Base stations or communications not required! RTK usable even out of range for centimeter-level positioning (cm level accuracy (half-inch accuracy)) anywhere

Table of Contents

• Challenges faced when surveying outside communication coverage

• How offline RTK "LRTK" works and its features

• Use in civil engineering and construction: one device per person changes site surveying

• Use in disaster response: powerful where communication infrastructure is unavailable

• Use in forestry and agriculture in mountainous areas: boundary surveying made easy without communications

• Summary: simple surveying with LRTK transforms the field

• Frequently Asked Questions (FAQ)

Surveying at sites deep in the mountains where mobile signals don’t reach or in areas where communication infrastructure has been severed by a major disaster has traditionally posed major difficulties. High-precision GNSS positioning using RTK normally requires receiving correction information from a base station via communications, which is impossible when out of coverage and thus accuracy cannot be achieved. Optical surveying instruments such as total stations also face challenges: in forests or rubble maintaining line-of-sight is difficult, requiring significant effort and time. However, with the recent emergence of a new technology called "LRTK," centimeter-level positioning (cm level accuracy (half-inch accuracy)) anywhere—without base stations or communications—is becoming possible. This article explains in detail the challenges encountered on sites without communication coverage, how LRTK solves them, and practical applications across fields. It covers a wide range of sites from civil works and construction to disaster response and forestry/agriculture. Please read through to the end.

Challenges faced when surveying outside communication coverage

Surveying at mountain construction sites, remote islands, or other areas out of mobile coverage presented the following challenges with conventional methods:

• Difficulty securing line-of-sight: Optical surveying with total stations requires straight-line sight (line-of-sight) between survey points. In mountainous terrain or forests, topography and trees obstruct sight, making it hard to secure line-of-sight; removing obstacles along survey lines or setting up relay points requires considerable effort.

• Unable to receive RTK corrections: The RTK method, a high-precision GNSS surveying technique, assumes correction data are received from a base station via radio or mobile network. In deep mountain areas or out-of-coverage sites, real-time corrections cannot be received, and even with GNSS receivers only errors on the order of several meters are obtainable.

• Burden of base station equipment and personnel: To perform RTK surveying where internet or mobile communications cannot be used, one option is to install your own reference GNSS equipment as a base station and use radio communication. In that case, a full set of base station gear—including large tripods and batteries—must be transported and installed in the mountains, placing a heavy burden on personnel.

• Limits on work time and accuracy: Movement in mountainous areas takes time, limiting the area that can be surveyed in a day. When communications cannot be secured, teams often have to forgo high-precision positioning and rely on manual surveying with tapes and compasses, reducing efficiency and increasing human error. As a result, re-measurement on a later date is often necessary, causing double work.

How offline RTK "LRTK" works and its features

To solve the above challenges, a new high-precision positioning technology called LRTK has emerged. LRTK is a GNSS positioning method that applies real-time kinematic (RTK) principles, but it can achieve centimeter-level positioning (cm level accuracy (half-inch accuracy)) using only satellite signals, without receiving correction data from a base station over the internet. The key to this is the CLAS (Centimeter-Level Augmentation Service) provided by Japan’s Quasi-Zenith Satellite System "Michibiki." LRTK-compatible receivers can directly receive this CLAS signal and obtain correction information generated from the Geospatial Information Authority of Japan’s GEONET reference station network, enabling real-time high-precision positioning even at sites without communication infrastructure.

Technically speaking, LRTK utilizes a positioning method called "PPP-RTK." It aggregates satellite orbit errors and atmospheric error information observed at reference stations nationwide and transmits these corrections via Michibiki satellites, allowing the receiver to apply corrections to its positioning. Because CLAS correction information is broadcast from satellites, it is revolutionary that, within Japan, centimeter-level accuracy can be obtained uniformly anywhere, including mountainous regions, remote islands, and at sea. Moreover, the satellite-based correction signals are provided free of charge, so as long as you have a compatible receiver there are no communication fees or service subscription costs as with some other services.

LRTK receivers themselves are very small and lightweight, offering excellent portability on site. For example, pocket-sized devices that attach to smartphones or tablets are available; they include an antenna and battery and weigh only about 100–200 g. As long as the sky is visible, no base station or communication line is required, and positioning within a few centimeters of error can be performed on the spot. They also support multi-GNSS—GPS, GLONASS, Michibiki, etc.—and multiple frequency bands, so they are designed to maintain stable accuracy even in environments where the view of some satellites is partially blocked, such as forests and mountainous areas. In short, LRTK is an innovative technology that realizes "RTK usable even out of network coverage."

The main features of LRTK high-precision positioning are summarized as follows:

• High-precision GNSS via satellite augmentation: Signals from multiple positioning satellites are augmented with Michibiki’s CLAS correction information to reduce errors that would be several meters in single-receiver (standalone) positioning down to several centimeters in real time.

• Offline operation without communication infrastructure: Because correction data are delivered directly from satellites, correction information can be received even in mountain areas or during disasters where mobile networks are out of coverage. Internet connections and base station gear are unnecessary, allowing stable, high-precision surveying even when communication networks are down.

• Small, lightweight, and easy to carry: Devices that fit in the palm of your hand can be attached to a smartphone, eliminating the need to carry large tripods or poles. They often have dustproof and waterproof ratings for ease of carriage on rugged mountain trails. They can also be mounted on monopods or poles when needed.

• Long-lasting internal battery: Low-power design allows the device to operate for a full day on a single charge. You can conduct continuous surveying from morning to evening without recharging, which is reassuring for extended fieldwork where power is hard to secure.

Use in civil engineering and construction: one device per person changes site surveying

LRTK brings major changes to field work in civil engineering and construction. Until now, centimeter-level positioning equipment was expensive and operated by specialized surveyors, but affordable pocket-sized LRTK devices make a "one device per person" approach realistic. Because no subscription to correction services is required, you can deploy multiple units on a site without worrying about running costs. If construction supervisors and workers each attach an LRTK to their smartphone, they can perform surveying and stakeout themselves whenever needed.

For example, when setting out foundation positions or checking as-built geometry, traditionally you would wait for the surveying team or stop heavy machinery for measurements. With LRTK, site staff can instantly measure coordinates on the spot, compare them with design positions on drawings, or collect additional survey points. Positioning data can be uploaded from the smartphone app to the cloud immediately, enabling instant sharing of results between the field and the office. This helps prevent rework and supports rapid decision-making, dramatically improving on-site productivity.

Also, smartphone-integrated LRTK can be combined with photo capture and AR features. You can take site photos with high-precision location tags or display drawing data in AR on site to confirm construction locations, making a single device a versatile surveying tool. LRTK is turning construction site surveying into something that can be done "anytime, by anyone, immediately."

Use in disaster response: powerful where communication infrastructure is unavailable

At major disaster sites, surveying to assess damage and plan recovery is urgent, but communication infrastructure is often disrupted. Traditionally, real-time high-precision positioning had to be abandoned and damage extents were recorded manually for later analysis. With LRTK, you can perform centimeter-level surveying on disaster sites even without network access.

For example, immediately after an earthquake or landslide, carrying a single smartphone fitted with an LRTK receiver allows you to accurately record the positions of collapsed terrain or displaced structures on site. Because there is no need to set up a base station or transport large surveying equipment, agile surveying can be conducted even under hazardous conditions such as aftershocks. LRTK has actually been used in recent disaster investigations, contributing to the immediate acquisition and sharing of important positioning data from areas that were out of radio range.

Disaster response requires both speed and accuracy, and LRTK supports both. With cloud connectivity, measured point data can be shared directly from the field with relevant agencies for fast recovery planning and damage assessment. LRTK, which reliably obtains position information even when communication infrastructure is down, becomes a reassuring tool for disaster response operations.

Use in forestry and agriculture in mountainous areas: boundary surveying made easy without communications

LRTK is also powerful in fields that were previously difficult to survey, such as forests and mountainous agricultural land. Tasks that once relied heavily on manual labor—like boundary confirmation in woodlands or topographic surveys for terraced field creation—can be carried out efficiently with LRTK.

For example, when measuring boundary markers within a forest, previously you might have had to clear undergrowth to secure line-of-sight or coordinate schedules with neighboring landowners for witnessed boundary surveys, which involved significant effort. With LRTK, you can simply go to each boundary point and press a button to obtain accurate world coordinates on the spot. Measured coordinates can be automatically converted and recorded into preconfigured plane rectangular coordinate systems and elevation datums, smoothing subsequent drawing creation and land registration procedures. Because both parties can confirm the same positioning results on location, reaching agreement in boundary meetings becomes easier. In administrative negotiations such as determining boundaries between national forests and private land, demonstrating real-time measured values with LRTK reduces discrepancies in understanding and helps achieve smooth consensus.

Also, when surveying across vast forests with traverse lines, LRTK allows continuous point acquisition without interruption. Because the survey area is not constrained by communication coverage or terrain conditions, you no longer need to give up by saying “beyond this point accuracy won’t be achievable.” With minimal carry equipment, long-duration treks into remote mountains impose less burden on workers and improve safety. The risk of carrying heavy gear over steep slopes is reduced, work can be completed in shorter time, and risks from worsening weather or nightfall are mitigated.

In this way, LRTK dramatically improves the efficiency and accuracy of surveying work in forestry and agriculture in mountainous regions where communications do not reach.

Summary: simple surveying with LRTK transforms the field

LRTK technology, which achieves centimeter precision without relying on communication infrastructure, is a groundbreaking solution across a wide range of sites from civil engineering and construction to disaster prevention and forest management. The long-standing challenge of “high-precision positioning out of coverage” has become a reality, and an era has begun in which anyone can survey anywhere with just a smartphone and a small receiver. Simple surveying with LRTK not only dramatically boosts work efficiency and result accuracy, but also contributes to improved on-site safety and relief of labor shortages. LRTK also supports i-Construction (ICT use in construction) promoted by the Ministry of Land, Infrastructure, Transport and Tourism and is attracting attention as part of digital transformation (DX) in the construction industry. Adopting such cutting-edge technology will drive productivity improvements and higher-level quality control at worksites.

In future surveying work, being able to complete measurements with uncompromised accuracy even when out of network range will be a major advantage. By leveraging base-station-less high-precision positioning like LRTK, conventional practices on worksites will change, and a faster, more reliable surveying style will take hold. Consider incorporating state-of-the-art LRTK technology into your sites to achieve centimeter-level positioning (cm level accuracy (half-inch accuracy)) anytime, anywhere, and take your operations to the next stage.

Frequently Asked Questions (FAQ)

Q: What is LRTK? How does it differ from conventional RTK positioning? A: LRTK is a new high-precision GNSS positioning technology that does not require correction data from a base station. Conventional RTK requires placing a nearby reference station or receiving correction information via network, whereas LRTK uses Michibiki’s CLAS signal for corrections, enabling centimeter-level positioning even without a base station or internet connection.

Q: Do I need an internet connection or a paid correction service subscription to use LRTK? A: No, you do not. LRTK obtains correction information directly from satellites, so there is no need to connect to a mobile network on site. CLAS augmentation information is provided free of charge, so you can use high-precision positioning without subscribing to expensive positioning services.

Q: What level of accuracy can actually be achieved? A: In favorable conditions, horizontal position errors can be within a few centimeters, and vertical accuracy is on the order of a few centimeters to several tens of centimeters. This achieves a level of precision comparable to conventional RTK methods and is a clear improvement over standalone GNSS positioning (errors of several meters). However, as with other GNSS methods, accuracy is more stable in more open-sky locations.

Q: What equipment is needed to use LRTK? Can I use it with a smartphone? A: To use LRTK you need a small CLAS-compatible GNSS receiver (an LRTK device) and a smartphone or tablet. The receiver is attached to a smartphone using a dedicated mount and connects wirelessly. Since the receiver includes an antenna and battery, no special power supply or large tripods are necessary. Install a dedicated app on the smartphone to intuitively start positioning and manage data recording and sharing.

Q: Can LRTK really position in forests and mountainous areas where satellite visibility is poor? A: Even in environments where satellite visibility is partially blocked, an LRTK that supports multi-GNSS and multiple frequencies can position relatively stably. In wooded areas or valleys, centimeter-level accuracy can be achieved if there is some open sky overhead. However, in very deep forests or beneath cliffs where satellite signals are extremely limited, accuracy may degrade. Even in such cases, unlike conventional optical surveying which requires long straight-line sight, you can move to points with visible sky and measure incrementally. As a result, surveying in mountainous regions that was formerly difficult becomes practical with LRTK.

Q: How long does the device battery last? A: LRTK receivers are designed for low power consumption and typically operate continuously for approximately 8 hours or more on a full charge. For a normal workday, you can use them from morning to evening without recharging. For long forest surveys, there is little worry about power running out and you can reduce the burden of carrying many spare batteries.

Q: How long does it take from starting positioning to achieving centimeter-level accuracy? A: It takes a short time for initial solution convergence, but thanks to multi-frequency support, high accuracy is achieved relatively quickly. Under good conditions, the receiver typically reaches a fixed solution (from float to fix) in on the order of several tens of seconds to about 1 minute, at which point centimeter-level accuracy begins to appear. Once a high-precision solution is obtained, centimeter-level positioning can be maintained even while moving.

Q: Can LRTK be used outside Japan? A: LRTK uses CLAS augmentation information broadcast by Japan’s Quasi-Zenith Satellite System "Michibiki." Therefore, it is basically intended for use within Japan. Within Japan, almost the entire area from Hokkaido to Okinawa and remote islands can achieve centimeter-level positioning, but overseas you cannot currently receive Michibiki’s CLAS signal and thus cannot use the service.