Advanced features not available with GNSS receiver rentals: CLAS-compatible LRTK enables 3D scanning and AR

Table of Contents

• Typical use cases and limitations of GNSS receiver rentals

• The advancement of centimeter-level positioning with CLAS-compatible RTK

• Unique advanced features offered by LRTK

• Differences from conventional GNSS receiver rental equipment

• On-site improvements expected from LRTK adoption

• Conclusion: The future opened by the simple surveying tool LRTK

Typical use cases and limitations of GNSS receiver rentals

When professional surveyors or construction engineers need high-precision location information, they often consider using GNSS receiver rentals. For example, in civil engineering works for establishing control points or checking as-built surfaces, GNSS surveying instruments capable of centimeter-level positioning are indispensable. However, renting and using conventional GNSS receivers involves several hurdles.

First, typical GNSS surveying equipment (such as RTK-GNSS receivers) requires not only the main unit and antenna but also a dedicated controller (data terminal) and large, heavy accessories like tripods and poles. At survey sites, transporting, assembling, and setting up these items and calibrating them to control points takes time. In addition, achieving high-precision positioning requires either installing a base station to transmit correction data or connecting to a network RTK service via mobile communication, so securing a communication environment and configuring equipment require specialized knowledge. Therefore, even when rented, such equipment generally requires training to operate effectively, and in many cases a survey specialist familiar with the site is needed.

Moreover, rental equipment is often limited in availability by time and quantity. It is common for the necessary devices to not be immediately on hand when needed, causing on-site waiting times for equipment. In mountainous surveys, the burden of carrying heavy equipment over long distances is also significant. Thus, while renting GNSS receivers is effective in terms of accuracy, it has constraints in size and weight, preparation complexity, and low responsiveness. Conventional GNSS surveying equipment is primarily intended for obtaining positional coordinates and generally lacks additional functions such as point-cloud scanning or AR-based site visualization. Therefore, when detailed 3D information or visual data sharing of the site is required rather than “just measuring coordinates,” it was necessary to prepare separate laser scanners or perform photography and drawing-based comparisons outside of surveying, which added to on-site workload.

The advancement of centimeter-level positioning with CLAS-compatible RTK

Recently, RTK and Japan’s quasi-zenith satellite system service CLAS (Centimeter-Level Augmentation Service) have attracted attention as technologies that address these positioning challenges. RTK (Real Time Kinematic) is a method that corrects satellite positioning errors in real time, reducing errors that could be several meters with standalone GPS to several centimeters. Traditionally, using RTK required installing a base station receiver at the site and performing relative positioning against that control point, or connecting to a network correction service such as Ntrip.

On the other hand, CLAS is a modern augmentation signal service provided by Japan’s satellite positioning system “Michibiki.” With a compatible GNSS receiver, centimeter-level correction information can be received directly from satellites overhead, enabling high-precision positioning even in areas without mobile or Internet coverage. In other words, even in mountainous regions, at sea, or in disaster zones where communication infrastructure is down, positioning accuracy can be maintained using only satellite signals. The emergence of CLAS-compatible devices that enable positioning anywhere in the country without a base station is a groundbreaking advancement that dramatically increases the mobility of positioning operations.

By combining RTK and CLAS, the latest GNSS devices can now achieve centimeter-level positioning at the push of a button. The ability to perform high-accuracy surveying without relying on specialist contractors is revolutionary for the surveying and construction industries. Next, let’s examine the unique advanced features provided by the smartphone-integrated positioning device “LRTK,” which supports RTK and CLAS.

Unique advanced features offered by LRTK

LRTK is a pocket-sized RTK-GNSS receiver designed to attach to a smartphone. Developed by a startup originating from the Tokyo Institute of Technology, it weighs only about 150–160 g and is approximately 1 cm (0.4 in) thick, yet enables positioning accuracy comparable to surveying instruments. It supports CLAS satellite signals and network RTK (Ntrip), and its strength is that it can provide centimeter-level positioning across Japan without the dedicated base stations that used to be necessary. By using LRTK, the following advanced on-site features — not available with conventional GNSS receiver rentals — become possible.

• cm-level high-precision positioning: LRTK incorporates a multi-band, high-precision GNSS antenna and receives RTK corrections and CLAS signals to continuously provide centimeter-level positioning. For example, horizontal accuracy is approximately ±1–2 cm (±0.4–0.8 in), and vertical accuracy is also on the order of ± several cm (± several in), achieving accuracy comparable to conventional large surveying instruments. A dedicated app displays latitude, longitude, and elevation in real time, and planar rectangular coordinates in the Geospatial Information Authority system (JGD2011/2020) and geoid heights are automatically calculated, allowing immediate use as survey results on site. The device also includes a function to repeatedly measure points and average them, enabling one-tap processing to improve accuracy in practical workflows.

• Excellent portability as an iPhone-integrated device: Unlike traditional GNSS receivers that were bulky or came with dedicated controllers, LRTK integrates with a smartphone and is therefore highly portable. It can be attached to an iPhone with a dedicated smartphone attachment in one touch and is small enough to fit in a pocket when not in use. It has a built-in battery that can operate continuously for up to about 6 hours and can be USB-charged from a mobile battery for extended surveying. The convenience of having one LRTK-equipped smartphone per staff member, ready to be used at any time, is a benefit unique to LRTK that rental equipment cannot offer. In practice, at major construction sites where all site supervisors carry LRTK-equipped phones, reports indicate that “waiting for the survey team has disappeared and construction interruptions have dramatically decreased.” Constant access to a high-precision positioning tool greatly improves on-site agility.

• Detailed 3D point-cloud scanning: LRTK not only measures positions but also supports 3D scanning using the smartphone’s camera and LiDAR sensor. On the latest iPhones, LiDAR laser measurements or photogrammetry from multiple photos can convert the surroundings into point-cloud data on the spot. When used with LRTK, all acquired point clouds are tagged in real time with absolute coordinates in a public coordinate system, so scanned data immediately becomes high-precision 3D survey results (for example, scanning a slope or bridge pier with an iPhone generates a 3D model whose points are tagged with latitude, longitude, and elevation on the spot). Tasks that formerly took several days with laser scanners or drone surveys can be completed by simply walking while pointing the smartphone. From the acquired point cloud, arbitrary two-point distances, areas, and volumes of fill or excavation can be calculated on site, allowing real-time earthwork estimates and cross-section checks. For example, in embankment work, scanning with LRTK and instantly calculating fill volume can help plan the number of dump trucks or revise embankment plans.

• As-built management and visualization with AR: LRTK incorporates augmented reality (AR) and allows survey data and design information to be used visually on site. For example, by inputting coordinates from drawings, the smartphone screen can display arrows or markers and guide the user to that point via an AR positioning guide function, enabling a single person to accurately mark pile-driving positions. It is also possible to overlay acquired point-cloud data or BIM/CIM design 3D models on the smartphone and compare design and actual conditions in AR. Users can compare slope finishes with the design model on the spot or display scanned buried object data in AR to avoid obstacles during excavation. Because LRTK continuously knows its position with cm level accuracy (cm level accuracy (half-inch accuracy)), AR overlays remain stable even as the user moves. This makes it easy to share completed images with stakeholders while viewing a tablet screen on site or to compare with past inspection photos from the same viewpoint in AR, contributing as a communication tool to site management.

• Indoor positioning and operation in communication dead zones: Even where GNSS signals do not reach, LRTK is designed to continue positioning and recording through various measures. For example, in locations where GPS signals drop out — such as under bridges or inside tunnels — LRTK’s app has an indoor positioning mode that accounts for movement from the last temporarily measured position, allowing cm-level tracking for short durations. This enables collection of survey points in global coordinates or attaching precise location tags to photos even under a bridge. Furthermore, CLAS compatibility allows reception of correction signals directly from satellites in remote mountains without mobile coverage, maintaining high-precision positioning and demonstrating great effectiveness in disaster situations where infrastructure is disrupted. In the 2024 Noto Peninsula earthquake, engineers used LRTK-equipped smartphones to rapidly scan collapsed buildings in areas with unstable communications and immediately shared highly accurate point-cloud models via the cloud. Being able to comprehensively record and transmit the disaster status with a single smartphone enabled remote headquarters to instantly grasp “how many centimeters a utility pole had subsided” or “how many centimeters wide a crack was,” aiding initial response.

• Cloud integration for data sharing and report output: Positioning and point-cloud data acquired with LRTK can be automatically uploaded to the cloud. By accessing the dedicated platform (LRTK Cloud) in the cloud, office personnel can check on-site survey data via a browser and share information in real time with remote supervisors or clients. On the cloud platform, surveyed points plotted on a map can be listed and searched, point clouds can be viewed in a 3D viewer to measure distances, areas, and cross sections, and measurement results can be downloaded in CSV or SIMA format for import into CAD software. Volumes or cross-section diagrams derived from point clouds can be output as reports with one click. There is also a function to issue data-sharing links via URL; sending such a link to partner companies or stakeholders allows anyone to view 3D data without logging in. Information that was previously exchanged flatly via email or drawings can, with LRTK Cloud, be communicated three-dimensionally and intuitively, improving the accuracy of communication and the efficiency of discussions.

As described above, LRTK completes “measure, record, and share” with a single device, dramatically simplifying tasks that previously required multiple devices and procedures. It truly converts a single smartphone into a universal surveying instrument.

Differences from conventional GNSS receiver rental equipment

So what exactly changes with the arrival of LRTK? Compared with conventional GNSS surveying equipment available for rental from other companies, LRTK has clear differentiating points.

First, the difference in portability and speed is obvious. Conventional rented GNSS receivers required operating equipment that could weigh several kilograms, including fixed base stations, pole-top antennas, and dedicated controllers. By contrast, LRTK completes the task with only a smartphone and a slim antenna device, allowing one-handed operation while walking the site. This eliminates the need to allocate heavy equipment or personnel to transport and install gear, matching the field’s need for the ability to “measure immediately when needed.”

Next, the breadth of functionality is another major difference. Conventional equipment can provide high-precision coordinates but offers limited additional functions. To obtain point clouds or AR visualization, separate 3D scanners, AR markers, or tablets had to be prepared, and differing data formats among devices complicated post-processing. With LRTK, positioning, point-cloud generation, photo and memo recording, and AR display are integrated on a single platform, so data flows seamlessly. For example, with LRTK you can review photos taken on site linked to point clouds or immediately compare measured coordinates with drawing models in one place. This integrated workflow yields efficiency gains that were not possible when borrowing single-function receivers.

Also, dependence on specialist knowledge and experience differs greatly. Operating conventional precision surveying equipment required experienced surveyors to handle equipment configuration, validate positioning results, and avoid coordinate conversion errors. LRTK’s smartphone app provides guided prompts so even beginners can operate it intuitively. Automatic coordinate conversion and averaging functions reduce human error, making it easier for non-experts to achieve the required accuracy. This changes the previous situation where surveying had to be outsourced to a specialized department, enabling site personnel to autonomously perform necessary measurements.

Additionally, there is an implicit difference in cost structure. Repeatedly renting expensive GNSS receivers accumulates costs as usage frequency increases. New-generation devices like LRTK are more affordable, making it realistic for organizations to procure multiple units and keep them on hand. This enables a shift from “renting when needed” to “having devices always available,” which not only prevents delays in site work but also contributes to long-term cost efficiency.

Overall, LRTK provides portability, multifunctionality, and ease of use that conventional GNSS receiver rentals lack, and it has the potential to transform on-site surveying methods.

On-site improvements expected from LRTK adoption

What specific improvements can be expected by introducing such an advanced tool on site? Here are several examples.

• Significant reduction of work waiting time: Even in situations that previously required waiting for a surveying team or equipment setup, if each person carries an LRTK they can measure immediately when needed. For example, a major general contractor reported that after equipping all site supervisors with LRTK phones, “idle time due to waiting for surveys was eliminated and overall site progress became smoother.” Being able to measure and check at short notice reduces interruptions in construction and improves productivity.

• Promotion of single-person operations and labor savings: Because LRTK is lightweight, compact, and easy to use, surveying tasks that previously required two to three people can be completed by a single person. For instance, checking control points or as-built inspections can be done by mounting LRTK on a monopod, pressing a button on the smartphone, and obtaining immediate results. This reduces the need for role-sharing like “one person holds a staff rod,” allowing efficient work even at sites short on personnel. The ease of pulling a smartphone from a pocket rather than carrying a heavy total station up to high locations reduces worker burden, benefiting mountainous surveys and high-elevation inspections.

• Improved surveying accuracy and quality: Automatic digital recording and real-time sharing reduce human errors and standardize measurement quality. LRTK saves surveyed points to the cloud immediately, reducing data omission and transcription errors. Moreover, less experienced technicians can obtain correct measurements by following app instructions, reducing errors due to inexperience. As a result, the reliability of survey data increases and rework or re-measurement is suppressed. Using acquired point clouds also allows checking details previously overlooked on 3D models, improving as-built management accuracy.

• Enhanced safety: LRTK’s non-contact and remote measurement capabilities contribute to on-site safety. For example, measurement points in dangerous areas such as cliff edges or deep excavations can be measured remotely without personnel entering hazardous zones by using remote target measurement functions. This reduces situations where workers must stand on unstable footing or remain on busy roads for long periods, lowering accident risk. In disaster-affected areas, the mobility of LRTK enables rapid situational assessment, helping prevent secondary disasters and enabling quick decisions for evacuation.

• Smooth information sharing and faster decision-making: Traditionally, survey data measured on site would be taken back to the office for drawing and report preparation before being shared with stakeholders. With LRTK, data is uploaded to the cloud from the field, allowing clients and designers to view and review data from multiple locations simultaneously. For example, sharing daily as-built data as point clouds allows remote offices to confirm progress three-dimensionally and issue correction or additional instructions on the same day. Faster decision-making leads to shorter construction schedules and improved quality, fostering unity between the site and the office.

As shown above, adopting LRTK on site yields not only time and labor savings but also many benefits in accuracy management and safety management. This is not simply a replacement of equipment but an impact that can transform site workflows themselves.

Conclusion: The future opened by the simple surveying tool LRTK

The emergence of “simple surveying” using a smartphone and a small GNSS receiver offers a new option in the high-precision surveying world that used to require specialists, and is poised to accelerate on-site digital transformation (DX). LRTK provides many advanced features not available from GNSS receiver rentals, integrating the processes of measuring, recording, and communicating seamlessly. As a result, it has succeeded in lowering the barrier to surveying while meeting both accuracy and efficiency — requirements that previously seemed at odds.

If one high-precision surveying device per person becomes the norm, site scheduling and management methods will become even faster and more flexible. Such solutions, which align with the Ministry of Land, Infrastructure, Transport and Tourism’s push for i-Construction, are expected to bring new value to construction and civil engineering sites.

Take this opportunity to experience the easy yet advanced “simple surveying” realized by LRTK. As high-precision measurement becomes accessible to anyone with a familiar tool, site possibilities expand dramatically. Your smartphone can evolve into the next-generation surveying and measurement platform. Why not take that new step?