Positioning, Point Clouds, and AR with Just One Smartphone! How LRTK Is Transforming the Field

Table of Contents

• Challenges in traditional surveying and positioning work

• Basics of high-precision positioning with RTK-GNSS

• The arrival of LRTK that enables RTK on smartphones

• Benefits of integrating point cloud acquisition and AR display

• Field work examples possible with a single smartphone

• Summary: How LRTK is transforming the field

• FAQ

Challenges in traditional surveying and positioning work

On civil engineering and construction sites, surveying to accurately determine positions based on plans and drawings is indispensable. High-precision position measurement is required in many situations, such as building layout marking (setting-out), installation of foundation piles, verification of as-built shapes, and recording of existing conditions. However, traditional methods have several issues. First, high-precision positioning required manual work by skilled surveyors and large dedicated equipment such as a total station (tripod optical surveying instrument) or GNSS receivers, making transport, setup on site, and multi-person operation time-consuming and labor-intensive. Even to establish a single point, one had to repeatedly measure distance and angle from control points and mark with stakes or chalk, and measuring many points across a wide site could take an entire day. Naturally, labor-intensive work carries the risk of human error—misreading measurements or marking mistakes can lead to rework or construction errors in later stages.

Work efficiency and safety issues cannot be ignored either. Surveying in rain or on complex terrain is difficult, and performing layout work in areas where heavy machinery is operating poses risks to workers. Surveying on steep, unstable slopes or muddy areas carries the risk of falls, and in some cases entering the area to check pile locations was itself dangerous. Moreover, traditional methods struggled to perform accurate layout in places where physical stakes or markers could not be installed (paved surfaces or elevated structures), forcing compromises with approximate positions. In short, traditional positioning work required manpower and time and faced challenges in accuracy control and safety.

Basics of high-precision positioning with RTK-GNSS

A key solution to these efficiency and accuracy issues in surveying is high-precision positioning using GNSS. GNSS (Global Navigation Satellite Systems) determines positions from signals from multiple satellites such as GPS and Japan’s Quasi-Zenith Satellite System "Michibiki", but the built-in GPS in ordinary smartphones typically has errors on the order of meters, insufficient for precise surveying. The RTK (Real-Time Kinematic) method addresses this. RTK-GNSS applies real-time correction information broadcast from a known reference point (base station) to greatly reduce satellite positioning errors, achieving centimeter-level positioning accuracy within a few centimeters (cm level accuracy, half-inch accuracy). With this technology, field personnel can obtain their coordinate positions with accuracy comparable to conventional total stations. In Japan, various services and infrastructure supporting high-precision positioning are being developed; for example, the free centimeter-level augmentation service (CLAS) provided by the Quasi-Zenith Satellite and network RTK correction distribution services via the Ministry of Land, Infrastructure, Transport and Tourism’s reference station network make it possible to use RTK precision surveying without installing a dedicated base station on site.

The arrival of LRTK that enables RTK on smartphones

However, using RTK in the field traditionally required expensive, bulky GNSS receivers, antennas, and surveying control equipment. The cost and expertise needed to assemble these made them accessible only to specialists or limited sites. LRTK is a groundbreaking device that recently emerged to change this situation. LRTK is an ultra-compact RTK-GNSS receiver that can be attached to a smartphone, turning an ordinary phone into a surveying instrument capable of centimeter-level positioning. A lightweight, compact receiver weighing a few hundred grams is attached to the smartphone’s back via a dedicated attachment or cover and connects wirelessly—setup is complete. The LRTK device supplies high-precision position information instead of the phone’s internal GPS, and surveying apps on the phone can use this real-time positioning data. LRTK supports CLAS signals from Japan’s Michibiki and internet-based RTK correction services, enabling centimeter-level positioning in real time anywhere in the country where the sky is visible. The days of carrying tripod-mounted equipment weighing several kilograms are over: a palm-sized device and a single smartphone can achieve professional-grade positioning.

Moreover, LRTK is not just a GNSS receiver; it’s designed as an all-in-one field DX tool including a dedicated smartphone app and cloud services. Attach the LRTK receiver to your phone and launch the app, and you can perform positioning, recording, and display of drawing data seamlessly. Design coordinate data and measurement results can be stored and managed in the cloud, and position information and point cloud data collected on site can be shared instantly via the cloud. The traditional separate steps of “measure, record, and instruct” that required different devices and procedures are completed with a single smartphone, which is a major strength of LRTK.

Benefits of integrating point cloud acquisition and AR display

With LRTK enabling high-precision positioning on a single smartphone, its full value is realized by combining point cloud data measurement with AR display. Modern smartphones have high-performance cameras and, on some models, LiDAR sensors, making it easy to 3D-scan surrounding structures and terrain to obtain point cloud data. However, ordinary smartphone scans can suffer from distortions or unclear overall coordinates due to small errors in the device’s position or orientation. By using LRTK, the phone’s position is known to the centimeter level during scanning, allowing accurate coordinates (latitude, longitude, elevation) to be assigned to each point in the point cloud. This keeps the consistency among point clouds intact even when scanning while walking, enabling anyone to easily obtain 3D point clouds with embedded position information. You can take your phone and LRTK out of your pocket, complete a 3D scan of the site in a short time, and immediately measure distances, elevation differences, and volumes on site—tasks that previously required specialized equipment or PC post-processing can now be handled in the field.

Collected point cloud data can be reviewed directly on the phone screen or automatically uploaded to the LRTK cloud for web-based sharing and use. Without expensive dedicated point cloud processing software, you can rotate and zoom 3D point clouds in a browser and perform measurements such as distances, areas, and volumes. You can also overlay design 3D models or drawing data on point clouds uploaded to the cloud. For example, scanning the pre-construction terrain and overlaying the designed final terrain model in the cloud allows automatic calculation of required cut-and-fill volumes or early detection of small discrepancies between design and reality. This kind of digital visualization dramatically improves the accuracy of construction planning and the efficiency of pre-construction reviews.

On-site, the combination of LRTK’s high-precision positioning and AR (augmented reality) enables various forms of real-time visualization. By overlaying acquired point cloud data or design lines and models on the phone’s camera view, virtual guides and check information can be projected into the real world. For example, you can display a design model in AR over excavated terrain to verify as-built conditions, or record the location of buried pipes and later project them onto the ground with AR to indicate their positions. Because site conditions can be understood and shared intuitively from digital data rather than relying on the intuition and experience of experts, alignment of understanding and consensus among stakeholders becomes smoother. Combining point cloud measurement and AR makes previously “invisible” elements visible, greatly improving the quality of decisions and work.

Field work examples possible with a single smartphone

The smartphone positioning system using LRTK makes complex surveying and measurement tasks accessible to anyone on site. Below are several concrete use cases.

• Setting-out (layout marking): Layout marking based on coordinates in design drawings is greatly streamlined with a smartphone and LRTK. When a target point’s coordinates are preloaded in the app, the phone screen displays AR markers or guide arrows, and the worker simply follows the instructions to reach the designated position. For example, the app can show “east 5 cm (2.0 in)” or “north 10 cm (3.9 in)” in real time, and as you approach the target point a virtual pin or line appears overlaid on the camera view. Even inexperienced workers can intuitively identify precise points, and layout tasks that formerly required two or more people can be completed by one person with a smartphone in hand.

• As-built verification: For as-built management after construction, smartphone-based positioning and point cloud measurement are highly effective. For example, after paving you can measure road surface elevation and slope with a point cloud scan and compare it to design values, or calculate fill volumes on site to check against specifications. Using AR, you can overlay a design model on the finished structure and visually detect centimeter-level differences that are hard to notice with the naked eye. In one case, projecting a planned temporary fence line in AR before construction revealed a slight discrepancy between the design and site terrain, allowing plan adjustments before work began and preventing rework after construction. Using LRTK enables quantitative and intuitive on-site assessment of as-built conditions, improving the speed and accuracy of inspections and quality control.

• Existing condition records: Recording existing conditions before and after works or during periodic inspections is important in surveying. With LRTK, photos and notes taken on site can be linked to precise position coordinates and saved, enabling tracking of changes over time. For example, when you photograph a boundary marker or structure with your phone, the photo is automatically tagged with its coordinates and uploaded to the cloud. When the same location is surveyed again in the future, you can retrieve the record and easily return to the exact same point, aiding in monitoring changes over time and in preparing reports. Scanning wide areas of terrain or structures as point clouds and preserving a 3D model of current conditions allows later design and review to be conducted while reproducing the site. Compared to paper records or manual notes, centralized digital data management for existing condition records is more reliable and reusable and greatly improves operational efficiency.

• Pile-driving guidance: For pile-driving work to install foundation piles at the correct positions, a smartphone with LRTK acts as an effective navigation tool. If you load pile position coordinates from the design into the app, the phone will guide you to the location on site and display a virtual pile (AR pile) on the camera to indicate the exact point to drive. Traditionally, aligning pile positions required batter boards set by a surveying team and repeated checks, but with the target point shown through the phone’s screen a single worker can accurately identify the pile location. This is especially advantageous where the ground is asphalt or concrete and physical marks cannot be placed—workers can rely on the AR virtual pile to pinpoint the correct position. You can also confirm pile positions from a safe distance, improving safety while maintaining accuracy when working near heavy machinery or on unstable terrain.

Summary: How LRTK is transforming the field

The fusion solution of high-precision positioning, point clouds, and AR using a smartphone and LRTK is bringing major transformation to the daily work of surveying and construction management professionals. Tasks that relied on experience and manpower are becoming intuitive and efficient through digital technology, and the era has arrived in which anyone—not only veterans—can perform precise surveying and inspection as needed. Equipping your smartphone with the pocket-sized ally LRTK makes it possible to “measure quickly and verify” anywhere, anytime, and alone, dramatically improving the speed and quality of on-site communication and verification.

These initiatives align with the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction and the broader construction DX trend, and the technology is expected to spread as a key enabler of site digitalization. By proactively adopting new technologies, sites will be able to accomplish more work safely and accurately with fewer people, improving service quality for clients and local residents. The next-generation field operation style that merges traditional expertise with advanced technology is steadily becoming a reality. Introducing smartphone positioning with LRTK is an innovative move that simultaneously raises productivity and reliability on site, enabling labor savings and visualization of previously difficult tasks. With new technology as an ally, the future of fieldwork is unquestionably brighter and smarter.

FAQ

Q: What is LRTK? How is it different from RTK? A: RTK is the name of the technique that corrects GNSS satellite positioning errors to achieve high precision, whereas LRTK is a compact device (product name) that makes RTK positioning easy to use with a smartphone. By attaching an LRTK receiver to a phone and using a dedicated app, the smartphone can perform RTK-based centimeter-accuracy positioning and function as a surveying instrument. In other words, LRTK is the tool that brings RTK technology within reach for everyone in the field.

Q: What do I need to start using it? A: You need a smartphone with GPS and a camera (a device with a high-performance camera or LiDAR is even better), the LRTK receiver unit, and a surveying app that supports LRTK. You also need a means to obtain correction information to improve positioning accuracy—either by connecting to an RTK correction service via the internet or by receiving Michibiki’s CLAS signals where available. To use AR features, preload the design data or control point coordinates you want to display into the app for smooth overlaying on site.

Q: What level of positioning accuracy can I achieve? Is it comparable to traditional surveying equipment? A: Using LRTK, you can achieve high-precision positioning with errors on the order of a few centimeters. This is comparable to conventional total stations and high-end GNSS equipment and is fully adequate for common tasks such as boundary checks, pile layout, and as-built inspections. Although environmental conditions can occasionally increase errors slightly, stable high precision is maintained when satellites are properly observed.

Q: Is operation and setup difficult? Can non-experts use it? A: Operation is simple and intuitive. Attach the LRTK device to the phone, launch the app, and follow on-screen guidance to perform measurements and AR displays. Initial setup involves configuring the correction information source (e.g., CLAS or network RTK) and connecting to the phone; once done, no special procedures are generally required. Basic knowledge of surveying terms and coordinates helps, but the app provides clear guidance so non-specialists can perform required tasks.

Q: Can GNSS positioning be used in any environment? What about places with poor signals? A: GNSS positioning is most accurate in open-sky environments where satellite signals can be received directly. In dense forests or urban areas with tall buildings, signals can be blocked or reflected, reducing accuracy. Underground or indoor locations typically cannot receive satellite signals, making GNSS unusable. In such environments, it is practical to calibrate the phone’s position using known local control points (calibration) or to combine GNSS with conventional surveying methods as needed. That said, Japan’s Quasi-Zenith Satellite System has improved stability even in urban areas, and outdoor sites with a clear view of the sky can generally achieve practically useful accuracy.

Q: If we have smartphone positioning and AR, does that mean traditional surveying equipment is no longer needed? A: While smartphone + LRTK can replace more and more tasks, traditional equipment will not become completely unnecessary. For instance, tasks requiring millimeter-level accuracy—such as establishing primary control points—or indoor dimensional measurements may still be better served by total stations or optical instruments. However, for uses like boundary meetings, temporary stake placement, as-built checks, and geotagged construction photos, smartphone positioning and AR will increasingly suffice. It is wise to use traditional instruments and new digital tools appropriately according to site objectives; integrating new digital tools while retaining traditional know-how will lead to greater labor savings and efficiency in future surveying operations.