Anyone Can Measure with Centimeter-Level Accuracy (cm level accuracy (half-inch accuracy))! The New Era of Civil Engineering Surveying Opened by LRTK

In recent years, the wave of ICT and DX (digital transformation) has been sweeping through civil engineering surveying sites, and surveying technology is entering a new era. Whereas surveying used to involve specialized technicians operating large instruments such as transits and total stations, a method that allows anyone to easily perform surveys with centimeter-level accuracy is now becoming a reality. A representative example is the high-precision GNSS receiver "LRTK" that can be attached to a smartphone. This article starts from the current state and issues of civil engineering surveying, compares GNSS (global navigation satellite systems) with conventional technologies, reviews the rise of smartphone-compatible surveying devices, and explains in detail the innovative functions LRTK brings and the effects it delivers on site. Finally, drawing on adoption cases in advanced municipalities and future prospects, we explore the potential of the new era opened by LRTK’s simple surveying that anyone can use.

Current State and Challenges of Civil Engineering Surveying

In Japan’s construction and civil engineering industry, chronic labor shortages and aging/insufficient numbers of surveying technicians are becoming serious problems. At the same time, the demand for surveying itself is increasing—for infrastructure deterioration inspections and disaster preparedness—so sites are required to conduct surveys efficiently with limited personnel. However, conventional surveying work requires operation of specialized equipment and advanced knowledge, and in many cases external surveying contractors must be engaged; even when someone on site wants to "quickly measure and check," the barrier of expertise often stands in the way.

Furthermore, conventional surveying instruments are large and heavy, making transportation and setup on site burdensome. For example, using a total station or GNSS surveying instrument requires setting up a tripod and mounting the device, and measurements often required teams of two or more and lengthy preparation time. Carrying equipment through mountainous areas or narrow sites is difficult, and for site managers with limited personnel and many tasks, preparing equipment and arranging specialized operators was a major burden. Low portability also led to situations where "we only want to measure briefly, but preparation becomes elaborate," causing necessary measurements to be postponed.

Given these circumstances, there is a strong demand on site for new surveying tools that are "easy for anyone to use, allow immediate measurement, and provide high accuracy." Although ICT-driven construction has introduced new technologies such as drone aerial photogrammetry and 3D laser scanners, these cannot always be used in urban areas where drones cannot fly or when detailed ground-level measurements are needed. Attention has thus turned to compact surveying instruments that are easy to carry yet can ensure accuracy. Surveying equipment is evolving ever more toward being compact, simple, and high-performance to solve on-site challenges.

Comparison with GNSS and Conventional Technologies

Conventional optical surveying (total stations, levels, etc.) can achieve millimeter-level precision, but installation on site is time-consuming and they are designed to measure limited areas sequentially, making it difficult to measure wide areas in a short time. In contrast, GNSS surveying determines position using signals from satellites, enabling positioning in terrains where line-of-sight is hard to secure and allowing autonomous location awareness even at disaster sites where reference points have been lost. Plotting measurement data on GIS maps to share damage status is also easy, and GNSS holds great potential as a means to efficiently cover widely scattered points.

However, standalone GPS/GNSS positioning typically incurs errors of about 5–10 m (16.4–32.8 ft), which is insufficient for the accuracy required in civil engineering and infrastructure management. To achieve higher accuracy, RTK (real-time kinematic) positioning was devised. RTK uses two receivers—a base station receiver and a rover receiver—that receive the same satellite signals; error information calculated at the base station is transmitted in real time to the rover, improving positioning accuracy to within a few centimeters. This enables centimeter-level positioning, and in addition to traditional RTK surveying with dedicated equipment, network RTK (such as VRS) that utilizes GNSS reference station networks has been spreading in recent years.

Nevertheless, conventional RTK surveying had constraints in the field. First, dedicated equipment must be installed and power supplied, which can be difficult to set up immediately amid post-disaster chaos. In large-scale disasters, widespread power outages can occur, or existing known reference points may be washed away. Network RTK also assumes internet or cellular connectivity, but if an area is out of coverage or communication infrastructure is down due to a disaster, correction information cannot be received and high-precision positioning cannot be performed. Moreover, RTK equipment operation and configuration require specialized skills, and in emergencies not everyone on site can necessarily use them effectively. In other words, even if centimeter-level precision can be obtained, there was a demand for a positioning method that could be used by anyone on site without dependence on communications or complex equipment.

The Rise of Smartphone-Compatible Surveying Devices

As a solution to the above issues, smartphone-compatible compact surveying devices have emerged recently. Modern smartphones support multiple GNSSs including GPS and have improved positioning accuracy, but standalone they still have meter-level errors. By combining a smartphone with an external high-precision GNSS receiver, individuals can now easily perform RTK surveying. Smartphones leverage their communication functions to receive network RTK corrections and serve as platforms for positioning calculations and data display. Compact RTK-capable GNSS receivers capture multi-frequency satellite signals that smartphones’ internal GPS cannot receive, and provide centimeter-level positioning data in real time through corrections. This smartphone + compact RTK receiver combination has realized RTK surveying that was once large and expensive in a pocket-sized form, making a "surveying device for each person" a reality.

So what conditions are required for compact surveying devices usable on sites? The three major points are:

• High accuracy: Even when miniaturized, it is essential to ensure centimeter-level accuracy with measurement errors of only a few centimeters. Precision instruments tended to be large, but recent advances in GNSS and sensor technology have made high-accuracy positioning possible even in pocket-sized devices.

• Easy operation: It is important that non-specialists can operate the device intuitively. Ideally, measurement can be done by pressing a button in a smartphone app, with complex settings and calculations automated. A user interface that allows site personnel to operate without consulting manuals is key.

• Portability: The device should be small and lightweight enough to carry daily to sites. If it fits in a workwear pocket, it can be taken out quickly when needed. Lightweight devices reduce the burden of carrying them for long periods. Built-in batteries that operate for several hours and an integrated design with few cables are also welcomed on site.

Many of the latest compact surveying devices meeting these conditions are appearing one after another, with the LRTK series being a representative example. With LRTK, which operates with just a smartphone, centimeter-level surveying that previously required specialized equipment and technicians is becoming accessible to anyone.

LRTK’s Innovations (centimeter-level accuracy, standalone surveying, point cloud scanning, AR, disaster response, etc.)

LRTK meets the above conditions while providing a variety of functions that add new value on site. Its main innovations are as follows.

• Centimeter-level positioning accuracy: Above all, LRTK’s greatest feature is its high-precision positioning. Horizontal positions can achieve ±1–2 cm (±0.4–0.8 in), and vertical accuracy is about ±3 cm (±1.2 in), enabling smartphone-based positioning comparable to conventional surveying GNSS receivers and total stations. This level meets the positional accuracy required for public surveys, and verification results have reported that coordinates obtained with LRTK differed by only a few millimeters from those of top-tier GNSS equipment. LRTK supports multiple frequencies of GPS, GLONASS, and QZSS (Michibiki), and includes multipath mitigation for urban canyon environments. Models that can directly receive the CLAS centimeter-class augmentation signal (L6 band) provided by the QZSS Michibiki can maintain accuracy even in areas without cellular coverage. Such technical capabilities have led to adoption by government agencies, and LRTK is gaining trust as a high-precision device.

• Simple operation and immediate positioning: LRTK simplifies on-site setup and operation so that anyone can use it intuitively. Attach the device to the back of a smartphone, turn it on, and launch the dedicated app; satellite acquisition and initialization begin automatically, and high-precision RTK positioning is established in about 30 s. Positioning can be started with a single button, and complicated base station settings or coordinate inputs are unnecessary. Once positioning begins, pressing the “Measure” button in the app records the current coordinates, and other functions like photo capture and point cloud scanning can be executed with one touch. The design enables even non-experts to operate without hesitation, offering excellent immediacy to "start measuring as soon as you arrive on site."

• Surveying tasks completed by one person: With LRTK, surveying work that used to require two people can be completed by one person. For example, height measurements can be taken solo by attaching a smartphone to a dedicated telescopic pole (monopod) and placing the tip on the ground; the app corrects for pole length and automatically calculates height. The need for one person to hold the instrument and another to hold a staff is eliminated, reducing the number of people entering hazardous areas and thereby improving safety. By simultaneously achieving labor savings and safety, LRTK significantly reduces the burden on surveyors and decreases human error.

• Pocket-sized, lightweight: LRTK devices are pocket-sized with a thickness of about 1 cm (about 0.4 in) and a weight around 150 g. The built-in battery operates for about 6 hours, and continuous operation while powered from a mobile battery is possible. Unlike conventional stationary surveying equipment, a smartphone + LRTK that can be carried in one hand allows agile movement over rubble in mountainous areas or steep slopes. This mobility is especially powerful at disaster sites and busy construction sites where time is critical.

• Support for 3D point cloud scanning: Combining a smartphone camera or LiDAR scanner with LRTK’s high-precision positioning enables recording terrain and structures as 3D point cloud data. For example, walking around a landslide site with an LRTK-equipped smartphone can capture a detailed point cloud model of the entire slope in just a few minutes. Since acquired point clouds are tagged with accurately positioned coordinates in real time, volumes of collapsed soil can be calculated immediately from the data, and the data can be used for as-built management and earthwork volume calculations. Tasks that previously required expensive 3D laser scanners or drone photogrammetry can now be completed with a single smartphone.

• High-precision on-site projection with AR: By combining RTK positioning with smartphone AR technology, it is possible to project design drawings or the positions of buried utilities into the real world. Conventional smartphone GPS had significant position errors that made outdoor AR impractical, but with LRTK’s centimeter-level self-positioning, 3D models in AR can be fixed precisely to map coordinates. For example, loading design data for buried sewer pipes enables visualization of the underground routing through the smartphone screen. With AR linked to surveying coordinates, even inexperienced workers can perform accurate stakeout (layout) simply by following on-screen guidance.

• Independence from communication infrastructure: LRTK can utilize augmentation signals from satellites, allowing it to maintain centimeter-level positioning in areas without cellular coverage or when communications are severed by disasters. This autonomy is extremely reassuring for emergency surveying. The device connects to the smartphone via Bluetooth, eliminating cumbersome wiring, and with spare batteries it can sustain long surveying sessions without power trucks or generators. High-precision, lightweight, and autonomous, LRTK is an innovative tool that realizes an environment where anyone can measure anywhere and immediately, especially for disaster response.

Effects of On-Site Implementation (Efficiency, Burden Reduction, Solving Labor Shortages)

Introducing LRTK brings various effects to surveying operations on site. The main benefits are as follows.

• Dramatic improvement in operational efficiency: The time and effort required for surveying are dramatically reduced. Previously, equipment preparation and coordinating multi-person teams consumed time, but with LRTK one person can go to the site and start measurements immediately. For example, as-built surveying that once took two people half a day can be completed by one person in a few hours. Measurement data can be uploaded and shared to the cloud from the site in real time, shortening post-processing and report preparation time. Overall, this speeds up operations and improves productivity.

• Reduced workload and improved safety: Smartphone-based surveying devices lighten the physical burden of carrying heavy equipment over long distances. Reduced fatigue lowers accident risk by shortening the time spent working in hazardous areas. Simple operation also reduces mistakes and mental stress. The need to coordinate multiple personnel for joint tasks is reduced, enabling small teams to work efficiently and safely.

• Alleviation of labor shortages and labor saving: Because surveying can be completed by a single person, limited personnel can cover more sites. Even when experienced surveyors are scarce, construction managers or municipal staff who are non-specialists can carry out surveys with LRTK. As a tool usable even by newcomers, it helps bridge the skills gap caused by retirements of veterans. In-house execution of surveying tasks that were previously outsourced can allow operations to continue despite personnel shortages.

Case Studies of Implementation (Use in Disaster Surveying in Fukui City, etc.)

Here are cases where LRTK was actually introduced and used for disaster response.

Fukui City in Fukui Prefecture was quick to introduce the LRTK Phone for surveying tasks at disaster recovery sites. When checking the as-built conditions of slopes and roads collapsed by heavy rain or earthquakes, they reported major efficiency improvements and cost reductions compared to conventional methods. Dangerous slopes could be surveyed remotely and a 3D point cloud of the damaged area obtained in a short time, enabling rapid grasp of the damage extent that would have been difficult with manpower alone. This use accelerated planning and commencement of recovery work and was evaluated as contributing to the restoration of residents’ lives.

LRTK also proved powerful at sites affected by the 2023 Noto Peninsula earthquake. Even in areas where communication lines were cut, the ability to directly receive Michibiki’s CLAS signal allowed standalone centimeter-accuracy surveying to continue, enabling recording of collapsed structures and damaged locations as photo data with high-precision coordinates. This data was used in subsequent recovery planning and contributed to detailed site records in the initial response phase that were difficult with conventional equipment. The ability to enter a site and start surveying immediately without heavy instruments has made LRTK an attractive tool for municipal disaster prevention staff and infrastructure managers to enhance emergency response capabilities.

Following successes in these advanced municipalities, the national government has also begun to take note of smartphone surveying technology. The Ministry of Internal Affairs and Communications and the Ministry of Land, Infrastructure, Transport and Tourism have begun recognizing LRTK’s effectiveness as an ICT utilization case in disaster response, and some municipalities are incorporating "smartphone surveying systems utilizing high-precision GNSS" into their disaster prevention and DX plans. Major general contractors and surveying companies have also begun using LRTK for as-built management and land surveying on construction sites. Feedback from the field includes high praise such as "one person can even perform stake driving, helping with labor shortages" and "newcomers can use it immediately," and smartphone surveying with LRTK is becoming a new on-site standard.

Future Prospects

Amid the national push for i-Construction and construction DX, smartphone surveying technologies like LRTK are expected to become the new norm on sites. The fusion of high-precision GNSS positioning and digital technology can free surveying from being the province of specialists, enabling all site staff to participate in data measurement and sharing. Indeed, the LRTK series is a solution compatible with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative and is expected to strongly support digitalization in the construction industry.

Adoption is likely to expand among more municipalities and companies, and a system in which centimeter-level surveying is standard for infrastructure management and construction may be built. For example, small local construction firms and municipal offices may be able to adopt LRTK at affordable costs and independently collect high-precision surveying and inspection data. Immediate cloud sharing of accurate 3D data acquired on site and real-time remote construction management from distant offices will become increasingly feasible. The spread of accessible surveying technology is expected to generate societal benefits beyond productivity gains, such as more frequent infrastructure inspections and strengthened disaster response capabilities.

Technologically, improvements in smartphones and GNSS satellite systems will further enhance accuracy and usability. The QZSS Michibiki satellite constellation expansion is planned, and enhanced augmentation services will further increase the reliability of RTK positioning. Smartphone-side multi-GNSS support and sensor performance are also improving year by year, and in the future it may become possible to achieve centimeter-level positioning with built-in smartphone functions alone. In that case, collaboration with devices like LRTK will become even smoother, and "high-precision surveying with just a smartphone" could be completed more seamlessly. The world of civil engineering surveying is truly advancing to a new stage.

Conclusion: The Potential of Simple Surveying Anyone Can Use with LRTK

Finally, I want to emphasize again the potential of the "simple surveying anyone can use" that LRTK is opening up. In the past, centimeter-level surveying required expensive dedicated equipment and specialist skills. With LRTK’s emergence, an era in which anyone can obtain high-precision surveying data with the familiar tool of a smartphone is becoming real. This is not merely a convenience; it is a democratization of surveying. If site technicians and municipal staff can measure and think for themselves, decision-making will be faster and operations more efficient, contributing to improved maintenance of social infrastructure and advanced disaster response.

The centimeter-accuracy world enabled by LRTK lowers the hurdles to civil engineering surveying and creates opportunities to increase the number of practitioners. For sites struggling with shortages of experienced personnel, the significance of obtaining both "accuracy" and "ease of use" in surveying is enormous. The new era of surveying is almost here. A future in which anyone can take a smartphone from their pocket and measure—the LRTK is a strong first step toward that realization. Why not try applying this innovative technology at your site?