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Of the 60 exhibitors at the Institute of Navigation’s Joint Navigation Conference (JNC) in San Diego this year, 16 make inertial navigation systems (INS). Many of the other exhibitors integrate INS with GNSS receivers or make simulators to test those integrations. Several exhibitors make a variety of other navigation systems, using active and passive optical sensors, wheel encoders and RF systems that map beacons of opportunity. Only seven manufacturers of GNSS receivers were present.

That’s because the conference — which took place June 6-9 and focused on technical advances in positioning, navigation and timing (PNT) — was hosted by ION’s Military Division for the Departments of Defense (DOD) and Homeland Security. “From an operational perspective,” said the conference program, it focused on “advances in battlefield applications of GPS; critical strengths and weaknesses of field navigation devices; warfighter PNT requirements and solutions; and navigation warfare.” In other words, it was mostly on how to navigate in environments in which the use of GNSS is challenged or denied due to jamming.

The conference program told the story of the GNSS/PNT community’s interests and concerns. Several sessions were on complementary PNT using terrestrial RF signals of opportunity, IMUs, geophysical fields (including gravity and Earth’s magnetic field), celestial objects, ground vision and new commercial sources of space-based PNT, such as satellites in low Earth orbit (LEO).

Other environments in which reliance on GNSS is hard or impossible — such as urban canyons, deep inside buildings, underground and underwater — pose the same navigation challenges to both military and civilian applications. Likewise, jamming is a threat to both. Therefore, several sessions focused on critical infrastructure, demonstrating that the concerns about GNSS vulnerabilities are not just military ones.

Hence the presence among the exhibitors of three manufacturers of atomic clocks, which continue to shrink in size, weight, power and cost (SWaP-C) and are used to assure holdover — that is, the time period required to keep networks synchronized when their primary timing source, usually GNSS, is disrupted or temporarily unavailable. Networks affected include cellphone providers, radio and television broadcasters, financial networks, and the biggest network of all, the Internet.

The JNC “experienced record attendance in both conference participants and exhibitors, hosting more than 1,000 attendees,” Lisa Beaty, ION executive director, told me. She attributed the increase to “the importance of PNT in the nation’s critical infrastructure, current innovation, programmatic funding, and the desire by the DOD community to collaborate and reconvene.” She confidently anticipates additional growth next year.

I am equally confident that much of the cutting-edge technology on display at this conference will find its way into civilian applications in the next few years. Whether in war or in urban canyons, GNSS navigation faces some of the same challenges.

Trimble has announced a new high-performance data collector for its Mapping and Geographic Information Systems (GIS) portfolio — the Trimble TDC650 handheld. Built for GIS data collection, inspection and asset management activities, the TDC650 provides users a rugged solution with scalable high-accuracy GNSS positioning for professional field workflows.

The TDC650 is fully integrated with today’s demanding GIS data environment, powered by the Trimble Software Development Kit (SDK) that enables precision GNSS positioning for apps such as Esri ArcGIS Field Maps and Trimble TerraFlex software. The TDC650 is also a scalable solution that allows customers to choose their desired accuracy down to the centimeter-level to meet needs and budget requirements.

“This is an ideal tool for customers tasked with modernizing critical utilities including electric, gas and telecommunications networks,” said Gareth Gibson, marketing director, Trimble Mapping and GIS. “The precision, quality and data integration workflows needed to map the physical world to a digital one in these projects requires a modern data-collection platform like the TDC650.”

City, state and local governments and utilities will benefit from this solution, which is part of the larger Trimble Public Sector ecosystem that includes Cityworks software for stormwater inspections and Trimble Unity for monitoring municipal water pressure and hazards. As GIS data continues to grow more complex, Trimble helps simplify, visualize and make sense of the data so customers can make better decisions in managing their communities’ assets.

Phone users can now be located by emergency responders within one floor level inside multi-story buildings 

Polaris Wireless, an innovator of high-accuracy software-based wireless location solutions, announces the company’s Z-axis location solution is commercially available nationwide.

The technology — demonstrated to meet the 3-meter vertical location accuracy requirement of the Federal Communications Commission (FCC) — is integrated into Schok Gear’s newly released flip phones.

Schok’s flip phones are typically used by consumers looking for a simple, yet powerful flip phone, that can now be accurately located in emergencies. Adding indoor and vertical location to these devices enables first responders to locate all wireless 911 callers with floor-level accuracy in multi-story buildings.

“This is a major milestone for the 911 industry to deliver FCC-compliant Z-axis emergency location technology for users of feature phones” said Manlio Allegra, CEO and Founder of Polaris Wireless. “Working with Schok and their partners has been straightforward and it’s exciting to see for the first time the complete Z-axis solution commercially available in a flip phone.”

“The Polaris Wireless location software was seamlessly integrated with our existing location and chipset vendors” said Samuel Gutiérrez, chairman and CEO, Schok, LLC. “Our Schok flip feature phone passed Tier I carrier acceptance testing, which for the first time included Z-axis location. Now our customers can be assured their accurate vertical location will enable first responders to find them faster in an emergency.”

The vertical component of wireless location is critical in today’s environment when most 911 calls are placed by mobile phones and increasingly indoors, where location determination is particularly challenging. Accurate indoor wireless location is a game-changer for first responders to quickly get to where they are needed, regardless of the phone being used by callers. The Polaris Wireless Z-axis service is available seamlessly nationwide for public safety and commercial deployments.

Fugro has signed a contract with Kooiman Engineering and Van Oossanen Naval Architects for the naval design of Blue Prism, Fugro’s next generation of unmanned surface vessels (USVs).

Engineered for both coastal and offshore operations, the Blue Prism will combine an ultra-low carbon footprint with high-quality data collection, weather resilience and endurance characteristics, Fugro explained in a press release.

Available in 2023, Fugro’s Blue Prism will acquire high-accuracy bathymetry and sub-bottom data using hull-mounted sensors, while also having the ability to tow multiple geophysical sensors. It will also be capable of beyond-visual-line-of-sight operations.

Together with Fugro’s smart data-management software, the speed and endurance of the Blue Prism will reduce risk and accelerate project delivery in offshore wind, hydrographic charting and coastal resilience.

“To re-think the design and layout of a vessel without a crew is a dream come true for a naval architect,” said Perry van Oossanen, managing director and naval architect at Van Oossanen Naval Architects. “We are thrilled to be part of this exciting project in which the best techniques in Dutch ship building are combined in this new uncrewed ultra-efficient vessel.”

“The collaboration between Kooiman and Van Oossanen has already led to innovative solutions, and we are pleased to be able to help Fugro take the next step in uncrewed vessels,” said Maarten Kooiman, director of Kooiman Engineering.

By Xavier Leblan and Giuseppe Rotondo, GUIDE-GNSS, Toulouse, France
Miguel Ortiz, Université Gustave Eiffel, Nantes, France
and Christelle Dulery,CNES (French Space Agency), Toulouse, France

Geolocation errors, degraded signal and environmental masking

In a perfect world, the positions calculated by trilateration using the signals transmitted by GNSS satellites would always be accurate to within a few centimeters. Unfortunately, in addition to the intrinsic quality of the receivers, many factors alter the measurements made by a GNSS receiver and degrade the final geolocation data.

To begin with, the GNSS system itself suffers from multiple imperfections including so-called “global” errors. For this reason, the satellite navigation system is complemented with the broadcasting of assistance messages to increase the performance of receivers compatible with SBAS systems, such as EGNOS for the European continent.

In addition, for terrestrial applications, the satellite signals are affected by several phenomena caused by the immediate surroundings of the receiving antenna. These are the so-called “local” errors, such as terrain, bridges, infrastructures, vegetation and interference of any type. Depending on the areas covered, the trajectories calculated by the terminals deviate more or less from that actually taken by the vehicle (antenna), i.e. the “reference trajectory,” also called “ground truth.”

Sources of error in urban geolocation include:

Global errors

• Orbits and clocks
• Satellite geometries
• Ionosphere, troposphere

Local errors

• Obstruction, attenuation
• Multipath and diffraction
• Interference, jamming, spoofing

Terminal errors

• Receiving chain
• Algorithms and services
• Navigation sensors

Classification of position errors

To study those phenomena having the greatest impact and likely to be the most frequent, the different types of errors are displayed as a risk matrix. As the “global” errors can be considered to be handled by the regional SBAS system, the pre-eminence of the so-called “local” errors should be addressed.

Description of the main sources of local errors

To observe the effects of local phenomena on the propagation of signals, a dozen identical receivers — with the same configuration and sharing the same antenna — were mounted on a vehicle and driven through urban and peri-urban areas.

We focus on four particularly impacting phenomena to visualize the trajectories calculated by the receivers.

Positioning errors due to bridges

In the picture, below, the test vehicle passes under a bridge in both directions. In both cases, the trajectories diverge under the bridge and converge further on. Here it is easy to understand the shortcomings of results based on a single pass, in other words based on a single measurement.

Positioning errors due to vegetation

In the image below, the test vehicle is on an avenue lined by trees whose branches and canopy cover the road. The foliage attenuates and, more importantly, diffracts the radio waves arriving from the satellites, thus degrading signal reception. This results in dispersed trajectories. Each receiver provides a different measurement. Note that due to the proximity of buildings, the center of the position distribution, in the presence of multipath, deviates slightly from the reference trajectory.

Positioning errors due to buildings

In the composite image (in order to show the main building) below, all the receiver trajectories are deviated towards the building alongside the avenue. The situation highlights the consequences of a phenomenon called “multipath.” When a receiver captures reflected waves, the signal propagation time — used to calculate the pseudoranges — is increased and the accuracy of the end position is degraded. This effect is well known and easily observable during static measurements.

Positioning errors due to interferences

In the image below, the on-board receivers have been disturbed by “transitory” interference. On the outward journey, twenty minutes earlier, no problem had been detected for the trajectories on the other side of the expressway.

On the return journey, this unidentified interference degrades the accuracy of the receivers with a visible dispersion of the trajectories. In other situations, intentional or unintentional interference could completely block out the GNSS band preventing any position measurement.

In this case, the source of the interference seems to come from the bottom right, guided by the two parallel buildings.

Trueness and precision of position measurements

Receivers of the same batch behave differently depending on the environment. For a predominantly multipath situation, they all converge to the same wrong position. On the other hand, when the propagation phenomena become more complex with multiple diffractions, such as reception under foliage, each receiver produces a position with a different error. For complex environments, we have a combination of these two behaviors.

The first behavior is deterministic. Metrology uses the term measurement “trueness,” which stands for “closeness of agreement between the average of an infinite number of replicated measured values and a reference value.”

The second behavior is non-deterministic. In this case, metrology uses the term measurement “precision,” which stands for “closeness of agreement between indications or measured values obtained by replicated measurements on the same or similar objects under specified conditions.”

Terrestrial applications often offer a varied mix of environments where “trueness” and “precision” errors accumulate. It is essential to consider both components in order to characterize and study GNSS receiver performance.

Statistic distribution of the different positioning errors:

Above, 95% of the positions calculated during a replay have an accuracy better than 1.5m; this same value is only reached with ~80% of the positions calculated during another replay — see vertical line [d]. The horizontal line [e] illustrates the spread of the horizontal position by considering 95% of the positions of two replays: for one the displayed accuracy is ~ 1.5m and for the other it is degraded to 3.5 m. This curve will always point to the same reference points [a], [b] and [c] recommended by the standard EN16803-1 and corresponds to the percentage of measurements respectively less than 50%, 75% and 95%.

By way of example, the evaluation of a single receiver on board a vehicle travelling in an urban environment does not allow separation of these two components. Indeed, signal degradation determines the degree of dispersion of the “random” component of the measurements. Thus, in certain environments, each additional receiver will produce a different result. However, the analyses of a single onsite campaign relies on just one single sample (single trajectory of the terminal under test), where a panel of measurements is essential. In fact, the available statistics prove insufficient to characterize a receiver, even at the cost of doing long runs.

Live testing is therefore rather intended for final integration.

On the other hand, a constellation generator will synthesize ideal signals derived from mathematical models, and, in any case, not representative of the real environment. The measurements will then only be deterministic, that is, subject to “systematic” errors. Repeated simulations on the same receiver will always produce the same measurements. Nevertheless, this type of test bench offers many advantages for simulating unobservable situations in the real world.

Disparities in analysis possibilities on position errors based on:

In summary, the main error profiles are described below.

Each situation combines both trueness and precision errors. This latter component requires several runs in the same configuration to determine the potential measurement spread.

What is GNSS metrology?

As a first approach, characterization of GNSS performance would require many receivers on the same test vehicle. This method is certainly useful in the experimental stage, especially to understand the impact of propagation phenomena on positioning errors. However, it has major disadvantages, both from a logistics point of view and because of the basic metrological requirements.

To obtain reliable and useful measurements, from an operational point of view, the tests must be “representative” of the areas to be covered and “reproducible” to check the results and make valid comparisons, for example, between two receivers, two firmwares, two settings, two antennas and even two hybridizations.

Under these conditions, replay techniques, often referred to as “record and replay,” meet the expected requirements. For the record, this metrology method consists in digitizing the GNSS signals received by the antenna on board the definition vehicle, taking care to collect all the data associated with the tests (VIDEO, INS, DMI, NRTK, …), above all, the ground truth. Thus, at the end of the campaign the GNSS signals and other data are synchronized and restored on a replay bench consisting of an “SDR replayer.”

Replaying the same scenario on a receiver makes it possible to reproduce the recording conditions identically. Each pass generates new measurements, equivalent to using an additional unit, virtually onboard. Compiling the results thus highlights the non-deterministic errors, that is, those which by their random nature emerge from the others.

Test laboratories such as GNSS GUIDE design and market test data that can be replayed directly on the main simulation instruments capable of operating in two modes: simulation and replay. The replay configurations are generally much more affordable than the larger, structurally more complex constellation generators. In addition, the implementation of replay sessions is simple, fast and requires no special training.

In addition to scenarios made on request, the available libraries already cover a multitude of cases, previously inaccessible for an isolated user. They open up the possibility of testing terminals in different latitudes with varied terrain and neighborhoods composed of typical architectures.

Conclusion

The French Space Agency (CNES) has financed several R & D contracts for the development and validation of this replay technique (record and replay). It is already recommended by CEN / CENELEC through the series of EN16803 standards to characterize and classify the performance of GNSS terminals. This methodology complies with the basic principles of metrology.

The test conditions are reproducible and representative of operational conditions. The measurements are repeatable and allow separating the systematic errors (trueness) from the random errors (precision). Measurement uncertainties are also accurately established.

During an on-site measurement campaign, the statistical distributions of two identical receivers on board the same vehicle lead to different results. Thus, no characterization can be established at this stage.

With a replay bench, after several iterations of the same scenario, the average values of the measurements on a CDF tend toward a curve characterizing the performance for that scenario.

Instrumentation dedicated to replay operations is less complex and less expensive. Statistical models of simulations are replaced by scenarios of GNSS signals previously digitized in the field or on constellation generators. Thus, whether they come from a real or synthetic environment, these GNSS signals are easily restored, while drastically reducing the preparation and execution times. The economic benefits of this test technique are now evident and are favoring its adoption by the transportation industries.

References

• Niels Joubert, Tyler G.R. Reid, and Fergus Noble (2020), Developments in Modern GNSS and Its Impact on Autonomous Vehicle Architectures
• Andrej Tern and Anton Kos (2018), Positioning Performance Assessment of Geodetic, Automotive, and Smartphone GNSS Receivers in Standardized Road Scenarios
• Ni Zhu, Juliette Marais, David Betaille, Marion Berbineau (2018), GNSS Position Integrity in Urban Environments
• C. Rouch, B. Bonhoure, F.X. Marmet, T. Chapuis, H. Secretan, V. Bienfait, X. Leblan (2016), Measurement campaigns and PVT experiments with new Galileo satellites
• B. Calvet, L. Montoya, P. Grandjean, X. Leblan (2015),  The GUIDE High-Precision test facility (GNSS laboratory)
• G. Duchâteau, X. Leblan, Y. Capelle, W. Vigneau and F. Peyret (2014), Certification of Road User Charging: Approach, standardization and role of laboratories

ComNav Technology has introduced its new-generation data collector, the R60. The powerful handheld has an ergonomic design and runs on Android 12 OS, providing a suitable workhorse for surveying professionals in the field.

Survey Master field software works seamlessly on the R60, which features a Qualcomm 8-core processor for massive data processing. Its 64-GB memory allows ample data storage and enables the opening of CAD drawings in seconds. A full QWERTY keyboard speeds up surveying efficiency.

The 9000 mA Li-ion battery provides more than 30 hours of continuous functioning and is fast charging, taking only 5 hours to fully charge with the USB-C interface port.

The 5.5-inch sunlight-readable, high-resolution screen provides a smooth and comfortable experience in outdoors. The IP67 dustproof and waterproof rating protects the R60 from most harsh environments.

The R60 data collector now is available through ComNav Technology authorized local distributors or ComNav Technology directly.

Initiative aims to increase the global coverage, quality and accessibility of seabed mapping data through collaboration and the creation of a more integrated marine geospatial sector

The UK Hydrographic Office (UKHO) is inviting UK government organizations involved in seabed mapping who share common interests in optimizing the UK’s national maritime assets to become members of the newly unveiled UK Centre for Seabed Mapping (UK CSM).

UK CSM is administered by the UKHO, and was submitted as a UK Government Voluntary Commitment to the United Nations at the UN Ocean Conference in Lisbon, Portugal, on June 27.

The UK CSM has a remit to increase the coverage, quality and access of seabed mapping data collected using public funds, as well as to better promote it as a critical component of national infrastructure.

Working groups established

Created to spearhead a coordinated approach to the collection, management and access of seabed mapping data – and to champion a more integrated marine geospatial sector in the UK – the UK CSM has established three working groups: National Data Collaboration, International Data Collaboration, and Data Collection Standards.

These working groups will further the discussion and coordination of data accessibility, collection and collaboration, as well as progress work on data standards, by creating the conditions and developing infrastructure to enable the diverse community of marine geospatial stakeholders to come together to deliver significant, sustained and strategic benefits to the UK – particularly in the context of the integrated review and the UK’s Global Britain vision.

So far, 22 government agencies are involved in the inaugural management group meeting of the UK CSM and volunteered to participate on the working groups.

The UK CSM will develop specifications that support UK and international standards for the collection of marine geospatial data.

Work supports climate change research, the 2020 Juneau landslide, and effects of the Exxon-Valdez oil spill

NV5 Geospatial marks its 65th year helping Alaska solve environmental and geospatial challenges, with new hydrospatial projects with the National Oceanic and Atmospheric Administration (NOAA), U.S. Geological Survey (USGS), Alaska Railroad Corporation, Alaska Department of Natural Resources, U.S. Fish and Wildlife Service and the U.S. Department of Agriculture.

“As climate change intensifies, so do the challenges that Alaska and its citizens face,” said Adam McCullough, NV5 Geospatial’s Alaska program manager. “From mapping the coastlines, to collecting lidar and imagery data to better understand geohazards and landslide risks, to mapping rivers, lakes and other surface water features, we are involved in critical projects across the state. We are proud to work side by side with national, state and local governments and agencies, as well as private corporations to facilitate climate-change informed decision making over the state’s valuable, unique resources.”

The following six projects provide a sampling of the work in which NV5 Geospatial has participated across the state:

• Revillagigedo Topobathymetric Lidar and Imagery Mapping – NV5 Geospatial is working alongside state and federal partners on a multi-year program to map Alaska’s 66,000 miles of complex coastline. This work is part of a larger national shoreline mapping project being undertaken by NOAA to gather baseline data to update nautical charts, manage coastal resources, and define U.S. territorial limits.

The data collected also can support maritime trade and transportation, as well as wave and wind energy site selection. The data supports coastal resiliency efforts that include modeling sea-level change, storm surge, coastal flooding and pollution trajectories, as well as analysis and monitoring of critical habitats, developing land and marine GIS base layers.

• The Alaska Railroad Corporation (AARC) Lidar Acquisition for Geohazards – AARC engaged Michael Baker and NV5 Geospatial to collect high-resolution topographic lidar and imagery data for analysis of geohazards, hydrology, engineering and landscape ecology across portions of its vast rail network in Alaska. NV5 leveraged its advanced combined low-altitude sensor solution (CLASS) mounted to a helicopter to simultaneously collect lidar, ortho-imagery and oblique images along the rail line that enables researchers to evaluate landslide and hydrological risks in areas of concern.

• USGS 3DEP Juneau Landslide Lidar Study – In the aftermath of unprecedented rain events in Southeast Alaska in December 2020, the City and Borough of Juneau, along with Alaska Electrical Light & Power, partnered with the USGS to acquire and process 3DEP-compliant airborne topographic lidar data covering the Juneau landslide impact area. The USGS contracted NV5 Geospatial to perform the lidar survey that included acquiring extremely accurate lidar to USGS’s highest quality level specification.

The lidar data will support planning and landslide assessment to enable the reinforcement of critical infrastructure resources in the area. Project stakeholders are able to use this data along with existing lidar collected by NV5 Geospatial in 2013 to study how the landscape is changing in precise detail.

• Alaska 3D Hydrography Program (3DHP) – The USGS, in partnership with state, local, and tribal governments and others, has embarked on a multi-year effort to enhance the mapping of rivers, lakes and other surface water features for the entire state of Alaska. Supporting that initiative, NV5 Geospatial has been repeatedly contracted by USGS to develop improved hydrography, covering 62,934 square miles to date.

NV5 Geospatial is leveraging the recently completed statewide interferometric synthetic aperture radar (IfSAR) coverage as the elevation data source to define drainages, impoundments and other hydrographic features in greater detail and accuracy. Once completed, the enhanced map data will be used to inform navigable waterways; conduct flood analysis; and delineate wetlands, fish habitat, recreational opportunities, coastal resiliency and more.

• Exxon-Valdez Oil Spill, National Wetlands Inventory and National Hydrography Dataset – The U.S. Fish and Wildlife Service is leveraging grant funds to map wetlands and hydrography for areas affected by the 1989 Exxon Valdez oil spill. These areas include Kodiak Island, Afognak Island and the shorelines of Shelikof Strait in Alaska. Wetlands data are used by natural resource managers to promote the understanding, conservation and restoration of wetlands, while the hydrographic data supports scientific studies, cartography and natural-resource management associated with inland surface water features.

• U.S. Department of Agriculture Aerial Orthoimagery Term Contract – NV5 Geospatial was awarded a large multi-year term contract to support aerial orthoimagery in Alaska. The contract has been used to acquire tens of thousands of square miles of high-resolution orthoimagery covering some of the nation’s largest national forests including Tongass and Chugach, as well as agricultural lands significant to the Natural Resource Conservation Service. These areas are in areas with some of the most challenging weather and terrain anywhere in North America and require aircraft on persistent standby to take advantage of the brief windows of opportunity to collect high-quality imagery.

We discussed Satellite Time and Location (STL) services and complementary PNT with Michael O’Connor, CEO at Satelles.

What is the problem with GPS/GNSS that Satelles aims to solve?

GPS and GNSS are amazing. We designed Satellite Time and Location (STL), the service that we offer, to complement those capabilities. We have focused on three unique aspects in the areas where GPS could use complementary service. First, we provide a fully independent backup. We all know that things can happen, so we aim to provide an independent source of position navigation, and timing (PNT). Second, we focused the high-power aspect of STL to enable us to reach indoors and other places where GPS does not reach. Because STL comes from low Earth orbit (LEO) satellites, the signals are naturally at a higher power.

We also focused on improving the indoor penetration capability by enhancing the signal design and doing some other things. Third, we use modern cryptographic techniques to ensure the security and resilience of the system, specifically to intentional misdirection attacks. If you can ensure that the signal is coming from the satellite and not from a third party you can have a more secure and resilient solution.

To what extent can you replace GPS during an extended outage?

We have never considered LEO PNT as a replacement for MEO (medium Earth orbit) GNSS. GNSS are the primary domain of PNT but there are applications that have additional needs. The more independence you can get, the fewer the common modes of failure, if you can at least have some survivability in the absence of GNSS. That’s one of the services we can offer. It is probably not the most important thing to our customers, honestly. The service we offer is similar to GPS and GNSS in that we have a space segment (the satellites), a ground segment, and a user segment. We have space vehicles, user equipment, and ground infrastructure that supports the space infrastructure.

What’s interesting about the way we work with the Iridium satellite constellation is that the satellites themselves include inter-satellite links. That provides a lot of resilience to ground-based events. The satellites themselves have a time transfer capability between them. So, we don’t require a direct connection to every satellite to propagate a time throughout the network. That’s one unique aspect we can take advantage of with this particular network, Iridium, which is pretty amazing.

Additionally, we have multiple ground infrastructure and monitoring sites and multiple sources of time at those ground monitoring and control stations. For example, some of them rely on GNSS combined with atomic clocks as their master timing source but we also have one installed at the National Institute of Standards and Technology facility in Boulder, Colorado. So, we have multiple primary time sources that we can integrate into our filtering across the network. That, combined, with satellite links, allows us to maintain time for substantial periods independent of GNSS.

How do you define “complementary PNT” and how does Satelles fit in that mix?

Several applications have additional needs beyond what GNSS offer. There are many technologies that can come to bear on that. There’s the LEO satellite base, which is where Satelles fits in, but there are also local and wide-area terrestrial radio navigation sources, network-based time transfer, signals of opportunity, and so on. They all have something important to offer, depending on the application. Satelles’ LEO satellite solution is available today, has global coverage, and is relatively affordable. It leverages the capital investments that have been made to launch the satellites to provide this service globally. The industry is working together to make sure that an awareness of these capabilities is propagated throughout the industries that we serve.

Besides the orbit height, which requires many more satellites, how does your system differ from GNSS?

We do not consider LEO PNT as something that might replace MEO PNT. The fundamental difference is being in lower Earth orbit, which results in a higher received power. That is what allows us to penetrate, just based on the 1/r2 losses. The measurable Doppler signatures give additional observables for PNT calculations, and higher satellite dynamics that can help with multipath. This service relies on many of the same physics and geometry as GPS. We measure the time of arrival of a very similar signal. The signals from the Iridium satellites are even in the L band. Very often we’re using a GPS chip that’s been reprogrammed to track and utilize our service as well as GPS or instead of GPS.

If I explained how GPS works to, say, a high school science class, how much of that basic explanation—about trilateration, spread spectrum, etc.—would also apply to your system?

It’s fundamentally the same. It relies on a lot of the same physics and geometry. We measure the time of arrival of a very similar signal. The signals from the Iridium satellites are even in the L band. Very often we’re using a GPS chip that’s been reprogrammed to track and utilize our service as well as GPS or instead of GPS. There are subtle differences—for example, a lower Earth orbit is faster—but it is very similar.

How would GPS user equipment have to be modified to make use of your service?

We don’t think of STL as something where we are modifying GPS user equipment. Rather, we think about what must be done in an end-user application to meet their needs. For example, one of our partners, Orolia, has a GNSS + STL secure synchronization product that we have delivered to customers in data centers and major stock exchanges around the world. Those are operational and in service. They integrate through standard interfaces, such as PPS or PTP, depending on the type of equipment to which they are connecting.
Ultimately, we don’t think of it is as replacing GPS user equipment. Rather, where a user has a need for PNT, they’re opting for this GNSS + STL solution because they have an indoor need, such as a data center, or they have a need for resilience in the case of a stock exchange.

Another example is Jackson Labs. The Jackson Labs 2600 is also a GNSS + STL solution that generally is integrating with existing 5g. It has a specialized transcoder interface that can work with any existing GNSS-type equipment. In some cases, we’ve taken a chip that was originally designed for GPS and modified its firmware.

Who are the earliest adopters?

Satelles’ LEO satellite solution is available today, has global coverage, and is relatively affordable. It leverages the capital investments that have been made to launch the satellites to provide this service globally. Data centers, stock exchanges and cell phone providers are implementing these capabilities today. The major wireless operators are seeing that more and more of the 5G infrastructure they roll out is going indoors, where GPS doesn’t reach. We provide a solution that integrates with their existing solutions and can provide reliable timing capabilities.

If your solution can survive on its own, why does it need GNSS at all?

In some cases, the user is not using GNSS at all. The product itself has a GNSS capability. User equipment is very affordable and the service is taxpayer-funded. In many cases, especially for indoor installations, the equipment that is installed is capable of tracking GNSS and STL signals, but often it relies on the STL signal itself for timing.

How do you predict STL spreading through various applications and industries?

We have our hands full with the markets we’re going after now, but there are certainly going to be other markets in which the customers will recognize that they have a critical need to implement a backup solution.

In the long run, could LEO satellites replace MEO ones for GNSS?

Sometimes there have been misperceptions in the industry. I’ve never considered that LEO PNT satellites might replace MEO ones. There are excellent reasons why Brad Parkinson, Jim Spilker, Gaylord Green and others decided almost 50 years ago to put GPS in MEO. Those physics haven’t changed. You can cover a large portion of Earth with each satellite. LEO will not replace MEO, but it has unique characteristics that make it a great complement to the GNSS MEO solutions.

Do you have any additional comments about complementary PNT?

It’s good to see that the federal government is encouraging the adoption of complementary PNT, which they often call “GPS backup.” It is encouraging to see the amount of activity on this issue that’s been going in Washington over the last couple of years. Although our company is very focused on delivering a LEO-based PNT service, which has several advantages for customers that need a global capability, many technologies can play an important role in those solutions.

The U.S. Department of Transportation did a fantastic job of looking at several of those technologies across those different categories. The European Union has also had a similar activity recently. Some reports will be coming out soon about that. It is very important that the government understands that this is an important issue for our society and encourages industry to adopt these solutions and is even starting to make some investments toward that. That includes executive order 13905 and some recent funding increases by Congress.

All of that has been very important and positive, as has modifying some of the legislation to be more inclusive of multiple technologies, such as removing the words “land-based” from the National Timing, Resilience, and Security Act this year.

I am involved in an industry consortium, the Open PNT Industry Alliance, with several other companies whose CEOs are in alignment that there is no single answer. Having a thriving ecosystem of technologies and companies trying to solve this important problem is incredibly important and it’s exciting to see.

After a negotiation process that began in December 2021, Orolia officially joined Safran Electronics & Defense on July 8.

Orolia employs more than 435 people in Europe and North America and has revenues of about €100 million. Its solutions include atomic clocks, time servers, simulation and resilience equipment for GNSS signals, and emergency locator beacons for commercial aviation and military applications.

These products and solutions will complement Safran Electronics & Defense’s activities as it meets the challenges of positioning, navigation and timing (PNT) in contested and vulnerable environments, Safran said.

In most situations, GNSS receivers are the reference providers of time and position data. Still, they need to be secured by combining them with accurate, high-integrity autonomous time or inertial references.

Through this partnership with Orolia, Safran Electronics & Defense, will offer a comprehensive set of resilient PNT architectures and equipment to meet the challenges of integrity and robustness for the aviation, defense, space, transportation, new mobility and critical infrastructure markets.

“Orolia could not imagine a better fit than with Safran to secure its growth and leverage its PNT leadership positions,” said Jean-Yves Courtois, CEO of Orolia. “Thanks to the addition of best-in-class timing and inertial technologies, premier access to the largest defense and aerospace markets, and a proven track record in government program capture and execution, Safran and Orolia now have all the cards in hand to establish themselves as the resilient PNT leader.”

Martin Sion, CEO of Safran Electronics & Defense, said: “The acquisition of Orolia makes Safran one of the few companies with the full complement of PNT technologies, bringing together Orolia’s precise time referencing and Safran Electronics & Defense’s proven inertial navigation solutions. Our shared ambition is to become the world leader in resilient PNT for all conventional and strategic applications.”