Surveyors' New Weapon! LRTK Phone Transforms a Smartphone into a Surveying Instrument

Challenges Faced by On-site Surveyors

Those of you who are surveyors working daily at construction sites undoubtedly face a number of challenges unique to the field. For example, the heavy labor of carrying large total stations and tripods while moving around, and setting up equipment in scorching heat or bitter cold. For precise positioning, you must coordinate with colleagues, align prisms, and repeat fine adjustments. With limited personnel you often have to run multiple surveying tasks simultaneously, and it is not uncommon to be forced into long hours amid staff shortages and tight schedules.

On-site, "quick and accurate" is always required, but achieving both is not easy. Workers strain every nerve to achieve cm level accuracy (half-inch accuracy) without mistakes, and there is also the extra step of recording measured points by hand in a field notebook and later transferring them into drawings. If there are omissions or recording errors, inefficiencies often arise because they have to return to the site and redo the work. Given this situation, many people may feel that they want a tool that makes surveying easier and reduces the burden on-site.

Centimeter-level accuracy required at construction sites (cm level accuracy (half-inch accuracy))

On construction sites, the accuracy of survey results is a critical factor that determines construction quality. If a building's position shifts by a few centimeters (a few inches), it may interfere with adjacent structures, and if a road's elevation differs by just a few centimeters (a few inches), the drainage slope can be adversely affected. In particular, the positions for foundation pile driving and the installation locations of structures must be precise, and an error of "just a few centimeters (a few inches)" can lead to significant rework or safety issues later on. Surveyors, in order to prevent such risks, pay meticulous attention to accuracy control in their daily work and carry out surveys using high-performance equipment and specialized techniques.

On the other hand, it is also true that traditional precision surveying requires considerable time and cost. For example, high-precision optical surveying used to require assembling a team of several people and transporting equipment, and real-time positioning using GNSS has demanded specialized instruments and advanced setup. You may have resigned yourself to the effort and time that seemed unavoidable to achieve centimeter-level accuracy (cm level accuracy (half-inch accuracy)). However, advances in technology are changing that conventional wisdom. If surveying could be made easier and more efficient while maintaining the accuracy required on site—such expectations are now being met by a new weapon.

Smartphone Transformed! What Is the **“LRTK Phone”**

A groundbreaking item attracting attention for solving the above issues is the “LRTK Phone”, which turns a smartphone into a surveying instrument. At first glance it looks like a slightly oversized smartphone case, but an ultra-compact RTK-GNSS receiving antenna is built into the case, and it works in conjunction with the smartphone. Simply attach this receiver device to an iPhone or iPad with one touch, and your everyday smartphone instantly becomes a surveying instrument with cm level accuracy (half-inch accuracy).

The LRTK Phone device weighs approximately 150 g and is extremely lightweight, with a pocket-sized thickness of just over 1 cm (0.4 in). Because it also has a built-in battery, there is no hassle of wiring—truly a surveying instrument you can carry with you anytime, anywhere. When you launch the dedicated smartphone app, it performs multiple roles with this single device, from measuring position coordinates to 3D scanning, on-site marking (layout), and even AR (augmented reality) display. If you attach it to the optional dedicated pole (monopod), the height offset when probing points on the ground is automatically corrected by the app, allowing you to take accurate survey points by yourself.

In short, what the LRTK Phone achieves is the combination of "all‑in‑one high‑precision surveying functionality" and "thoroughly field‑oriented ease of use." By leveraging the familiar device of a smartphone, the interface is approachable, and because the entire unit is compact, its mobility is excellent. This device, which packages RTK positioning technology that was previously expensive and specialized into a form anyone can use, has the potential to greatly change on‑site surveying practices.

Main Features of the LRTK Phone

• Surveying work completed by one person: The biggest feature of the LRTK Phone is that surveying tasks can be completed by a single person. Traditionally, operating a total station and positioning a prism required a two-person team, but with the LRTK Phone a single operator can walk the site with a smartphone in hand and collect survey points. By mounting the device on a dedicated pole, placing it on the ground, and simply pressing a button on the smartphone, coordinates are recorded easily, enabling high-precision surveying even without an assistant. This reduces workflow delays caused by waiting for surveying on sites with labor shortages and provides the flexibility to take measurements whenever needed.

• Intuitive iPhone/iPad integration: Because LRTK Phone runs on a smartphone, operation is done through intuitive app operation. Rather than screens cluttered with complex surveying-device settings and technical jargon, familiar smartphone touch controls let you take measurements and check data. Measurement points are plotted on a map, and clear prompts like "measure here" and "drive a stake here" appear, so even non-experts can use it without hesitation. The large screens of smartphones and tablets offer high visibility, making it far more efficient than squinting at paper drawings or notebooks. The reassurance of being able to survey with a familiar everyday smartphone is helping drive adoption in the field.

• Centimeter-level high-precision positioning: Don't be fooled by its compact size—the LRTK Phone achieves professional-grade centimeter-level positioning accuracy (cm level accuracy, half-inch accuracy). By utilizing a correction technology called RTK-GNSS, errors are contained to about ±1–2 cm (±0.4–0.8 in) horizontally and about ±3 cm (±1.2 in) vertically. Conventional smartphone GPS typically had errors of 5–10 m (16.4–32.8 ft), so this represents a dramatic improvement. In practice, accuracy has been confirmed to be such that measuring the same point with a high-precision GNSS device yields only differences of a few millimeters. Altitude (elevation) can also be measured accurately, making it reliable even for construction where vertical control is important. In addition, in locations without internet access it can receive augmentation signals (CLAS) broadcast from Japan’s quasi-zenith satellite Michibiki to maintain high precision, enabling stable positioning across a wide range of environments from urban areas to mountainous regions.

• AR-assisted layout and staking support: LRTK Phone not only measures but is also adept at reflecting design information at the measured positions. While viewing the site through the smartphone camera, it can overlay planned lines and target points from the drawings onto the scene using AR (augmented reality). For example, it can show virtual AR stakes at the building's foundation positions or draw a string line in space at a specified height. This allows parts of layout work that typically rely on "feel and experience" to be visually confirmed, and enables a single person to intuitively perform reverse staking (transferring design coordinates to the site). Traditionally the procedure was to mark measurement points and then everyone would compare them with the drawings, but with the AR feature you can share the smartphone screen on site to align the completed image with clients and tradespeople, making it effective as a communication tool as well. The non-shifting AR projection, made possible by high-precision positioning, is an innovative feature unique to the LRTK Phone.

• 3D Scan (Point Cloud Measurement): Utilizing the LiDAR sensors built into the latest iPhone and iPad, LRTK Phone can also perform on-site 3D point cloud scans. By simply walking around a structure or terrain while holding a smartphone, you can capture point cloud data comprising millions of points and generate a three-dimensional as-built model on the spot. The captured point clouds are, of course, tagged with global coordinates (latitude, longitude, elevation), so there is no need to align them later to control points as with conventional laser scanners. For example, you can easily scan terrain before and after excavation to calculate earthwork volumes from the differences, or overlay the point cloud of a completed structure with the design model to verify the finished result. Because 3D measurement can be completed with just a smartphone, without large dedicated surveying equipment, being able to record the site immediately when needed is a major advantage.

• Cloud sharing of positioning data: All data acquired with LRTK Phone can be shared by being uploaded to the cloud in real time. Just press the upload button on the smartphone screen immediately after recording a survey point, and the position coordinates and point cloud data are automatically plotted on a map in the cloud. Staff in the office or colleagues at another site can immediately view that data via a web browser. Furthermore, the cloud provides robust URL-sharing functions, so you can send a link to a client or partner and they can view the data without logging in. It also supports downloads in CSV and industry-standard SIMA formats, making downstream documentation and import into CAD drawings smooth. Because there is no need to bring measured information back on paper or USB, being able to eliminate the information gap between the field and the office is an unprecedented efficiency gain.

On-site Use Cases and Examples

The LRTK Phone, with its wide range of features, proves powerful in a variety of on-site scenarios. Let's look at some representative use cases to see specifically how it can be helpful.

• Use in pile-driving operations: In pile driving for building and bridge foundations, accurate positioning of piles and rapid work are required. With the LRTK Phone, a single person can perform on-site pile position layout (marking of pile centers) according to the coordinates of the pile locations shown on the design drawings. By walking along the guide displayed on the smartphone screen you can reach the target pile-driving point and then simply mark it on the spot. This also reduces the need for communication between the crew that sets out survey points and the pile-driving crew as was previously required, and because the surveyor can directly indicate the pile positions, it helps prevent transmission errors. This function, which can be described as pile navigation, is expected to improve the accuracy of pile-driving operations and shorten working time.

• Surveying at disaster sites: At earthquake and landslide sites, rapid understanding and sharing of damage conditions is key to recovery operations. The LRTK Phone is small enough to fit in a pocket and easy to carry to the site, so it can be brought on foot into disaster areas that vehicles cannot reach. Moreover, even if the Internet is down, it can receive correction information from satellites and perform high-precision positioning, so cm-level surveying (half-inch-level surveying) can be maintained even under radio interference. For example, one person can survey the collapse area of a landslide from a safe position and immediately share the point cloud data with headquarters via the cloud. Even in situations that previously required waiting for a survey team to arrive or for heavy machinery to level the ground, with a single LRTK Phone one can collect and share accurate on-site information the same day, greatly enhancing initial response to large-scale disasters.

• Utilization for infrastructure inspections: LRTK Phone is also useful for routine inspections of infrastructure such as bridges, tunnels, slopes, and dams. Inspections require not only visual checks and hammer sounding but also quantitatively measuring displacements and inclinations. With LRTK Phone, you can measure and record pier coordinates and settlement amounts with high precision, and perform displacement measurements inside tunnels—enabling precise positioning measurements that were previously difficult. A particular strength is that coordinates of locations that cannot be reached directly can be obtained without contact. For example, the ends of bridge girders at height or specific points on steep slopes can be safely quantified by capturing them with a camera from a distance and using its function to measure the subject’s position. This makes it possible to omit arranging elevated work platforms or erecting scaffolding, not only streamlining inspection work but also contributing to worker safety.

• Use in as-built management: After construction is completed, the LRTK Phone is also highly effective for as-built management (inspections to verify whether the delivered work was constructed according to the design). Traditionally, as-built measurements required the surveying team to measure on-site, return to the office, and compare with drawings… which was time-consuming, but with the LRTK Phone you can compare and verify measurement results against design data on the spot. For example, you can measure multiple points for pavement elevations and slopes, upload them to the cloud immediately, and display differences from design values as a color-coded heat map. By using the point cloud scanning function to perform a 3D measurement of the entire as-built terrain and overlaying it with the design 3D model, you can detect minute discrepancies that are not noticeable to the naked eye. Being able to check and correct immediately on-site directly leads to reduced rework and quality assurance, and preparing documents for client inspections is simplified to merely exporting the cloud data. The LRTK Phone will be a strong ally in speeding up and improving the accuracy of as-built management.

Differences from Traditional Surveying Methods

To better highlight the features of LRTK Phone, we compare it with representative conventional surveying methods. Understanding the differences will make the value this new tool brings to on-site work even clearer.

• Difference from optical surveying such as total stations: With total stations and optical levels, you must secure a line of sight and perform distance and angle measurements between the instrument and the prism. You set the instrument on a tripod, level it and adjust its height, and because measurements require coordination with the person holding the target, at least two people are generally needed. Additionally, during layout (positioning), tasks are split between someone marking the survey points and someone reading the instrument, which consumes manpower and time. In contrast, because the LRTK Phone uses satellite positioning, line-of-sight along the survey line is unnecessary and measurements can be taken even through obstacles. It offers mobility where one person can move and rapidly collect successive points, and there is no need to carry a heavy tripod. The advantages of LRTK are particularly evident on confined urban sites with poor visibility and on mountainous sites with elevation differences, where there is no equipment setup hassle. Optical surveying is highly accurate but has the drawback of complex preparations, which the LRTK Phone compensates for with its ease of use.

• Differences from conventional GNSS surveying equipment: When it comes to high-precision RTK-GNSS surveying, traditionally a stationary base station and a receiver (rover), plus a dedicated controller to operate them — in short, large-scale equipment — were required. Both weight and cost were substantial, and there are reports that simply bringing the gear to the field was a major hassle. Configuration also required specialized knowledge; tasks such as obtaining satellite correction information and installing the base station presented high barriers. LRTK Phone overturns all of that, achieving a minimal setup of smartphone + small antenna terminal only. The entire system fits in the palm of your hand, making it easy to carry, and the app automates the configuration to connect to correction information services over the internet. Its user-friendly design allows people without surveying qualifications to operate it, so anyone on site can benefit from RTK positioning — a major difference from conventional equipment. And as noted above, because its accuracy rivals that of first-class GNSS equipment, LRTK Phone can be described as lowering the barriers without sacrificing performance.

• Differences from drone aerial photogrammetry and terrestrial laser scanning: Photogrammetry (SfM) using drones, which has become widespread in recent years, and terrestrial laser scanners are also powerful methods for on-site 3D measurement. However, drone aerial photography is constrained by weather and flight permissions, and processing the captured images into point clouds after shooting takes time. Laser scanners can provide high-precision point clouds, but the equipment is expensive and transportation and setup are laborious, and, again, post-measurement data analysis in the office is required. In other words, there have been challenges in terms of real-time capability and ease of use. In that respect, with LRTK Phone you can simply hold up your smartphone at the location you want to measure and press a button to immediately obtain point clouds and coordinates, and you can check and use the results on the spot. No large equipment or prior preparation is required, and the sense of immediacy in responding to “I want to measure this point right now” is a strength that drones and laser scanning do not have. Conventional methods are suitable for capturing entire large-area terrain, but for pinpoint high-precision measurement and immediate on-site verification, LRTK Phone has the advantage.

• Difference from positioning with the smartphone alone: In fact, recent smartphones are also equipped with high-performance GPS, and simple surveying apps are available. However, the positioning accuracy of typical smartphones is at best on the order of several meters, which is far from the level usable for construction surveying. The LRTK Phone functions as an external antenna for a smartphone, capturing signals from multiple satellites and correcting error sources, thereby enabling a smartphone to achieve accuracy that professional surveyors would accept. It is, so to speak, a device that upgrades a smartphone to professional standards, and what sets it apart is that it transforms smartphone GPS—which until now could only provide approximate positions—into surveying equipment that yields precise positions. While retaining the convenience of turning the smartphone you always carry into a surveying tool, it does not compromise the reliability of the results—this delicate balance is precisely the kind of advancement unique to the LRTK Phone.

Benefits of Introducing the LRTK Phone

As introduced above, the LRTK Phone offers many advantages in terms of functionality and operations. So, what benefits can be gained by actually deploying it on site? Here we summarize the main points.

• Lightweight, compact, and easy to carry: The pocket-sized LRTK Phone is a surveying instrument so portable that it fits into a workwear pocket or a small waist pouch—a highly portable surveying device. It weighs just approximately 125 g, about the weight of a smartphone case, so moving around a site won’t be burdensome. Traditionally, transporting and setting up surveying equipment required time and physical effort, and installing equipment at height or on steep slopes involved risks. With the LRTK Phone, there’s no need to worry about that; you can quickly take it out and start measuring whenever necessary. This agility contributes to rapid surveying response and excellent on-site mobility.

• Easy operation, no specialized skills required: Thanks to the familiar smartphone interface, LRTK Phone is a tool that is easy for anyone to use. This means it becomes easier to support surveying tasks even for staff who are not surveying specialists. Site supervisors and construction managers can, for example, measure minor as-built conditions themselves, enabling on-site staff to handle a certain amount of measurement even at sites where a surveyor cannot be stationed. As a result, it helps reduce the burden on veteran surveyors and contributes to alleviating labor shortages. In addition, training costs are low, and newcomers can participate in field surveying after a short briefing, helping to raise the overall skill level of the organization. The reassurance of being operable without specialized knowledge will promote its adoption and effective use on site.

• Reduction in personnel and working hours: The introduction of LRTK Phone is expected to achieve a significant reduction in the personnel and time required for surveying. If more tasks can be completed by a single person, survey teams that previously required 2–3 people can be reduced, and the freed personnel can be reassigned to other tasks. Especially with the 2024 issue (overtime regulations resulting from work-style reform) making securing manpower and improving efficiency urgent, the significance of being able to handle the same workload in fewer labor hours is considerable. Because setup and takedown time for equipment is also reduced, the actual time available for measurements during the day increases, creating leeway even in tight schedules. For example, even if you realize "we forgot to measure that point," with an LRTK Phone you can immediately go to the site and take additional measurements, allowing recovery without stopping other work. Efficient single-person surveying will directly contribute to shorter project durations and reduced overtime.

• Real-time data sharing and utilization: The advantage of having data uploaded to the cloud on the spot and being able to share it in real time with the office or other sites is immeasurable. Until now, time lags such as "process and share the point cloud data measured today at the office tomorrow" were common, but with LRTK Phone all stakeholders can check the latest data immediately on the same day. Not only does this speed up decision-making, but two-way interactions such as measuring on site → the designer immediately checks the data → asking to measure an additional spot can also be completed within the same day. Because it eliminates the hassle of emailing data or handing over USBs, it also reduces mistakes and communication omissions. Ultimately, communication based on survey data becomes smoother and helps strengthen teamwork between the field and the office.

• Reassurance of accuracy and quality improvement: LRTK Phone overturns the conventional wisdom that "convenience and accuracy are a trade-off," because it is easy to use while providing the necessary and sufficient level of accuracy. Being able to measure easily on site also means you can increase the frequency of inspections (double-checks). You can measure and verify critical points immediately after construction and, if any deviation is found, correct it on the spot—allowing the PDCA cycle to be completed within the same day. The reassurance of being able to obtain high-accuracy data at any time will be a major support for site supervisors and quality control personnel. Also, because you can leave documentary evidence such as "measured and verified with LRTK Phone," the objectivity of quality assurance is enhanced. The fact that you can easily ensure accuracy and quality is another benefit of adopting it.

• Improved safety: Labor-saving in surveying work also contributes to improved safety. Traditionally, surveying scree or talus slopes and performing layout marking at heights involved risks of staff working in unstable postures or being close to heavy machinery. With the LRTK Phone, coordinates can be obtained remotely and conditions can be assessed without entering hazardous areas, reducing situations in which workers are exposed to danger. In addition, reducing equipment transport lowers the risk of falls while moving and traffic accidents. Furthermore, because work becomes mainly single-person, contact accidents with others (such as collisions caused by not paying attention to what’s behind them) are less likely to occur. For sites where safety comes first, introducing the LRTK Phone will be a significant plus for safety management.

Future prospects: The future smartphone surveying will open

The world that LRTK Phone enables—"high-precision surveying by anyone with a smartphone"—aligns with the broader construction industry trend of DX (digital transformation). Within productivity improvement measures that utilize ICT, such as i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism, improving the efficiency and sophistication of on-site surveying is an important theme. Going forward, if tools like LRTK Phone become widespread, each person on site becoming a surveyor may become a reality, and a style of taking measurements and verifications as needed, whenever needed, might become commonplace.

This will also bring changes to the role of surveyors. Surveying work that was previously left entirely to specialist teams will be distributed, allowing surveyors to act as spatial information managers for the entire site and focus on data analysis, management, and guidance. Conversely, in situations where surveying expertise becomes more important, human resources will be concentrated, while routine verification tasks that do not require such expertise will be streamlined with digital tools, advancing an optimization of role allocation. Even against the chronic shortage of skilled personnel, if the scope covered by smartphone surveying expands, it will be possible to support more sites with a limited workforce.

The LRTK Phone itself is also expected to evolve further based on feedback from the field. Even now it is packed with features such as AR, point clouds, continuous positioning, and indoor positioning, but in the future the possibilities will continue to expand to include integration with construction machinery, automated cruise surveying, and linkage with cloud-based AI analysis. A future in which smartphones approach becoming a surveying robot for each person may not be far off.

In this way, the future worksites that smartphone surveying will open up will no longer have surveying itself as a bottleneck, and will have the speed and flexibility to advance construction based on real-time data. Because accuracy management and as-built inspection can also be performed quickly and reliably, further improvements in quality and safety can be expected. As a technology that can truly become the key to on-site DX, the LRTK Phone is poised to have a major impact on the construction industry going forward.

Conclusion

LRTK Phone revolutionizes previously cumbersome surveying tasks and is a groundbreaking tool that serves as a reliable partner for surveyors and field technicians. By reducing the personnel and time losses that were unavoidable with traditional methods while firmly ensuring the required accuracy and quality, it is a solution that directly addresses on-site challenges. Its familiar smartphone-based operation also makes it easy to adopt on site, which is another appealing feature despite being cutting-edge technology.

Of course, this does not mean that surveying expertise and experience will become unnecessary, but if the introduction of the LRTK Phone makes "high-precision surveying anywhere, by anyone" a reality, on-site productivity and safety will improve dramatically. By combining the advanced judgment and analytical skills of surveyors with the smart measurement capabilities provided by the LRTK Phone, even more powerful on-site capabilities than before should be realized.

Introducing new technology naturally brings anxiety, but once you actually use it you'll surely be surprised by its ease and usefulness. LRTK Phone-based smartphone surveying has the potential to become the standard going forward. If you are working on site and struggle to ensure accuracy or cannot spare time for surveying, why not pick up this new device and try it out? You will surely experience the convenience that can change the concept of field surveying.