Achieving Remote Site Attendance with RTK AR! Check Sites in Real Time from the Office

In the construction industry, efforts to perform “remote site attendance,” where conditions are checked remotely without visiting the site, are accelerating. In particular, the Ministry of Land, Infrastructure, Transport and Tourism has been promoting the introduction of remote site attendance as part of on-site DX (digital transformation), and its adoption has advanced—for example, it has been essentially applied to directly managed projects since fiscal 2022. Remote site attendance allows supervisors to perform stage confirmations and as-built inspections while remaining in the office, and it is expected to reduce travel time and business trip costs and contribute to work style reform (improving operational efficiency and reducing burdens). It has also attracted attention as a measure against infectious diseases and labor shortages, and active adoption by local governments and private companies has begun.

However, conventional remote site attendance has mainly relied on fixed camera footage and wearable cameras for broadcasting, which have limitations such as restricted fields of view, difficulty checking fine details, and difficulty conveying measurement values accurately. For example, it is hard to read the small graduations on a tape measure or inspection instrument through a camera, making it difficult to verify dimensions remotely. Also, situations in areas not covered by the camera cannot be grasped, so the range of confirmation inevitably becomes limited. In sites with poor communication environments, such as mountainous areas, there is also a risk of real-time video interruption. To solve these problems and enable more accurate and detailed understanding of site conditions remotely, a new approach called RTK AR has emerged. This article explains in detail how “RTK AR,” which combines high-precision positioning by RTK and AR display technology, realizes remote site attendance, the technical background, and the effects obtained.

What is RTK AR: High-precision remote verification realized by GNSS × AR

RTK AR is a technology that fuses high-precision satellite positioning (GNSS RTK positioning technology) with augmented reality (AR) to accurately overlay digital information on real site footage. RTK (Real Time Kinematic) positioning secures position accuracy to a few centimeters (a few inches), and based on those precise position coordinates, construction drawings, 3D models, measurement data, and the like are displayed in AR on local camera footage. It is, so to speak, like creating a digital twin of the entire site and peeking into it from the office.

For example, if a 3D model of the design is overlaid in AR on a structure under construction, deviations in as-built condition can be grasped intuitively. Progress that was difficult to understand in flat photos or video broadcasts can be immediately recognized with AR for spatial deviations or missing parts. With RTK AR, site checks can be performed from a distance as if you were standing there and looking around.

Achieving centimeter-level GNSS accuracy with RTK positioning

The key supporting RTK AR is RTK positioning technology using GNSS (Global Navigation Satellite System). Ordinary GPS positioning incurs errors on the order of several meters (several ft), but RTK reduces errors to about a few centimeters (a few inches) by using real-time differential positioning data between a reference station (base) and a rover (mobile station). With network-type RTK that receives correction information from base stations via the internet and by leveraging Japan’s Quasi-Zenith Satellite System (QZSS) centimeter-level positioning augmentation service (CLAS) (cm level accuracy (half-inch accuracy)), it is possible to obtain stable high-precision GNSS coordinates on site. In recent years, not only GPS but also signals from multiple satellites such as GLONASS and Galileo are used, and multi-GNSS and multi-frequency support using L1/L2/L5 and others have been implemented to enable stable positioning even at sites with many surrounding obstructions.

To obtain high-precision position information, it is also important to use multi-band GNSS receivers and antennas, secure an open sky environment, and address radio interference and multipath. However, recently compact high-performance GNSS sensors and smartphones that support augmentation signals have appeared, making it easier to employ RTK positioning. In RTK AR, by linking such centimeter-level accuracy coordinates (cm level accuracy (half-inch accuracy)) to all data, accurate alignment between the site and digital information is realized.

Real-time visualization of site conditions through AR display

AR (Augmented Reality) technology overlays virtual information on actual scenery seen through a camera. Applied in the context of site construction, AR display is powerful for understanding site conditions. Specifically, BIM/CIM models of the design, reference lines, inspection items, and so on that were prepared in advance are overlaid on tablet or smartphone camera footage so they can be checked on the spot. Because AR allows users to walk around freely and view footage from various angles, checking fine details and blind spots that are difficult with fixed camera footage becomes easy.

For example, in roadworks, displaying shoulder and pavement design lines on the ground with AR lets workers immediately confirm discrepancies with current conditions. During as-built inspections, overlaying the finished model on the actual object allows visual checking of finishing deviations. In remote site attendance, on-site staff capture or live-stream this AR screen, and office-based supervisors view the shared screen. Compared to simple video broadcasting, AR makes design information and measurement results immediately apparent, making it easier to give accurate instructions and make decisions remotely.

Progress and quality management using point cloud data and photo records

Another aspect of RTK AR is that it allows recording and sharing site conditions as point cloud data and high-precision, georeferenced photos. Recent smart devices are equipped with LiDAR sensors and high-resolution cameras, making it easy to perform 3D point cloud scanning and photography on site. Combining this with RTK precise coordinates makes it possible to assign absolute coordinates to acquired point clouds and photos.

Acquired point cloud data is useful for closely recording as-built shapes. For example, volumes of excavation or embankment can be calculated from point clouds, and if the as-built shape of a structure is stored in 3D, it can be remeasured later in the office. Also, if photos taken at fixed points are stored in the cloud with timestamps, construction progress can be tracked chronologically. Comparing photos of a given location in order over time allows remote confirmation of work progress and completion level.

In this way, point cloud recording and cloud sharing of photos via RTK AR also aid remote construction management. If data captured and scanned on site is instantly synchronized to the cloud, supervisors can understand the current situation in real time from office PCs. Advanced quality control such as cross-checking coordinates on drawings or overlaying with BIM/CIM models is possible regardless of location provided the data is available.

On-site DX through integration with ICT construction and BIM/CIM

RTK AR’s remote site attendance proves most valuable when combined with other digital construction technologies rather than used as a standalone convenience tool. The Ministry of Land, Infrastructure, Transport and Tourism’s promoted ICT construction (i-Construction) is advancing a trend of utilizing ICT (information and communication technology) consistently from surveying through design, construction, and inspection. Alongside 3D surveying by drone and construction automation through machine guidance, remote site attendance is one method of managing sites with data.

The trend of utilizing 3D design data such as BIM/CIM at the site is also accelerating. RTK AR provides a means to take BIM/CIM models to the site and directly overlay them, serving as a bridge that digitally connects design and construction sites. Furthermore, if point cloud data and as-built measurement results are fed back into BIM models as construction records, they will also be useful for future maintenance and verification. By sharing these data instantly via cloud and IoT, real-time decision-making and advanced construction management become possible. RTK AR is precisely an enabling technology that supports on-site DX and can be integrated compatibly with existing ICT utilization platforms.

Effects of RTK AR introduction on labor reduction, safety, and quality improvement

The realization of remote site attendance and data sharing brings benefits to sites such as labor reduction and improved safety. The following effects collectively raise productivity and safety/quality levels on construction sites.

• Labor reduction and work style reform: Remote site attendance reduces the number of times supervisors and inspectors must visit sites, significantly lessening travel burdens. A single supervisor can check multiple sites in a day, enabling efficient construction management despite labor shortages. Reduced travel time also contributes to less overtime and more rest time, aiding work style reform.

• Improved safety: Reducing on-site attendance at hazardous locations and long-duration site work lowers accident risk. Replacing checks at heights or on scaffolding with AR-based remote confirmation directly ensures worker safety. Fewer people on site reduce the risk of contact with heavy machinery, improving overall safety management levels.

• Remote support from experienced technicians: Experienced technicians can monitor sites remotely and provide real-time advice and guidance to junior staff. One qualified person can oversee multiple sites, allowing quality to be maintained even where skilled personnel are scarce.

• Improved quality assurance and construction accuracy: Using RTK AR makes objective checks based on measured data and design information easier. Parts of the work that were previously left to craftsmen on site can be double-checked digitally, enabling earlier detection and correction of human errors. As-built deviations are easier to detect on the spot, reducing rework costs and helping ensure compliance with quality standards.

National promotion of on-site DX and the trend of ICT utilization

As mentioned above, the Ministry of Land, Infrastructure, Transport and Tourism positions remote site attendance and ICT utilization as important measures within the push for DX across the construction industry. By creating an environment where quality and as-built aspects can be confirmed without visiting the site, it is expected that supervisory and inspection methods themselves will be transformed in the future. In practice, sites that have introduced remote site attendance have reported average reductions in inspection work time of around 80 minutes and overall project efficiencies totaling over 24 hours compared to previous methods. Adoption is likely to spread not only among central government agencies but also at the local government level, and private projects will likely be adopted for cost reduction and efficiency.

As a trend in construction DX, the movement to obtain and utilize data from sites in real time is spreading to other fields. Remote site attendance is becoming established not merely as a temporary remote response but as a new form of construction management linked to BIM/CIM and the cloud. As ICT technologies advance and communication environments such as 5G improve, instantaneous sharing of all site information for real-time construction management may become commonplace. Toward such a future, remote site visualization via RTK AR will play an increasingly important role.

Examples of RTK AR use on sites

The technologies of remote site attendance and RTK AR are already being practiced at various sites with positive results. Below are some examples. In real sites, RTK AR is actively used for a wide range of purposes, including improving efficiency of as-built inspections, conducting remote attendance, and explaining projects to residents.

Case 1: As-built inspection in roadwork At a road improvement site, before paving, the design model was displayed in AR on a tablet at the subbase stage to check target finishing elevations. By overlaying the final design on the subbase surface, on-site personnel could immediately correct low or excessive fill. Remote supervisors in the office were also able to grasp as-built deviations instantly from photos of the AR screen sent to them, completing inspections without issuing additional rework instructions.

Case 2: Remote attendance for revetment work For riverbank revetment reinforcement work, images in which a 3D design model was overlaid on the completed revetment blocks were shared to enable attendance inspection without being on site. Supervisors confirmed block placement and tilt against quality standards from office PCs and approved them remotely. In this case, travel times of several hours each way from site to office were eliminated, achieving significant time savings and cost reductions.

Case 3: Sharing completed-image views and building consensus In a municipal park development, AR was used to project 3D models of planned playground equipment and planting on site and used to explain the project to nearby residents. By showing the park’s completed appearance through smartphone screens, residents were able to concretely grasp the completed image and more readily provide understanding and cooperation. In this way, AR is effective not only for remote site attendance but also as a communication tool with stakeholders.

Realizing simple surveying and AR display with LRTK

Finally, as a solution for easily utilizing RTK AR on site, we introduce LRTK. LRTK is a system that combines a compact high-precision GNSS receiver with a dedicated app to enable centimeter-level positioning and 3D scanning and AR display with just a smartphone. It also features a coordinate guidance function (AR staking) that navigates to set coordinates on site, making it useful for staking and layout tasks. Designed so that complicated setup and bulky equipment are not required and so on-site personnel can operate it intuitively, LRTK is easy to use even for technicians with limited surveying experience.

For example, using LRTK a single person can perform everything from reference point surveying to as-built checks simply, and that data can be shared internally via the cloud. Photos and point clouds obtained are automatically organized on a map, streamlining tasks such as confirming conditions from the office and compiling reports. It also includes a function to import design data into a smartphone for AR display on site, allowing construction mistakes to be prevented by comparing drawings with actual conditions.

Thus, LRTK is a powerful tool for putting the RTK AR concept into practice. Surveying firms and construction technicians considering labor-saving and efficiency improvements through remote site attendance should try LRTK’s simple surveying and AR functions. As a new standard in the era of on-site DX, LRTK can contribute to your operations by balancing accuracy and efficiency regardless of location.

With RTK AR, let’s make the distance between site and office zero.