RTK devices pioneering construction site DX — the digital revolution starting from surveying

Table of contents

• [Challenges in the surveying industry: labor shortage, high costs, and analog work](#測量業界の課題人手不足コスト高アナログ作業)

• [What is RTK? The mechanism of Real Time Kinematic positioning](#rtkとは何かリアルタイムキネマティック測位の仕組み)

• [Network RTK and the latest high-precision positioning technologies](#ネットワークrtkと最新の高精度測位技術)

• [Latest trends in RTK devices](#rtkデバイスの最新動向)

• [Use cases of RTK devices in infrastructure, civil engineering, forestry, and disaster response](#インフラ土木林業災害対策などrtkデバイスの活用事例)

• [Benefits of introducing RTK devices (accuracy, portability, ease of use, cost)](#rtkデバイス導入のメリット精度携帯性使いやすさコスト)

• [Accelerating construction-site DX with LRTK: single-point positioning, point-cloud scanning, AR, and heatmaps](#lrtkで加速する施工現場dx単点測位点群スキャンarヒートマップの活用)

• [Start the digital revolution with simple surveying using LRTK](#lrtkによる簡易測量で始めるデジタル革命)

• [FAQ](#faq)

Challenges in the surveying industry: labor shortage, high costs, and analog work

Japan’s surveying and construction industries face a serious labor shortage and challenges in passing on skills. As veteran surveyors age and retire, the number of young technicians declines, and there are increasing complaints that “there aren’t enough people who can do surveying.” If reliance on skilled veterans continues, work can be delayed when they are unavailable, potentially disrupting site progress. Much of the work remains analog and dependent on experience and intuition, making skill transfer to younger staff time-consuming. These workforce shortages and person-dependent practices create an urgent need to improve efficiency and reduce labor in surveying tasks.

Moreover, traditional surveying has aspects of being high-cost and inefficient. Measurements with dedicated instruments such as total stations (TS) and levels are usually conducted by teams of two or more, and setup and teardown of equipment take both effort and time. On large sites, measuring point by point can take more than a full day, driving up labor and calendar days. Collected data were recorded in paper field books and brought back to the office for drawing creation and reporting, introducing time lags and risks of human error (transcription mistakes, missed measurements, etc.) due to these analog workflows. In short, conventional methods demand substantial manpower and time, making them costly and error-prone.

Against this background, the industry as a whole urgently needs labor-saving and efficiency improvements using digital technologies. Initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction” aim to improve on-site productivity by 20% by fiscal 2025, accelerating DX (digital transformation) from surveying through construction. One solution attracting attention is high-precision digital surveying using RTK devices. Leveraging RTK devices can help address labor shortages and inefficiencies while digitizing surveying work, offering the potential to significantly improve on-site productivity and quality.

What is RTK? The mechanism of Real Time Kinematic positioning

RTK stands for Real Time Kinematic, a positioning technology that corrects GNSS errors in real time to achieve centimeter-level precision. Normally, position measurements using GNSS such as GPS produce errors of several meters (typically around 5–10 m (16.4–32.8 ft)). These errors arise from signal delays in the atmosphere and satellite clock errors, and are insufficient for construction surveying. RTK positioning uses two GNSS receivers (antennas): one set up at a known point as a base station, and the other as a rover at the point to be measured. Because the base station knows its exact coordinates, it can calculate the discrepancy (error) between its measured GNSS position and its true position in real time. The base station sends this error information to the rover via radio or other means, and the rover applies corrections to its own positioning results to instantly cancel out the errors. As a result, positioning errors that used to be on the order of meters are reduced to a few centimeters, enabling immediate high-precision positioning. Properly operated RTK can achieve horizontal errors of ±1–2 cm (±0.4–0.8 in) and vertical errors on the order of a few to a dozen or so centimeters.

To maximize RTK accuracy, it is important not to place the base and rover too far apart (short baseline). The closer the two stations, the more common the error sources (such as ionospheric delays) and the easier they are to cancel out, resulting in higher accuracy. Therefore, traditional RTK surveying typically places a base station as close to the site as possible (ideally within a few kilometers) and transmits correction information continuously via low-power radio or UHF while surveying. This allows immediate centimeter-level positioning on site and enables surveying at speeds and with convenience not possible with optical instruments like total stations (TS). However, the need to set up a base station on-site each time was a constraint of traditional RTK methods.

Network RTK and the latest high-precision positioning technologies

The constraint of “having to set up a base station each time” has been overcome by network RTK. This method establishes a network of many fixed reference stations (continuously operating reference stations) across a country or region and provides correction information as if there were a virtual reference station (Virtual Reference Station, VRS) near the user. The user (rover) transmits an approximate position via cellular data, and a server computes what corrections would look like if a base station were placed at that location by processing data from nearby reference stations. The generated virtual reference station correction data are delivered over the Internet (typically via the Ntrip protocol), enabling the rover to perform RTK positioning as if “a base station were right next door.” With network RTK (VRS), centimeter-level positioning is possible by bringing just a single rover to the site, eliminating the need to set up a base station and allowing surveying to begin immediately on arrival. Because a virtual reference station is effectively placed close to each measured point, baseline-length-related accuracy degradation is almost eliminated, and consistent precision is maintained even when moving over wide areas.

Another notable high-precision positioning method is PPP-RTK. For example, Japan’s Quasi-Zenith Satellite System (QZSS, “Michibiki”) offers a centimeter-class augmentation service (CLAS) that transmits high-precision correction information directly from satellites. With a compatible receiver, even in mountainous areas outside of cellular coverage where Internet is unavailable, high-precision positioning comparable to RTK can be maintained using only satellite augmentation signals. In the 2024 Noto Peninsula earthquake disaster site, compact RTK devices compatible with CLAS were used effectively even when communication infrastructure was down, helping to accurately record and share damage assessments. These latest technologies make centimeter-level positioning possible offline, expanding the applicability of RTK surveying.

Latest trends in RTK devices

RTK devices for exploiting RTK positioning have evolved significantly in recent years. Where RTK-capable GNSS receivers were once large, expensive professional instruments, miniaturization and cost reduction have produced RTK devices small enough to fit in a pocket. Ultra-compact GNSS receivers that work with smartphones and tablets have been released by multiple manufacturers, making centimeter-precision positioning accessible simply by attaching a receiver to a smartphone and launching an app. For example, solutions that use a dedicated smartphone cover housing an RTK receiver weighing about 125 g have appeared, turning iPhone/iPad devices into versatile surveying instruments and quietly gaining popularity among field practitioners. These devices typically adopt an all-in-one design integrating battery and antenna, eliminating messy wiring. They connect to smartphones via Bluetooth or Wi‑Fi and seamlessly handle correction data reception and cloud data transmission, allowing even workers without specialized knowledge to operate them intuitively.

RTK devices have also become more capable: recent models support multi-band GNSS (GPS, GLONASS, Galileo, Michibiki, etc.), improving positioning accuracy and fix time in environments where satellite signals are weak, such as urban areas and forests. Some devices include internal tilt sensors and offer tilt compensation, automatically correcting for a pole or device tilted slightly off vertical to obtain accurate nadir coordinates. This enables accurate point measurement even when antennas must be angled to avoid obstructions, improving efficiency in confined spaces. Durability has improved as well, with more RTK devices offering rugged, dust-proof, and water-proof designs to withstand harsh construction sites.

On the communications side, connecting to RTK correction services has become easier. Smartphone apps now allow one-touch login to national or commercial network RTK (VRS) services to retrieve corrections, minimizing on-site setup time. Subscription-based monthly services for high-precision positioning are increasingly common, allowing users to enjoy centimeter accuracy without owning an expensive base station. RTK-equipped drones for aerial surveying and GNSS sensors mounted on heavy machinery for machine guidance/machine control are also becoming widespread. RTK devices are diversifying from handheld to aerial and terrestrial machine-mounted types, evolving into a foundational technology central to construction DX.

Use cases of RTK devices in infrastructure, civil engineering, forestry, and disaster response

Next, let’s look at specific use cases of RTK devices across various fields. Because high-precision position information can be obtained instantly, RTK technologies are useful in a wide range of settings—from infrastructure maintenance to civil construction, forestry operations, and disaster response.

• Infrastructure inspection and maintenance: RTK devices are used to measure structural displacements and record crack locations on bridges and roads. For example, periodic RTK measurements can monitor pier settlement, or RTK can precisely locate road subsidence points to inform repair plans. When combined with cameras or 3D scanning, subtle changes that are difficult to detect visually can be quantified, aiding aging-infrastructure countermeasures. Inspection results can also be shared to the cloud immediately so stakeholders can view conditions in real time.

• Civil engineering and construction: On civil works sites, RTK devices play a central role in ICT-enabled construction. For instance, RTK can be used for stakeout tasks—locating piling or excavation points according to design plans—by allowing operators to mark points in the field based on coordinate data. Where staking was previously performed by surveyors with total stations, construction managers can now complete stakeout guidance themselves in a short time using an RTK receiver-equipped device and guided app. For earthworks, RTK-compatible drone surveys and terrestrial LiDAR scans are being used for as-built management to precisely calculate daily cut-and-fill volumes and monitor progress. If site supervisors carry pocket RTK devices and perform their own measurements, “waiting for surveying” can be eliminated and construction management sped up.

• Forestry and forest management: RTK devices are also used for forest surveying and surveys. In woodlands where trees and terrain can block GNSS signals, high-performance RTK receivers that support multi-GNSS and satellite augmentation signals can achieve more stable positioning in forests than before. Forestry use cases include boundary surveying, planning logging roads, and capturing tree positions. A single person can walk through mountains recording boundary stake coordinates or logging high-precision track logs for planned forest roads. Tasks that once relied on paper maps and compasses are being streamlined and made more precise with RTK devices and tablet-based maps.

• Disaster prevention and response: In disaster sites such as after earthquakes or floods, small and easily portable RTK devices are powerful tools for rapid damage recording and sharing. For example, at a large landslide site that would traditionally require a surveying team, a single responder with an RTK-equipped smartphone can scan the collapsed terrain to produce 3D point-cloud data and upload it to the cloud immediately. In the Noto Peninsula earthquake, RTK devices capable of receiving satellite augmentation signals were used in the field even when communications were down, enabling precise measurement of utility pole settlement and road cracks; the resulting data were used for later analysis and sharing. Even amid the confusion immediately after a disaster, a lightweight RTK device allows detailed on-site recording and information sharing with stakeholders to support rapid recovery decisions.

As shown above, RTK devices support digital data collection and utilization across diverse settings—from precise data measurement for infrastructure inspections to rapid as-built management on construction sites, efficient surveying in forests, and situation assessment in disasters. By enabling tasks that once required specialized teams to be performed by a single person, RTK devices are expected to help overcome labor shortages while improving safety and quality.

Benefits of introducing RTK devices (accuracy, portability, ease of use, cost)

What concrete benefits do RTK devices bring to the field? Here we summarize advantages from the perspectives of accuracy, portability, ease of use, and cost.

• Accuracy: The most significant benefit is improved positioning accuracy. With RTK enabling positioning at the centimeter level, construction quality and reliability improve dramatically. For example, errors in location layout for foundation work are nearly eliminated, greatly reducing rework for correcting as-built errors. Processes that used to be “measure and then correct if it doesn’t match the drawing” can now be done correctly the first time, boosting overall productivity. RTK devices also provide height (vertical) positioning, making it possible to directly obtain elevation references without separate leveling. This is valuable for earth volume calculations, cut-and-fill management, and installing structures with height constraints—situations requiring precise vertical measurements.

• Portability: Modern RTK devices are extremely compact and lightweight, making them easy to carry. A receiver comparable in size and weight to a smartphone can fit in a work jacket pocket or bag and be taken to the field with ease. This portability far surpasses large tripods or installed GNSS base stations, allowing quick spot checks when needed. For example, if a supervisor spots something during a site walk, they can immediately take an RTK measurement and record coordinates. Most devices have built-in batteries so no external power is required, enabling independent measurements far from the office. This portability is especially valuable in mountainous or wide-area inspections and disaster sites.

• Ease of use: RTK devices are increasingly designed for intuitive operation. Models that pair with smartphone or tablet apps display real-time positioning status (satellite lock count, accuracy) and enable one-tap point recording, photo capture, and cloud sync, making them accessible to beginners. A single operator can walk to a point, press a button, and automatically save latitude, longitude, and height along with notes and point names. Devices with tilt compensation automatically correct for a tilted pole, eliminating the need for strict verticality during measurement. This simplicity lowers the barrier that “surveying is only for specialists,” allowing site supervisors and construction managers to use the tools in daily operations. Measured data are plotted on a map automatically and multiple points can be measured and displayed in real time, removing the need for paper field books and later transcription.

• Cost: The cost benefits of introducing RTK devices are also notable. Although high-precision equipment may seem expensive at first glance, prices have fallen and subscription services have emerged, allowing GNSS surveying equipment that once cost several million yen to be acquired for a few hundred thousand yen in some cases. More importantly, RTK adoption promises reductions in labor and time costs. If a survey that once required two people for half a day can be done by one person in an hour, that frees personnel for other tasks and shortens the construction schedule, yielding significant cost savings. Improved measurement accuracy also reduces rework and material waste. Some compact RTK devices are designed to be used with existing smartphones or tablets, eliminating the need to purchase a dedicated controller and reducing initial investment. Overall, RTK devices are a cost-effective investment that simultaneously raises quality through precision and reduces costs through labor savings.

Accelerating construction-site DX with LRTK: single-point positioning, point-cloud scanning, AR, and heatmaps

Among RTK devices, LRTK (an RTK solution developed by Refixia Inc.) has features that strongly support construction-site DX. LRTK was developed with the concept of a “single device solution on an iPhone or similar,” offering a wide range of functions from centimeter-precision positioning to 3D scanning and AR visualization. This section introduces representative LRTK functions and the concrete effects they bring to site DX.

• Single-point positioning: The basic function of LRTK is single-point positioning. Attach an RTK receiver to a smartphone, hold it over the point you want to measure, and press the positioning button in the app to instantly record the latitude, longitude, and height of that point. The record automatically saves date/time, point name, and positioning precision information (such as RTK fix status), fully digitizing the work that used to be done in a paper field book. Positioning data can be automatically converted and displayed in Japan Plane Rectangular Coordinates, and the app can calculate distances and elevation differences between points on the spot. This makes distance and height checks that used to require manual calculation possible with a single tap, giving immediate access to required values. If each worker carries an LRTK, small as-built checks and ad hoc surveying can be completed without additional personnel, greatly increasing site agility.

• 3D point-cloud scanning: One advanced LRTK feature is 3D point-cloud scanning using the smartphone’s built-in LiDAR or camera. Combining the position information of measured points with surrounding shape data captured by the phone’s sensors produces a point cloud representing the entire space. This enables immediate generation of detailed 3D models of the ground or structures on site. For example, scanning ground conditions before excavation allows easy calculation of earthwork volumes by comparing pre- and post-work data and visualizing shape changes. LRTK’s app acquires scanned point clouds with high-precision global coordinates, facilitating smooth integration with design data on office PCs later. Combining multiple scans across time to record progress in 3D is effective for as-built management and monitoring terrain changes. Tasks that previously required subcontracted laser scanning can now be handled by anyone using LRTK to obtain high-density point clouds, accelerating DX from surveying to construction management.

• AR visualization: LRTK leverages high-precision position data and 3D models to support AR (augmented reality) display on site. If BIM/CIM models or drawing lines are preloaded into the LRTK app, they can be overlaid on the camera view so users can compare design and as-built conditions on the spot. Virtual structure models can be displayed in register with the real view without noticeable offset, making it easy to intuitively confirm whether construction is progressing according to plan or where a structure will be located. For stakeout and piping layout, a “coordinate guidance” feature can navigate users to the next work point via audio or AR markers, enabling accurate layout without relying on veteran intuition. Photos taken on site can be automatically tagged with precise coordinates and orientation, allowing later review of images on a map or obtaining coordinates for inaccessible parts such as the underside of a bridge via photogrammetry. AR usage enables real-time overlay of drawings and the field, aiding early detection of construction mistakes and improving stakeholder information sharing.

• Heatmaps for progress management: LRTK offers the ability to visualize differences between scanned point clouds and design data as heatmaps. For earthworks, the heatmap can show where current terrain is overfilled or underfilled relative to the design final surface. Color gradations quickly indicate “over-cut” or “insufficient fill,” enabling immediate decisions on additional fill or correction in the field. The heatmap can be overlaid on the actual ground via the phone’s AR function so operators can visually identify areas requiring correction as they look across the site. Instead of calculating fill volumes and then making decisions, LRTK lets you visualize deviations in real time simply by scanning, minimizing rework. Constantly checking discrepancies between as-built and design with heatmaps provides DX benefits in both quality and schedule management.

• Cloud sharing and status verification: LRTK can immediately sync all positioning data, point clouds, and photos acquired on site to the cloud. With one click, data uploaded to the LRTK cloud can be viewed by office staff and clients from a web browser without requiring a login, and measurements such as two-point distances or area/volume calculations can be performed in the cloud. This allows stakeholders to hold meetings or issue additional instructions based on site data right away. For example, coordinates measured on site are instantly shared on a map so designers in the office can confirm as-built status and prepare for the next phase. Using the continuous positioning (track logging) feature, workers can log coordinates at high frequency (e.g., 10 points per second) while moving, and the track can be displayed in 3D in the cloud. This enables advanced analyses such as automatically generating cross-sections by continuously measuring the finished ground surface. Cloud sharing lets all stakeholders instantly grasp “what’s happening on site,” greatly accelerating decision-making and ensuring reliable information transfer. As a result, the effort required for status checks and reporting is greatly reduced, realizing a seamless new workflow between field and office.

Together, LRTK’s functions—single-point positioning, point-cloud scanning, AR, heatmaps, and cloud sharing—comprehensively support construction-site DX. By consolidating tasks that previously required separate devices or software into a single platform, the cycle of “measure → view → share” can be executed with unprecedented speed and accuracy. This enables site teams to collect and use surveying data without relying solely on surveyors, addressing labor shortages while enabling real-time decision-making and higher-level quality control. As a solution that truly embodies a “digital revolution starting from surveying,” LRTK is poised to become a decisive tool for site DX.

Start the digital revolution with simple surveying using LRTK

As shown above, RTK devices transform surveying itself and are thus a key to advancing DX across construction sites. Solutions like LRTK that work with smartphones provide an environment where anyone on site can master digital tools through “simple surveying.” When surveying that used to be the domain of specialists can be completed on the palm of the hand, digitalization begins to permeate every corner of the site.

The first step in DX is to try digitizing small tasks. For example, switching routine as-built checks that were done with paper and pen to simple surveying with LRTK can produce significant benefits. Once staff experience the workflow of recording conditions with an easy-to-use RTK device and sharing data to the cloud instantly, the efficiency gap with manual processes becomes obvious. Time spent waiting for surveying or creating paperwork can be redirected to core tasks such as construction management and quality improvement. Providing younger field staff with opportunities to use modern tools also helps develop digital talent. With intuitive simple-survey tools, veterans and newcomers can collaborate on data handling, advancing both skill transfer and DX simultaneously.

As the subtitle “the digital revolution starting from surveying” suggests, beginning DX from familiar surveying tasks is the shortest path to transforming the entire site. Simple surveying with LRTK is an ideal entry point for sites introducing digital technology for the first time. With a compact RTK device and a smartphone, you can immediately take the first step toward site DX. When high-precision data become easy to handle, previously hidden inefficiencies and waste will be revealed as data, raising awareness of improvement. Accumulating those improvements will ultimately enhance overall site productivity and competitiveness.

Finally, for readers considering DX, know that “difficult reforms are not necessary.” Start with simple surveying using LRTK and experience small changes on site. That experience will reduce resistance to digital technology and inspire further ideas for use. Changing the field’s surveying fundamentals is the first step toward changing construction norms. Step into the digital revolution that RTK devices are opening up and take your site to the next stage.

FAQ

Q: What is an RTK device? A: An RTK device is a general term for equipment that achieves high-precision GNSS positioning using the Real Time Kinematic (RTK) method. In addition to a GNSS receiver, it typically includes a wireless communication module to receive correction information from a base station and can reduce positioning errors to the order of centimeters. Recently, compact RTK receivers that pair with smartphones and tablets have appeared, and these more portable and economical “RTK devices” are becoming widespread compared to traditional installed GPS surveying instruments.

Q: How much does RTK improve positioning accuracy? A: Standalone GPS positioning typically exhibits errors of 5–10 m (16.4–32.8 ft), but using RTK reduces errors to about 1–2 cm (0.4–0.8 in) horizontally and a few to a dozen or so centimeters vertically. Static measurements can achieve even more stable centimeter-level precision (cm level accuracy (half-inch accuracy)). Using network RTK (VRS) helps maintain conditions close to a base station across a wide area, making it easier to sustain accuracy when moving long distances.

Q: Can RTK positioning be used in mountainous areas without network connectivity? A: In areas without cellular coverage, network RTK using VRS over the Internet cannot be used. In such cases, it is necessary to set up a local base station for conventional RTK. However, in Japan, the QZSS “Michibiki” CLAS service provides satellite-based augmentation that can be used even without communications. A CLAS-compatible receiver can continue centimeter-level positioning in coverage-out areas such as mountains using satellite augmentation alone. For example, higher-end LRTK series models support CLAS reception, enabling high-precision surveying even at sites without communications infrastructure.

Q: Can RTK surveying be done with just a smartphone? A: A typical smartphone’s built-in GPS chip cannot provide the accuracy or the data needed for RTK, so a dedicated RTK-capable GNSS receiver is required. Recently, various compact RTK receivers that connect to smartphones via Bluetooth have been released. By attaching such a receiver to a smartphone and using a dedicated app, centimeter-level positioning can be achieved with a smartphone. Although a smartphone alone cannot perform RTK, smartphone-based RTK surveying is fully feasible by adding a dedicated receiver.

Q: Is there a cost-benefit to introducing RTK devices? A: Yes, introducing RTK devices often yields high cost-effectiveness. Device prices have generally decreased, and rental or subscription options are available. Most importantly, RTK can significantly reduce labor and time costs. Streamlining surveying can reduce the number of survey personnel or shorten project schedules, lowering labor and indirect costs. Improved accuracy also reduces rework and material loss, which is economically beneficial. For example, halving the time required for daily as-built surveys frees time for other productive tasks. Overall, RTK device adoption contributes to both quality improvement and cost reduction on projects.

Q: What is LRTK? A: LRTK is the name of a compact RTK positioning device and app service developed by Refixia. By attaching a thin receiver for smartphones and using a dedicated app, an iPhone or iPad can be transformed into a centimeter-precision surveying instrument. The compact device integrates antenna, GNSS chip, battery, and communications module into a unit weighing about 125 g and approximately 13 mm thick; simply wirelessly connect it to your smartphone to begin RTK positioning. LRTK offers a wide range of functions including single-point positioning, point-cloud scanning, AR display, and cloud sharing, serving as a versatile surveying tool anyone on site can use to support DX. No specialized configuration is required, and carrying one device per person provides immediate usability, making it an attention-grabbing solution for dramatically improving site surveying efficiency.