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.
PRECISION AGRICULTURE reduces inputs of seed, water, fertilizer, pesticides and fuel. (Photo: CHCNAV)
Precision agriculture refers to the ability of farmers to observe, measure and respond more precisely to the variability of soil and crop characteristics within and between fields by using maps of these characteristics and GNSS navigation. It enables them to reduce inputs of seed, water, fertilizer, pesticides and fuel while increasing outputs. Adoption of precision agriculture technology and practices has increased steadily over the past three decades and now covers the majority of U.S. farmland.
We asked three companies that manufacture GNSS receivers optimized for precision agriculture about their challenges and plans.
What are the key challenges for precise positioning in agriculture?
One of the main concerns is the impact of obstructions — both natural, such as tree canopy and topographies, and manmade, such as buildings, silos, etc. The mounting location of the GNSS antenna on an agricultural vehicle or implement can emphasize multipath effects and limit GNSS signal availability.
Our solution for these challenges is the use of a multi-frequency receiver. In this case, the increased number of tracked GNSS signals (from GPS, Galileo, GLONASS and BeiDou), as provided by the latest Hemisphere GNSS technology used with the A631 Smart Antenna product, allows the receiver to overcome challenging conditions to ensure a stable and robust positioning solution. For example, if a tree line blocks a part of the sky at the headland of the field, it can be compensated for with additional satellite signals available outside of the blocked area, so that guidance, automated steering and application control are not interrupted. Dust and vibrations are not an issue for us due to the rugged design of the A631 GNSS Smart Antenna. However, depending upon the radio link used, long-distance RF communications for real-time kinematic (RTK) corrections can become a limiting factor. In this case, we often propose using RTK corrections over NTRIP or considering our Atlas L-band correction service for the as an RTK-like alternative.
What is the requirement for start-up time?
Although farmers spend hours in the field during the season, the planting and harvesting windows are limited; therefore, time is critical. The requirement from farmers is to be ready to go when they start their machine. During busy times in the season, farmers often leave their equipment in the field, so startup times may only be a few minutes. We meet this requirement with our startup times for SBAS and RTK corrections and the Atlas AutoSeed feature for L-band corrections. Atlas AutoSeed allows users to suspend Atlas use for any period of time, and upon returning to their last location, the Atlas system uses AutoSeed to rapidly reconverge to a high-accuracy converged position.
What is the accuracy requirement for planting?
Especially row crop planting over what we refer to as broad acre farming requires accuracy to within a few inches, which we offer with our Atlas H10 correction service. Depending upon the farming practices used (such as controlled traffic or inter-row applications), these demands are not only for accuracy, but also for repeatability of the positioning solution.
Another area that demands high accuracy is the production of specialty crops. Per our experience, this farming practice requires sub-inch accuracy and repeatability, which we meet with our RTK solutions.
What is the difference between Atlas and Atlas Basic?
We think of Atlas Basic as a global solution comparable to the different regional offerings for SBAS corrections in terms of accuracy. This means a radius 95% pass-to-pass (R95 P2P) accuracy of around 30 cm with absolute accuracy in the submeter area. We feel that this meets the “basic” needs for all precision agriculture applications.
If a customer is looking for higher accuracies, we offer the H30 and H10 Atlas Correction Services. For comparison, Atlas H30 provides R95 P2P accuracy of 15 cm, and H10 provides R95 P2P accuracy of 4 cm.
Besides your GNSS receivers and corrections services, what hardware, software and services do you provide for precision agriculture?
We announced our new MaveriX precision agriculture solution in September 2021. It uses our recognized A631 Smart Antenna and provides a complete precision agriculture solution combined with the M7 and M10 terminals, eDriveM1 steering controller, ESi2 electric steering wheel and AC110 application controller. The MaveriX precision agriculture application software, which runs on our MaveriX terminals, is the centerpiece of the system. The first production systems are being used by customers in North America this spring.
Ling Hu, Precision Agriculture Business Development Manager
What are the key challenges for precise positioning in agriculture?
Normally in the agricultural field, the environment is harsh (mud, slopes, shocks), which requires the system to be rated IP65 and above and vibration resistant. In some areas, the signal coverage of cellular phones may be insufficient. When that is the case, a UHF modem-type communication is more commonly used with a distance constraint related to the propagation of UHF signals, strongly related to the quality of the installation of the GNSS base station (height of the UHF antenna, gain, immediate environment of the station). Our NX510 SE overcomes that issue by integrating two communication modes, 4G and UHF.
CHCNAV’S GNSS RECEIVERS can be easily switched between tractors. (Photo: CHCNav)
Is planting the application that requires the highest accuracy? What accuracy can you consistently provide?
Certainly, planting requires the highest accuracy of 2.5 cm from pass to pass. With a stable GNSS RTK correction, centimeter accuracy can be provided reliably.
What is the requirement for startup time? What do you deliver?
The startup and initialization of the system should take as little time as possible and is usually done within 1 to 2 minutes from cold start. Farmers usually start their system when they drive the tractor out of the shed and are therefore ready to work as soon as they arrive in their field. Warm start (reacquisition + RTK fixed) is more important in case of obstacles or loss of the RTK correction used by the customer, when using the auto-steering/guidance system in the field. It is typically about 10 seconds.
Besides your GNSS receivers, do you provide any additional hardware, software or services (such as support and training) for precision agriculture?
Our NX510 autopilot kit consists of a receiver, display, motor, angle sensor, camera and accessories, so users can start working immediately without purchasing additional options.
In addition to automated steering systems, CHCNAV also provides complementary solutions that allow farms to be autonomous in terms of GNSS RTK corrections. These solutions consist of GNSS base stations with an integrated or external radio modem and GNSS NTRIP stations for connection over 4G. Individual GNSS stations can be networked using our CPS Net software, which can be operated by a group of farmers, agricultural cooperatives or tractor dealers. Training and user support is provided by our network of authorized agricultural resellers to ensure the closest possible service to our users.
Wang Xiaohui, Technical Director, Antenna Department
What are the key challenges for precise positioning in agriculture?
Obtaining accurate position information in real time requires real-time kinematic (RTK) positioning. There are many ways to obtain differential data. One is to establish a reference station and broadcast differential data through short-distance communication methods. This method’s disadvantage is the high cost of stations and the limited transmission distance. Another is to broadcast RTK data through an LTE network. This is convenient, but if the LTE signal coverage is poor, RTK positioning may not be achieved. A third method is to rely on satellite-based augmentation. This is independent of ground communication equipment, but has a relatively long convergence time and may be greatly affected by signal occultation.
Agricultural machinery must work in harsh environments, such as extreme heat, severe cold and strong vibrations. Consequently, the antenna must be enclosed in a robust housing with excellent protection to guarantee long-time outdoor work.
When agricultural machinery operates near densely packed and tall trees, positioning accuracy will be significantly affected. Limits on the size and cost of antennas for agricultural machinery prevent the use of choke-ring structures. Therefore, the key to achieving high-precision positioning lies in how to receive more satellite signals and avoid multipath interference in a small antenna size.
How can the antenna help with these challenges?
Harxon’s X-Survey antenna is highly integrated and multi-functional. It embeds antennas for GNSS (GPS, GLONASS, BeiDou, Galileo, QZSS, NavIc, other regional systems and SBAS), 4G, Bluetooth/Wi-Fi 900M/2.4G radio, and other frequencies. The X-Survey enables users to choose the most appropriate way for them to acquire differential data — LTE, Wi-Fi, radio or SBAS — making high-precision positioning possible in most environments.
Harxon has designed many high-precision antennas with different structures for various application environments, including those that are waterproof and dustproof and those that can withstand very high and low temperatures and violent vibrations.
Additionally, Harxon’s antennas adopt unique cross-polarization suppression technology, with good circular polarization characteristics, providing effective suppression performance for multipath signals.
How does Harxon support TerraStar correction services?
Harxon’s TS112 PRO Smart Antenna provides reliable positioning solutions for agricultural automatic guidance. It can obtain RTK-level positioning information by receiving correction data from the embedded UHF radio or its GSM modem. Also, TS112 PRO embeds a Hexagon | NovAtel OEM GNSS module, and TerraStar multi-constellation corrections are available globally on this compatible module. TerraStar corrections are available as a termed subscription from Hexagon | NovAtel.
CHC Navigation (CHCNAV) has launched the i73+ pocket-sized GNSS receiver. The i73+ is a compact, powerful and versatile receiver with an integrated UHF modem that can be used either as a base station or rover. Powered by 624 GNSS channels and the latest iStar technology, the i73+ delivers survey-grade accuracy in all jobsite configurations.
“Building on the legacy of the i73 GNSS receiver, the new i73+ receiver is designed to maintain its proven compact and lightweight concept, but adds the ability to be operated as either an RTK base station or a rover,” said Rachel Wang, product manager, Surveying and Engineering Division, CHCNAV. “To enable this extra feature, we have built in the latest UHF modem technology, allowing the reception and transmission of RTK corrections without sacrificing receiver size and power consumption.”
Integrated Tx/Rx UHF modem extends capacity
The i73+ has a built-in transceiver radio module compatible with major radio protocols, making it a suitable portable built-in UHF base and rover kit with fewer accessories. The i73+ is a highly productive NTRIP rover when used with a handheld controller or tablet and connected to a GNSS RTK network via CHCNAV LandStar field software.
The integrated, advanced 624-channel GNSS technology takes advantage of GPS, GLONASS, Galileo and BeiDou, in particular the latest BeiDou 3 signal, and provides robust data quality at all times. The i73+ extends GNSS surveying capabilities while maintaining centimeter-level survey-grade accuracy.
The i73+ GNSS receiver. (Photo: CHCNAV)
Built-in IMU technology
With its inertial measurement unit (IMU) compensation ready in 3 seconds, the i73+ delivers 3-cm accuracy at up to 30º pole tilt, increasing point measurement efficiency by 20% and stakeout by 30%. Surveyors are able to extend their working boundary near trees, walls and buildings without the use of a total station or offset measurement tools.
The i73+ is the lightest and smallest receiver in its class, weighing only 0.73 kg including battery. It is almost 40% lighter than traditional GNSS receivers and easy to carry, use and operate without fatigue. The i73+ is packed with advanced technology, fits in hands and offers high productivity for GNSS surveys.
The i73+ includes a built-in UHF modem. (Photo: CHCNAV)
Both lightweight, compact airborne laser scanners are easily installed on various UAV platforms or small survey aircraft and helicopters. They are adapted to high-density point corridor mapping applications, day or night, under leaf-on and leaf-off conditions or with dense vegetation to provide reliable results.
“Nowadays, it is critical to obtain the highest data quality for the majority of aerial survey projects,” said Andrei Gorb, product manager of CHC Navigation’s Mapping and Geospatial Division.
Combining with industrial-grade GNSS receivers and high-precision inertial measurement units (IMUs), the AA1400 and AA2400 provide 2 to 5 cm survey-grade accuracy. They also integrate Riegl’s VUX lidars with waveform-lidar technology, allowing echo digitization and online waveform processing.
“Multi-target resolution is the basis for penetrating even dense foliage,” Gorb said. “The continuously rotating polygonal mirror wheel enables scanning speed of up to 400 lines per second, allowing for effective coverage of large areas when used from fast drones or aircraft.”
The BB4 UAV equipped with the AA2400 scanner for the city mapping task. (Photo: CHCNAV)
Their built-in premium Riegl VUX-120 and VUX-240 lidar sensors feature a high-speed data acquisition rate of up to 1.8 MHz and a scan speed up to 400 lines per second. This provides a linear accuracy of 1cm to 2 cm on long-range scanning, suitable for fixed-wing UAV corridor mapping.
CHCNAV offers several external cameras for add-ons to the AlphaAir. Setups can include nadir or nadir and oblique cameras from Sony or PhaseOne. By obtaining high-resolution geo-referenced and oblique imagery, more applications can be supported, increasing the return on investment for the client.
The scanning results of the AA1400 and 2400 lidar series. (Photo: CHCNAV)
The one-click connection of the AlphaPort to the power source and camera makes the installation of the AA1400 and AA2400 quick and easy, eliminating the need for additional accessories and time for camera calibration. The AA1400 and AA2400 reduce the risk of cable damage caused by aircraft vibration and acceleration during takeoff and landing.
CHCNAV provides a full range of solutions that allows a complete lidar solution to be added to the users’ geomatic services. The software suite includes CoCapture UAV field application for fully automated reality capture and real-time mission tracking, and the CoPre desktop software for semi-automated point cloud processing.
The AA1400 and AA2400 lidar series solutions are available worldwide today through the CHCNAV distribution network.
In recent years, the architecture, engineering and construction (AEC) industry has benefited greatly from growing GNSS accuracy, smaller laser scanners, UAVs, and more efficient management, collaboration and visualization software. We asked five companies operating in this space to address three questions:
What are the key challenges of surveying for the AEC industry today, compared with traditional boundary surveying and other types of surveying?
Which of your products are particularly relevant for this kind of surveying?
What was a recent AEC surveying success story?
In the following articles, five companies briefly describe their experience with the AEC industry:
Increasing urbanization is creating pressure to manage housing, utilities and infrastructure holistically. Hence the concept of digital twins. Digital twins enable the integrated operation and maintenance of any geospatial asset to meet the increased demand for efficient and intelligent transportation systems, the green expansion of urban areas and sustainable infrastructure.
Traditional GNSS or optical measurement instruments no longer suffice to capture all the necessary information in a timely manner and with the right levels of detail. Integrating technological advances — GNSS, inertial systems, lidar sensors and 360° spherical imagery — into a single mobile-mapping system has greatly increased the ability to produce complete 3D models with high accuracy and precision. Mobile mapping also directly reduces workload, lowers project costs, simplifies data use, and provides reality-based design.
Mobile mapping surveys have been proven to be four to 10 times faster and three to seven times less expensive than traditional methods, delivering the required results up to three times faster. Integrated, multi-platform mobile-mapping solutions bridge the gap between the real world and the digital world for greater interoperability and accessibility of data in near real-time.
The high-accuracy and cross-platform design of CHC Navigation’s AlphaUni 900 lidar system provides an innovative solution for 3D spatio-temporal data acquisition, which is necessary for the digital transformation of the AEC industry.
Smart Cities
After developing for more than a decade, digital-twin technology is now a complex and comprehensive technical system to support the construction of new smart cities. It is an advanced model for the continuous innovation of urban development and a future form of modernization combining the virtual and real worlds. The creation of digital-twin cities brings to the forefront high-level topographic tools capable of providing comprehensive, multi-dimensional, large-scale, high-resolution data sets.
To illustrate typical digital-city projects, CHC Navigation conducted a proof-of-concept demonstration in the Jinshan District of Shanghai, which covers an area of about 600 square kilometers. This area has rich terrain features and characteristics typical of large modern cities, such as tall buildings, power lines, rivers and vegetation.
Versatile and easy-to-use platforms are essential for the democratization of lidar systems. Capturing 3D data with a single-platform lidar system can leave some areas blank in the point-cloud data. The AlphaUni900 lidar solution, with its multi-platform capability, can easily capture complete data from a UAV, car, backpack or unmanned surface vessel (USV) and provide a sophisticated and comprehensive 3D model. The AlphaUni 900 integrates seamlessly with real buildings, provides exterior and interior mapping, and dramatically changes the way high-precision data is collected.
The derived 3D models can be easily merged and correlated with social or economic spatial data, for example from building-integrated internet of things (IoT) and cloud computing data. As a result, complex operations can be optimized in real time, potential problems can be anticipated, and planned maintenance can be implemented to ensure the sustainability of urbanization projects over their entire lifespan, all in a fully connected model.
Affordable, user-friendly solutions for capturing and processing airborne lidar data and imagery have triggered a strong adoption of UAV technology in the AEC industry. For CHC Navigation, 2021 was marked by the huge success of the AlphaAir 450, a breakthrough in 3D UAV mapping technology. With its ease of use, high accuracy and affordability, the AA450 expands the scope of lidar surveying to non-professional users in geospatial reality-capture applications and to those who have never been able to afford such technology before.
Automated steering systems have been widely deployed in advanced industrial countries and on large farms to improve agricultural productivity. However, technological and price barriers have constrained their wider adoption. Reliable RTK positioning and the expected accuracy of automated steering systems enable farmers to optimize their work efforts while reducing input costs and fuel consumption.
CHCNAV customer Niva LLC in Voronezh, Russia, was particularly interested in acquiring an automated steering system able to provide consistent high accuracy, even in scattered fields over long distances and with unstable coverage for GSM (the Global System for Mobile communication, a cell phone standard used in most of the world). Some systems Niva tested would lose GNSS RTK network correction signal reception while working in difficult terrain with gullies. A dual GNSS RTK correction source was therefore a key technical feature to ensure uninterrupted auto-steering operation in all terrain configurations.
The CHCNAV NX510 SE’s built-in connectivity modules include a 4G modem and an additional UHF radio module to allow farmers to work with RTK correction sources from local RTK networks or GNSS RTK base stations for no additional cost. As a result, the NX510 SE can receive GNSS RTK corrections from various GNSS network operators as well as from a local radio modem input to compensate for possible poor GSM coverage. The system’s combined GNSS+INS terrain-compensation technology ensures automated steering accuracy of 2.5 centimeters and offers excellent performance in ditching, seeding and harvesting applications.
Niva also wanted an auto-steering system that could be quickly and easily mounted on a variety of tractors and other farm vehicles at a price that would allow for rapid return on investment. The NX510 SE can be moved from one tractor to another in less than 40 minutes, as farming operations change. The software’s user interface for controlling field operations is designed for both experienced and casual users to allow even greater flexibility.
Approaches to providing real-time kinematic (RTK) solutions at high rates have existed in various forms for decades, providing value for high precision applications. This technique is nearly universally adopted in the industry, and many surveyors may have been using it for years without realizing it. Yet there are persistent misconceptions about the subject.
By Gavin Schrock, PLS
For many on the development side of high-precision real-time kinematic (RTK) GNSS, like those we interviewed for this article, the incorporation of high-rate solutions into their RTK products is a given — and has been for a very long time. Yet, in some end-user communities there may still be many question marks: Does my gear do it? Does other gear do it? What can it do for me? What are the pluses and minuses?
We asked for insights from 10 prominent firms that develop and manufacture RTK-enabled high-precision GNSS solutions and equipment, spanning multiple applications:
By high rate, we mean higher than 1 second (1 Hz) increments, such as 0.2 second (5 Hz), 0.1 second (10 Hz), etc. Part of the confusion about high-rate RTK is that there are two scenarios. One is transmitting corrections from a base or network at high rate, receiving and solving on-the-field sensors or rovers at a high rate (for example, 5 Hz base + 5 Hz rover).
The other is base transmission of corrections at a lower rate and receiving/solving on the rover at a higher rate (for example, 1 Hz on the base + 5 Hz or more on the sensor/rover).
While both can be valuable for different applications, what has been adopted as standard for most surveying, construction, agriculture and mapping applications is the latter.
What are applications that would run the base and rover at higher than 1 Hz? “Moving Base” applications are prime examples, where you are seeking to resolve positions for one or more sensors relative to a base that is also on a moving platform. Think of a barge on the ocean where a helicopter (or rocket) might be landing. Here is a definition from the user manual for a popular OEM receiver that has been in many makes and models since 2003:
“Moving Baseline RTK is an RTK positioning technique in which both reference and rover receivers can move. Moving Baseline RTK is useful for GPS applications that require vessel orientation. [For example, the] reference receiver broadcasts [correction] data at 10Hz, while the rover receiver performs a synchronized baseline solution at 10Hz. The resulting baseline solution has centimeter-level accuracy. To increase the accuracy of the absolute location of the two antennas, the Moving Reference receiver can use differential corrections from a static source, such as a shore-based RTK reference station.”
Beyond such specialized applications, running the base at a high rate is a burden on radios or bandwidth. Additionally, as industry experts explain below, it is of little (or no) value and may only unnecessarily use excess bandwidth and burden broadcast radios.
When would you run the base at 1 Hz and the rover at higher than 1Hz, such as 5Hz, 10Hz, or more? When the base is static. That pretty much covers nearly all surveying, mapping, precision agriculture and construction applications. What is meant by high rate in the sensor/rover receiver and its RTK engine, in the context of such applications? As one of the firms interviewed stated:
“The number of RTK position fixes generated per second defines the update rate.”
For most of the surveying, mapping, precision agriculture and construction applications, that means base 1 Hz + rover 5 Hz or 10 Hz. Then there are specialized applications, such as structural monitoring and geophysical studies, that may run sensors/rovers at 20 Hz, 50 Hz or (though rare) as high as 100 Hz. Whether a higher rate is a default, or 1 Hz is the default, changing the rate is almost always a user-configurable option.
A general perception is that base-rover gear defaults to base 1 Hz + rover 1 Hz. However, as the experts below note, that is not necessarily the case — often the rover rate is higher by default.
By any other name…
The respective approaches, and their appropriateness for different end-use applications, may seem fairly straight forward. However, part of the confusion about the subject for end users comes from the wide range of terminology used to describe how high rate is applied across the industry.
The understanding of processing approaches is clear among GNSS engineers, and in specific terminology, but this rarely gets translated well or consistently in terms meaningful to end users in documentation or marketing.
Developers might have different approaches to achieving high-rate solutions and would of course not wish to completely reveal their cards, but many of the fundamentals are the same. A mutual recognition of parallel development among GNSS engineers, and the manufacturers they develop for, in that each strives to continually improve solutions, means that the high-rate element of RTK generally does not get much marketing hype.
Often, when high-rate RTK does get laterally mentioned — in manuals, marketing or labeled as configuration options in GNSS field software — the mix of terms can confuse the user. Such terms as extrapolation, prediction, update rate and solution rate could evoke a negative connotation to an end user who is used to hearing one set of terms, and they might view otherwise like terms as contrasting terms.
GNSS engineers do not have issues with mixed terms. As some indicated in their respective interviews, they seem a bit puzzled as to why anyone would misunderstand the subject, and how marketing spin might lead users to be confused.
In recent years, the subject seemed to get discussed a lot more than usual in various high-precision end-user social media platforms. Perhaps this was a natural progression in growth of understanding of the nature of GNSS among these constituencies, and a desire to know more about what goes on in those black boxes — a positive thing. There may also have been some instances of marketing nudge.
For whatever reason it became a subject of discussion, we heard from readers who asked us to look into it. So here, in alphabetical order, are insights from of the experts in this field. You can jump ahead to the specific section for your equipment vendor, but we encourage you to read through each; combined, they provide a more complete picture of the subject.
Bad Elf
With Larry Fox, VP for Marketing and Business Development
Larry Fox uses the Bad Elf Flex. (Photo: Bad Elf)
Bad Elf has long provided GNSS solutions for aviation- and mapping-grade field applications. Several years ago, the company introduced a survey-grade-precision system, Flex. It is offered with an option for a modest initial investment in the hardware, and an innovative token system for enabling and operating at centimeter precision.
Larry Fox has been in the industry for a long time and has seen the evolution of real-time GNSS. He is Bad Elf’s vice president for marketing and business development, but he also had a key role in the development of the Flex system. Fox said that, of course, high-rate RTK is supported. “We allow options up to 20 Hz on the rover if the user has this enabled.”
For the approach of 1-Hz base and higher rates on the rover, he said that Bad Elf does not have a specific term for this. “For purposes of description, I could refer to it as high update rate, but I suspect high solution rate is pretty much synonymous.”
Fox explained how the standard approach works. “The rover knows the location of the fixed base and therefore applies the same processing techniques by simply reusing the last received data.”
He also mused about various hypothetical scenarios. “Given that the converse is also possible — a slow data rate from the base, say, 0.2 Hz at the base and 1 Hz at the rover — is there fundamentally any difference?”
For many applications, Fox does not see a substantial advantage in running at higher rates: “I see no benefit for higher data rates in a static situation such as a survey. I would argue that in a survey workflow, one should allow the RTK algorithm to settle over the static shot being taken, as the RTK algorithm likely benefits from aging out some of the data it used while moving.”
He adds, “I would suggest that once you have occupied a point for a modest amount of time and you remained fixed, I can’t see any benefit. My argument here is that by the time you have leveled and prepared your collector of choice, any decent RTK receiver with a good sky portrait and good corrections will not observe any benefit.”
As for disadvantages and trade-offs, “More and faster data,” Fox said, “must be better, correct? Sarcasm included. Unless there is a tangible need for more samples, what is one going to do with all the extra data? I could have seen a possible argument that a single constellation receiver may benefit from averaging, but that could be a be a whole different subject as multi-constellation is now standard. Arguably, at a higher data rate one could capture more epochs and reduce the time on station. With multi-constellation receivers I am just not convinced that these techniques have the same merit they may have had in the past.”
Bad Elf doesn’t support higher correction transmission rates from the radio. “The current module only supports RTCM3 at a 1Hz rate,” Fox said. “Even if we could transmit faster, the payload required would exceed the capability of the message transmission rate of the radio. The battery life of a radio is directly correlated to the transmission duty cycle. The more you are transmitting, the less battery life you will have. I would argue this would impact the useful field time you would have without an external battery solution.”
Fox notes that any application where a rover is moving — such as on a vehicle or for machine control — could benefit from high rate. “I could see a potential application for drones,” he added. “I would want to have the epoch of an image recording very tightly coupled to the image captured. Fundamentally, an RTK drone’s imagery is only as good as that. If one was taking video at any reasonable framerate, a higher frequency RTK GNSS may benefit the geolocation of more individual frames with less extrapolation.”
What about rates higher than 20 Hz? “We have run our receiver up to 20 Hz on the rover side. Although there are units capable of even higher rates, I don’t have any data that would convince me that this is viable, for mapping or surveying.”
I asked about some of the misunderstanding out there about high-rate RTK, and Fox replied, “We can be creatures of habit and tie ourselves to beliefs that ‘this is the way I did it and it worked then.’ People should always ask themselves the question, ‘do I still need to do it this way?’ Again, there is the premise that more is better. I can’t tell you how many times I have seen people collect very high-rate data for lines and poly features only to decimate the data because it reduced performance, increased storage, or lowered the performance of the apps rendering the data.”
Emlid
With Svetlana Nikolenko, Lead Application Engineer
Photo:Svetlana Nikolenko with an Emlid GNSS receiver. (Photo: Emlid)
Emlid, a relatively new entrant to the market for high-precision GNSS, has made a splash with their line of affordable systems, such as the Reach RS2 rover and base-rover kits, and RTK systems for UAVs.
“All our devices support this,” said Svetlana Nikolenko, lead application engineer. “We do not have a special term for this, as it is simply a standard. We recommend 5 Hz and higher for a moving rover, but it can be overkill for a stationary one.”
Asked why one would want to run at high rate, Nikolenko explained, “The need to set a higher update rate depends on the rover’s velocity and acceleration. The higher the update rate, the more solutions per second are calculated. So, if you’re moving fast, the higher update rate simply allows you to keep your position current. If the rover is stationary, there are no issues with working at 1 Hz. Still, there is nothing wrong with running a stationary rover at 5 Hz or higher: it is excessive, but produces more samples with different satellite geometries.”
For moving applications such as UAVs, higher rates are of value. “It really depends on velocity,” Nikolenko said. “For example, if the rover is on a drone flying at a speed of 5-20 m/s and the update rate is set to 1 Hz, you won’t have the actual positions of the images. The higher update rate our devices have is 10 Hz, and at a drone speed of 20 m/s, even if you take photos each second (which might be a bit excessive), you’ll get accurate positions.”
Using an Emlid receiver in harsh conditions. (Photo: Emlid)
Emlid does not support a moving base. However, if there is a strong demand from users, they will consider adding this. For non-moving applications, Nikolenko said, an approach of broadcasting from the base at a high rate is excessive. “This increases the load on the radio (or any other connection link) because the base sends its position and corrections to the rover as often as it calculates it. Anything excessive simply adds load to processors and batteries.”
CHC Navigation
With Carlos Cao, Technical Manager for the Asia-Pacific region
CHC Navigation, or CHCNAV, has steadily grown as a recognizable brand of GNSS and other geospatial products internationally. While the brand might be new to some in North America, in some regions of the world CHC has a substantial share of the market, selling hundreds of thousands of units over the past 15 years. The company develops its own solutions, but also incorporates OEM components. In all cases, CHCNAV has provided high rate as standard from its earliest days.
Multi-constellation rover with tilt compensation. (Photo: Schrock)
Carlos Cao, technical manager for the Asia-Pacific region, said that his company supports the approach of broadcasting at 1 Hz and solving at higher rates on the rover. “For example, you can get coordinates every 0.2 seconds in the Landstar 7 Topo Survey software,” said Cao. “Meanwhile, with different OEM boards, RTK models and supported software, [the equipment] can also reach 10-Hz or 20-Hz static data recording and NMEA data output (including GNGGA coordinate data).” Their term for solving RTK solutions at a high rate on the rover is “high update rate.”
This can bring advantages, specifically for moving applications, Cao said. “When you stake out, the 5-Hz update rate brings faster coordinate updates, especially when surveyors walk quickly. When you survey by time during movement, you can get denser points; while you survey by distance, the accuracy will be better if you are at high speed. For example, speed is 6 m/s, and you want to survey a point every 5 meters; 1 Hz update rate cannot do this with high accuracy.”
When would 1Hz be sufficient? “Normally,” Cao said, “a 1 Hz update rate is enough for a topography survey because users won’t survey at a high speed, so our default setting is 1 Hz, though you can choose higher rates if enabled and as needed. Unless you are moving, however, such as when some surveyors mount a rover on a vehicle, there is no significant difference in the final results.” He added that running at high rates can drain the battery faster.
Broadcasting at higher rates has several major issues. “With more satellites launched, especially BeiDou, correction data becomes much larger,” Cao said. “It means that network RTK requires more data flow, and UHF radio RTK needs a UHF modem that can send data at a high rate. It is a very big challenge for base RTK.”
Meanwhile, notes Cao, “The rover could even have a correction age of 5 or 10 seconds, and it will use the previous package to calculate the position. Since 1-Hz base and 5-Hz rover can work without degradation of precision, there’s no need to change the base to 5 Hz.”
Other applications CHC supports often use higher rates. “Navigation, machine control and precision agriculture normally use a 10-Hz, 20-Hz or 50-Hz update rate,” Cao said, “because these devices work under high-speed movement status, especially navigation. Also, they need to combine with high-update inertial measurement unit (IMU) data. The max update rate is 50 Hz. Normally the application data for these uses is NMEA data output by COM port or TCP/IP protocol. For surveying applications, such as topography, 1-Hz base and 5-Hz rover is enough. For other applications that need higher rates, we also provide such devices.”
Hemisphere GNSS
With Kirk Burnell, Senior Product Manager
Kirk Burnell
“At Hemisphere, we simply refer to this as RTK,” said Kirk Burnell, senior product manager for Hemisphere GNSS. Burnell added that they do not have any special term for this — it is simply a standard.
We were discussing specifically the approach of solving on the rover at higher rates than the base corrections. “All Hemisphere RTK products can work in this way, meaning corrections can come in at 1 Hz or slower, and rover output can be at 1 Hz, 5 Hz or 10 Hz as the user sees fit and as the application demands.”
Hemisphere develops GNSS and multi-sensor solutions for many industries: surveying, construction, agriculture and more. While Hemisphere has its own branded survey rovers, its OEM boards are in many other popular rover brands, makes and models. So, whichever you are running, you get high rate as a standard option.
Hemisphere’s receivers are frequently used in construction applications. (Photo: Hemisphere GNSS)
Burnell explained further that this is a given in the industry. “This is the standard expectation for RTK amongst our competitors, based on their product offerings, documentation, and standard operation. When describing RTK, the expectation is for 1-Hz base-station corrections, and a user-selectable rover output rate. Understandably, when people discuss RTK in technical terms, they may use different phrases to help distinguish between different techniques, which is why there might be different phrases out there. For us, it is simply RTK.”
As for the benefits of high rate, Burnell explained that inside the receiver, the measurement engine and RTK algorithms are typically running at 10 Hz or 20 Hz, and the selected output rate of the solution does not impact the RTK engine’s performance. The receiver will fix as fast and as accurately as possible given the quality of the RTK correction stream. Survey users could see a smoother update rate on their screen using 5 Hz compared to 1 Hz. This makes such tasks as leveling the rod or watching the change in height on screen while moving from the bottom to the top of a curb feel more natural. The user is not waiting an extra second each time to see the stability of the output. “A 5-Hz update rate is a good tradeoff for smooth workflows versus consuming CPU and battery power, compared to 10 Hz or 20 Hz,” he explained.
Would there be a disadvantage to simply running the rover at 1 Hz? “When using a 1-Hz update rate to the data collector, there will be fractions of a second spent waiting for the screen to update,” Burnell said. “Over the course of a day’s work, this could add up to a few minutes of extra time spent. In reality, this does not impact the ability to deliver a job on time. If the user does not feel impeded by the slower update rate of the screen, there is not a significant difference between the quality of the data, comparing 1 Hz and 5 Hz.”
Addressing one misconception that some users have about high rate, that it might significantly improve precisions, Burnell clarified, “For classic RTK surveying, outside of the workflow differences for the surveyor, the same quality of data is produced.”
Disadvantages? “Once you move beyond 5 Hz you start to exceed people’s hand-eye coordination ability, and the benefits diminish,” said Burnell. “Additionally, the data collector has a lot of communication to process, data to unpack, calculations to do, and screen refreshes to accomplish. Faster than 5 Hz leads to stresses in these aspects of the user experience, and ultimately can consume the data collector’s batteries at a faster rate.”
There have been instances of high rate being marketed as enabling users to save a lot of time, but as Burnell noted, this might actually be a potential problem. “There could be a false sense of having no latency, which could lead to rushing through a job, increasing the chances of making a mistake. A surveyor’s observations and measurements are the currency of their trade, and they should be made with care and attention to the work being done. Most surveyors take pride in a job well done.”
Regarding the other scenario, broadcasting at a high-rate and solving on the rover at the same high rate, “This mode of RTK operation has little or no benefit and a host of drawbacks,” Burnell said. “The biggest issue is the volume of data. For a multi-frequency multi-GNSS solution, there is an immense amount of data to be transmitted from the base to the rover. Running a link at 5 Hz requires huge data bandwidth generally only possible using an internet link as compared to a 450-MHz or 900-MHz radio link. Drawbacks for internet links are data volume costs. For dedicated radio links, the issue is most likely to impact radio range. To send five times as much data, the over-the-air baud rate needs to be five times greater. This means that the energy per bit of data is five times less when at high speed. The signal will lack the ability to punch through obstacles. While some may suggest that having five times as many corrections reach the rover compensates for this, some radio protocols can be configured to transmit multiple retries with 1-Hz data.”
However, there are advantages to running at higher rates for specific applications, Burnell said. “If data is being collected in a kinematic fashion as compared to shooting individual points, there will be more detail when collecting at 5 Hz. For example, driving along a road with a receiver mounted to the roof, in 1 minute of driving there will either be 60 measurements at 1 Hz or 300 measurements at 5 Hz. For many non-survey applications, this is critical. For example, at highway speed, 1-Hz data means 1 point every 30 meters (100 feet) or so. In machine control, the systems are not relying on hand-eye coordination and reaction time, and 20 Hz or 50 Hz are common speeds. Autonomous applications also typically use between 10 Hz and 50Hz for GNSS, and often combine this with 100-Hz or 200-Hz IMU data. Aerospace and defense applications have demanding conditions and use 100-Hz to 200-Hz IMU data to navigate, often combined with 1-Hz, 10-Hz or 20-Hz GNSS data.
There are even some applications for which it is warranted to broadcast corrections at rates slower than 1 Hz. “One example was a user in Japan, where radio links are often throttled to 4800 baud,” said Burnell. “They were looking to see how to slow down corrections to less than 1 Hz so that they could take advantage of multifrequency multi-GNSS RTK. Another example: I recently asked for some 10-Hz rover data for analysis. With very large files, analysis took much longer — I wished I had asked for 1-Hz data!”
Hexagon | NovAtel
Hexagon | NovAtel is a prominent tech firm providing positioning, navigation and timing (PNT) solutions for multiple industry segments, including defense, surveying, construction, agriculture, autonomy and more. While GNSS is a core technology, NovAtel develops multi-sensor systems (including inertial) and has a broad reach with its OEM products. Surveyors, for instance, might not be familiar with NovAtel first-hand, but have likely used its technology via NovAtel’s many OEM customers.
Iain Webster
Iain Webster, senior director of Geomatics and Software Engineering for NovAtel, said that not only does NovAtel support high-rate RTK, but the customer can choose the position output rate desired — 1 Hz, 5 hz, 10 Hz, 20 Hz, etc. — and the receiver will output RTK positions at that rate.
“We distinguish between a matched solution (where a correction is matched with a rover observation at the same time tag), and a low-latency solution, where base observations are extrapolated for position computation at the rover,” Webster said. He provided a description from a company manual:
“The RTK system in the receiver provides two kinds of position solutions. The Matched RTK position is computed with buffered observations, so there is no error due to the extrapolation of base station measurements. This provides the highest accuracy solution possible at the expense of some latency, which is affected primarily by the speed of the differential data link. The MATCHEDPOS log contains the matched RTK solution and can be generated for each processed set of base station observations.
The Low-Latency RTK position is computed from the latest local observations and extrapolated base station observations. This supplies a valid RTK position with the lowest latency possible at the expense of some accuracy. The degradation in accuracy is reflected in the standard deviation. The amount of time that the base station observations are extrapolated is in the “differential age” field of the position log. The Low-Latency RTK system extrapolates for 60 seconds. The RTKPOS log contains the Low-Latency RTK position when valid, and an “invalid” status when a Low-Latency RTK solution could not be computed. The BESTPOS log contains either the low-latency RTK, PPP or pseudo range-based position, whichever has the smallest standard deviation.”
NovAtel does not brand this as a specific feature — it is just a standard part of its RTK solutions, but the company refers to it in their documentation as a “low-latency” solution.
The main benefit of this solution, Webster explained, is for kinematic users to allow better representation of their actual trajectory (such as in applications on moving vehicles). “The higher the dynamics, the more impact the latency of the matched solution will have to the point that we recommend the low-latency solution to all but specialist customers with known static positioning needs. For surveyors, there may be improved workflow with the low-latency solution as they will be able to move from point to point more quickly.”
NovAtel produces GNSS and inertial hardware and software, including OEM boards, for multiple applications. (Photo: NovAtel)
Webster noted that for applications where the rover is static for observations, 1 Hz can be fine, but for moving rover applications — kinematic — running at 1 Hz is probably unacceptable, so low latency is quite standard.
Additionally, he pointed out, there are applications where longer periods between corrections may not necessarily be detrimental. “Note that some manufacturers, including NovAtel and Leica, offer the possibility of using PPP corrections to extend RTK solutions beyond, for example, a 60-second timeout,” Webster said. “There are various proprietary methods to achieve this, but ultimately the RTK solution could be extended without limit in this way.”
Are there tradeoffs to using extrapolation or other high-rate approaches? “With corrections coming in at 1 Hz,” Webster said, “there is very little error over that period, so for most users, there is little disadvantage and perhaps some productivity advantage with a higher rate. If there is any trade-off, it is between getting the highest accuracy possible versus the lowest latency solution.”
As for the other scenario — the base broadcasting at greater than 1 Hz and the rover solving at greater than 1 Hz — “There is little advantage,” Webster said, “except in some specialized applications such as when the base is moving (called moving baseline) to provide a cm-level baseline between the base and the rover for relative positioning. For typical surveying applications with a static base, the rover would have to wait until the corrections arrived before outputting a solution. Other downsides include increased bandwidth on the communication link and more loading on the rover CPU, meaning lower battery life.”
What are the non-surveying applications where a high rate (in either scenario) can yield a specific benefit? Webster noted that, in fact, they deal mostly with non-surveying applications. “Most use cases need 10 Hz or 20 Hz for machine control or precision ag. We do have some very specialist applications that have required up to or beyond 100 Hz — but it is often best in those cases to do a GNSS/inertial navigation system (INS) solution and use the IMU to output at that a high rate. As previously mentioned, there are other specialist applications where the base is moving. In this case, we run a matched solution at a high rate between the base and the rover.”
Leica GeoSystems
With Xiaoguang Luo, Senior Product Engineer, GNSS Product Management Group
Rover with calibration-free tilt compensation and camera-based offset point capabilities. (Photo: Schrock)
Leica Geosystems (part of Hexagon) has been a major global developer and manufacturer of GNSS systems for multiple disciplines for several decades, introducing its first GPS receiver, WM101, in 1985. Since then, Leica has been among the leaders in GNSS receiver innovation, including integrated systems such as a rover that incorporates calibration-free tilt compensation and an image-point capture feature (GS18 I). Therefore, it is no surprise that for Leica Geosystems equipment features high-rate RTK as standard.
Xiaoguang Luo is a senior product engineer in the GNSS Product Management group at Leica Geosystems. He confirms that this option is supported in all Leica Geosystems RTK rovers of the current product portfolio, and this option is enabled by default in the Leica Captivate (surveying field) software. A term Leica Geosystems uses is prediction for its high-rate RTK approach.
Xiaoguang Luo
The standard positioning rate is 5 Hz on the rover. “As far as GNSS processing is concerned, there is no fundamental need to go to higher positioning rates,” Luo said. “The need for high rates is mainly driven by applications. For example, we are using the 5-Hz position update rate at the rover by default for an improved staking workflow and user experience. The 10-Hz rate is also supported in Captivate, for example, when streaming NMEA messages.” He added that 10 Hz is supported for other applications, such as structural monitoring, and 20 Hz for machine control.
As for the advantages of a rate higher than 1 Hz, Luo said that working at high observation and solution rates enables the possibility of modeling fast-changing error effects with a period below 1 second, and allows for high-rate non-surveying applications such as bridge monitoring. Does a high rate have any significant effect on the final results? He said that it strongly depends on the use case where high-rate observations and positions are involved. In addition, the quality of prediction also affects the final results.
Bernhard Richter
By this he means that while the standard approach for applications where the base is stationary, such as surveying, can work so well with a base data rate at 1 Hz and rover at 5 Hz, the key conditions do not change much over a single second.
Luo’s colleague Bernhard Richter, vice president of geomatics, explained it. “To understand this, you need to separate the elements of corrections into those that are fast changing and range dependent (see the graphic below). If the errors change slowly, then they can be estimated and predicted very well. Or, if the range dependency is low, errors could come from a different source than the base station. If the range dependency is medium or high, then the corrections are more difficult to estimate on the rover side, but if such errors change very slowly, they can still be predicted very well with the precondition that corrections have been received at least once.”
The rate of change and dependencies for the elements of corrections. (Source: Leica GeoSystems)
You’ll notice that multipath is high in both regards. This brings up another misconception about high-rate RTK — some users have an expectation that it will improve their performance in limited sky-view situations (like thick tree canopy) or high multipath environments. This is not so. Any improvements in such environments come from having more satellites, more observations, and more modernized signals. With regard to high-rate and multipath, Richter said, “It is anyway futile, since multipath decorrelates so quickly that the advanced mitigation has to happen both in an analog and a digital way on the rover.”
While there are benefits to running at high rate, such as for staking, a balance has to be struck — for instance, in not running it at too high a rate. Luo outlined disadvantages that must be considered when performing high-rate RTK.
High processing load and battery drain, particularly with multi-constellation and multi-frequency RTK.
High temporal correlations between observations, which may not be considered in a sophisticated manner in the RTK algorithms.
High base rates provide challenges for the RTK data link devices, such as radios.
In addition, he noted that while any kind of predictive solution will introduce some amount of error, that would be so small in, for instance, a base data rate at 1 Hz and rover at 5 Hz solution, as to not even be noticeable in the positioning results.
Septentrio
With Bruno Bougard, Research and Development Director
Bruno Bougard
“Our rover solution computes RTK up to 100 Hz,” said Bruno Bougard, R&D director at Septentrio. “Update rate requirements for industrial machine control applications are typically 20 Hz. This is necessary to capture the motion dynamics. Also, it is not only the update rate that matters in those applications, but also the latency, which should be low (<20 ms typically) and constant.”
Septentrio NV is a designer and manufacturer of high-end multi-frequency GNSS receivers and integrated solutions. Markets they serve include surveying, mapping, construction, science, timing, agriculture, marine, autonomy, and more — all with specific applications where high-rate RTK may be employed They also provide OEM boards and modules for further integration by others.
Surveying users for instance may be familiar with their Altus line of rovers, such as the NR3, where high rate is a standard option. “There are new applications where a higher update rate is required,” said Bougard. “Surveying with UAV, using photogrammetry or lidar scanning requires at least 10Hz. In mobile mapping in general, RTK-INS solutions such as SPAN, Applanix or Septentrio SBi, require update rates up to 200Hz.”
Bougard acknowledged that manufacturers use many terms for their high-rate solutions. “Some may be used to masquerading a low-rate solution as a high-rate one. This is not what we do. The rover observables are captured at high rate and can be up to 100 Hz. The rover RTK filter is also run on high rate. Fixed base-station data does not have to be high rate. 1 Hz is typically enough. For moving base applications — for example, when the base station is on another vehicle, and we want to compute the baseline between the moving base and the rover — 10 Hz is required.”
Bougard said that the benefit is to track the motion of the rover. This is critical in machine control, but also relevant for new survey flows (such as UAV-based and mobile mapping). The disadvantage, he explained, is that it requires higher CPU loads. “Suppliers, who focus on cost, tend to compromise on this, notably running higher rate only for a subset of the constellation or signals. We use them all.”
Is running the base station at a higher rate advantageous? “It is possible to increase the output rate of our base station correction stream but, as explained, this is not needed if the base is static,” Bougard said. “This is applicable to moving base scenarios as explained above. Indeed, if you increase the base-station correction rate, the bottleneck becomes the datalink.”
Tersus GNSS
With Xiaohua Wen, Founder and CEO, Tersus GNSS
Xiaohua Wen with a Tersus GNSS receiver.
Xiaohua Wen, based in Melbourne Australia, is the founder and CEO of Tersus GNSS, another new entrant in the centimeter-grade GNSS market. One distinction about Tersus is that the company has developed and produces its own GNSS boards, instead of using OEM boards from other companies. Tersus implements its own tech, including GNSS receivers and IMUs in its own survey rovers, such as the Oscar, and for other high-precision applications. Additionally, it produces OEM boards for integration by others. Tersus entered the market with full multi-constellation support and, of course, high-rate RTK options, and has recently announced a PPP (precise point positioning) service.
“Our RTK boards support up to 20 Hz,” said Wen. “Often, surveyor will choose 5 Hz. We do a 5-Hz solution in this manner: the baseband takes raw measurements at a wanted moment, say at 1.2 s or 1.4 s, and RTK calculates solutions with the raw measurements. We understand that some older solutions might simply extrapolate or interpolate based on a position and velocity sequence, which is sometimes called predicted RTK or extrapolated RTK (though those terms get used in different ways by different developers). That is not how we approach our RTK solution updates. All Tersus RTK boards also support a maximum 20 Hz raw measurements outputs.”
Multi-constellation rover with calibration-free tilt compensation. (Photo: Schrock)
We asked about some of the advantages users may envision of high-rate RTK in general. Wen said there may be little or no gain with regard to faster initializations. Likewise, there is no significant gain with precision and accuracy. However, Wen said that higher rates can sometimes improve staking workflows. “For example, in the case of our Oscar rover with tilt compensation, the RTK outputs solutions at 10 Hz, while the IMU samples at 100 Hz. Oscar calculates the pole tip’s position at 10 Hz, aligned with the RTK solutions, and the data controller or tablet displays the point of the pole tip on the screen. We find that the point better refreshes at 2 Hz or higher to respond to the pole tip movements without noticeable lagging.”
That movement is an example of a key value of high rate,“Speed or movement,” Wen said. “For surveying applications, I would say that 1 Hz could suffice, considering the characteristic very low speed. Usually, applications like machine control and precision agriculture require an RTK update rate at 5 Hz or higher. Some UAV applications may use a 100-Hz position update. Most of these applications use an INS+RTK solution. With INS, it’s easy to get a 100-Hz position update, while for an RTK solution, a rate of 20 Hz is probably enough.”
Wen said that broadcasting corrections at a higher rate is pointless for most applications, “because the base data is highly correlated in the short term. If it’s a moving base, the high-rate base data would make some sense. Otherwise, it just imposes a greater load on communications and computation, with almost no gain.”
Topcon Positioning Systems
With Alok Srivastava, Director of Product Management
Alok Srivastava
“It is a standard option in our rovers,” said Alok Srivastava, senior director of Product Management (PM) at Topcon. “Around the time I joined the PM team, in 2010, the decision was made to make 10 Hz the standard, though this is user configurable and can be 5 Hz, 20 Hz, up to 100 Hz.” He explained that faster rates have been available through several generations of their receivers.
Typical applications consist of a static base and a moving rover. Fast-moving applications can benefit from higher rover position update rates since the RTK engine is computing real positions at a faster rate. Higher rates on the rover side provide accurate changes in position that can be missed by interpolating between positions computed at a slower rate.
A Topcon multi-constellation rover with tilt compensation. (Photo: Schrock)
High update rates on a base station do not provide advantages except in rare cases where the base is moving. While rovers are computing movements of the rover antenna, base stations are providing GNSS satellite corrections. A rate of more than 1 Hz for a static base station does not benefit rover accuracy; it only creates a burden on the communication between base and rover. Base and rover communication needs to be optimized to reduce bandwidth requirements. This is especially true as we continue to add constellations and signals to GNSS solutions.
Sufficiently high rates have been standard on Topcon rovers for a long time. Srivastava would rather see more focus put on other aspects of GNSS — such as interference, spoofing, the impacts of 5G, precise point positioning (which Topcon provides through its Topnet Live service) and sensor integration. “In many of our construction applications, we have IMUs,” Srivastava said. “When an application has an IMU for tilt compensation or for machine control, the IMU and GNSS complement each other. In kinematic mode, the IMU can help reject outliers.”
“High rate can be considered a common default mode of operation,” said Stuart Riley, vice president, Technology – GNSS, Trimble. “Typical rover position solution rates are 5 Hz, 10 Hz and 20 Hz.”
Trimble is one of the pioneering companies in GPS and GNSS, and Riley has been directly involved in the evolution of the company’s GNSS solutions for more than two decades. He has seen a lot of change, and in noting the nature of key technological advances, offered this intriguing observation about high rate: in many ways it has become less relevant.
“There have been considerable advances in RTK technology in recent years that make many of the earlier concepts related to how base and rover data should be combined for baseline processing largely irrelevant,” said Riley. “Most recently, survey receivers have included INS support for tilt compensation applications, and these receivers have available high-rate IMU data — at a much higher rate than GNSS observables — which drive the final GNSS/INS integrated solution. Thus, the rover GNSS data rate is not so important.”
Riley noted another relevant technology that Trimble has implemented: the use of precise satellite clock and orbit corrections — such as from the Trimble RTX precise point positioning (PPP) service — to augment RTK when there is a loss of the base correction stream. The implementation of PPP is broadening across the industry, and the company was an early implementer of a global service. It has the RTX-based xFIll feature that runs on and high-end survey receivers. One of the misconceptions about PPP services such as xFill is that it is just there to “take over” should the RTK or NRTK corrections be interrupted. Yes, it does that as well, but to be able to do that, it is running all the time, simultaneously with the RTK, so the rover is getting these enhanced PPP service clock, orbit and other data. This improves what the rover can do. “The emphasis in modern survey receivers,” Riley said, “is based more on the availability of rover data, and a fundamental base data rate of, say, 1 Hz, is all that is required.”
Along with various advances in the rover RTK engine, the GNSS constellations have expanded considerably, requiring increased bandwidth for the corrections from base to rover. “Our products can use various communication technologies to transmit corrections, such as Wi-Fi, cellular, and UHF (450 MHz or 900 MHz) radios,” Riley said. “Maintaining a 1-Hz correction rate enables all the GNSS observables to be broadcast from the base, providing a suitable highly compressed data format such as when Trimble’s proprietary CMRx format is selected.”
Many terms are used in the industry, and they typically refer to some proprietary aspect of an RTK engine. Riley said that a generic term would simply be high update rate. “Providing the position is based on the most current phase observables at the rover, a low latency solution is possible,” he said. “Thus low-latency solution goes hand-in-hand with a high update rate. Predicted RTK may refer to an old method where the static base corrections are propagated forwarded to account for radio latency and thus synchronize base/rover data. This is not used in modern PVT (position, velocity, time) RTK engines.”
High rate on the rover is standard, but what benefits should the user expect from it? “A fast update rate provides the best user interface experience in the field, in particular for stakeout,” Riley said. “Quite simply, nobody wants to be working with a laggy display. For survey field work, 5 Hz is typical. Other applications, such as machine control, benefit from higher update rates where a default of 10 Hz would be used, with options for higher rates.”
If the user chooses 1 Hz on the rover, what would be the downside? “Running at a 1-Hz rate is not really suitable for stake out,” Riley said. “For occupying static points, 1-Hz updates would suffice, as a typical occupation has a minimum time of 1 or 2 seconds. Very high rates for survey applications do not really buy anything in terms of field look and feel or performance.” I asked him about any points of diminishing returns, and he responded, “The higher the rate, the wider the measurement bandwidth (that is, the noise increases — you cannot get something for nothing), so in fact going for an unnecessarily high rate would start to be a disadvantage. For example, there would be no advantage to using a 50-Hz or 100-Hz rate for a land survey application. There is a relationship between measurement bandwidth and position noise.”
When is a high base rate a good idea? High rates are supported for some machine control and “moving base” applications where the reference frame has to move with the moving base, Riley said. In this case, the base and rover observables must be synchronized and the final solution has a fundamental latency depending on the base rate. For this reason, moving base rates are more typically 10 Hz or 20 Hz. For a static base, it is possible to use a higher rate. However, as Riley noted, “It’s more likely that a lower rate such as 0.5 Hz might be desirable to accommodate the radio when using repeaters (time multiplexing the data) or low data rates. There are disadvantages to high base rates, mostly related to radio bandwidth. Other factors, such as ‘high rate = more radio transmit power’, may need to be considered (affecting battery life).”
Are there other cases for even higher rover rates? “As mentioned, machine control applications use higher rates — necessary to reduce position latency in control loops,” Riley said. “Other applications such as UAVs and autonomous driving clearly benefit simply because of the speed of the platforms (higher dynamics). Precision agriculture is an excellent example of machine control, where auto guidance is used. Although high rates are possible, nearly all applications manage perfectly fine at rates up to 20 Hz. A more important consideration is system performance in terms of positioning accuracy and convergence times, which is dependent on the technology used in the PVT engine, such as Trimble ProPoint technology, rather than the correction stream data rate. ProPoint also includes xFill, as mentioned earlier, which provides centimeter-level backup for continuous operation when RTK or VRS correction streams are interrupted.”
Other Manufacturers
This was only a sampling of the developers and manufacturers, but it should be noted that several of the above firms produce OEM boards featured in dozens of other brands and models, such as Carlson and GeoMax. To try to list them all would be a challenge and might be missing a key point: high rate is quite standard, is not big news anymore, and you probably have it by default (or optional) no matter what system you are using.
Hypeful
As the insights the from industry experts above show: high rate can be essential for many applications, but unnecessary for others. It seems more about user experience (staking workflows or moving rover) than some way to seek higher precision.
Additionally, to borrow the gaming term hypeful, some users believe (or have been led to believe) that running at high rate will yield higher precision or work some kind of magic in dense tree cover or high multipath environments. Some may argue that it could get a result faster, but in practical terms even that might not be the case.
High rate has been around for a long time. And like any tech, has gone through different development and adoption phases. Think about automatic transmissions for motor vehicles; they have been around in one form or another for more than a century. There was a period in the mid-20th century where the development of different approaches was promoted in marketing campaigns with fanciful product names, like Durashift, Presto-Matic, Geartronic and Torque-Flite. But rarely do you see auto transmissions highlighted with such marketing flourish since then.
High-rate RTK was never singled out like that; it is common, and any differences are mostly in how it has been adapted for different applications. I suppose a firm could choose to emphasize it for marketing purposes and give it a buzz name like “Turbo Thrusted RTK”, which his fine for marketing purposes (albeit a bit “cheugy”). Every developer and manufacturer will have slightly different approaches, but if you believe, or are led to believe, that any represent high-rate fundamentals exclusively, that would be inadvertently misleading, if not subtle gaslighting.
As one of the experts said, “It does not really matter what manufacturers claim or don’t claim. You cannot beat physics. You can only understand and manage the physics.”
Coolness Ahead
While high-rate might seem a bit old hat, where GNSS development is going is not. The developers we interviewed are more interested in highlighting their complete high-precision solutions. For example, adding inertial measurement units (IMUs) for no-calibration tilt compensation, additional sensors for imaging (and likely soon, lidar), and multiple real-time GNSS solutions complimenting RTK, such as L-band precise point positioning (PPP).
The “high-rate” that is truly exciting is that of R&D, multi-sensor integration, automation of certain elements of workflows, artificial intelligence and multi-constellation/multi-signals.
High accuracy and economical steering solution for most tractors in any field type
Photo: CHCNAV
CHC Navigation (CHCNAV) has released the NX510 Pro, a high-accuracy automated steering system designed for tillage, seeding, fertilization, pesticide application, and harvesting. With a steering controller and full GNSS RTK capability, the NX510 Pro can be quickly and easily mounted to various types of tractors and other farming vehicles to achieve ±2.5 cm pass-to-pass accuracy.
“The NX510 PRO is the new generation’s auto-steering system, engineered to dramatically reduce installation time, simplify daily operations and increase the productivity of farms of all sizes,” said Yorke Tang, product manager of CHCNAV’s Precision Agriculture division. He said the NX510 Pro allows farmers to afford a high-performance yet affordable auto-steer kit to retrofit their tractors to optimize their work, reduce input costs and fuel consumption, and meet the main goals of sustainable agriculture:
Increase farm income
Promote environmental stewardship
Enhance the quality of life for farm families and communities
Increase production for human food needs
Installation of the NX510 Pro auto-steering system to a tractor. (Photo: CHCNAV)
Quick installation. NX510 PRO takes less than one hour from installation start to operator use. The entire system can be installed in 30 minutes and calibrated in about 15 minutes, significantly reducing downtime costs in the field.
The intuitive AgNav software controls operations. It supports multiple guidance patterns to fit field layouts, including Straight AB line, A+ line, circle line, irregular curve and headland turn. It eliminates steering errors and overlapping passes on the field. The AgNav software also features real-time remote technical support from the local dealer’s help desk.
Powered by local, network or satellite-based RTK corrections, the GNSS+INS terrain compensation technology ensures ±2.5 cm hands-free accuracy on any terrain. The advanced controller ensures full RTK accuracy in seconds, provides smooth auto-steering and ensures repeatable long-term accuracy.
A roundup of recent products in the GNSS and inertial positioning industry from the June 2021 issue of GPS World magazine.
OEM
Grandmaster Clock
Multi-constellation receiver
Photo: Microchip
The upgraded TimeProvider 4100 2.2 is now more redundant and resilient. It provides secure, precise timing and synchronization for critical infrastructure such as 5G wireless networks, smart grids, data centers, cable and transportation services. The 4100 2.2 introduces a software-redundancy architecture for flexible deployment, and supports a new GNSS multi-band, multi-constellation receiver to protect against time delay from space weather, solar events and other disruptions. The 4100 2.2 offers options for software and hardware support.
The NETZ 5-in-1 multiple-input and multiple-output (MIMO) solution combines two LTE antennas and two Wi-Fi antennas with a GNSS antenna for high data throughput and streaming, video, industrial and internet of things (IoT) applications. It offers a low-profile design with integrated SubMiniature version A (SMA) connectors and is designed with rugged PC+ABS plastic black housing for demanding environmental challenges.
The GW16143 is a high-precision GNSS/GPS Mini-PCLe adapter card that provides precise positioning to applications using Gateworks single-board computers. Based on the U-blox ZED-F9P, the GW16143’s multi-band real-time kinematic (RTK) technology enhances convergence times and performance. The module receives GPS, GLONASS, Galileo and BeiDou; supports L1 and L2/L5 bands; and provides GNSS positioning accuracy
of <2 cm.
Tactical grade for higher order integrated applications
The IMU-NAV-100. (Photo: Inertial Labs)
The IMU-NAV-100 is a fully integrated inertial solution that measures linear accelerations, angular rates, and pitch and roll with high accuracy utilizing three-axis high-grade micro-electro-mechanical systems (MEMS) accelerometers and three-axis tactical-grade MEMS gyroscopes. It features continuous built-in test, configurable communications protocols, electromagnetic interference protection, and flexible input power requirements that allow it to be easily integrated in a variety of higher order systems. The IMU-NAV-100-S offers high performance stabilization for line-of-sight systems, motion-control sensors, and platform orientation and stabilization systems. The IMU-NAV-100-A is for GPS-aided INS, AHRS and motion reference units.
The SimpleRTK2B single-board computer is built around up to three u-blox ZED-F9P high-precision GNSS receivers to simplify development of centimeter-level positioning solutions supporting real-time kinematics (RTK). It was developed to make RTK technology as close to plug-and-play as possible, and make the technology accessible to broader audiences. In addition to working as a stand-alone solution, customers can program their own applications with the company’s microPython API. The SimpleRTK2B-SBC delivers mechanical integration with centimeter position on three axes (heading, pitch, roll), outputting on NMEA, RTCM, RS232 and CANBus interfaces via Ethernet, Bluetooth, Wi-Fi and 2G/3G/4G communication.
PointMan software is now integrated into the Vivax Metrotech vLoc3 with a GNSS real-time kinematic (RTK) receiver to create a utility-locate device. Using the RTK-Pro internal cellular module with 4G LTE capabilities, the operator can connect to the NTRIP RTK caster that provides RTCM 3 corrections. With the integration of PointMan with the vLoc3 RTK-Pro, critical buried infrastructure can be captured, recorded and displayed at survey-grade without additional external equipment or post-processing. The integration provides centimeter accuracy of the precise location of buried utilities in real time. Data collected includes the type of utility, the depth of cover and the utility’s precise location.
ProStar Holdings, prostarcorp.com
GIS platform
Geospatial and location intelligence for smart cities
Screenshot: Hexagon Geospatial
M.App Enterprise 2021 is a significant update to the platform for creating geospatial and location intelligence applications. The latest release features new browser-based 3D capabilities and enhanced visual effects, plus the ability to create and configure custom applications more easily. It allows users to access LuciadRIA’s 3D features with support for panoramic imagery, shading, ambient occlusion and other visualization effects to build browser-based solutions. It also features a new browser app configurator that makes it easier to create spatio-temporal dashboards, or Smart M.Apps. Feature Analyzer now allows users to add and manage multiple datasets on the fly and set up workflows.
Measures positioning, heading, attitude, velocity and heave
Photo: Hexagon | NovAtel
The MarinePak7 marine-certified GNSS receiver is designed for nearshore applications. The multi-constellation, multi-frequency receiver was engineered to receive the Oceanix Correction Service from NovAtel, providing horizontal accuracy up to 3 cm (95%) in a marine environment. With SPAN GNSS+INS technology capabilities, the MarinePak7 couples GNSS and inertial measurement units (IMUs) for 3D positioning.
The ANNA-F9 high-precision GNSS Mini-PCIe card can achieve centimeter-level accuracy. It integrates the U-blox ZED-F9 receiver platform, providing multi-band GNSS (GPS, GLONASS, BeiDou, Galileo, QZSS and SBAS) and RTK positioning, and can be integrated with embedded systems. It provides high-accuracy positioning for applications including lane-level navigation and railway transportation. The ANNA-F9 series supports RTCM formatted corrections and centimeter-level positioning from local base stations or virtual reference stations in a network RTK setup.
Marine vessels often host both Iridium (1616–1626.5 MHz) and Inmarsat (uplink: 1626.5–1660.5 MHz) satellite communication antennas that transmit and receive signals. The VSP6037L-MAR and VSP6337L-MAR VeroStar marine antennas strongly attenuate interference from both signal sources, providing 75 dB to 85 dB of attenuation over Iridium and 85 dB to 95 dB over Inmarsat uplink, enabling clean GNSS signal reception and precise positioning. The VSP6037L-MAR supports the full GNSS spectrum; the VSP6337L-MAR supports GPS/QZSS-L1/L2/L5, GLONASS-G1/G2/G3, Galileo-E1/E5a/E5b, BeiDou-B1/B2/B2a, and NavIC-L5 signals. Both antennas support L-band correction signals. Every VeroStar antenna features a robust pre-filter and a high-IP3 LNA architecture, minimizing desensing from high-level out-of-band signals, including 700 MHz LTE, while still providing a noise figure of 1.8 dB. They meet IEC 60945 and IEC 61108 marine certifications for challenging marine environments.
The managed internet of things (IoT) Acculink Cargo can track the location and condition of high-value and sensitive assets, providing real-time visibility, product-level tracking and exception-based monitoring as goods move through their supply chains. Tracking can be used to avoid delays, minimize dwell time, prevent theft and remediate environmental conditions that can cause asset damage.
The GNS1559MPF or Mini GNSS is a rugged, high-performance and cost-effective solution for most GNSS or asset-tracking applications. The small form factor makes it easy to install on or in vehicles or buildings. It is IP67 rated to withstand impact as well as water and dust intrusion in demanding environments and operating conditions. The antenna can be configured with different cable types in varying lengths and with various connector types. Uses include public safety, in-building, fleet management, asset tracking, vehicle and personnel tracking.
The Zala 421-16E5G long-flight UAS is a domestic unmanned aerial system with a hybrid power plant. The non-aerodrome-based system is capable of providing aerial monitoring covering distances of more than 150 kilometers and staying in the air for more than 12 hours. Its power plant charges a buffer battery for an hour, allowing the UAV to fly long distances. It is equipped with two thermal imagers and a 60x video camera. Alternatively, it can carry a payload of up to 10 kg.
The xNAV650 inertial navigation system (INS) provides surveyors with absolute position, timing and inertial measurements (heading and pitch/roll) that they can integrate into their projects. When combined with data from other devices (such as lidar sensors and cameras), the INS measurements can greatly enhance the surveying process. The xNAV650 has the latest micro-electro-mechanical (MEMS) inertial measurement unit (IMU) technology and survey-grade GNSS receivers. At 77 x 63 x 24 mm and 130 grams, it is suitable for a wide range of UAV data-collection applications: surveys of bridges, buildings, forests and rail; coastal monitoring; map creation; and pipeline exploration. Data collected can be fused with data from almost any lidar sensor. OxTS NAVsuite software is included with all OxTS INS. Other optional software is available, including precision time protocol and GX/IX tight-coupling technology.
The AlphaAir 450 (AA450) lidar system is a lightweight, compact all-in-one sensor. Featuring an inertial measurement unit (IMU), GNSS receiver and 3D scanner and camera, the AlphaAir 450 is suitable for power-line inspections, topographic mapping, emergency response, agricultural work and forestry surveys. The unit can be rapidly deployed in the field to collect geospatial data. It achieves absolute accuracy of 5 cm (vertical) and 10 cm (horizontal) for small survey areas. Adjustment algorithms applied in CHCNAV CoPre software further improve precision and accuracy. The AA450 weighs 1 kilogram for easy mounting on a UAV. It is IP64 rated against dust and water spray and operates at –20° C to +50° C.
The True View 635/640 3DIS is GeoCue’s second-generation lidar/camera-fusion platform designed to generate high-accuracy 3D colorized lidar point clouds using the Riegl miniVUX-3UAV. All 3DIS platforms include GeoCue’s data-processing software suite True View EVO, which integrates with the Applanix POSPac. With its 120° fused field of view, the True View 635/640 provides 3D mapping with excellent vegetation penetration and wire detection in a payload package of 3.2–3.6 kg. True View EVO supports the direct creation of ground classified point clouds, surface models, contours, digital elevation models, volumetric analysis, wire extraction and similar products, without the need for additional third-party software.
CHC Navigation (CHCNAV) has released the AlphaAir 450 (AA450) lidar system, a lightweight, compact all-in-one sensor for unmanned aerial vehicles (UAVs).
Featuring an inertial measurement unit (IMU), GNSS, 3D scanner and camera, the AlphaAir 450 solution is suitable for power-line inspections, topographic mapping, emergency response, agricultural and forestry surveys. The unit is easy to use, and can be rapidly deployed in the field to collect geospatial data.
“Despite the fact that the lidar scanning is an efficient technology to capture 3D data, it still often remains costly and complex to operate,” said Andrei Gorb, product manager of CHC Navigation’s Mobile Mapping Division. “Taking that into account, we introduce the AlphaAir 450 (AA450), a breakthrough lidar scanner that delivers user-friendly and high-accuracy capabilities at a reasonable price.”
Key aspects of the AlphaAir 450
Lightweight. The lidar’s weight is a constraint for any drone. The AlphaAir 450 weighs 1 kg, which is suitable to most drones’ payload requirements. The lighter the unit, the longer the operating time of the drone, and the greater the productivity. The AlphaAir 450 can be easily mounted on UAVs, making data capture efficient.
Advanced Accuracy. By combining industrial-grade GNSS with a high-precision IMU, the AlphaAir 450 can easily achieve an absolute accuracy of 5 cm (vertical) and 10 cm (horizontal) for small survey areas — typically adequate for the most use cases. To further improve precision and accuracy, users can apply adjustment algorithms in the CHCNAV CoPre software.
Industrial Reliability. Featuring IP64 high-level protection, the AlphaAir 450 extends its operating temperature capabilities, down to –20° C and up to +50° C in any field environment. This can increase users’ return on investment by providing more field survey days in a year.
As in January 2020, we are starting the year by providing insights from manufacturers of GNSS receivers. We asked these industry leaders to look back at the past two years and forward at the next two, and discuss key innovations in the following areas:
utilizing Galileo and BeiDou
dealing with jamming and spoofing
integration with inertial measurement units (IMUs) and other sensors
positioning using cell phones and other consumer devices
any other areas or challenges they find particularly significant
Photo: Emma Hardy/Eos Positioning Systems
The single most important trend that emerges from manufacturers’ responses is the improvement in receiver performance due to the increase in the number of satellites (now 150) and signals (now more than 100). With four usable constellations, GNSS is now a reality. Multi-constellation receivers are quickly becoming the norm, even in consumer devices, and new user segments are benefiting from satellite-based PNT. Already, some smartphones and tablets are achieving decimeter-level or even centimeter-level accuracy. Over the next two years, new GNSS services will become available and, as the GNSS constellations continue to develop, the availability, reliability and repeatability of their signals will improve further.
A second important trend is the growth in satellite-delivered correction data, which substantially lowers the entry barrier for high accuracy applications by obviating the need for costly local infrastructure. This is starting to change the traditional cost-benefit calculation regarding real-time kinematic (RTK) vs. precise point positioning (PPP) corrections (see also our Editorial Advisory Board PNT Q&A).
A third and continuing trend is the increasing threat from intentional and unintentional jamming and interference across the globe, paralleling the increasing ubiquity of GNSS and potentially impacting most users. Therefore, receiver manufacturers continue to improve hardware and software techniques to defeat, or at least mitigate, this threat, greatly assisted by the increase in the number of available signals.
Finally, as automakers and high technology companies continue their efforts to develop autonomous vehicles (aka “self-driving cars”), the concept of GNSS integrity is getting renewed attention. Here, too, the increase in the number of available signals is extremely helpful.
With François Martin, Vice General Manager, International Division
Utilizing Galileo and BeiDou
The addition of Galileo and BeiDou to GPS and GLONASS not only extends GNSS positioning to more obstructed environments, but also allows the use of new survey methods, such as the hybrid IMU-GNSS pole-tilt compensated surveying and stakeout with survey-grade accuracy. Further expansion of GNSS navigation systems will result in even greater availability, reliability and repeatability.
Dealing with jamming and spoofing
As an integrator and developer of GNSS systems, we focus our design on strong electromagnetic shielding and sealed isolation chambers. From a technology standpoint, the combination of advanced GNSS signal processing, optimized antenna design, and advanced filtering ensures minimal interference.
Photo: CHC Navigation
Integration with IMUs and other sensors
The integration of interference-free, high-dynamic IMU fused with GNSS technology brings an obvious benefit to surveying and autonomous navigation applications. The latest algorithm developments make it possible to get rid of tedious initialization processes, increase the productivity of typical survey tasks, bring extra safety to operators, and compensate for transient GNSS outages.
Positioning with consumer devices
Multi-constellation GNSS chips are accelerating the development of untapped user segments, but the repeatability of position accuracy remains an issue. The integration of high-performance GNSS chips and helical antennas as high-precision add-on modules on smartphones and tablets enables centimeter- or decimeter-level accuracy. This democratization of technology is increasing earlier adoption of GNSS technologies by a broader user base.
Eos Positioning Systems
With Jean-Yves Lauture, Chief Technology Officer
Utilizing Galileo and BeiDou
The past two years have seen considerable maturation of the Galileo and BeiDou constellations. Considering the now four usable GNSS constellations and the aggressive launches of Galileo and BeiDou, the number of available satellites and the list of frequencies they use have considerably increased. Accuracy itself is slightly improving with the availability of BeiDou phase 3 signals, whereas performance and productivity experience a significant boost under tougher conditions with more satellites and stronger signal availability. It is not uncommon for our customers to use 30 to 35 satellites out of 40+ in view using an Arrow Series GNSS receiver. We are waiting for the availability of the High Accuracy Service (HAS) (PPP) on the Galileo E6 frequency, hopefully in a couple of years.
Photo: Eos Positioning Systems
Integration with IMUs and other sensors
Eos has put a lot of effort recently in supporting external sensors and accessories to facilitate mapping of certain types of assets or mapping in certain types of conditions. For instance, this past year Eos released our underground mapping solution called Eos Locate for ArcGIS (see cover photo), which integrates with external utility locate devices to allow a user to precisely map buried assets. Eos Laser for ArcGIS interfaces with laser rangefinders to map assets in GNSS-impaired environments.
Positioning using consumer devices
With our bring-your-own-device (BYOD) approach on the market to support high-accuracy data collection for GIS, we have made it possible to override the consumer devices’ locations with accuracies down to the centimeter from our Arrow receivers. Customers can use any of their cell phones or tablets and immediately start mapping with submeter or centimeter accuracy.
Hemisphere GNSS
With Kirk Burnell, Senior Product Manager
Utilizing Galileo and BeiDou
The Galileo and BeiDou phase 3 systems introduce modern signal structures that allow more accurate measurements to be made than GPS first introduced. The new signals and increased satellite count are significantly improving receiver performance. Our Phantom and Vega product lines harness these new signals.
Dealing with jamming and spoofing
The increasing number of incidents of intentional and unintentional jamming and interference across the globe has impacted nearly every type of GNSS user. Our Cygnus interference mitigation technology automatically detects and mitigates the interference in real time, as well as providing spectrum analysis of the GNSS signal bands.
Photo: Hemisphere GNSS
Integration with IMUs and other sensors
Today’s autonomous-focused environment increases the need to share data across platforms. Both Vector and Vega provide robust GNSS heading, position and velocity to marine, machine control, UAV and internet of things (IoT) integrators, helping augment their sensor data.
Positioning with consumer devices
Positioning in consumer products will continue to drive innovation, while chasing accuracy and precision requires a strong understanding of geodesy fundamentals. As design requirements push well beyond the limits of what consumer GNSS delivers, and with the help of our knowledgeable staff, our precision receivers are delivering reliable performance in some very impressive applications.
Other significant challenges and opportunities
New GNSS signals and new surrounding technologies continue to come online, and the RF environment continues to see increased activities. Our underlying Lyra II ASIC technology and Cygnus enable our Phantom and Vega integrators and users to reliably coexist with these changes.
Hexagon | Novatel
With Sandy Kennedy, Vice President Innovation, Hexagon’s Autonomy & Positioning division
Utilizing Galileo and BeiDou
GNSS is now reality, not just inclusive phrasing to replace GPS. We are well into the era of multi-constellation receivers, and users will notice distinct improvements in solution availability with the addition of Galileo and BeiDou measurements. Over the next two years, we expect users in a variety of applications to start exploiting our globally available, fast-converging RTK From the Sky technology, which is enabled by the addition of quad-frequency signals supplied by Galileo and BeiDou (see page 29).
Dealing with jamming and spoofing
The RF spectrum is crowded and will only become more crowded over time. In 2020, we introduced our GNSS Resilience and Integrity Technology (GRIT), a suite of firmware options for the OEM7 receiver family. In addition to interference detection and mitigation, GRIT adds spoofing detection and time-tagged digitized samples for advanced situational awareness of the RF spectrum. With GRIT’s spoofing detection, opponents can try to spoof us. But fool us? Not a chance.
Photo: Hexagon | NovAtel
Integration with IMUs and other sensors
IMUs have become more accessible to more applications due to size, weight, power and cost reductions. At the same time, our algorithmic capability has significantly advanced to use lower quality inertial measurements for greater benefit. Originally reserved for truth systems, high-end mapping, and aerospace and defense applications, GNSS+INS solutions are now available in products like our SMART7 line of smart antennas for precision agriculture applications. Closer integration of the inertial and GNSS processing will bring further benefits in hostile RF or just plain difficult positioning environments. There is no perfect single sensor, but you can get more accurate by combining a set of sensors that offset each other’s vulnerabilities and limitations.
Positioning with consumer devices
The general population is accustomed to looking at their smartphone to see not only their location, but also the size of the “blue dot” of positioning uncertainty that accompanies it. We have always said accuracy is addictive, and we will no doubt start to see consumer demands for smaller blue dots with increasingly accurate positions. Making the digital reality match our real world demands continuously available and reliable positioning. Being lost is a terrifying feeling, especially for those who have been staring at their phone for the past 30 minutes and have no recollection of the physical world through which they have passed.
Other challenges and opportunities
The transition to autonomous vehicles, for both on-road consumer and off-road industrial applications, is inevitable. It is becoming increasingly necessary to prioritize the development of functional safety and integrity requirements to achieve the safe operations of autonomous systems. These requirements are necessary and entirely non-trivial to develop.
Photo: Stephen Drake
Javad GNSS
With the Javad GNSS Team
Utilizing Galileo and BeiDou
Simultaneous RTK and PPK processing of all available GPS, GLONASS, Galileo and BeiDou signals in receivers powered by our 874-channel TRIUMPH chip has resulted in significant productivity gains. User Darren Clemons told us “These Plus units are at least 40%–50% faster… The combination of the four super engines and the RTPK is unbeatable. You can get an accurate shot just about anywhere.”
Dealing with jamming and spoofing
Usually, more than 100 signals are available at any given time, and we need only a small number to compute a position. By tracking and verifying all these constellations and their signals, it is extremely unlikely that we can be spoofed without our knowledge. Javad GNSS receivers will immediately recognize spoofing and take corrective actions. Spoofing protection is available on all Javad GNSS receivers and OEM boards.
Integration with IMUs and other sensors
The Javad GNSS engineering team relentlessly works to identify and integrate the latest sensor technologies that can boost productivity. Our TRIUMPH-LS’s integrated camera sensor has for years supported onboard photogrammetry, and now our TRIUMPH-3 receiver’s integrated IMU provides high-precision tilt compensation.
Other challenges and opportunities
Our innovative RTPK feature is improving GNSS surveying and monitoring. Our Triumph-LS and Triumph-3 RTK rover systems combine the strengths of RTK and PPK into a system that can post-process RTK data and verify its results in parallel and real time. Users get the best of both worlds. If RTK fails, RTPK comes to the rescue in a fraction of a second.
Septentrio
With Gustavo Lopez (pictured) and Stef van der Loo, Market Access Managers
Utilizing Galileo and BeiDou [GL]
With 150 GNSS satellites in space, multi-constellation has been a natural transition for improved GNSS availability. We see this in rover applications and in upgraded reference networks modernizing correction services. The next two years will be transcendent as constellations finally start delivering new services. We see our products soon integrating
GAL-OSNMA for anti-spoofing and then moving to new high-accuracy services.
Dealing with jamming and spoofing [GL]
We have witnessed a large increase in jamming and spoofing events as GNSS ubiquity increases. Users are becoming conscious of this, yet many integrations are still using vulnerable receivers, and we see manufacturers falsely claiming to have proper resilience. Septentrio’s AIM+ technology uniquely mitigates all these risks, and users come to us for expert advice on this area. In the coming years, we expect further receiver innovations and developments in adjacent technologies.
In 2020, Septentrio opened an R&D center in Espoo, Finland. (Photo: izhairguns/iStock/Getty Images Plus/Getty Images)
Integration with IMUs and other sensors [SVL]
Integration of sensors and sensor fusion moved from the research stage to the major production and adoption phase as an element in autonomous systems. Using a GNSS/INS (see our AsteRx-i products) is crucial for various applications — for example, being able to work in difficult environments — and for vehicle orientation. The development of lower cost IMUs while keeping high performance will enable a shift in focus from hardware to software. This will result in multi-sensor technology that is better scalable, easier to use, and more stable to integrate in relation to a full system with various sensors.
Positioning with consumer devices [GL]
We see further integration of dual-frequency GNSS chipsets in mobile technology for increased accuracy, which is key for future consumer applications. Septentrio has also witnessed the important involvement of telecom operators in GNSS correction services. Septentrio products (such as the PolaRx5 or AsteRx-SB) are deployed on new generation networks as operators prepare for the new generation of positioning in cell technology.
Other significant challenges and opportunities [GL]
Two areas are emerging thanks to the autonomy era and due to further regulations in the market. The first is the concept of GNSS integrity, which has a strong link to the reliability of autonomous solutions. The second is security, which, beyond anti-spoofing, is linked to the cybersecurity of GNSS systems as the demand increases for the protection of electronics and software.
Trimble
With Stuart Riley, Vice President of GNSS Technology
Utilizing Galileo and BeiDou
Most Trimble precision receivers can utilize any combination of GNSS satellite constellations (GPS, GLONASS, Galileo, BeiDou and QZSS) to deliver centimeter accuracy and optimize performance, even in degraded conditions. Users can select the constellations they want the receiver to use.
Dealing with jamming and spoofing
Spoofing is rare and low risk in locations in which Trimble’s precision GNSS agriculture, construction and geospatial customers operate. However, to protect users, modern Trimble Maxwell-based GNSS receivers implement hardware- and software-based techniques to detect and mitigate spoofing. Jamming sometimes impacts customers, but is not their primary challenge. The same issues are still present today as they were in the early days of precision GNSS. The main productivity concerns remain related to multipath and problems around obstructions and trees. Trimble continues to improve our GNSS systems’ robustness with advances in processing algorithms and hardware enhancements such as integrating inertial technology.
Trimble SiteVision uses Catalyst and augmented reality to preview a new housing development in an open field. (Photo: Trimble)
Integration with IMUs and other sensors
The Trimble R12i and SPS986 represent Trimble’s third-generation receivers (preceded by the R10 and the R12) capable of integrating inertial measurements into 3D GNSS positioning. In addition to speed and convenience for the user, integration with IMU provides immunity to magnetic interference and real-time integrity monitoring.
With the introduction of the Trimble R12 with the ProPoint GNSS positioning engine, we significantly improved the performance in challenging environments. This was further enhanced with the addition of an IMU for tilt compensation in the R12i. The new solution provides a system that delivers more accurate results in more places and in less time.
Positioning with consumer devices
The Trimble SiteVision augmented reality solution and Trimble Catalyst GNSS receiver operate on Android devices. Trimble Catalyst technology provides a software-defined GNSS receiver capable of survey-grade accuracy. Catalyst is the ideal solution for third-party applications that benefit from precise real-time positioning. Trimble SiteVision combines Catalyst positioning with augmented reality to deliver real-time, on-site visualization of proposed structures and existing underground assets.
Other significant challenges and opportunities
An ongoing challenge in GNSS positioning is the ability to obtain positions with suitable accuracy when and where they are needed. Solutions such as RTK and VRS provide solid performance at local and regional levels. Today, these technologies are complemented by subscription-based Trimble RTX positioning services, a global approach that uses a network of GNSS tracking stations and satellite-delivered correction data to achieve required accuracies. In 2020, coverage for Trimble CenterPoint RTX Fast, which enables users to achieve two-centimeter or better accuracy with initialization time of less than one minute, was expanded to cover the continental United States as well as much of Canada and Western Europe. The CenterPoint RTX Fast network now covers more than 5 million square miles worldwide. Trimble RTX coverage enables global users such as farmers, land surveyors and GIS professionals using RTX-capable receivers, to untether from the cost and complexities of GNSS base stations. In addition, the service offers a single, continuous corrections network ideal for enabling a broad range of safety-critical autonomous applications in markets such as automotive, agriculture and construction.
