GNSS receivers face the same old challenges (extremely weak received signal, orbit and satellite clock errors, ionospheric and tropospheric delays, multipath, dilution of precision, urban canyons, etc.) and new ones (increased interference). However, compared with just a few years ago, they benefit from new signals, many more satellites, a panoply of options for corrections, and improved integration with inertial navigation systems (INS).
For example, pole-tilt compensation is quickly becoming standard. This feature enables users to locate dangerous or hard-to-reach points by measuring them at an angle with just the tip of the pole to which the receiver is attached.
Pole-tilt compensation also makes surveying and mapping easier by removing, in many situations, the need to use total stations or offsets. Together with improvements in work processes, this makes GNSS receivers more user friendly. This is particularly welcome now that more surveyors are retiring than there are new surveyors entering the profession.
The greater accuracy of GNSS receivers enabled by the increase in the number and quality of satellites, signals, corrections services and integration of GNSS with other sensors is also increasing the number of use cases, especially at the high end of the accuracy requirements, such as lane-level vehicle navigation. (Next month’s cover story will center on this year’s Google Smartphone Decimeter Challenge contest, in which competing teams aim to bring smartphone location down to the decimeter or even centimeter resolution using raw location measurements from Android smartphones. This could enable services that require lane-level accuracy, such as estimated time of arrival when using a high-occupancy vehicle lane.)
This month’s cover story highlights what has changed “inside the box” to improve the accuracy and resilience of GNSS receivers for surveying, mapping and a variety of other applications. Read the success stories from five different companies below.
The CivDot UGV marks thousands of coordinates per day precisely and efficiently
Trimble Ventures, Trimble’s corporate venture capital fund, is investing in Civ Robotics, a San Francisco-based construction tech startup focusing on transforming surveying layout for civil engineering and infrastructure projects.
The investment supports Trimble Ventures’ mission to invest in early and growth-stage companies that are accelerating innovation, digital transformation and sustainability in the industries Trimble serves: agriculture, construction, geospatial and transportation. The investment terms were not disclosed.
The construction industry faces a variety of challenges including shortage of skilled workers, safety and productivity. Civ Robotics addresses these challenges with CivDot, a new autonomous surveying solution that empowers efficiency, productivity and safety on the job.
CivDot is an unmanned ground vehicle (UGV) designed for civil engineering and infrastructure projects such as solar farms, roadways, data centers, power plants and more. Augmenting the surveyor’s work, CivDot marks thousands of coordinates per day precisely and efficiently, while delivering layouts faster than traditional methods.
“We are focused on investing in companies that are seeking to address important challenges in markets that align with Trimble’s mission of transforming the way the world works,” said Aviad Almagor, vice president of technology innovation at Trimble and technology advisor for Trimble Ventures. “Civ Robotics technology supports surveyors and field workers and helps remove the burden of repetitive and risky work.”
Civ Robotics uses Trimble’s high-precision GNSS positioning technology and surveying software to improve productivity and increase safety, Almagor said. “This is an exciting opportunity to help accelerate innovation in autonomy, surveying and construction.”
“Trimble and our vision are in lockstep towards construction automation with a sharp focus on the highest standards of safety and quality,” said Tom Yeshurun, co-founder and CEO, Civ Robotics, which announced its $5 million seed funding round this morning. “Through Trimble’s latest GNSS technology in our autonomous surveying products, our customers can benefit from an end-to-end workflow.”
Civ Robotics will be showcased at the Trimble Dimensions+ User Conference, taking place Nov. 7-9 in Las Vegas.
The CivDot UGV, equipped with Trimble high-precision GNSS. (Photo: Civ Robotics)
According to Fact.MR, a market research and competitive intelligence provider, the global surveying and mapping services market was worth US$9 billion in 2021 and is expected to expand at a CAGR of 3% during the forecast years of 2022-2032.
The survey and mapping industry has significantly benefited from drone technologies, because UAVs are less expensive and more accessible compared to traditional methods. Conventional surveying methods require rental aircraft and trained pilots, along with attached recording instruments — a costly and resource-intensive process. The introduction of UAVs has substantially created a future opportunity for surveying and mapping services to gather spatial information in a tighter structure. This also allows the collection of geospatial information with easy storage, processing and sharing capabilities.
For instance, in May 2022, India-based software company PDRL introduced a software-as-a-service platform — DroneNaksha — under the Svamitva Yojana scheme by the government of India for mapping land parcels using drone technology across the country. Similarly, in March 2022, Australia-based Emesent introduced Hovermap ST autonomous drone lidar mapping and surveying payload.
The integration of advanced technologies such as Wi-Fi, first-person view cameras, and GPS technology to make UAVs highly flexible and eliminate the need for a skilled pilot is expected to stimulate the demand for drones for survey and mapping activities, thereby driving market expansion.
Key Takeaways
The global surveying and mapping services market is projected to expand at a CAGR of 3.4% and reach US$13 billion by 2032.
Over the 2017-2021 historical period, the market evolved at 3.2% CAGR.
Forestry and agriculture account for a leading share in the market at a valuation of US$1.80 billion in 2021.
North America and East Asia account for leading shares in the global mapping services market at 24% and 32%, respectively.
ComNav Technology Ltd. has released the N2 Palm RTK GNSS receiver. The release coincides with the company’s 10th anniversary. With its advanced technologies, the N2 is suitable for surveying, mapping and construction.
The N2 has a highly integrated main board and a three-in-one antenna, yet is extremely thin and portable, weighing about the same as a basketball (0.72 kg with battery) and measuring 48 mm, the thickness of AirPods.
Powered by ComNav’s SinoGNSS K8 high-precision module, the N2 can track 1,590 channels, including all existing and planned signals of GPS, BDS-2, BDS-3, GLONASS, Galileo, QZSS and SBAS. Its advanced satellite-tracking technology ensures it works well even in harsh environments, such as under heavy foliage or close to buildings.
A third-generation inertial measurement unit (IMU) makes the N2 immune to magnetic disturbance, which greatly improves its reliability. Pole-tilt compensation of up to 60° allows surveyors to locate difficult points precisely and easily while maintaining positioning accuracy within 2.5 cm. By using the company’s Quantum algorithm, the N2 achieves calibration-free operation — after 10 seconds of initialization, users can make tilt measurements with centimeter-level accuracy for an extended period, greatly improving efficiency.
With its integrated UHF modem, the N2 can reach a working range of up to 15 km. It can be used as either a base station or a rover.
The N2 features a 10,000 mAh intelligent Li-ion battery, along with ComNav’s patented low-power-consumption technology. It fully charges in five hours and works continuously in the field for 20 hours. The built-in USB-C port makes it convenient to charge with standard smartphone chargers or external power banks.
As with ComNav’s other products, the N2 meets ComNav’s high quality and durability standards; it is rated IP67 (dustproof and waterproof) and can work in temperatures from –35° C to +65° C. It can be used in a wider range of outdoor working conditions.
With near-field communication (NFC), the N2 can connect to other NFC-enabled devices, such as the R60 data collector. V5.0 dual-mode Bluetooth inside allows users to connect at ultra-long distances with low energy requirements.
The N2 Palm RTK GNSS receiver now is available through ComNav Technology authorized local distributors or directly from ComNav Technology.
“Nothing can remain immense if it can be measured,” Hannah Arendt wrote in 1958 in The Human Condition. This could be the guiding inspiration for any geodesist or surveyor throughout history. In about 240 B.C., Eratosthenes became the father of geodesy by ingeniously measuring Earth’s circumference using the Sun, a well, a vertical column, the distance a camel caravan traveled from Syene to Alexandria and some basic mathematics. His estimate of 46,000 kilometers was 16% too large but remarkably close considering that he lacked any modern measuring tool. (For a great account of this epic feat, see John Noble Wilford’s The Mapmakers.)
Geodesy, a branch of applied mathematics, is concerned with accurately measuring and understanding three of Earth’s fundamental properties: its geometric shape, its orientation in space, and its gravity field. Earth’s true shape varies from the mathematically smooth surface of an ellipsoid due to local differences in its density that cause variations in the strength of the gravitational pull, in turn causing regions to dip below or bulge above a reference ellipsoid.
This undulating shape is the geoid, which geodesists have defined as the three-dimensional surface along which the pull of gravity is a specific constant. It serves as the zero-level surface for height measurements globally, and all GNSS are pegged to it. It is a hypothetical surface that essentially represents an extension of the idealized mean sea level over (actually, mostly under) Earth’s land surface. Unlike the surface of the oceans, however, it is unaffected by wind, waves, the Moon, or forces other than Earth’s gravity.
Surveyors are content with measuring much smaller portions of Earth’s surface, from single lots to national boundaries. Unlike Eratosthenes, they work with the latest fruit of modern science and technology — including GNSS receivers, robotic total stations, inertial measurement units, lidar, other sensors and unmanned aerial vehicles — and can measure distances with millimeter precision.
When I started in this business a little more than 20 years ago, we used to group GPS receivers by accuracy into three buckets: consumer grade, resource/mapping grade and survey grade. As accuracy has increased for all GNSS receivers, the boundaries between those categories, especially between mapping and surveying, have blurred. Additionally, we now have way more GNSS satellites — in some parts of the world, as many as 70 are in view at one time — and a panoply of public and private, ground-based and satellite-based corrections services.
So, surveyors have a growing set of tools, and they are constantly getting more accurate and more user-friendly.
Now, let me throw another number in the mix: 66. That is the average age of surveyors in the United States. In the short run, employment for surveyors hinges in part on the vagaries of the economy. In the long run, however, population growth and climate change will force large investments in infrastructure. On most construction sites, the first to arrive and the last to leave are the surveyors. We know what their tools are, but who will they be?
Land surveying is an ancient practice, dating back at least 5,000 years to when Egyptian rulers used it to tax land plots. Over the centuries, it has been repeatedly transformed by new technologies — the compass (about 200 B.C), the theodolite (1550s), Gunter’s chain (1620), the sextant (1757), electronic distance measurement (1950s), and total stations (1970s). Then came GPS, followed by the other GNSS and corrections services.
Now comes sensor fusion, which aims to compensate for the limitations of GNSS — orbit and satellite clock errors, ionospheric and tropospheric delays, multipath, dilution of precision, urban canyons, jamming, extremely weak received signal, etc. — by integrating it with other sources of positioning data, including inertial measurement units (IMUs), lidar sensors and cameras. Even crowdsourced geolocation data collected with cell phones help expedite surveys by guiding surveyors to landmarks.
In the following article, representatives of five companies share their perspectives on recent advances in surveying and the remaining challenges.
Many More Satellites
City Rail Link is New Zealand’s first underground rail network and the largest transportation project ever undertaken there. In this photo, taken at Karangahape Station, the Mined Tunnel Team installs a lattice girder secondary support structure using a Trimble SX12. (Photo: Link Alliance)
Compared to just a few years ago, there are many more GNSS satellites, signals and options for correction services. Over the past decade, the average number of satellites in view has more than doubled to more than 40 today. Some parts of the world have more than 70 satellites in view, said Boris Skopljak, vice president, Surveying & Mapping Strategy and Product Marketing at Trimble Inc.
“The developments in GNSS field systems have always been geared toward simplifying workflows, improving accuracies and increasing productivity,” Skopljak said. “In the last few years, we’ve seen that on a massive scale. In some of our materials, we no longer even quote how many signals our GNSS receivers are tracking.”
The vast increase in the number of satellites has extended high-precision applications to the robotics and automotive markets. The challenge now is “position solution,” not just GNSS, said Simon Peng, director of the Overseas Department at ComNav Technology. The improvements in the satellite constellations, antenna technologies and algorithms also enable surveyors and other users to obtain results faster and to operate in environments previously impervious to GNSS, such as under heavy canopy and very close to buildings.
“Our customers can now operate in environments where there is no virtual reference station (VRS) infrastructure or real-time kinematic (RTK), by leveraging precise point positioning (PPP) solutions, such as the Trimble RTX corrections service,” Skopljak said.
“Additional satellite signals and constellations (like Beidou),” Skopljak said, “improved antenna technology and continuously evolving algorithms are contributing to improving the RTX accuracy while bringing the convergence times to almost instantaneous in normal conditions and making technology available in more regions.”
“When I first started surveying, if we had a 12-channel receiver, that was doing very well,” recalled Jesse Huff, head of Sales and Marketing, JAVAD GNSS. “Now, we’re tracking 36 birds in the sky at one time with an 874-channel receiver. That’s phenomenal.”
Huff described a patent-pending feature called real-time post-processed kinematic (RTPK). “It combines RTK, PPK and PP techniques, with multiple core processing engines and a single solution coming out of that. It is impressive standing underneath a giant oak tree and surveying that monument with GPS and knowing what your accuracies are. We’re not even chasing RMS values; we can report the actual positional uncertainties, which is amazing.”
Pole tilt compensation enables surveyors to precisely and easily localize points that are difficult or dangerous to access. (Photo: ComNav Technology Ltd.)
“With so many signals and the new ways of how we compute positions based on PPP technology, we can almost globally get to centimeter-level positioning within a couple of minutes from just one global correction link,” said Bernhard Richter, vice president of Geomatics at Leica Geosystems AG, part of Hexagon. “Under optimum conditions, you can have almost an instantaneous global accuracy of a couple of centimeters.” In mature areas, he added, a local RTK network infrastructure enables achieving centimeter accuracy within a couple of seconds.
Galileo, Richter pointed out, will be fully operational in 2023 with great signals, though he’s “a bit skeptical” about the system’s target date for its high-accuracy service. “So, we will basically get global constellation corrections that allow us also centimeter-level positioning.” BeiDou has been fully operational since 2020. “GLONASS is more unpredictable,” Richter said. “It looks like modernization is slowing down a bit, in particular the CDMA developments.” Additionally, he pointed out, it is possible that one or more governments may decide not to use those signals, for military or political reasons. “It’s not the manufacturers who decide which signals to take.”
“In open-sky conditions, additional satellites have added redundancy — which is always good for position integrity — but it’s only when obstacles start to appear on the horizon, blocking out parts of the sky, that all-in-view RTK really comes into its own,” said François Freulon, Head of Product Management at Septentrio. When they did not have a full view of the sky, he recalled, GNSS users used to have to carefully schedule their work to coincide with times of high satellite visibility. “Nowadays, by using multiple constellations and signals, RTK can reach the parts that receivers in the past could not tread. More signals and constellations have also helped in easing the collection workflow for surveyors, making the capture of data in difficult conditions much quicker and more efficient.” New correction services are further simplifying the workflow “thanks to new positioning techniques, pricing business models and simplified network density.” However, corrections companies still face challenges in ensuring that centimeter accuracy can be uniformly achievable at a global scale.
Sensor Fusion
The ongoing evolution in computing power and communication technology “leads to many more sensor combinations,” Skopljak said. “We are not talking about GNSS alone anymore. We are talking about integrating a GNSS antenna, a receiver, an IMU, power and communications into a single compact housing.” The integration of inertial sensors makes it possible to localize the instrument rod tip when the pole instrument is tilted. “That allows our customers to measure more safely in dangerous environments.”
“We are reaching a maturity stage of what we can do only with GNSS,” said Richter. “It’s all about sensor fusion. The problem when signals are obstructed, that’s not solved, even though we can do positioning from Wi-Fi hotspots or from local pseudolites.” So, fusing data from cameras, lidar, GNSS and IMUs in better ways is the way to go and presents “a huge open research ground.”
For Richter, the challenge is not just positioning, the orientation of objects is almost as important as that, especially for such tasks as machine control. “It’s also about what you do with the data that you collect. Hexagon’s vision is of an autonomous future where we put data to work in connected ecosystems to boost efficiency.” However, he pointed out, this requires large amounts of data, such as those from aerial photogrammetry, lidar and mobile mapping systems used to create city models and digital twins of buildings. “If you really want a car to drive autonomously through a city with all the things that could happen, you must rely on a perfect replication of the real world,” he said. Other examples he cited are more efficient evacuation plans and flooding simulations. “GNSS will never be enough, but it will always be a very good enabler because it works.”
Classes of Receivers
JAVAD GNSS designed its TRIUMPH-LS Plus receiver to work under heavy tree canopy. (Photo: JAVAD GNSS)
Two decades ago, we would often group GNSS receivers by accuracy into three buckets: consumer grade, resource or mapping grade, and survey grade. As accuracy has increased for all GNSS receivers, the boundaries between those categories — especially between mapping and surveying — have blurred. “The performance of GNSS has increased so much that we are not using the traditional accuracy-based differentiation between surveying and GIS,” said Skopljak. “For mapping professionals, 10 years ago it was all about points, lines and polygons; now it is all about locating assets and adding the most accurate positions as attributes to those assets. For our survey and engineering customers, what matters is still geometry and working with the models to serve the connected construction in the field.” As for the pure GNSS technology stack, “we are seeing fewer differences between mapping and surveying receivers, but we are focusing on serving the customer in terms of product-as-a-service or as a productivity tool.”
Huff made two points. First, that “survey grade” does not necessarily equal RTK. “Some education needs to happen so that people understand RTK as a technique, not an accuracy. You can get poor accuracy and poor fixes with RTK, even when you’re using good techniques. So, when I say ‘survey grade’ I’m still talking about the full frequency receivers, using all available signals.” Second, that consumer-grade receivers, such as the chipsets in our phones and computers, do not require the same robustness as professional ones. “While they may be achieving the same precision, surveyors must be able to defend their position in a court of law.”
Huff cited the “phenomenal” success of the simultaneous localization and mapping (SLAM) movement with all kinds of positioning challenges. “From a survey perspective,” he said, “we’re dealing with a much more feature-rich dataset than we were even just 10 years ago, with everybody having some type of GPS device on their phones. There are location tags on everything. That creates evidence for the surveyor to be able to go out and recreate things, reduce trips to the field, reduce rework times — all those things that make a surveyor’s life much easier.”
Surveyors now can fly aerial surveys of hundreds of acres in less than half an hour using drones with RTK, Huff said, instead of having to wait for the flying season with traditional airborne photos. If needed, they can pick a few ground-control points for ground truthing. “We’re able to do that with photogrammetry techniques, but using GNSS technology to position drones, whether it’s real time or post-processing, has definitely made surveying jobs easier.”
Correction Services
The adoption of GNSS in construction is growing and receiver manufacturers are making it easier to use their equipment in the field. (Photo: Leica Geosystems)
Correction services — such as satellite-based augmentation systems (SBAS), the ground-based Wide Area Augmentation System (WAAS) and the European Geostationary Navigation Overlay Service (EGNOS) — make a big difference along with PPP and similar techniques when base stations are not available. “We have the whole CORS network here in the United States,” Huff pointed out. “We also have services available from the National Geodetic Survey.”
Those who don’t want to have to fully engage in post-processing can upload their data to the Online Positioning User Service (OPUS), AUSPOS (a free online GPS data-processing facility provided by Geoscience Australia) or other corrections services that will post-process positioning data. “It has made it more accessible for all the surveyors all the way around, especially as the technology has improved and the cost barrier to entry into a survey-grade GPS receiver has come down significantly as well,” Huff said.
Growing Adoption of GNSS
The greater number of satellites in orbit significantly reduces convergence time and increases the accuracy of the solution, which makes the technology much more user-friendly for professionals and nonprofessionals alike.
For surveyors and mapping professionals, the increasing levels of GNSS performance means that “GNSS continues to be the dominant equipment and they can operate in challenging GNSS environments while still meeting the accuracy and precision requirements,” Skopljak said. GNSS usage is also growing in such industries as agriculture, construction, transportation and logistics. “Now, when farmers are on a combine, they don’t have to wait for an RTX or PPP solution to converge for 20 minutes. The solutions just work, and they can perform their task.”
Skopljak also pointed to “more flexible business models, such as pay-as-you-go or equipping seasonal workers or fleets of spatially enabled consumers to use GNSS,” that reduce the required upfront investment. “Surveyors now can go for longer and be productive in more areas where they could not use GNSS technology before. The non-surveying professionals — such as in natural resources, farming or construction — now can just turn on the machine and things work for them. They don’t have to worry about coordinate transformations and things like that.”
“Twenty years ago, when RTK and networks kicked in and then became popular, we were discussing whether it was the end of the automated total station,” Richter recalled. “Yet, the number of automated total stations has grown ever since.” To him, this is proof that GNSS alone will never solve all surveying problems. GNSS’ weak signal will always require surveyors to supplement it with other sensors, such as reflectorless total stations. “These instruments always need to work in harmony,” Richter said.
Success on both construction sites and in machine control require a very good robotic total station and a very good GNSS receiver, Richter said. “The simple problem of leveling a pole is actually solved, and we are using the technology that we developed for tilt-compensating GNSS receivers. We’re leveraging this now into the world of the total station.” This has solved one of the fundamental problems surveyors have long had, because they no longer need to level up and can measure tilted poles with a total station and with a GNSS receiver. “We have also made it very seamless for surveyors to switch between using GNSS receivers and total stations,” Richter said.
Geneq Inc. has released the SXblue SMART to meet the requirements of professionals looking for an accurate, flexible smart antenna for field work.
The SXblue SMART features a GNSS engine capable of quickly tracking all-in-view GNSS signals. Its design includes interference mitigation technology and optimization for handling a wide frequency band.
Weighing 850 g including battery, the SXblue SMART is compact, supplying the accuracy, ruggedness and maneuverability needed by surveying professionals. Its radio link is based on the Farlink protocol that allows a range of up to 8 km, a performance achievable while reserving a wide bandwidth for transmission of real-time kinematic (RTK) data.
In addition to a tilt sensor for measurements in hard-to-reach places, the SXblue SMART features a high-performance attitude measurement module that can detect and measure movement of the device. An integrated inertial measurement unit provides even more accurate and stable measurements and increased productivity. The SXblue SMART also has a built-in thermometer for monitoring and controlling its internal temperature.
Compared to the company’s previous products, the SXblue SMART has improved communication features, including near-field communication that facilitates close communication with a controller or mobile phone equipped with this technology.
Antenna manufacturer Harxon has launched a new company website, which features eye-catching animations and dynamic illustrations.
“We’ve optimized the website in both the layout and the content,” the company stated in a news release. “You’ll find more detailed product pages, seven major industry applications, and more information about Harxon Corporation.”
New additions include Antenna Customization and Antenna Selection pages, designed to help customers determine which products meet their project needs.
Harxon’s latest products include the survey GNSS antenna HX-CSX633A, the ruggedized HX-CVX606A and the X-Survey OEM antenna HX-CSX179A.
Jason Poitras (left) and Marc Veinotte of MicroSurvey test a multi-constellation OEM rover with the FieldGenius for Android field controller software. (Photo: Gavin Schrock)
It’s about more than advances in technology — peak times demand peak productivity
Trusty legacy rovers have served surveyors well. Under the right conditions and with proper procedures, a 20-year-old rover might still deliver precisions that could match the latest and greatest.
We’ve become so used to the limitations of legacy gear that we’ve built our workflows, expectations, and job estimates around them. However, in the past few years, the state of GNSS rovers has experienced a sea change, with gains in productivity, the ability to work in mixed environments, ease of use, and increased speed, repeatability and reliability — these developments have come at an opportune time.
Peak Times
Surveying always has been a feast-or-famine prospect; the rises and dips in economics are felt sharply within the profession.
In many places, there is more work than surveyors can accommodate, with competition to recruit and retain enough field personnel to meet demand. It is unclear how long this peak will last. Surveying firms recognize this and do their best to take on as many projects as they can.
Staffing is an acute challenge. Firms have had to dip into incentives beyond the usual pay and benefits packages to attract and retain qualified field personnel. Having the latest gear is a definite plus. Experienced surveyors know much they struggled with legacy gear: GPS-only or GPS + GLONASS only, slow processors, poor multipath performance, and field-data-collector operating systems and software that are obsolete or no longer supported.
Despite the immediate need, it’s generally less desirable to hire people with no surveying experience and train them from scratch. However, newer rovers and field software often do not have the same steep learning curve posed by legacy systems and methods.
Productivity Now
It is hard to say how much of the productivity gains, stated by various manufacturers for their newest systems, will be realized for your specific workflows, but simple testing can give you an idea.
When surveyors try out new rovers, they tend to find themselves so impressed by the first unit tried, they conclude it must be “the best” and eschew due diligence in the selection process. That aside, I believe it is safe to say that there is a near across-the-board productivity improvement with the latest generation of rovers.
Most rovers now provide no-calibration tilt compensation. (Photo: Gavin Schrock)
A Confluence of Factors
We haven’t seen such a sea change in GNSS rover technology in decades; most gains have been incremental. Similar jumps in the past included going from the static-only world to real-time and the first additional constellation beyond GPS.
While the early days of GLONASS were rocky, and most manufacturers were hesitant to productize an unreliable and noisy solution, it did eventually improve. The effect of nearly doubling satellites in view translated to productivity gains. But that was two decades ago.
The recent advent of true, multi-constellation GNSS has had a profound impact on the state of rovers. In 2020, both the Galileo and BeiDou constellations reached a full level of global coverage and signal integration.
Many rovers were already equipped to utilize some (but not all) of the newest satellites and signals. Interface control documents (ICD) for some of the signals have only been released by the constellation providers in the past few years. ICDs provide signal specifics that manufacturers need to integrate them into GNSS solutions.
Some rovers (and base receivers) developed four or more years ago may not be able to take advantage of the full complement of signals. And many did not have the processing power to utilize so many signals from so many satellites in real-time solutions.
By contrast, nearly every new GNSS board released in the past few years has greatly increased processing power, often double that of legacy gear.
Newer rovers are able to work better in sky-view-challenged and multipath hazard-prone places than rovers from only a few short years ago. And it is not just about the total number of channels on a rover datasheet, it is about how many are actually being utilized, how much of that data the processors and real-time kinematic (RTK) engine can handle, and how modernized signals are being leveraged.
Modernized signals are yielding additional advantages. The expected benefits of L5 for the GPS constellation have been widely promoted. L5 was designed to be robust enough for certain safety-of-life applications. The L5 signal is being deployed incrementally to the GPS constellation and should be broadcast from 24 satellites by 2027.
Modern receivers incorporate multi-GNSS signals that can improve performance under tree canopy. (Photo: Gavin Schrock)
I have heard surveyors say they won’t bother upgrading until L5 is complete. But wait — two other constellations already have third-signal capabilities. Indeed, there are 3, 4, 5, even 6 usable signals (in the case of Galileo) already available — modernized, robust signals.
Although L5 will only make this better, you can reap the benefits of signal modernization right now. Some of the innovation put into these modernized signals contributes to reducing certain sources of error. For instance, the Galileo E5a-E5b AltBOC — multiplexing signals in a wide band — is particularly beneficial for dealing with multipath.
Rovers have evolved in other ways besides multi-constellation integration. The decades between these sea changes brought developments such as electronic bubbles, better operating systems, and automation of some functions, but essentially the form factor and functionality of a surveying rover has not changed much. There have been some gadgets and gimmicks along the way, but otherwise rovers had remained pretty much standard in those intervening years.
Real-time precise-point positioning (PPP) has matured to the point that it could be viewed as survey-grade (at least in the horizontal). The delivery of clock, orbit and other data broadcast from geostationary communications satellites (as a service) for PPP means that, for many applications, high-precision positions can be processed by a rover over much of the globe — no base, no radio, no network and no cell phone connection required.
Once research and development removed the lengthy convergence times that plagued legacy PPP, it became commercially viable for many applications. Commercial providers such as Trimble (RTX), Hexagon | Leica (SmartLink), Hemisphere GNSS (Atlas) and others provide subscription services for surveying, construction, agriculture and the growing autonomy market. Most new survey rovers have a PPP option.
Multi-sensor integration, particularly of inertial measurement units (IMU), is becoming standard on new rovers. While there was some value from magnetometer-oriented tilt compensation in the past (though it could be cumbersome and somewhat unreliable), it served as a precursor to modern-day integrated GNSS/IMU no-calibration tilt.
The first no-calibration tilt system hit the market as recently as 2017; now it is hard to find a rover without it. Accessing hard-to-reach points and improved stakeout workflows are some of the benefits of tilt compensation. The development of reliable IMU/GNSS processing was also the key to fully integrating camera-based offset point capture — and soon other sensors such as lidar might be incorporated.
Market Choices
Another set of changes in the high-precision GNSS industry coincided with the above developments, growing a more competitive marketplace. This equates to more choice. The secret sauce of high-precision GNSS is no longer in the hands of the few. The glass floor has been broken, with more rovers than ever available.
Many tiers for choice have emerged.
The Top End. The manufacturers traditionally considered to be the top end continue to innovate and are usually the first to productize developments such as multi-sensor integration and PPP. They continue to lead in integrated surveying solutions, track record, performance, quality, service, support and peer user networks — which continues to appeal to many users. However, they also have second-tier offerings to suit various markets, regions and value propositions.
Whether to Use OEM Devices. For many users, there are compelling reasons to stick with top-end solutions, but there always has been room for other price point options. Until recently, most lesser-known rover brands exclusively integrated GNSS boards from a handful of well-known original equipment manufacturers (OEMs) such as Trimble and NovAtel. Sometimes new developments hit the OEM market quite rapidly — for instance, IMU integration. These third-party manufacturers may add their own touches, but in effect, nearly every rover out there offered a narrow set of DNA — until recently.
Rolling Their Own. Globally, technical universities are graduating GNSS engineers at an unprecedented rate; the prospect of mass applications such as vehicular autonomy and robotics are driving demand. With this expanding pool of engineers, it is now much more practical to develop GNSS solutions from scratch and to fully leverage multiple constellations.
Some third-party manufacturers began working with OEMs but have started developing their own boards and related technologies. I’ve tried several, and performance is, in most cases, as good as that of new boards from traditional sources..
The Rise of Mid-Price Rovers. There are a growing number of breakout rovers from lesser-known brands or rebranded models. These are about half the price of some of the top-end models, yet performance is in most cases nearly par. Some include OEM boards, or the new wave of independent boards.
I’ve seen a sharp rise in the popularity of mid-level rovers among small and mid-sized firms. However, there has not been a corresponding drop in sales of top-end rovers. It seems that surveyors are simply buying more rovers during this peak time.
Receivers-as-a-Service. Another approach for surveying and asset-mapping rovers is pay-as-you-go. This means you do not have to make large up-front investments in hardware. Instead, you pay for high-precision capabilities through subscriptions or tokens when you need it. This can be a good choice for occasional or seasonal users.
One example is Trimble’s Catalyst system. For Catalyst, the hardware investment is an inexpensive antenna, and then you access a subscription service via your mobile field data collector, tablet or smartphone to activate the software-defined receiver (SDR).
Another such model is Flex. With Flex, you have the option to pay full price for the full receiver/antenna to operate as a conventional rover. Alternatively, you can choose to pay a lower up-front price for the rover and use tokens to activate the high-precision capabilities.
Surveyors should put new rovers through their paces before choosing. (Photo: Gavin Schrock)
Low-Priced Rovers. Two external factors have fostered a mini boom in low-cost rovers: R&D for mass markets such as autonomy, and RTK/post-processed kinematic (PPK) solutions for drones, which are often used to reduce the need to set ground control points.
In both segments, inexpensive and often small GNSS boards have been developed. For drone applications where a base was needed for RTK/PPK methods, developers sometimes took the same GNSS board in the drone and packaged it as a base. It did not take long for some of these developers to package the rover for surveying or asset mapping (with geographic information system, or GIS).
While these rovers can perform just as well as top-end or mid-priced rovers in optimal conditions, they may struggle in mixed environments. I’ve tried some, and I can see why every surveyor I’ve asked about performance adds “for the price” to their assessment.
Other developers have taken this a step further, selling a bare-bones rover for less than $1,000, though these can take a lot of tinkering and extra attention to fit into a production workflow. There are even folks creating do-it-yourself rovers. I am not seeing many large firms, who have high-ticket projects and need to conduct integrated surveying, opting for lower priced systems.
We are riding a new wave of GNSS rovers, awash with more choices than ever. In this period of increased demand for surveying services, it might be a great time to upgrade and boost productivity.
New Players
A “roll your own” example is Tersus GNSS, which has designed and manufactured in-house GNSS boards and RTK engines since its inception in 2014. I asked Winston Wen, founder and CEO of Tersus, why they chose this strategy.
“I’m a hardware guy; electronics, computer science, signal processing, etc.,” Wen said. “In 2014, I took a look at the price and portfolios for high-precision, and for equipment for surveyors — the price point looked exceptionally high. From my point of view, it looked like there was room for a new player, and I felt we could do better. There are also growing markets for applications for high-precision GNSS, such as the internet of things (IoT) and autonomy.”
Tersus has experienced solid reception for its products globally. I asked Wen if he felt GNSS for surveying has reached a new level of performance. “Yes, nowadays with 50 satellites, that is huge. Surveyors will be very happy with performance, especially in environments with limited sky view. At this time, there don’t appear to be any new signals announced, so rovers bought today should be top performers to, say, 2025 and beyond.”
Industry Insights
GNSS executives told Gavin Schrock about recent developments in their companies.
Neil Gerein, Senior Director of Marketing,
Autonomy & Positioning Division, Hexagon
As satellite constellations were modernized, GNSS receivers kept pace to offer multi-constellation and multi-frequency capabilities to culminate in the latest technologies in PPP corrections.
For example, Hexagon’s RTK From the Sky technology is able to achieve highly available corrections with centimeter-level accuracy globally. However, modern GNSS receivers also offer other benefits, such as interference mitigation and spoofing detection for improved positioning robustness, multipath mitigation, and more powerful sensor fusion.
Miles Ware, Vice President,
Marketing & Global Customer Care, Hemisphere GNSS
Much like the constantly evolving world of smartphones, tablets, and computers, the improvements in multi-constellation GNSS receiver performance have been significant, even over just the past few years.
Many legacy rovers, bases and reference stations that are older than four years cannot track some of the newest signals, such as from BeiDou Phase 3 satellites. This means some of the highest performing signals available are now accessible to many users. As fewer BeiDou Phase 2 satellites continue to transmit, many legacy receivers will no longer have the performance they once did.
With upcoming services such as OSNMA (the Galileo GNSS data authentication service) and global PPP signals, many receivers from a few years ago do not have the CPU capacity to employ them. Today’s GNSS engines track more satellites, more signals per satellite, and have more CPU to perform advanced operations, all while consuming the same or less power than previous generations.
Francois Martin, Vice General Manager,
CHC Navigation
The latest GNSS RTK rover technology evolutions are based on the maturity and enhancement of satellite navigation systems, as well as the integration of IMU sensors into the receivers.
The most recent generation of our GNSS rovers, such as the CHCNAV i83, is based on the sophisticated iStar algorithm that significantly improves the efficiency of GNSS satellite signals tracking for unmatched performance in GPS, GLONASS, BeiDou, Galileo and QZSS constellations, utilizing all available frequencies, including BeiDou 3.
Moreover, the fusion of GNSS and IMU technologies enables centimeter-level positioning, maintains fixed and reliable RTK accuracy, and collects points faster than ever before, even in challenging conditions. GNSS survey productivity is increased by up to 30%, and the user base expands from experienced users to new users such as construction site foremen.
Gavin Schrock, PLS, is a practicing land surveyor, the operator of a cooperative real-time GNSS network in Washington state, and a technology writer.
Fugro has completed a hydrographic survey to determine a safe channel through the Star Reef Passage in Papua New Guinea.
Fugro worked with the National Maritime Safety Authority (NMSA) and with funding from the Asia Development Bank (ADB) on the survey, which will be used to update nautical charting and improve coastal zone management.
The project is a key initiative contributing to Papua New Guinea’s sustainable economic development.
Fugro used its LADS HD+ Airborne Lidar Bathymetry (ALB) system, which was deployed with a team of surveyors from both the NMSA and Fugro working in collaboration.
Fugro’s ALB system meets International Hydrographic Organization (IHO) standards with the data now set to be used to update nautical charts. The data was collected safely and with minimal environmental impact on the sensitive reef environment or local marine activity.
Through this Maritime and Waterways Safety Project, Fugro has successfully worked with the NMSA and ADB to help deliver both hydrographic data and training of NMSA staff.
The project is designed to improve the safety and efficiency of international and national shipping in coastal areas and waterways of Papua New Guinea by improving maritime safety information infrastructure and practices and capacity. Safer maritime activities that improve trade and tourism, as well as information to help manage the environment, will bring direct benefit to PNG’s coastal communities.
Mobile mapping using an OxTS xNAV650 INS and lidar sensor. Photo: OxTS
We discussed mobile mapping with Jacob Amacker, application engineer, OxTS.
How do you define “mobile mapping” as opposed to “surveying”?
We use the two terms interchangeably. Each one has a different connotation depending on where you are in the world and both can be useful. We use them to cover a broad range of use cases, but “mobile mapping” is used more specifically for land-based mapping of the environment. A typical application might be a van equipped with an INS [inertial navigation system] and lidar sensors.
“Surveying” can be used a bit more generally, applying to aerial or pedestrian-based mapping, but it does have the connotation of static mapping, which we do not typically handle.
What are your main markets for mobile mapping?
It is very hard to say. The world of mobile mapping is so diverse. However, lidar mapping could be seen as both the largest and the fastest-growing market in the surveying world as lidar has become widely affordable. Although our technology can be used with any surveying devices, at OxTS we particularly like to use lidar and are focusing on getting the best results from lidar data. This has included making our own point-cloud georeferencing software to maximize the potential of our navigation data in making point clouds.
What are the main differences between your devices for aerial mapping and for ground-based mapping?
We use the same INS device for both ground and aerial mapping. For use on manned aircraft, we would always recommend our highest accuracy system with the best IMU, the Survey+. The main source of inaccuracy in survey data will come from the IMU error over the range to the objects. Because most of this range is the aircraft’s altitude, this error is quite significant. For land-based mapping work, the measurements provided by the lighter and smaller xNAV650 are still suitable for many high-precision applications.
GNSS-INS integration has been done for decades. What is new and what are the remaining challenges?
It is now much more affordable to have very high-grade IMUs and GNSS receivers. Nevertheless, there will always be further improvements to be made to how the data streams are combined. On a similar note, other navigation aiding sources are increasingly being considered to supplement the IMU and the GNSS receiver — such as wheel speed sensors, lidar, camera odometry and others that can also be integrated to stabilize and improve the navigation data. Overall, it is very exciting what is yet to come out of INS technology. In recent years, it has become so good that people expect more and more from it, and this demand must be met. What happens when GNSS drops out? We are seeing increasing development to make the navigation data robust against challenges of any environment.
Given the IMU’s drift, for how long can your system function at an acceptable level in case of a GNSS outage?
It is difficult to put a number on what kind of drift is acceptable, as it depends on the application and the end-user requirements. Typically, half a meter of drift in one minute of GNSS-outage might be the goal for some of the higher-grade surveyors. Still others might only be satisfied with negligible drift.
What keeps the INS and the lidar unit synchronized during a GNSS outage?
The INS has an internal clock to keep the timing during a GNSS outage. Of course, this will not be as accurate as the atomic clocks on the satellites, but it is quite adequate to maintain survey-grade accuracy during GNSS outages. GNSS is still necessary to get the timing information in the first place, and this is a reliance that INS devices will want to remove in the future.
Hexagon | NovAtel’s CPT7 integrates a GNSS receiver and an INS to deliver up to centimeter-level accuracy. (Photo: Hexagon | NovAtel)
We discussed mobile mapping with Bryan Leedham, product manager of enclosures and post-processing software, NovAtel, Autonomy & Positioning division, Hexagon.
How do you define mobile mapping?
It is getting broader in scope, as more folks find reasons to map the world. The key goal is to capture reality from mobile platforms to build a digital representation of reality for some large area, such as a city, a road or a factory. Most of the time, that means from a ground vehicle on public roads.
It’s also safer and faster than traditional surveying because you don’t have to stop traffic or dodge it.
Right! In an ideal world, rather than spending days setting up traditional survey equipment, you could strap some sensors on a mobile platform and gather accurate map data in minutes.
What are the key remaining technical challenges?
Picture one of Google’s or Waymo’s mapping vehicles. The first sensors that come to mind are GNSS, inertial, lidar and radar. Each of those has its own unique strengths and weaknesses. The first technical challenge that remains is to mature each of those technologies for a lower enough cost that it’s affordable.
Right now, mobile-mapping vehicles are quite expensive, especially in areas where some of these sensors will struggle more than others. To map very dense urban spaces — with underground areas, overpasses and tall buildings where GPS is challenged — you need a very strong localization system that can survive those conditions for however long it takes to drive through them. If I’m building a car to map rural Alberta, I could choose much cheaper sensors than if I were trying to map downtown Chicago every week.
On the flip side, you must deal with the massive amounts of data collected.
Yes, that is a very large challenge. Lidar data, in particular, is guilty of generating very large point clouds. It’s a balancing act. More accurate and higher resolution maps require lidar sensors with even denser point clouds. So, you need data management and sufficient processing power to get accurate results quickly.
What are the key technical challenges in sensor fusion?
Sensor fusion is how we approach the goal of mapping as accurately as possible in increasingly difficult environments. On their own, GNSS receivers struggle in obstructed areas but, when you pair them with other sensors, they become very complementary.
Lidar and cameras, for example, are quite good at measuring the distance to nearby objects and at classifying them, but they have no idea where they are relative to one another. Likewise, if you let an IMU [inertial measurement unit] sit in your car, it will no longer know its location. However, once you give it a position update, it is very good at maintaining a trajectory over a short period of time. When you combine absolute and relative localization, all the sensors play to their own strengths.
What is NovAtel’s SPAN software?
It stands for synchronous position, attitude and navigation. It is the sensor-fusion software that combines the GNSS, inertial and whatever other sensors. It is based on core NovAtel GNSS receiver software. We can use NovAtel receivers in combination with IMUs from a wide range of manufacturers and, in the future, hopefully, other sensors from a variety of manufacturers as well.
SPAN started with blending just GNSS and inertial but we’re now researching how to bring in such things as lidar and cameras. Autonomous Stuff, another Hexagon company, works on the greater sensor fusion using SPAN as well.
