Jam proofing drones

“Collect 1 million data points from a 15-minute flight compared to 300 points in a day from a traditional ground survey. It’s no wonder that drones equipped with GPS technology and remote sensors are revolutionising data collection. But will jamming spoil all the fun?”

Who let the drones out?

Recent years have seen the appearance of affordable, high-end drones which, coupled with easy-to-use mission-planning tools, has created the perfect environment in which drones can flourish. No longer the preserve of specialist drone users, applications using drones have been venturing into areas such as survey, inspection and volume analysis with an impact that is little short of revolutionary.

Interference can spoil it all

In the air, the stakes are higher. When things go wrong, the consequences are invariably much more serious than they would have been on the ground. One of the biggest threats to drone safety is GNSS interference. At the very least, disruptions to satellite signals can degrade position quality causing fall-backs from high-precision RTK and PPP modes to less-precise modes. In the most extreme cases, interference can result in complete loss of signal tracking and positioning.

Self interference

A significant source of interference on UAVs is often the other components installed on the UAV. The restricted space means that the GNSS antenna is often in close proximity to other electrical and electronic systems.

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Figure 1: GoPro Hero 2 camera pick-up monitored by an AsteRx4 receiver

Figure 1 shows what happened to the GPS L1-band spectrum when a GoPro camera was installed on a quadcopter close to the GNSS antenna without sufficient shielding. The three peaks are exactly 24 MHz apart pointing to their being harmonics of a 24 MHz signal: the typical frequency for a MMC/SD logging interface.

An AsteRx4 receiver was used in this setup which includes the AIM+ system. As well as mitigating the effects of interference, AIM+ includes a spectrum plot to view the RF input from the antenna in both time and frequency domains. At the installation stage, being able to view the RF spectrum is an invaluable tool for both identifying the source of interference and determining the effectiveness of measures such as modifying the setup or adding shielding. For the quadcopter installation in this example, the loss of RTK was readily diagnosed and solved by placing the camera in a shielded case while the quadcopter was still in the workshop.

External sources of interference

GNSS receivers on-board UAVs can be particularly vulnerable to external sources of interference, be they intentional or not. In the sky, the signals from jammers can propagate over far longer distances than they would be able to on land.

In the case of UAV inspections of wind turbines for example, many countries encourage windmills to be built next to roads, a situation that increases the chance of interference from in-car chirp jammers. These devices though illegal are cheap and can be readily acquired on the internet. Using a chirp jammer, a truck driver can, for example, drive around undetected by the GPS trackers on the truck and car thieves can disable GPS anti-theft devices on stolen vehicles.

External interference: the effect of a chirp jammer on a UAV flight

Although transmitting with a power of around only 10 mW, chirp jammers are powerful enough to knock out GNSS signals in a radius of several hundred metres on land. In the air, the UAV is much more vulnerable as the jamming signals have a far greater reach, unhindered as they are by trees, buildings or other obstacles.

Figure 2 shows how a 10mW chirp jammer can knock out RTK positioning over more than 1 km in a high-end receiver. Even a low-end consumer-grade L1 receiver, being less accurate and thus less sensitive, loses standalone positioning over several hundred metres.

 With AIM+ activated, the AsteRx4 is able to maintain an RTK fix throughout the simulated flight as well as showing no degradation to its position variance. The full details on these simulations can be found in a recent white paper.

Solving interference on UAV systems

A comprehensive approach puts interference considerations at the forefront of receiver design and incorporates it into every stage of signal processing. In the case of the AsteRx4 and AsteRx-m2, the antenna signal is immediately digitised after analogue filtering and automatically cleansed of interference using multiple adaptive filtering stages.

As each interfering signal has its own individual footprint, being able to visualise the RF signal in both time and frequency domains allows drone users to identify sources of self-jamming and adapt their designs accordingly before the drone gets in the air.

When it is in the air, AIM+ is able to mitigate jamming from external sources: a set of configurable notch filters are complemented by an adaptive wideband filter capable of rejecting more complex types of interference such as that from chirp jammers, frequency-hopping signals from DME/TACAN devices as well as high-powered Inmarsat transmitters.

chirp_jammer_interference

Figure 2: RTK position availability for the AsteRx4 with AIM+ activated and a comparable high-end receiver. The low-end receiver tracks L1 only and outputs less-precise standalone positions. A 10mW chirp jammer is located on the ground at position (0,0) as shown.

Targeting Interference with AIM+

 Radio interference is everywhere. GSM, LTE, FM broadcast radio, VHF/UHF communications, Wi-Fi, satellite phones and GNSS signals are all competing for a finite space on an already heavy populated radio spectrum.

The weakness of the GNSS signals makes them very vulnerable to radio frequency interference which can directly impact the quality of your measurements and the reliability of positioning. Even GNSS frequencies which are legally protected for military and civilian radio-navigation use are not immune.

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These disturbances are usually very weak and your GNSS receiver is capable of extracting the necessary data from the GNSS signal. However, in many cases, the interference effect is more noticeable.

For example, radio navigation for assisting aircraft navigation and landing share their radio spectrum with one of the GNSS signal bands. The L5 band which has a centre frequency of 1176.45 MHz is shared by Distance Measuring Equipment (DME) and Tactical Air Navigation (TACAN). These radio beacons are deployed in the areas surrounding aerodromes and emit high-power radio pulses which can disturb GNSS receivers trying to use GPS and Galileo signals in this band.

At Septentrio, we devote considerable attention to interference throughout the design of our equipment. Working with customers over many years to solve real problems, we have developed Advanced Interference Mitigation (AIM+). These algorithms counteract the effects of interference. AIM+ is a standard feature of all Septentrio’s receivers including our newest reference receiver, PolaRx5.

AIM+ minimises the effects of continuous wave (CW) and narrowband interference on receiver performance. In the identification stage, the adaptive notch filter continuously scans the incoming signals for the presence of an interferer. Whenever an interferer is detected, the signal is digitally processed such that the interferer is suppressed.

One key element of AIM+ is the set of adaptive notch filters to target and eliminate narrowband interference on receiver performance.

A conceptual diagram of the adaptive notch filter is shown below.

Sepetentrio_Accurate_reliable_GNSS_positioning_Insight_PolaRx5_Interference_AIM+_advanced_interference_mitigation_radio

 

Note that AIM+ can incorporate one or several adaptive notch filters, depending on receiver type. The core of the adaptive notch filter is a digital bandpass filter with an adjustable centre frequency. When an interferer is detected, a software-controlled switch (see Figure 1) routes the filtered signal to the remainder of the signal processing engine (suppression stage) instead of the input signal. During the suppression stage, the filter bandwidth is narrowed down and its centre frequency is fine-tuned. The installation process of the notch filter, including the fine-tuning of its bandwidth and centre frequency, is fully automated. If required, user controlled manual operation is also possible.

Septentrio recently won the tender to become the “preferred reference station vendor” to UNAVCO. In commercial testing of the PolaRx family with competitors, UNAVCO mentioned that:

            “Configuration of a notch filter to mitigate the interference was well documented and the effect of the filter was visible in the control software. The spectrum view feature can help users to rapidly identify the sources of RF noise and mitigate the using the built in mitigation tools”.

Septentrio delivers PolaRx5 GNSS reference receivers for volcano monitoring

TORRANCE, Calif. – Dec. 12, 2016 – Septentrio has completed delivery of PolaRx5 multi-constellation GNSS reference receivers and antenna systems to the U.S. Geological Survey (USGS).

The monitoring systems will be deployed through the Volcano Hazards Program (VHP) for volcano monitoring stations in Alaska and at various international locations through the Volcano Disaster Assistance Program (VDAP) – a cooperative effort between the USGS and the U.S. Agency for International Development’s Office of U.S. Foreign Disaster Assistance.

The PolaRx5 receivers take full advantage of the new 5.1.0 firmware which includes support for on-board PPP and dynamic response tuned for seismic applications. The PolaRx5 tracks all visible signals from Galileo, GPS, GLONASS, BeiDou, IRNSS and QZSS constellations. It provides industry-leading measurement quality and robust interference mitigation thanks to Septentrio’s patented AIM+ technology. The PolaRx5 supports these advanced features and more with a power consumption that is scalable from less than 2.0 watts.

“USGS and their partners will be among the first to exploit the PolaRx5’s seismic monitoring features,” said Neil Vancans, vice president of Septentrio Americas. “The PolaRx5 is Septentrio’s most complete GNSS receiver to date and provides the ideal upgrade for modernizing any continuously-operating reference station (CORS) network.”

More information about VHP and VDAP can be found via http://volcanoes.usgs.gov/index.html and http://volcanoes.usgs.gov/vdap respectively.

Disclaimer: Representations as to the capability of these commercial products are made by Septentrio.  The United States Geological Survey and/or other federal agencies mentioned above shall not be construed as having endorsed or otherwise recommended these products.

PolaRx5 CORS receiver

Septentrio PolaRx5 with NEW Firmware specifically designed for Seismic and Volcanology

About Septentrio:

Septentrio designs, manufactures and sells high-precision multi-frequency multi-constellation GPS/GNSS equipment, which is used in demanding applications in a variety of industries such as marine, construction, agriculture, survey and mapping, geographic information systems (GIS), and unmanned aerial vehicles (UAVs) as well as other industries. Septentrio receivers deliver consistently accurate GNSS positions scalable to centimetre-level, and perform solidly even under heavy scintillation or jamming. Septentrio receivers are available as OEM boards, housed receivers and smart antennas.

Septentrio offers in-depth application and integration support to make its customers win in their markets. Septentrio is headquartered in Leuven, Belgium, and has offices in Torrance, California, and Hong Kong, and partners around the world.

APS3G’s are marching out the door

Satisfying the RTK GNSS needs of provinces and water districts is demanding.

Today we prepare 2 x Septentrio APS3G’s using the Juniper Allegro 2 field tough computers to connect with an existing AsteRxU base receiver to provide RTK correction via the Internet.

Just over a year ago the water district engaged Elliott Enterprises to develop a solution for a city wide RTK GNSS system to provide accurate height data to design a 21st century water system to deliver water to the household at the right pressure on demand. After some testing and R&D we recommended an Altus Positioning System.

Upper Cases: 2 x APS3G Kits for Internet connection via GSM. Lower Case: APS3G RTK kit

Upper Cases: 2 x APS3G Kits for Internet connection via GSM.                        Lower Case: 1 x APS3G RTK kit Peer-to Peer UHF radio

The third case (on the floor) consists of 2 x Septentrio APS3G’s as an RTK GNSS Kit with a Juniper Allegro 2 field tough computer to operate Carlson SurvCE software for road design, drainage design and subdivision developments across a province.

The Altus Positioning System is chosen consistently for speed, accuracy and versatility in the most challenging surveys. With free firmware for the life of the receiver, the province will enjoy continued free upgrades and support for an even better survey solution for many years to come.

Call Nelia Elliott on 0917 557 971 to join our business family!

Septentrio seismic monitoring and advanced CORS

Leuven, Belgium and Torrance, California – 8 December – Septentrio, a leading provider of accurate and reliable GNSS receivers, announces today the release of 5.1.0 firmware for the PolaRx5 product line of GNSS reference receivers. The 5.1.0 firmware brings new features for file management, usability, security and seismic monitoring. Septentrio’s PolaRx5 product line of GNSS reference receivers includes the PolaRx5 for CORS and network operations, the PolaRx5TR for time and frequency transfer and the PolaRx5S for space weather applications.

Improvements in Precise Point Positioning (PPP) has opened the door on seismic monitoring using GNSS technology.  As well as allowing precise measurement of long-term slow surface displacement, PolaRx5 now allows real-time recording of the high-frequency vibrations typically accompanying earthquakes. Firmware 5.1.0 introduces the support for on-board PPP and dynamic response tuned for seismic applications.

The 5.1.0 firmware release brings greater logging efficiency to the PolaRx5 users. Storage integrity is crucial for many applications. Re-transmitting data can be an expensive business, especially when using Iridium telemetry.  To improve archival functionality, Septentrio has developed a storage integrity feature to retransmit only the data which has been lost in the initial transmission. This avoids the common and unnecessary overhead of re-transmitting complete files.

Preventing unauthorised access is a crucial aspect of cyber security. PolaRx5 product line is now equipped with firewall and IP filtering, SFTP and ssh keys. This complements and strengthens the user management and access level protection of the PolaRx5 product line.

Land Deformation New Zealand November 2016

Earthquake Land Deformation New Zealand 2016

Various independent tests have shown PolaRx5 consistently ranks highest among GNSS receivers in many areas of measurement quality, including lowest measurement noise and fewest number of cycle slips, and this at the lowest power consumption on the market. The PolaRx5 products offer robust and high-quality GNSS tracking of GPS, GLONASS, Galileo and BeiDou as well as regional satellite systems including QZSS and IRNSS.

Some of those who have recently deployed the PolaRx5 include the Oregon Department of Transport (DOT), UNAVCO, the Jet Propulsion Laboratory (JPL) and the SAPOS CORS network in Germany.

“The 5.1.0 PolaRx5 firmware continues Septentrio’s commitment to its customers.” stated Francesca Clemente, PolaRx Product Manager. She continued: “The new features of the 5.1.0 firmware complement existing standard features of the PolaRx5 GNSS receivers such as Advanced Interference Mitigation technology (AIM+) and the web UI offering full user control and status to make PolaRx5 the most complete GNSS reference station on the market today.”

This firmware is now available on Septentrio’s website and will be showcased at the American Geophysical Union (AGU) Fall Meeting from Monday, 12 December.

About Septentrio

Septentrio_photo_company_employees

Enabling our customers’ success with GPS and GNSS

Septentrio designs, manufactures and sells highly accurate GPS/GNSS receivers, for demanding applications requiring accuracies in the decimeter or centimeter range, even under difficult conditions. Whether it’s on the high sea, in scintillation prone areas or at high latitudes, our customers know that Septentrio receivers deliver fast, accurate and reliable positions. In urban canyons, under canopies or even under circumstances where there is deliberate interference, our receivers make our customers excel.

Our Roots

Septentrio was started as a spin-off of IMEC – the world’s largest and most advanced semiconductor research institute with over 2500 researchers. From the start, we used the most advanced semiconductor designs for low power, high performance and disturbance mitigation. The nearby KULeuven University is one of Europe’s leading universities and is an excellent source of top talent in areas such as signal processing and advanced algorithms, although we attract top specialists from around the world. We continue to work with IMEC and several highly specialized partners to build the best GNSS receivers in the world.

Rocket Science

From its inception, Septentrio has been involved in many programs for the European Space Agency and the Galileo GNSS program. As an example, we developed the first receivers to decode the advanced signals from a Galileo satellite and have tested and validated all Galileo signals ever since, including the PRS signals.

Your reliable OEM long term partner

We see it as our mission to make you win in your markets, while we stick to making the world’s best GPS/GNSS receivers for demanding applications. As your long-term partner, our job is to provide you with competitive products, our deep understanding of the technology, and the committed support that make all the difference to your success.

Septentrio receiver tracks newest Japanese GNSS signals

Hong Kong – 12 October 2016Septentrio and its Japanese partner, GNSS Technologies, are proud to announce that they have successfully tracked and decoded the QZSS LEX signal. This achievement marks a milestone in the development of the Japanese QZSS satellite navigation system and is the result of a trusted partnership between Septentrio and GNSS Technologies. The partnership is committed to enable the success of their Japanese customers with the very latest in satellite navigation technology.

QZSS (Quasi-Zenith Satellite System) is Japan’s regional satellite navigation system. When completed, it will consist of 4 satellites: the first satellite was launched in 2010 and the remaining three are scheduled to become operational in 2017. All satellites will be equipped with a revolutionary CLAS (centimetre-level augmentation service). This service will send correction signals straight from the QZSS satellites to end-user receivers and enable them to calculate their position with centimetre-level accuracy. The CLAS corrections are broadcast in the LEX and L6 signals.

By implementing LEX signal tracking and decoding before the completion of the QZSS constellation and before the CLAS service becomes operational, Septentrio and GNSS Technologies are showing their long-term commitment to Japanese customers.

Using Septentrio technology, customers will be able to eliminate the need for investment in ground infrastructure to create correction signals or in subscriptions to commercially available correction signal streams. This opens up possibilities in new application domains in sectors such as marine, construction, agriculture, survey and mapping, geographic information systems (GIS) and unmanned aerial and vehicles (UAVs).

All NEW Juniper Geode submeter GPS receiver

Today, Juniper Systems would like to introduce to you… the Geode™ – our new real-time, sub-meter GNSS/GPS receiver! This compact, all-in-one receiver collects precise location data, without the huge price tag or complexity of other precision receivers. We designed it with an emphasis on simplicity so you can start collecting data at the touch of a button. The Geode is also highly versatile, and will connect via Bluetooth with Juniper Systems’ rugged handhelds, or any other Windows®, Windows Mobile, or Android ®device. Speaking of versatility, the Geode can also be carried in a number of different ways. It can easily be carried in-hand, in a pack, or mounted on a pole, depending on your specific use case and what your individual needs are.

Geode Real-Time Sub-meter GNSS Receiver

Geode Sub-Meter GPS ReceiverAnd of course, the Geode doesn’t compromise on ruggedness. It features IP68-rated protection against water and dust, and operates in extreme temperatures, providing reliable performance wherever you need to collect data.

Here are a few other Geode features:

  • SUB-METER ACCURACY – Collect precision GNSS data with your handheld device
  • REAL-TIME DATA – Multiple correction sources provide precise, real-time data
  • JUNIPER RUGGED™ – IP68-rated and designed to withstand harsh environments
  • AFFORDABLE – Professional accuracy at a budget-friendly price
  • COMPACT SIZE – Small and lightweight for all-day use
  • OPEN INTERFACE – Works with Juniper Systems’ handhelds or your own device
  • SIMPLE TO USE – Intuitive and easy operation, one-button simplicity
  • ALL-DAY BATTERY LIFE – Ideal for long work days
  • CONNECTIVITY OPTIONS – Connects to a handheld or tablet via Bluetooth or an optional 9-pin RS232 port
  • BUILT-IN ANTENNA – Comes with a built-in GNSS/GPS antenna, but also includes a port to connect an external antenna, depending on the user’s preference

Juniper Systems’ products are designed to reliably collect data in any environment,” said Debbie Trolson, Geomatics Market Manager at Juniper Systems. “Whether users need a GNSS solution that provides 2–5 meter accuracy, or one that provides even more precise, sub-meter accuracy, Juniper Systems can deliver a high-quality solution that enhances both productivity and data integrity.”

How GPS brings time to the world

 Knowing the correct time is something we take for granted but who is it that decides what the correct time is? How do they determine it? And where does GPS fit in to the story?

Banner Theme 3 GEOtime

The short answer: the International Bureau of Weights and Measures (BIPM, Paris), as well as telling us the length of 1 metre also tell us what time it is. To determine the time, they rely on the contributions from a worldwide collaboration of timing laboratories who each maintain their own measure of time and compare it with GPS time.

Septentrio_Altus_Septentrino_PolaRx5_PolaRx5TR_PolaRx4TR_PolaRx_timing_receiver_frequency_transfer_auto_calibration

One clock to rule them all

Timing labs employ precise clocks, with Cesium atomic clocks and Hydrogen masers being among the most popular. Although these clocks are very reliable (accurate to about 2 nanoseconds per day) there are still small variations. At BIPM in Paris, they compare the performance of clocks in timing labs around the world and, by using a weighted average of all contributions, calculate what is known as UTC (Coordinated Universal Time). Labs with better performing or more stable clocks are given more weight in the calculation of UTC.

Septentrio_Altus_PolaRx_PolaRx5TR_making_UTC_clocks

Figure 1: UTC time is the result of input from many timing labs around the world

 

This means that real-time UTC is only an approximation albeit a very accurate one, with the more precise calculation determined retrospectively. The Circular-T journal, published monthly by BIPM contains the small corrections to be applied to UTC during the previous month.

Where do GPS receivers fit in?

Each timing lab contributing to UTC measures its own version of UTC for example, UTCBrussels is the Belgian measure of UTC. So how does BIPM compare the performance of all these different clocks? The answer is that it uses the GPS receivers or more accurately, GNSS (Global Navigation Satellite System) receivers which besides GPS, also track constellations such as GLONASS, Galileo, BeiDou and IRNSS.

The precise measurement of time is at the heart of every GPS receiver. The distances between satellite and receiver, used to calculate position, are determined by measuring the transit times of the satellite signals to the receiver. An error of 1 nanosecond in the transit time translates into an error of 30cm in the distance. The GPS satellite constellation uses its own precise measure of time called GPS time with each satellite having its own, on-board set of atomic clocks. Satellites can thus be viewed as very accurate flying clocks.

By tracking a GPS satellite, a receiver can record the time differences between its own receiver clock and the satellite clock, e.g. UTCBrussels  – GPS time. These time differences, along with other information, are collected in a data format called CGGTTS and sent to BIPM. Using CGGTTS and other data, BIPM can compare a clock in Brussels with a clock in New York by subtracting the individual differences with GPS time: a technique known as “common view”.

UTCBrussels – UTCNew York = (UTCBrussels – GPS time) – (UTCNew York – GPS time)

The two GPS time terms above cancel each other out leaving the difference between UTCBrussels and UTCNew York.

Septentrio_Altus_PolaRx5TR_UTC_New_York_UTC_Brussels

Figure 2: By comparing individual clocks with GPS time, they can be compared with each other

 

Setting up a timing laboratory

To compare the atomic clocks used in timing labs around the world, they need to be connected to a GPS timing receiver. This is a special type of receiver that can use an external atomic clock instead of its own clock which is does using two output signals from the atomic clock:

  • a pulse every second synchronised to UTC (PPS IN) and
  • a 10 MHz frequency reference that is essentially a sine wave (REF IN)

The basic ingredients of a timing laboratory are shown in Figure 3. However, to reach the nanosecond accuracies required, a great deal of expertise and preparation are also needed. Signal delays in all elements in the setup should be accurately calibrated and for this, BIPM maintains a set of pre-calibrated travelling receivers as calibration references. As well as providing 1/3 of the timing receivers used for the calculation of UTC, Septentrio also provides BIPM with timing receivers for calibration.

Septentrio_muggen_set_up_timing_lab_PolaRx_PolaRx5TR_timing_receiver

Figure 3: The basic ingredients for a time transfer laboratory: a Cs atomic clock, a PolaRx5TR timing receiver and an antenna

 

Pushing the boundaries of science

Beyond defining and disseminating UTC, recent years have also witnessed GPS timing receivers staking their place at the forefront of science. In the case of the T2K experiment for example, by measuring precisely the transit time of neutrinos between two locations, limits can be placed on their mass thus shedding more light on the nature of these elusive particles.

At the other end of the size spectrum, the technique of VLBI (Very-Long-Baseline Interferometry) uses radio telescopes at distant locations which are linked together in networks by time-synching their observations using GPS common view. The resulting resolution is far in excess of anything that can be achieved by any single telescope on its own.

From the relatively mundane activity of time-stamping banking transactions to the truly extraordinary worlds of astronomy and high-energy physics, GPS technology continues to find new ways to improve our world and advance our knowledge of it.

Septentrio to supply Jet Propulsion Laboratory

Septentrio to Supply GNSS Reference Stations and Timing Receivers to Jet Propulsion Laboratory

TORRANCE, California. – September 14, 2016 – Septentrio has received a contract to supply 35 high-precision GNSS receivers to the Jet Propulsion Laboratory (JPL) for use in the NASA Global GNSS network (GGN).

The NASA GGN is one of the world’s largest global GNSS tracking networks with nearly a hundred reference receivers deployed worldwide and is a participant in the International GNSS Service (IGS). The GGN is also the core tracking network of JPL’s Global Differential GPS (GDGPS) System, a highly available and reliable service providing mission-critical position, navigation and timing data, as well as environmental monitoring for industry and government operations.

PolaRx5 CORS receiver

PolaRx5 GNSS receivers for the NASA Global GNSS network

Under the contract, Septentrio will supply 35 of its PolaRx5 GNSS receivers, including 25 reference stations and 10 timing instruments. Deliveries began in August and will be completed in September.

The PolaRx5 incorporates Septentrio’s most advanced multi-frequency GNSS engine, which tracks all major satellite signals including GPS, GLONASS, Galileo and BeiDou, as well as the regional QZSS and IRNSS satellite systems. It provides industry-leading measurement quality and interference mitigation, and operates on less than two Watts when receiving GPS and GLONASS satellite signals.

Neil Vancans, CEO Altus Positioning Systems

Neil Vancans, Vice-President of Septentrio Americas

“This major contract with JPL – a widely recognized industry leader in GPS and GNSS technology – is an important validation of Septentrio’s position as the number one preferred supplier of highly accurate GNSS receivers for scientific applications, and recognition of the superior performance of our next-generation GNSS receivers,” said Neil Vancans, Vice-President of Septentrio Americas.