• Differences between traditional surveying and smartphone positioning

• What is QZSS CLAS?

• What is a CLAS-compatible LRTK Phone?

• Features and functions of the LRTK Phone

• Improved efficiency with one-person operation

• LRTK use cases and examples

• Conclusion

• FAQ

Surveying DX starting with a smartphone: One-person operation and efficiency with a CLAS-compatible LRTK Phone

Have you ever faced a situation on site where you needed to check the elevation or position of a point immediately but had no surveying specialist available? In such cases, it would be reassuring if the smartphone in your hand could become a professional surveying instrument. That is now becoming a reality. An era in which smartphones serve as surveying instruments is beginning. Until now, high-precision surveying required expensive, large dedicated equipment and skilled technicians. However, by simply attaching a palm-sized GNSS receiver to a smartphone, anyone can perform centimeter-level positioning. The key to this is Japan’s unique satellite positioning system, QZSS (known as “Michibiki”), and the latest device compatible with that service, the LRTK Phone. Smartphones can be rapidly transformed into high-precision surveying instruments, ushering in a new era that dramatically improves on-site accuracy and work efficiency. In the field, there has been a growing number of cases where site managers attach an LRTK to their own smartphones and perform the necessary surveying on the spot, and the idea of “one surveying device per person” is becoming the new norm.

Differences between traditional surveying and smartphone positioning

In construction and civil engineering, traditional surveying work typically used specialized instruments such as total stations and GNSS survey equipment, with multiple people cooperating. For example, total station surveying usually requires a two-person team—an operator and a staff member—to operate the instrument and set up the prism. Even high-precision GNSS surveying required time-consuming preparation, such as setting up a local base station or configuring communications with roving receivers. These traditional methods imposed significant burdens in terms of equipment costs and securing personnel, hindering efficiency. Furthermore, the number of experienced surveyors has been declining year by year, making labor shortages a serious issue. As a result, high-precision surveying was often outsourced to specialist contractors or achieved by renting expensive equipment, leading to increased costs and scheduling losses. A new technology that allows on-site staff themselves to easily perform accurate surveying had long been in demand.

On the other hand, built-in smartphone GPS can measure position easily, but its errors are on the order of several to a dozen meters, making it insufficient for high-precision surveying. Recently, however, innovative surveying solutions using smartphones have emerged. These combine a smartphone with an external high-precision GNSS receiver to perform RTK positioning (real-time kinematic). By fusing the convenience of a smartphone with cutting-edge satellite positioning technology, surveying that achieves both ease of use and accuracy has become possible. This enables smartphones to attain accuracy on the order of a few centimeters. Behind this change is the utilization of Japan’s Quasi-Zenith Satellite System, Michibiki. The high-precision positioning services provided by Michibiki are beginning to change the conventional wisdom about smartphone positioning.

What is QZSS CLAS?

Japan’s Quasi-Zenith Satellite System, Michibiki (QZSS), complements and augments GPS to enable stable positioning across Japan. Michibiki offers various services, and the one attracting particular attention is the Centimeter Level Augmentation Service (CLAS). CLAS distributes error correction information derived from the Geospatial Information Authority of Japan’s continuous operating reference station network via Michibiki satellites, delivering real-time correction data to compatible receivers. This can boost GNSS positioning, which alone may have meter-level errors, to centimeter-level accuracy.

Traditionally, achieving centimeter-level RTK surveying required users to deploy their own base stations or receive correction information through communication lines. However, with CLAS, high-precision positioning is possible by receiving correction information directly from satellites without preparing a dedicated base station. Even at sites where cellular signals do not reach—such as mountainous areas or remote islands—centimeter-level real-time surveying becomes feasible as long as you have a compatible receiver. Michibiki currently operates with four satellites, ensuring that at least one is always above Japan, allowing stable reception of multiple satellite signals even in mountainous terrain or downtown areas with tall buildings. Another major advantage is that CLAS correction signals are provided free of charge, so there is no monthly service fee, helping to reduce operational costs. In this way, CLAS is a groundbreaking service that delivers uniform high-precision positioning anywhere in Japan, including areas outside internet coverage.

What is a CLAS-compatible LRTK Phone?

The small GNSS receiver that pairs with smartphones and supports CLAS is the LRTK Phone. The LRTK Phone is a device developed by Refyxia, a startup originating from Tokyo Institute of Technology, and is attached to a smartphone (mainly iPhone※) via a dedicated phone case. It features an all-in-one design integrating the antenna, high-precision GNSS chip, and battery, weighing about 125 g and measuring 13 mm (0.51 in) thick—pocket-sized. By simply attaching this small device to your smartphone, the phone instantly becomes a centimeter-level surveying instrument. The LRTK Phone connects wirelessly to the smartphone via Bluetooth, eliminating the hassle of cables. The device can also be used standalone away from the smartphone, so it can be mounted on a monopod or tripod to measure fixed points.

Because the LRTK Phone can receive the CLAS signal (Michibiki L6 band), centimeter-level positioning via satellite augmentation is possible even at sites outside cellular coverage. It also supports network RTK via cellular networks (VRS/Ntrip), allowing you to choose the optimal method of high-precision positioning according to the area and operation. For example, you can use existing reference station networks in urban areas and switch to Michibiki CLAS augmentation in mountainous regions. With the antenna and battery built in, there is no need for field wiring, and the device attaches to the dedicated case with a single touch for quick setup. By attaching the LRTK Phone to your smartphone and launching the dedicated app, anyone can easily start centimeter-level positioning.

※ Android device support is planned sequentially.

Features and functions of the LRTK Phone

The “smartphone surveying instrument” formed by combining the LRTK Phone with a smartphone offers many features and convenient functions not found in traditional surveying instruments. Here are the main points.

• Easy smartphone integration: The device integrates with your smartphone simply by sliding it into the dedicated case and connects easily via Bluetooth. No complicated instrument operation is required—positioning can be started from the smartphone screen. It is pocket-sized and easy to carry, allowing you to start surveying immediately when needed.

• Compact, rugged all-in-one design: With the antenna, high-precision GNSS module, and battery all built in, there is no need to wire external devices in the field. The unit weighs approximately 125 g while offering dust and water resistance, providing the robustness needed for harsh outdoor sites. Higher-end models include tilt compensation, allowing accurate positioning even when you cannot hold the pole perfectly vertical.

• Multi-GNSS and tri-frequency support: The LRTK Phone supports multiple satellite systems including GPS, GLONASS, Galileo, and BeiDou, and receives multiple frequency bands such as L5 and L6 with tri-frequency capability. This enables stable positioning by capturing as many satellites as possible even in urban canyons or mountainous areas. In particular, support for CLAS signals from Japan’s Michibiki is a major strength, enabling standalone centimeter-level positioning even outside communications coverage. In fact, during the 2023 Noto Peninsula earthquake, CLAS-compatible LRTK models were reported to have been useful for independent surveying in areas where communications were disrupted.

• Diverse surveying app functions: The dedicated smartphone app lets you utilize position data obtained by LRTK in various ways. Single-point coordinate measurement can be recorded with a single tap on the phone, and results are automatically calculated and displayed not only as latitude/longitude but also in Japan’s plane rectangular coordinate system and elevation (including geoid height). Each measured point can be saved with date/time, notes, and photos, enabling accurate survey records without paper field books. The app can compute distance, area, and volume from multiple recorded points on the spot, which is useful for earthwork quantity calculations and as-built management. It also supports coordinate guidance (layout) to help stake out points from design drawings or models, and AR features that overlay design information on the smartphone screen. In addition, it supports 3D point cloud acquisition using the smartphone camera or LiDAR sensor, allowing you to record the site as a high-precision digital point cloud model.

• Cloud integration and data sharing: Data measured and recorded in the LRTK app can be uploaded to the LRTK Cloud with one tap. On-site position data and photos are automatically plotted on a map so office staff can immediately check results from a web browser. Cloud-stored data can be exported in CSV or SIMA formats, making it easy to import into existing CAD or as-built management systems. If you share a dedicated URL issued from the cloud, recipients can view survey results in a browser without logging in. This dramatically improves information sharing between the field and the office.

Improved efficiency with one-person operation

Centimeter positioning enabled by the LRTK Phone dramatically improves on-site surveying accuracy and work efficiency. In terms of accuracy, real-time centimeter-level positioning that was previously difficult can now be achieved by anyone. In verification tests, when the LRTK was fixed and the same point was measured repeatedly, single-shot horizontal accuracy was about 12 mm (0.47 in), and averaging multiple measurements improved accuracy to about 8 mm (0.31 in). With such high accuracy below 1 cm (0.4 in), tasks that were previously left to specialist surveying teams—such as as-built management, control point placement, and heavy machinery guidance—can be accurately performed by site personnel themselves. Reducing surveying errors decreases rework and re-measurement, directly improving quality and shortening schedules. Moreover, when on-site staff can obtain and use high-precision position data themselves, they can verify construction accuracy on the spot and prevent mistakes. For example, by overlaying design models or lines on the smartphone screen via AR and comparing with the real scene, you can check stake positions or installation alignment in real time and help prevent construction errors.

Work efficiency also improves significantly. With LRTK, there is no need to transport and set up heavy tripods and large equipment, creating the nimbleness of being able to “measure whenever you want.” Coordinate checks that used to require arranging a surveying team and half a day can be completed by site staff in minutes with LRTK, and results can be shared to the cloud immediately. If each site worker carries a personal LRTK surveying device, multiple locations on site can be surveyed concurrently, dramatically increasing overall productivity. There is no need to hire external specialists or coordinate schedules, increasing flexibility in the workflow and reducing costs. The intuitive smartphone-based operation makes the device easy to use for anyone, so personnel can become operational with short training, preventing work from becoming dependent on specific individuals. Reducing required manpower also lowers the risk of contact between workers and heavy machinery on active sites, contributing to improved safety. Additionally, the new surveying style enabled by LRTK aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction, and strongly supports DX (digital transformation) in the construction industry.

LRTK use cases and examples

Looking at actual sites, the LRTK Phone demonstrates effectiveness across a range of scenarios. Here are some examples.

• Remote mountainous areas and islands outside cellular coverage: At remote construction sites or islands where mobile signals previously did not reach and high-precision positioning was difficult, the LRTK Phone can directly receive Michibiki CLAS signals and perform accurate positioning. Leveraging its “out-of-coverage” capability, a single operator can complete surveying in fields without infrastructure, such as surveying outside tunnel portals or mapping conditions in logged forest areas.

• Disaster-affected areas immediately after an event: Communications infrastructure can be down after large-scale disasters, but with the LRTK Phone you can still obtain high-precision positioning and records as long as satellites are receivable. During the 2023 Noto Peninsula earthquake, a local construction company that happened to have CLAS-compatible LRTK devices was able to record high-precision, geo-tagged photos, which proved extremely useful. Even when it’s impossible to bring in large surveying equipment to a disaster site, a pocket-sized LRTK enables rapid situational assessment and documentation.

• Small-scale construction and routine inspections: LRTK is also useful for tasks that do not justify calling a dedicated surveying team, such as small residential construction sites or routine infrastructure inspections. For example, site supervisors can immediately measure elevations at a housing development site or check the as-built condition of a road repair location. For infrastructure inspections, if an inspector repeatedly photographs the same coordinates and orientation with LRTK during fixed-point monitoring of bridges or tunnels, even tiny displacements can be reliably captured. Using a high-precision positioning device one per person brings great benefits for routine maintenance tasks.

• Complex construction: On roadworks and structural construction sites, AR functions that let you verify design lines and finished appearance on site are useful. By overlaying a 3D model on the smartphone screen based on precise coordinates obtained with the LRTK Phone, you can instantly judge whether construction is proceeding according to design. This reduces rework and contributes to quality assurance and efficiency.

Some forward-looking construction companies and local governments have already begun trialing LRTK on site. It is being recognized as a revolutionary tool that enables anyone to perform high-precision surveying easily, with the potential to change how site work is done. The “surveying with a smartphone” style is expected to become more widespread, contributing to industry-wide DX and productivity gains.

Conclusion

With the combination of a smartphone and the LRTK Phone, the surveying world is now undergoing a major transformation. With a compact device and a smartphone, centimeter-level surveying that previously required specialist technicians and expensive equipment is now accessible to anyone. This is changing on-site workflows, making it the new norm to “measure accurately in a short time with few people.” If each worker carries a personal high-precision positioning tool and can measure, record, and share results immediately when needed, the downtime caused by “waiting for surveying” will disappear and overall productivity will soar. Instant utilization of high-precision data also elevates quality control, leading to construction without waste or mistakes.

The LRTK Phone condenses a wide range of powerful functions—high-precision positioning, smartphone integration, AR display, and cloud synchronization—into a single device. It enables flexible surveying workflows unconstrained by conventional thinking and provides great value as a first step toward on-site DX. It is truly a device that makes low-cost, one-per-person high-precision surveying possible and powerfully drives digitalization in the construction and surveying industries. Start your surveying DX with a smartphone—introduce the simple LRTK surveying solution to your sites and experience its ease and effectiveness.

FAQ

Q: What is the LRTK Phone? A: It is a small high-precision GNSS receiver that attaches to and is used with a smartphone. It supports Michibiki’s CLAS and can turn a smartphone into a centimeter-level surveying instrument. The antenna, GNSS chip, and battery are integrated, it connects to the smartphone via a dedicated case, and positioning and recording are performed through a dedicated app.

Q: What is CLAS? A: CLAS stands for Centimeter Level Augmentation Service, a high-precision positioning service provided by Japan’s QZSS Michibiki. It distributes correction information from ground reference station data via the satellite, and compatible receivers that receive this information can reduce GPS positioning errors to the centimeter level. A key feature is that correction signals can be received directly from satellites even in areas without cellular coverage.

Q: Can I survey in places outside cellular coverage? A: Yes. The LRTK Phone can receive Michibiki CLAS signals, so centimeter-level positioning is possible even when your smartphone is out of cellular coverage. Even in mountainous areas without internet access or in disaster situations where communications are down, high-precision positioning is possible as long as satellites are visible.

Q: Can it be used without specialized surveying knowledge or special skills? A: Yes. The LRTK Phone is designed to be operated intuitively through a dedicated smartphone app. Positioning and recording can be done with a single button, and coordinate conversion and distance calculations are automated. No complicated instrument operation is required, and users familiar with smartphones can learn to use it with short training. Because it uses smartphones that site staff are already comfortable with, the training burden for introduction is low.

Q: What level of positioning accuracy can be obtained? A: It depends on the environment, but real-time accuracy of a few centimeters can be achieved. In favorable sky conditions for static positioning, horizontal accuracy of about 2–3 cm (0.8–1.2 in) can be obtained, and averaging processing has been demonstrated to achieve accuracy of 1 cm (0.4 in) or better. This level of accuracy is sufficient for general construction surveying and as-built management.

Q: How can positioning data and recorded photos be shared? A: Measurement data can be uploaded to the cloud from the smartphone with one touch. Points and photos plotted in the cloud can be viewed immediately from an office PC. Survey results can be downloaded in CSV or SIMA formats for use in CAD drawing creation and reporting. Photos saved in the cloud display the capture location and orientation on a map, and sharing a link allows stakeholders to view the site situation in a browser.

Q: Are there additional fees to use correction information? A: Michibiki’s CLAS signals are provided free of charge, so using CLAS for positioning does not incur additional costs beyond communication fees. There is no usage fee for the LRTK Phone itself (no ongoing maintenance fees after purchase). If you use network RTK (VRS, etc.), you need to subscribe to the provider of that service to receive corrections via communication, but a CLAS-compatible LRTK Phone can basically achieve high-precision positioning without subscriptions.

Q: Which smartphones are compatible with the LRTK Phone? A: Currently, integration with iPhone via a dedicated case is the primary configuration (some iPads are also supported). It connects via Bluetooth for cable-free use, and positioning is performed using an iOS app. Android support is planned, and future expansion will enable use with a wider range of smartphones and tablets.

Q: Can it be used in rain or harsh environments? A: Yes. The LRTK Phone is built with dust and water resistance and is rugged enough for use on rainy or dusty construction sites. Operation tests have been conducted under direct summer sunlight and in cold regions, and the device has the durability required for construction sites. However, GNSS positioning itself requires reception of satellite signals, so indoor locations or inside tunnels where satellites are not visible make positioning difficult. In such cases, relative measurements from outdoor reference points or transferring positioning results may be necessary.