Table of Contents

• Efficiency demands and the latest technologies for field surveying

• What is CLAS? A centimeter-level positioning service usable even out of range

• How a smartphone becomes an all-purpose surveying instrument: the mechanism of LRTK Phone

• Key points where LRTK Phone improves field surveying efficiency

• LRTK enabling simple surveying anyone can do

• FAQ

Efficiency demands and the latest technologies for field surveying

In recent years, construction and civil engineering sites have faced strong demands to improve work efficiency. With a serious shortage of skilled workers and delays in DX (digital transformation) posing challenges, technologies that make surveying, recording, and as-built verification on site easier and faster are attracting attention. The industry-wide expectation for smart construction using ICT, such as the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*, is also growing.

Against this backdrop, new surveying tools that leverage smartphones are changing on-site norms. A representative example is the LRTK Phone. By simply attaching a compact high-precision GNSS receiver to a smartphone, anyone can measure positions with centimeter-level accuracy, making it a next-generation all-purpose surveying instrument. With this single device you can handle point cloud scanning, stakeout (positioning), and AR visualization, without special training or bulky equipment. Because each field staff member can easily perform surveys, a significant productivity increase is expected.

As noted in the title, LRTK Phone supports Japan’s satellite positioning service “CLAS”, enabling high-precision positioning even where cellular signals do not reach. This article first explains what CLAS is, then describes the mechanism and features of LRTK Phone. It then examines concretely how LRTK Phone streamlines field surveying and finally considers the new possibilities for simple surveying enabled by LRTK.

What is CLAS? A centimeter-level positioning service usable even out of range

CLAS (Centimeter Level Augmentation Service) is the abbreviation for the centimeter-level augmentation service provided by Japan’s quasi-zenith satellite system “Michibiki.” Simply put, it is a service that directly transmits from satellites the information needed to correct GNSS positioning errors down to a few centimeters. Normally, centimeter-level positioning using RTK (Real-Time Kinematic) surveying requires receiving correction data from a base station over the Internet or installing your own base station. But with a CLAS-capable receiver, high-precision positioning is possible even at sites without Internet access by receiving only the correction information directly from the Michibiki satellites overhead.

Because CLAS is distributed from quasi-zenith satellites that cover the entirety of Japan, a major advantage is that high-precision positioning can be achieved in mountainous areas, remote islands, and other places beyond cellular coverage—as long as the sky is open. Moreover, CLAS is a government satellite service and has no usage fees, so it can be used without worrying about additional costs. For example, even in situations where communication infrastructure is severed—such as disaster sites—accurate positioning and recording can be performed if you have CLAS-compatible equipment. In fact, CLAS-compatible LRTK devices were useful in field surveys of the 2023 Noto Peninsula earthquake, and it was reported that small devices alone could quickly record and share site conditions even when out of cellular range. In this way, CLAS is an innovative foundational technology that brings “centimeter-level positioning usable anywhere” to the field.

How a smartphone becomes an all-purpose surveying instrument: the mechanism of LRTK Phone

LRTK Phone is a smartphone-mounted high-precision GNSS receiver developed by Reflexia Inc. By attaching a compact device that integrates an antenna and battery to an iPhone or compatible Android device and connecting via Bluetooth, the smartphone itself becomes a centimeter-accurate surveying instrument. It weighs about 125 g and is thin—about 1–1.3 cm (0.4–0.5 in)—and, despite fitting in a pocket, it contains the GNSS antenna and a tri-frequency receiver necessary for high-precision positioning. It is revolutionary that RTK surveying, which used to require fixed installations or large antennas, can now be performed with just a smartphone and a small device.

The LRTK Phone setup is simple. Attach the device to a dedicated phone case or attachment, install and launch the dedicated app on the smartphone, and then simply power it on outdoors; the device will acquire GPS and Michibiki satellites and start positioning. As a CLAS-capable device, it can receive correction signals from Michibiki and perform real-time high-precision positioning without network connectivity. In environments with Internet access, the device will automatically switch to more stable network-based RTK corrections and cloud synchronization.

Because the positioning device communicates wirelessly with the smartphone, it can be used comfortably one-handed while attached, and it can also be detached from the phone and used by mounting it on a monopod or tripod for measurements when needed. For example, to measure the coordinates of a high point, you can place the LRTK Phone on a monopod at that point and simply press the measurement button on the smartphone app to record the exact position. Being cable-free makes measurements flexible in narrow or elevated locations.

The smartphone’s dedicated app allows you to attach photos and notes to measured positions, and plot acquired coordinate data on a map in real time. Measurement data can be uploaded to the cloud with one tap and immediately checked or downloaded from an office PC via a web browser. Latitude/longitude and height data are automatically converted to Japan’s plane rectangular coordinate system and geoid height, so the results can be used directly as public coordinate outputs on site. With this software completeness, LRTK Phone becomes a total surveying solution integrating hardware, app, and cloud.

Key points where LRTK Phone improves field surveying efficiency

The advent of LRTK Phone streamlines on-site surveying operations in various ways. The main points are summarized below.

• cm level accuracy (half-inch accuracy) positioning even out of range: Thanks to *CLAS support*, high-precision GNSS positioning is possible at sites outside cellular coverage, such as mountainous areas or around underground structures. Because you can survey without worrying about base stations or Internet connections, the work area expands greatly.

• Pocket-sized portability: With an integrated antenna and built-in power, the compact device *adds almost no burden to transport*. You can walk around the site with it attached to a helmet or pole and measure whenever needed.

• Multi-purpose use with a single unit: A single LRTK Phone handles single-point surveying, 3D point cloud measurement, stakeout guidance, photogrammetry, and AR display. Tasks that traditionally required separate devices or methods—such as capturing point cloud data for as-built conditions, calculating earthwork volumes and areas, as-built inspection via AR overlay of drawings, and visualization of buried objects—can all be handled in one.

• No expert knowledge required and easy operation: The smartphone app’s intuitive UI realizes simple operation—just press a button at the point you want to measure. Advanced functions such as positioning photos and continuous measurements can be executed with one tap. Because construction managers and workers without surveying expertise can operate it, *anyone on site can become a surveyor*.

• Real-time data sharing: Measurement data are uploaded to the cloud instantly from the field, allowing office staff to confirm results in real time. This eliminates the need to record in paper field books and bring them back, letting stakeholders share information on the spot and make prompt decisions.

• Improved cost performance: It is offered at an accessible price point for high-precision surveying instruments, with subscription plans available. Expensive surveying equipment that used to be shared among several people is becoming per-person equipment with LRTK Phone, enabling multiple people to survey and record concurrently, drastically improving site productivity.

LRTK enabling simple surveying anyone can do

The spread of LRTK Phone means the arrival of a world where “anyone can easily survey anywhere.” Surveying used to require licensed surveyors and costly equipment, and simple on-site measurements were often done with tape measures or levels. But with LRTK, from quick distance or elevation checks to large-scale 3D site recording, all kinds of on-site measurement tasks can be performed accurately with just a smartphone.

For example, simple surveying that used to be done approximately can now be precisely digitized with LRTK Phone, ensuring reliability for subsequent construction and verification. Because the tool can be used without specialized skills, young staff and workers from other trades can voluntarily perform surveying and recording, smoothing information sharing and communication on site. Indeed, LRTK lowers the barriers to surveying and supports on-site DX.

Going forward, it may become standard that field teams use smart surveying devices like LRTK Phone so that anyone can perform high-precision measurements whenever needed. CLAS-compatible LRTK technology, which provides “peace of mind even out of range,” is expected to revolutionize field surveying and even redefine the concept of simple surveying.

FAQ

Q: Can LRTK Phone really be used in environments without Internet? A: Yes. Because LRTK Phone supports CLAS satellite augmentation signals, centimeter-level positioning is possible even in locations without cellular or Wi‑Fi coverage, as long as satellites can be received. Since correction information is received directly from Michibiki (quasi-zenith satellites), high-precision positioning can be performed in environments where networks are cut off, such as mountainous areas or during disasters.

Q: What kind of positioning accuracy can be achieved? A: It depends on the environment, but in typical open outdoor conditions you can expect horizontal and vertical accuracies on the order of ± a few centimeters. The more stably you receive satellite signals, the better the accuracy; by averaging stationary measurements you can sometimes achieve errors less than 1 cm (0.4 in). This is an order of magnitude improvement over standard smartphone GPS (errors on the order of several meters).

Q: Does operation require specialized knowledge or training? A: No special expertise is required. The dedicated app has a simple interface so you can press a button at the point you want to measure to perform positioning and recording. Coordinate system conversions and reception of correction data are automated, so even those not familiar with surveying equipment can use it intuitively. Of course, basic surveying knowledge expands the range of possible uses, but it is designed so anyone on site can start immediately.

Q: What applications can this surveying instrument be used for? A: There are many use cases. In addition to basic point coordinate measurement, you can use the smartphone camera to perform 3D point cloud scans for as-built management, use the stakeout guidance feature to assist construction positioning, and utilize the positioned photo function that automatically tags photos with high-precision location and orientation for site records and maintenance. AR features allow overlaying design drawings or buried-object locations in the real world for checks, making it useful across surveying, construction management, and infrastructure inspection.

Q: Which smartphones and output data formats are supported? A: Currently it supports iOS devices such as iPhone and iPad, and some Android devices (supported models are listed on the product site). Output position data include geodetic latitude/longitude and ellipsoidal height, as well as Japan’s plane rectangular coordinate system and geoid height. Acquired data can be managed in the cloud and downloaded as CSV or PDF for import into CAD software. Flexible data output allows direct use as public-coordinate surveying results on site.

Q: What are the advantages of adopting it over conventional surveying equipment? A: The greatest advantages are mobility and versatility. With just a smartphone you can start surveying anywhere with LRTK Phone, eliminating the need to transport heavy tripods or fixed equipment. Because a single unit can handle various measurements and records, there is no need to assign different devices to different people. As a result, small teams can perform field surveying efficiently, and digital data workflows make downstream analysis and reporting faster. It is also easier to introduce from a cost perspective, and provisioning multiple units can realize DX benefits across the entire team that traditional equipment could not provide.

CLAS-compatible and Reliable Even of Range! LRTK Phone Streamlines Field Surveying

Table of Contents

• What is CLAS? High-precision positioning realized by satellite communication

• Surveying challenges in mountainous and disaster sites

• What is LRTK Phone: a high-precision GNSS device usable with a smartphone

• Features of LRTK Phone: CLAS support streamlining field surveying

• Use cases: powerful in disaster surveys and mountain-area construction

• Introduction benefits: simple surveying by one person and cost reduction

• FAQ (frequently asked questions)

When the site is deep in the mountains or a disaster area and cellular coverage is unavailable... what would you do if you needed high-precision surveying in such a situation? Traditional surveying required base stations (reference points) and communication lines, and in environments without cellular reception real-time high-precision positioning was often abandoned. But now, with new technologies and devices, an era has begun in which you can “measure with confidence even out of range.” The keys are Japan’s satellite positioning system Michibiki’s CLAS and the latest surveying device LRTK Phone that can utilize CLAS signals. This article explains what CLAS is, differences from conventional technologies and their challenges, and how CLAS-capable LRTK Phone streamlines field surveying. Please pay attention to this solution that is powerful in mountain-area construction and immediate disaster response.

What is CLAS? High-precision positioning realized by satellite communication

CLAS (Centimeter Level Augmentation Service) is the centimeter-level augmentation service provided by Japan’s quasi-zenith satellite system “Michibiki.” Standalone GPS (GNSS) positioning typically incurs errors of several meters, but by using CLAS you can greatly improve accuracy to within a few centimeters. Its biggest feature is that it achieves high precision without relying on ground-based base stations or correction data distribution over the Internet; the necessary information is provided directly from satellites.

The CLAS-dedicated signal transmitted from Michibiki (in the L6 band) contains the correction information required for high-precision positioning. Correction values calculated from satellite orbit and clock errors, ionospheric delays observed by the Geospatial Information Authority of Japan’s GEONET network, and other data are broadcast nationwide via Michibiki. With a compatible receiver, you can receive and process this CLAS signal and apply real-time corrections to your GNSS positioning. As a result, users can achieve centimeter-level positioning with a single receiver without setting up a local base station or downloading correction information over a cellular connection.

CLAS covers all of Japan (generally within Michibiki’s service area). As long as the sky view is maintained, you can obtain uniform accuracy in mountainous regions, remote islands, and coastal areas where terrestrial signals do not reach. Furthermore, there is no usage fee, and anyone can use it simply by obtaining a compatible receiver. For these reasons, CLAS is attracting attention as a new option for high-precision positioning without costly equipment or communication fees.

Surveying challenges in mountainous and disaster sites

So why was being “out of range” a problem for conventional surveying? Typical high-precision GNSS techniques—RTK surveying (Real-Time Kinematic)—require constant receipt of correction data from a base station to obtain centimeter-level accuracy in real time. For example, in an “independent RTK” (local base station) workflow where the user installs a GNSS receiver as a base station nearby and transmits corrections via radio, preparing and setting up base station equipment is time-consuming and the effective range is limited (usually on the order of a few kilometers). Even in “network RTK” (VRS and similar) where correction data is provided from national or private networks over the Internet, positioning cannot be established without cellular coverage. Thus, conventional RTK surveying depended on either installing a base station or using communication infrastructure, meaning that in remote mountains, sites with no signal, or regions where communications were down after a large disaster, high-precision positioning was often impossible.

Consequently, in such environments, on-site measurements were often done with low-accuracy GPS to obtain rough positions, and later reprocessed (PPK) in the office to obtain precise coordinates, adding extra work. The inability to obtain accurate real-time survey results leads to reduced work efficiency, delayed initial response, and increased costs. Especially in disaster surveys and emergency responses, the inability to “know accurate positions immediately on site” was a major problem.

What is LRTK Phone: a high-precision GNSS device usable with a smartphone

The trump card for solving these issues is the LRTK Phone. LRTK Phone is a GNSS receiver designed to work with smartphones to achieve centimeter-level positioning. Pocket-sized and compact, it is designed so anyone can easily carry out high-precision surveying by combining it with a smartphone.

Its biggest feature is CLAS support. LRTK Phone is specially designed to receive Michibiki’s CLAS signal, enabling centimeter-level positioning using only satellite-derived correction information even in mountainous areas without cellular coverage or disaster sites with destroyed communication infrastructure. In other words, with LRTK Phone you no longer need to carry heavy base station equipment or mobile routers for network connectivity.

Also, because positioning is performed through an intuitive dedicated app on the smartphone screen, people unfamiliar with specialized surveying instruments can use it easily. As a “surveying instrument that works with a smartphone,” it strikes a balance between on-site mobility and ease of use.

Features of LRTK Phone: CLAS support streamlining field surveying

LRTK Phone offers various features to streamline field surveying. The main points are as follows.

• Extremely compact and lightweight: The LRTK Phone unit weighs about 165 g and is approximately 1 cm thick, making it very compact. It is easy to carry along with a smartphone and convenient to bring to the site.

• Built-in battery for long operation: The internal battery supports about 6 hours of continuous positioning. It can be charged via a USB Type‑C port, and using a mobile battery reduces the risk of power running out outdoors.

• Centimeter-level positioning accuracy: By using multiple GNSS constellations (GPS/GLONASS/Michibiki, etc.), it achieves high-precision positioning of approximately horizontal ±1–2 cm and vertical ±3 cm. Considering that conventional handheld GPS had errors of several meters, this is a dramatic improvement. The acquired coordinates include height as well as latitude and longitude, enabling three-dimensional surveying.

• Supports Michibiki CLAS signals: As noted above, it can directly receive CLAS correction information broadcast from satellites. There is no need to set up a base station, and accuracy does not degrade even out of cellular range—true to the claim “reliable out of range.”

• One-touch accuracy management: The smartphone app lets you check current positioning accuracy and includes functions to average measurement data over multiple seconds as needed. For example, averaging 60 measurements at a single point to improve accuracy is easy.

• One person can perform full-scale surveying: By mounting LRTK Phone and a smartphone on a dedicated monopod, tasks that traditionally required two people can be done by one. The app automatically calculates height offsets (the distance from the monopod tip to the instrument), removing the need for difficult correction work. This realizes “simple surveying” that enables accurate measurements even for non-expert users.

• Integration with smartphone extended functions: It connects via Bluetooth/BLE to iPhone and iPad and operates through a dedicated app. On recent iPhones it can combine with LiDAR scanners for 3D point cloud measurement and AR functions, allowing you to complete everything from terrain scanning to stakeout guidance (displaying design coordinates on site) with one smartphone. LRTK Phone provides the high-precision positional foundation while the smartphone supplies a user-friendly UI and additional measurement capabilities, consolidating tasks that previously required separate devices.

As such, LRTK Phone is a high-precision positioning tool developed to be “usable by anyone, anywhere, immediately.” CLAS support removes dependence on communication infrastructure and dramatically improves on-site mobility.

Use cases: powerful in disaster surveys and mountain-area construction

So where specifically is LRTK Phone most useful? Below are some anticipated use cases.

• Post-disaster field surveys: Immediately after events like earthquakes or heavy rain causing landslides, rapid assessment of damage is required. Disaster sites often have disrupted communications and nonfunctional ground infrastructure. With LRTK Phone, you can go to such sites and start surveying immediately to accurately record the extent and heights of collapsed terrain and the positions of critical facilities. Municipal staff and support teams can complete essential surveys quickly by bringing an iPhone and LRTK Phone, enabling fast recovery planning and hazard area identification. In fact, Fukui City and some other municipalities have started adopting smartphone-based field surveying systems for early recovery and cost reduction.

• Mountain-area construction and surveying: LRTK Phone is ideal for surveying in deep mountains or remote islands with weak or no cellular reception. For example, in forestry civil engineering or mountain tunnel surveying, previously you had to set up base stations in advance for a limited working area or hire a surveying specialist and wait for results. With CLAS-capable LRTK Phone, simply powering on on site starts high-precision positioning. Even when surveying large forested areas you can maintain centimeter accuracy while moving, enabling efficient data collection for many points. Because it can be used without worrying about communications, it expands the surveying range and is flexible for mobile platforms such as drones or vehicle-mounted setups.

• General small-to-medium site work: LRTK Phone is also useful for small-to-medium construction sites that cannot afford large surveying instruments or specialist staff, and for agricultural field measurements. Its smartphone-based ease means it meets everyday measurement needs like “I want to measure the height at this point” or “I need the accurate distance between two remote points.” If companies can perform surveying in-house rather than outsourcing to specialists, they can reduce costs and speed up operations.

Introduction benefits: simple surveying by one person and cost reduction

Introducing LRTK Phone to the field yields significant benefits. First and foremost, completing high-precision surveying by a single person dramatically increases work efficiency. Tasks that used to require a measurer and a recorder can be handled end-to-end by one person with LRTK Phone, reducing personnel coordination and labor costs.

Also, acquiring accurate coordinates in real time enables on-site decision-making and optimization of work procedures. For example, design changes or additional work decisions that previously had to wait for surveying results can now be made the same day. Faster initial responses shorten overall project durations and help prevent further damage.

Furthermore, reducing reliance on external surveyors can cut costs. CLAS itself is free, and once LRTK Phone is introduced, monthly fees for high-precision positioning services (subscriptions) are unnecessary. There are no rental costs for expensive specialized equipment or expenses for establishing reference points. Over the long term, owning and operating your own units is economically advantageous.

Finally, consider the technological innovation and potential LRTK Phone brings. The combination of smartphones and CLAS-capable devices makes “high-precision positioning accessible to everyone.” This means not only surveying professionals but also municipal disaster response personnel, construction workers, and agricultural workers can utilize location information. On-site DX will accelerate, leading to safer and more efficient work environments.

LRTK Phone, which you can rely on even out of range, has the potential to significantly change how surveying and measurement work are done. If your site needs “easy high-precision positioning” or “rapid surveying during disasters,” consider adopting this CLAS-compatible solution. Simple surveying with LRTK Phone should directly improve on-site efficiency and safety.

FAQ (Frequently Asked Questions)

Q: What is LRTK Phone?

A: LRTK Phone is a GNSS receiver that works with a smartphone to provide centimeter-level high-precision positioning. It can receive Michibiki’s CLAS signals, allowing high-precision positioning using only satellite-derived augmentation information even out of cellular coverage.

Q: Why isn’t a smartphone’s GPS sufficient?

A: Typical built-in smartphone GPS (GNSS) has errors on the order of several meters and does not meet the centimeter-level accuracy required for surveying and civil engineering. Combining a dedicated GNSS receiver like LRTK Phone with CLAS correction information is what makes such high-precision positioning possible.

Q: Can it really be used out of cellular range?

A: Yes. LRTK Phone does not rely on Internet-distributed correction data from base stations; it receives CLAS signals directly from satellites. Therefore, it can be used while maintaining positioning accuracy in areas without cellular coverage, such as mountainous regions or disaster sites. However, positioning requires an open sky where satellite signals can be received.

Q: Is CLAS available only within Japan?

A: Currently CLAS is provided primarily for areas centered on Japan. Michibiki satellites cover the Asia–Oceania region, but centimeter-level augmentation is mainly guaranteed within Japan. To obtain similar precision overseas, you need to use that region’s GNSS augmentation services (for example, SBAS or RTK networks in Europe and the Americas).

Q: What positioning accuracy can be expected?

A: Under good conditions, horizontal accuracy of about 1–2 cm and vertical accuracy around 3 cm can be expected. Actual accuracy depends on satellite visibility and surrounding environment (e.g., obstructions), but it is far more precise than conventional handheld GPS. On LRTK Phone, when the positioning mode is in “Fix,” you generally achieve centimeter-level accuracy.

Q: Can beginners use it?

A: Yes. LRTK Phone is operated via a smartphone app and is intuitive to use. No complicated setup is required—power on, connect to the phone, and positioning begins automatically. Measurement results are displayed in real time on the app, so even those without specialist knowledge can use it without confusion.

Q: Is it compatible with any smartphone?

A: Currently it is primarily intended for use with iPhone and iPad (iOS devices). The dedicated app for connecting to LRTK Phone is provided for iOS, and pairing with the latest iPhone models yields maximum performance. Android support may be developed in the future.

Q: In what specific scenes is it useful?

A: As introduced in the article, representative examples include surveying in mountain areas without reliable communications and post-disaster damage surveys. It is also applicable to stakeout checks at small-scale construction sites, farm field measurements, and as-built surveying in urban planning. Whenever the on-site need is “I want accurate positions quickly,” LRTK Phone can help.