for our RTK and GNSS modules. So, you might have noticed that the AsteRx-m, which is a small form factor board, has a power consumption of 500mW, while the competition is well above 1W. This is clearly a differentiator. This is something very important for application in survey and GIS, because it directly translates into longer battery life. This is increasingly important in such applications as robotics, UAS, and also in scientific applications. You might have noticed that we announced this week the PolaRx5, which is a receiver that we have developed in cooperation with UNAVCO. We won the UNAVCO tender notably on the fact that we had a receiver with a consumption of less than 2W for a fully featured system.

Our second differentiator is all-signal capabilities. When we started Septentrio in 1999, we already had a multi-constellation technology. Our first ASIC, the AGGA was already a GPS-Glonass receiver. In the meanwhile, we have been for almost 13 years now part of the Galileo program. In the last ten years, we have even led the test user segment for the Galileo program, for both IOV and FOC phase. We are developing the receivers that are used to test the satellites and also to equip the tracking stations. We have acquired very significant experience handling all of the Galileo signals, including the PRS signals. You might also have noticed the PolaRx4TR, basically a receiver for time transfer application. That receiver is also at the heart of the Galileo timing system, making sure of the alignment of Galileo and GPS time for example. We have also been the first to track the Beidou signal in real time, after the code has been cracked by Stanford University students. We are constantly looking at new signals with a pioneer spirit, such as QZSS and IRNSS. So, for us, Multi-constellation is a musthave. All of our new products, like AsteRx4 and PolaRx5, are multi-constellation, all-signals-in-view receivers. They are capable of using all signals to compute the most accurate and reliable position, This is with or without augmentation. We use all the signals that are in the sky, whatever the constellation, whatever the band.

The third point for our boards is that they are optimized at hardware and software level to operate in the most difficult environments. The first element is the resilience to multipath, which is definitely a key feature for precision GNSS. One of the Septentrio’s initial asset in 1999 was to have a patented a posteriori multipath estimation (APME) technology, which is the only multipath mitigation method which is bias-free, so it doesn’t change the observations themselves. This bias-free character is perhaps a bit technical but it is fundamental when you deploy the receiver for a reference network, a network that will be used to compute corrections for instance for Precise Point Positioning (PPP). The fact that we are not altering the observable is also highly valued by the scientific community, who really want to see the observables as they are, without the post-processing.

Beyond multipath, we are clearly differentiating in our ability to treat interference. This is something that we have learned in our long experience in the offshore sector, in offshore construction and dredging applications. Our receivers there were mounted in quite interference-rich environments and we really learned how to mitigate interference as well in-band and out-of-band interference. Our chipsets have specific capabilities deep in the hardware to mitigate as well the out-of-band interference, meaning that we have very strong filtering in our front-end chips, as in-band interference, meaning that we have a very high dynamic range and that we have specific digital signal processing that can cancel interference, even wide-band interference like those of chirp jammers. This technology is built in the chipset that goes in all the product we are shipping, like the AsteRx4 and the PolaRx5.

This is combined with a strong monitoring capability. The AsteRx4 and PolaRx5 have a built-in spectrum analyzer, so that using our Web interface, the user can really monitor and see whether there is an interference. We are also developing some cognitive methods to detect and suppress interference without the user having to interact. We are doing that because the user is less and less GNSS-savvy. They just want a positioning system that works. They don’t want to know how it works. They don’t know what a spectrum is, so we are developing methods that handle interference on their own, without any user interaction.

Finally, for the boards, we have been pioneering, since the PolaRx2 already, multi-antenna GNSS receivers, offering attitude determination capabilities. If you look at the AsteRx4 today, it is a dual-antenna, quad-constellation, twice all-in-view receiver — so it gets all the satellites, all the signals on both antennas, which is actually unique — and this is done in the footprint and the power consumption of a typical single-antenna receiver, so it is a really unique product.

What is special about your algorithms?

BB: For the algorithm side, what differentiates us is our ability to provide scalable accuracy, with the best availability and the best reliability. What we mean by reliability is the ability to generate a trustable error indicator and not outputting misleading information, so not outputting a position with an error that is higher than the error indicator that we are giving. We have been investing a lot in our software to be able to increase the reliability, for both code-based and phase-based positioning. We have state-of-the-art solutions from meter-base to centimeter-base, but it is mainly centimeter and decimeter level applications, with technologies like RTK, PPP, that we are looking at as our core business.

Resonating with the multi-constellation capability of the hardware, we have also developed a very deep understanding of the system biases, in particular for the Glonass system, which suffers from inter-frequency bias issues. This knowledge allows us to benefit from all constellations in the same way. So, we are using, for positioning, Glonass constellation, Galileo constellation, and Beidou constellation in the same way that we are using the GPS constellation. We really get the best of all the satellites, of all signals in space. This allows us to increase enormously the redundancy and increase both the availability and the reliability accordingly.

Another strong asset in our algorithms suite is our integrity monitoring algorithms. We have developed receiver-autonomous integrity monitoring (RAIM) algorithms not only for code-based positioning, like is typical RAIM, but also for phase-based positioning and these algorithms allow us to greatly increase the reliability by detecting outlier measurements and excluding them from the solution. So, those are basically the strong points of our algorithms and enable us to have one of the best RTK engines with the highest performance and reliability under foliage and next to building. We have also developed with inertial partners a mobile mapping solution that has the highest RTK availability in downtown areas and urban canyons.

Which market segments naturally gravitate toward your products and which markets do you target for growth?

JVH: Prior to the partnership with Altus, which was a growing relationship, Septentrio was very strong in marine, heavy construction, and mining types of activities, in an OEM environment. When we were spun out of IMEC, which is a microelectronics company, the original idea was that we would be a company that made chips for high-precision GPS receivers. However, as you can imagine, that was a little complicated, because of the close tie of board design and algorithm design. So, we fairly quickly decided to do board and algorithms and tried to apply it in high precision industrial markets.

We found a way and are quite active in the heavy construction side of things and the marine parts. As often is the case, this is partly the consequence of a few early successes that you then continue developing your know how, your market understanding, and one develops the other, which then develops the original one again. So, we had some early successes with machine control. We made some choices in technology as a consequence of that, which reinforced our position in machine control.

The same is true in marine. Some of the requirements of what we use in marine construction are very similar to some of the heavy construction requirements. For instance, we were one of the very early companies to use dual-antennas on our machines. Then, Belgium and Holland are actually hub spokes for the world’s leading marine construction and dredging companies. In fact, the four biggest dredging companies in the world have their headquarters in Belgium and Holland. So, that is sort of a natural way for us to get into that side of activities.

Other than that, we have quite a strong foothold in the scientific sector. A number of people who came out of the science world joined our team a the very beginning of our existence. That gave us an insight into what the scientists wanted from a GPS receiver and it also gave us links to that community. From the beginning, for instance, we’ve had a unique, ultra-precise time transfer receiver, which is actually the receiver that is used to synchronize the world’s time clocks — for instance, between the BIPM in Paris, the international standard of time, and the many capitals in the world that hold their national time standards. That is one example of a very specific and unique receiver that we have been supplying in the markets since the very beginning of our company. We are the number one, for instance in scintillation monitoring, which is another example of a very specific scientific receiver.

We’ve been involved in the Galileo program from the early 2000s. We are supplying also part of the timing solution for the Galileo ground network. We have been developing the test receivers for Galileo and the first to track live Galileo signals from space, but also creating the receivers that are used for testing the satellites. We’ve been the first, actually, to test, with a GNSS receiver, the Beidou signal, based on some work that was done at Stanford and almost concurrently with work that was done at Stanford to try to crack the code, if you want. There was an article about that in Inside GNSS or GPS World, several years ago. So, we’ve been pretty strong in that kind of activities really from the beginning and people gravitate to us on that and the recent INAVCO contract award is also part of that history.

What has been your company’s growth curve?

JVH: Since the beginning of the company, we’ve been growing. You know as well as anybody that there was a little glitch in the economy around 2008-2009. … Unfortunately, that was exactly the moment when we were starting production in the United States. So, we’ve had a somewhat more difficult time to get our foot on the ground in the United States, due to the economic impact. We see that picking up quite nicely.

On the other hand, as you can imagine, we’ve been quite active in off-shore marine construction, so in oil & gas; gas in particular is a buoyant market at the moment. So, the growth curve is a little flatter now than it used to be prior to 2008. On the other hand, we do have a number of different segments, as you can imagine. Marine, but also on-shore construction. We are present in all continents, including Antarctica, although that is not a large number, so there is always some place where things are going well. All in all, it has been a pretty exciting ride so far.

What did Altus Positioning Systems bring to the company?

JVH: We started working with Altus around 2005-2006. Prior to that we were mostly concentrated on machine control markets. When Altus was starting, they were looking for a partner to supply the GNSS engine for their survey products. So, that really pulled us into survey and GIS. You know Neil Vancans’ pedigree in the survey market. Altus brought us into a completely new market segment. A pretty important one, considering that survey has traditionally been the trailblazer for accurate GPS. They did accurate GPS when there was nothing on machines yet. By a fluke of our history, we are now active in survey.

Apart from opening up a significant market segment and certainly, also, the consequences that we see today in GIS, which is a market that, in terms of accurate GPS is more or less new, certainly for accuracy, it also expanded our activities from a GNSS- and board-centric activity, to a much broader system requirement because of course now we need a lot of communication capabilities. The user interaction is different. We were doing machine-to-machine and survey is machine-to-man, so there are quite a number of new capabilities that we have to build and that were developed thanks to our increasing collaboration with Altus. We started as a supplier, we increasingly worked together to develop competitive products and technology, to the point that we became so intermeshed that the companies merged.

What assets, in terms of IP, personnel, etc., did Altus bring to Septentrio?

JVH: Altus is mostly a customer-oriented company, not a technology company, which is another reason that the collaboration worked so well. They brought rich market insight. It is not IP in the classical sense of the word, but know-how about the requirements and the use case in that market and then, of course, the relationships and the networks and everything else that goes with that, but it was more commercial, customer-oriented, market-oriented enrichment. The technology was and has been growing from the inside of what was the traditional Septentrio side.

The market … that they brought, of course, forced us to expand in certain directions. They were not part of Altus as a technology components, if that makes sense to you. For example, most excavators don’t work under trees, so, working under tree cover was not our radar and Altus put it on our radar, which forced us to improve our technology and our algorithms to cope with that type of environment.

What differentiates your products from one another?

JVH: We have several different product lines that are really packaging our technology and configuring our technology. The core is exactly the same for all of it, but packaging it in an adaptive way for certain market segments. So, we have OEM boards, which is still a significant part of our business, which is still mostly targeted towards a machine integration and machine control-type of environment. We have more system-level products, for instance on the marine side, which combine those core boards with typical marine type of interfaces and user control … and things like that. Then we have the smart antennas, which are really mostly directed toward the GIS and survey market.

Then, finally, we have the reference station products, the scientific products, which are, again, our technology configured and enriched with the requirements that are typical for that environment. For instance, the PolaRx5 receiver will be deployed in unmanned stations with solar power and satellite communications for long-term observation and collection somewhere in the desert. So, these things have network capabilities and low power capabilities, … that a surveyor wouldn’t be interested in because what he is looking for is an x, y, z. In that sense, these things are packaged and differentiated on a product level.

 

Fifteen years ago, you could segment the market for GPS receivers into consumer grade, resource grade, and survey grade, based on accuracy. How would you segment the market now?

The way we see the market, is really consumer and professional. You say, “resource grade, “survey grade”… That is not the distinction that I would still make. The distinction we make is really between consumer — from what goes into your phone probably up to car navigation (where that is moving is an interesting debate) — and then professional. It is more accuracy, but it is especially also more reliability that is important. Probably more so than before. Ten years ago, even in professional environments, surveyors knew that they couldn’t take a receiver for a measurement next to a wall, because everybody knew it could not work there and that is no longer accepted in the market. So, robustness and availability have become much more important. I think it is a bit difficult. We’ve seen that also with mobile phones: 10 or 15 years ago, if you were in an elevator or in a building car park, everybody knew that they couldn’t expect their mobile phones to work, whereas now assumes that it works everywhere all the time.

That expansion also happens in professional GNSS. More and more people use it, and fewer and fewer of them are necessarily GNSS specialists. They just want to measure points or use it on a machine or whatever and their acceptance of the limitations of the technology as it was ten years ago is no longer there. So, robustness is almost more important now than accuracy. That is maybe a bit of an extreme statement, but I guess you know what I mean. I would make that distinction much more and it is based on segments or use cases, like using it in a marine environment or in a machine environment or in a survey/GIS environment, which are quite different.

What are currently the key technology challenges for GNSS receiver manufacturers? Is this a good list?

• accuracy
• power requirements
• size and weight
• cost
• number of channels
• time to first fix
• imperviousness to jamming and multi-path

BB: Our products are more than GNSS receivers. If we look at the GNSS part, I can summarize that challenge in one sentence: it is to get cost-effective, dependable accuracy with transparent augmentation services. It is really where we have to go. Dependable implies availability and reliability, as we have defined above. These are things where we differentiate today, but in the future dependability is more than that. It is also taking care of the safety and security issues.

You are talking about the number of channels but, actually, the number of channels is a bit of a concept of the past, of the 90s, in the time when we had to make compromises between the cost and the number of channels. The approach at Septentrio is not to compromise on performance. When it is about the dependability, we don’t want to make compromise and we really want to be able to track all signals in space, meaning that the receiver has enough channels to track all signals and all the constellations that are planned beyond 2020. We have dimensioned our channel matrix accordingly. So, the number of channels doesn’t matter, it is the all-signals-in-view-concept that matters.

The other dimensions, the safety and security, these are things that are being researched. Those concerns will be more and more important with the emergence and the proliferation of autonomous vehicles, like UAVs, autonomous boats, and self-driving cars. As the first step toward autonomous vehicles, you have ADAS, the driving assistance systems. So, these are things that are emerging and will be heavily using high-precision GNSS, but in a larger scale and in a system that has safety and security considerations.

When it is about security, we see that there are increasing threats of attack, like denial of service attacks using jamming. Jamming is a real nuisance already today because you can buy inexpensive jammers on the Internet. To mitigate that, today we have the capability to cancel typical jammers, like chirp jammers, but we are also looking further than that in research, we are looking at more aggressive attacks, such as spoofing, in which the signal is mis-formed to try to get another position than the one where you really are. We are looking at spoofing in the context of the Galileo program, where we also look at encrypted signals, like for the PRS signals, which is the equivalent of the M code from GPS, but also the commercial service authenticated signals. So, we have the technology and we are ready to implement it in the commercial products as soon as those signals are operational. Next to that, there are many other techniques that can be used to prevent spoofing, there is a lot of statistical testing that can be done, we can also leverage our multi-constellation and our integrity monitoring experience to tackle those challenges. Those are clearly the key technical challenges in the future.

Another challenge is increasing the availability and reliability, notably in urban canyons and natural canyons and also increasing the sensitivity for applications like in forestry, under deeper canopy. For this, we see that the way to go is hybridization with other sensors. This is increasingly important and when you see the technology trends with MEMS, like MEMS accelerators and MEMS gyros, you see that the performance of those devices is increasing dramatically, while the cost is very low. You see MEMS systems that are getting performances very close to those of fiber optics gyros. We will soon be able to consider integrating those MEMS in our receivers, and put them also in the positioning systems. So, this is clearly another technical challenge, because this is not exactly the same expertise. We have to evolve our R&D team to also address those technologies.

Another aspect is the correction services. Getting RTK or PPP is still pretty cumbersome, but if we really want to have a proliferation of high-precision GNSS — for GIS, UAS, or advanced driver assistance systems, then we really need to have augmentation services that are transparent. The image that I typically use is that it should be as easy to set up an augmentation service — RTK or PPP, it doesn’t matter — as it is to set up the Vodafone service on your iPhone. At the end of the day, it is the same, it is service provisioning. We really have to work with the service providers to improve on the transparency of the augmentation services.

Last but not least, for the GNSS part, all of this has to be done in a very cost-effective way. We see that there are trends toward proliferation, so you see UAS, you see autonomous vehicles, these are applications that are intrinsically high volume but which are also cost-sensitive. So, if you look at ADAS driving assistance, it’s looked at using high-precision GNSS there, but it cannot be with equipment and in the price range that we know today. This means that we really have to improve the cost-effectiveness and, considering that at Septentrio we don’t want to compromise on the performance, the only way we can do that is to leverage silicon integration and use advanced microelectronics technology. So, it means that for us we have to invest a lot in the chip set. We are using the most advanced technology so that we can really push down the cost to enable those new applications.

Besides, one of the main challenges we have today is that GNSS is not enough. If you look at our latest products, the Altus NR2 or the AsteRxU, those are more than GNSS receivers. They definitely have a GNSS receiver on board, but you will see that they are packed with wide telecommunications capability. So, we have 3G modems on board, we have WiFi mobile access point capability, we have integrated UHF radios, and we have an advanced user interface. So, if you look at the NR2, which is a survey-class receiver that can also be used for GIS, that receiver can be used as a personal hot spot, so you can connect to the Internet with it, actually. If you look at the recent release from us, the PinPoint-GIS software suite, this is effectively used to facilitate GIS jobs using the NR2. It is a really powerful approach where you can connect any tablet or smart phone to the Altus NR2 and via its Web interface you can proceed with the GIS workflow directly interfacing with geo-database over 3G. All this know-how is complementary but is not same as GNSS. This is really a lot of expertise that we have to put together to bring those products to life. It is not just about GNSS anymore.

What are the most demanding applications and/or environments? Is this a good list?

• natural and urban canyons with few satellites in view
• natural and artificial surfaces creating multipath
• thick tree canopy
• signal interference

BB: I was trying to rank those. For us, the rich multi-path environment and the rich interference environment today is business as usual. Multi-path resilience is a must-have, interference resilience as far as the differentiation angle is something we have. What we also have is resilience under canopy and close to buildings but it is in continuous development for harsher and harsher environment. These are things that also have been developed for RTK and for PPP primarily.

If we project into the future, what we still have to improve for the whole industry and not specially for us is the capability of operate under denser canopy that would allow applications like forestry, which are currently completely untapped and, next to that, the availability and reliability in deep urban and natural canyons. So, resonating with applications like mining, for the natural canyons, but also applications like autonomous vehicles will have to work in very difficult urban environments with low sky visibility. This can be addressed with the all-constellations, all-signals approach, it is really key, but it also needs hybridization with sensors, initially inertial ones, but you can see others coming.

Then there is other and more exotic technology that we also have in research, like beam steering. Using antenna arrays, provided that you can make such antenna array affordable like for instance with printed antenna, and if we solve export regulations that are still touching those technologies, we can consider to make another leap in sensitivity and availability.

What are the key emerging markets for GNSS?

JVH: I will limit my answers to the markets that Septentrio is into, I will not look at consumer-type markets, although, again, when we talk about automated driving you are going back into a consumer environment. At this point, I think that the most interesting evolution in terms of emerging markets for us is precision GIS. I think that with the proliferation of GIS, more people are becoming aware of the lack of reliability of the actual position data and the lack of precision of the position data. I would call that an emerging market. GIS is a bit of a general term, like IP, but … GIS for infrastructure-type projects, where I think there is change and growth happening. We are working on that, basically giving the capability of acquiring accurate and reliable georeferencing data while doing GIS data collection I think it is an important point, for instance, for products like PinPoint GIS play to, where people are using their traditional or their familiar GIS data collection environments to collect data directly into the cloud and we enable that with our high precision technology to collect that type of data directly to the cloud as well. It is not the traditional “create a file, transfer the file in the office, do the network closing of the file” survey mode. That is one part.

The other part is the whole professional use and mapping of UAVs. That is, I think, a very exciting emerging market. It is moving from the hobbyist to the professional user and it is creating a whole host of new opportunities and new challenges also for the GNSS component. Also, generically, automation and robotics I think is an emerging and growing market. One of the ultimate results are things like the autonomous driving type of activities, where the professional and the consumer requirements probably will have to meet. Professional in the sense of reliability and increased accuracy that currently cannot be reached with consumer equipment, together with the requirement to have it cheap and the automobile requirements, which is not necessarily a traditional consumer requirement of extreme reliability of the hardware itself, by which I mean the production reliability. If you look at the quantities shipped in cars, they are talking about parts per million or better. In professional surveying at this point that is not yet the quality standard that is traditionally bandied about. So, that’s more or less where I think the important emerging markets are, at least for our type of activities.

Which GNSS constellation is growing/changing fastest and is, therefore, most challenging for receiver manufacturers?

JVH: In terms of challenges of GNSS constellations, it is not the growth of the constellations that is challenging, it is more the fact that if you look at the Chinese, probably the lack of transparency of what they are doing is the biggest challenge. The last two satellites that they launched, the signals were not according to the previous ICDs and that’s the challenge there, more so than the fact that there are more satellites around. That doesn’t create an additional technical challenge, at least not a significant one.

The biggest challenge with the Indian constellation is if they keep pushing for a … signal. That, of course, would be completely away from the traditional GNSS … spectrum, so it would require new antennas. The whole … design would need to change. Interpreting the signal is not so much of a problem, but the problem is the fact that there is no ready GNSS technology there. Again, I am thinking of things like antennas which would mean that we would have to start from scratch and that would require an enormous investment for, frankly, a marginal improvement. So, that would be more of a challenge if they cannot be dissuaded from going that way.

Other than that, we’ve been multi-constellation since the beginning. We were working for an ESA program in our IMEC times, before we were Septentrio and, at that time, we developed an ASIC of IAGA, which was already a GPS-Glonass ASIC. So, for us, as a professional provider, we’ve never not been in a multi-constellation world. Due to our role in Galileo, we are familiar with that kind of thing.

BB: I can only agree with Jan. GPS, Glonass, we have that, we control that. All the Glonass biases are under control. Galileo is something that we also have been in for a long time. Those that are most troubling now are Beidou and the difficulty there is not so much in the system and the signal structure, which are very pragmatic, but it is more in the transparency from China. They are changing the system without notice and we see, for instance, now that they launched two new satellites that are no longer transmitting the B2 signal like the previous generation. We know that they are working on the interoperability with Galileo, but there is still no information whatsoever on the code that they are using on the new interoperable frequencies.

This is also where there is a chance of Galileo. We have seen with Beidou the benefit of triple constellation in the regional area. With Galileo, which has launched two other satellites yesterday, which apparently are on the right orbit ;-), we will have a triple constellation, globally.

We are also looking at the Indian IRNSS. So, for there, I think they are bringing a very big challenge with the use of the S band instead of the L band. The S band is basically overlapping with the ISM band, which is the band that is used for Wi-Fi, for Bluetooth, which is also the band of your microwave. So, this is a band which is very much polluted with all kinds of interference and it would be very challenging to use that band for GNSS applications.