RTK ARで施工イメージをその場表示！完成形を現場でプレビュー

In recent years, the surveying and construction industries have been paying attention to "RTK AR," which combines RTK positioning technology using GNSS with AR (augmented reality). With RTK AR, you can overlay a 3D model from the design phase directly onto the site scenery and intuitively preview the finished form on location. For surveying companies, municipal public works departments, and construction contractors, this technology is a groundbreaking solution that simultaneously improves construction management efficiency and quality by allowing stakeholders to share the completion image before construction and instantly check as-built conditions during construction.

However, to understand the benefits of new technology, it is also important to look back at the challenges of conventional methods. On traditional construction sites, workers had to imagine the construction image based on paper drawings or stake-out positions, and as-built inspections required measuring heights and dimensions point by point with surveying instruments after completion and comparing them to the drawings. Measuring many survey points over a large site could take multiple people several days, and it was not uncommon for errors or defects to be discovered too late on site, leading to rework. Moreover, imagining the finished form from drawings alone is not easy, and it took time to reach agreement with clients and nearby residents. High-precision surveying with expensive total stations or GPS equipment is accurate, but there is also the reality that smaller companies face high barriers to adoption. RTK AR emerged to solve these inefficiencies and communication issues.

RTK ARとは何か：GNSS×ARで実現する高精度な現場可視化

RTK AR is a technology that combines high-precision GNSS positioning (RTK method) with AR display to accurately overlay a three-dimensional digital model onto the real world. First, a brief explanation of the RTK (Real Time Kinematic) method: signals from GNSS satellites are received simultaneously by a base station and a rover (device), and by correcting positioning errors in real time based on the difference between the two, positions can be determined to within a few centimeters (a few in). Traditionally, RTK positioning required stationary receivers, but recently the advent of small antennas and receivers that can be attached to smartphones has made mobile RTK positioning possible. For example, by attaching an RTK-capable GNSS receiver to a smartphone and receiving correction information, GPS accuracy that is normally on the order of several meters (several ft) can be improved to centimeter-level accuracy (half-inch accuracy) and, in some cases, to millimeter-level accuracy (a few hundredths of an in).

On the other hand, AR (augmented reality) technology overlays digital information onto camera images from smartphones or tablets. Although this has become widespread in recent years, typical smartphone AR relies on built-in GPS and image analysis from the camera for alignment, yielding coarse accuracy on the order of meters—unsuitable for placing design models accurately on large civil engineering sites. Also, methods that require installing AR markers (image targets) are cumbersome outdoors. RTK AR is characterized by using high-precision GNSS positioning so that models can be matched exactly to real-world coordinates without placing markers. Combined with the device’s gyroscope and compass, the 3D model remains fixed in the correct position and orientation in real space even when the user moves or changes the camera direction. In short, RTK AR can be described as a technology that “projects” digital design drawings onto the site with positional accuracy on the order of a few centimeters (a few in).

RTK ARがもたらす施工管理上のメリット

The introduction of RTK AR brings groundbreaking benefits to various aspects of construction management. Here are the main advantages.

• Dramatic improvement in work efficiency: By leveraging AR, surveying and inspection tasks that traditionally required manpower and days can be significantly streamlined. For example, as-built measurements that used to take several people half a day could be completed quickly by one person using an AR app in many cases. Because drawing preparation and report creation can be automated on site, shortening the workflow from surveying to recording leads to overall schedule shortening and cost reduction.

• Improved construction accuracy and error prevention: RTK AR visualizes design models and reference lines with centimeter-level accuracy, allowing positional offsets and dimensional errors to be detected and corrected on the spot. By comparing design data and reality through the camera, even millimeter-scale deviations are not overlooked. This prevents construction mistakes that would otherwise require major rework later. Visual guidance via AR also helps reduce human error. For example, where operators previously moved machinery based on ground markings made by surveyors, AR enables direct guidance of people and machines to precise digital target points, eliminating miscommunication or misreading. Piling and excavations by heavy equipment can be executed at the intended positions and depths, greatly reducing the risk of quality defects.

• Facilitated agreement formation and smoother communication: Sharing completion images and construction status with AR contributes to better internal and external communication. For instance, displaying the planned structure at full scale on a tablet makes explanations to clients and nearby residents much easier to understand, smoothing project consensus. Stakeholders can discuss the site while viewing the same AR visualization, reducing misunderstandings and improving communication. Also, displaying construction procedures and precautions in AR for on-site workers allows inexperienced staff to work with a shared image alongside veterans, aiding skills transfer and training.

• Addressing labor shortages and improving safety: RTK AR is powerful even where experienced surveyors are scarce. Intuitive AR operation makes surveying and as-built checks possible for anyone, enabling tasks that previously relied on veterans to be handled by younger staff. If surveying tasks can be completed by one person, labor savings follow, helping to alleviate personnel shortages and reduce labor costs. Additionally, many situations allow remote confirmation and guidance via AR without entering hazardous areas, reducing the number of times personnel must enter high places or deep excavations and thus lowering safety risks. Not having to send survey teams into zones where heavy equipment is operating is a major advantage, and AR use is expected to help prevent workplace accidents.

主な活用シーン：RTK ARの具体的な使い方

RTK AR can be applied in many situations on civil engineering and construction sites. Here are representative use cases.

• Pre-construction checks by AR display of design models: 3D design models created with BIM/CIM for buildings, bridges, roads, etc., can be displayed in AR on site to confirm placement and dimensions in advance. For example, projecting a 3D model of the planned structure over an empty lot and checking its interaction with the actual terrain and surrounding environment can reveal clashes or layout problems that were not noticed in the design phase. Even during construction, you can confirm on site whether columns or walls under construction are offset from their design positions. Differences between the design image and the actual finished form, which are hard to grasp from drawings alone, become obvious when viewed in AR in the real space. For works that connect new structures to existing ones, AR enables consistency checks between structures, eliminating positional or dimensional discrepancies in advance.

• Real-time visualization of as-built differences: As-built data obtained after construction (e.g., point clouds from a smartphone LiDAR scanner) can be compared with design data to instantly check deviations on site. Comparing design models and as-built point clouds on a dedicated cloud service can automatically generate heat maps color-coding excesses and shortages of embankment or concrete thickness. Downloading that to a smartphone and displaying it in AR instantly shows which areas are higher or lower than the design. This allows intuitive on-site management of the as-built deviations required for inspections. For example, evaluating pavement or base course thickness across areas and correcting insufficient spots the same day helps accelerate the PDCA cycle. The advantage is that inspection data can be used on site rather than only compiled into reports.

• AR visualization of buried utilities: Structures and pipelines buried underground can be displayed in AR so their positions and depths can be confirmed even after pavement is laid. For example, in sewer pipe works, scan the pipes with a smartphone before burial and store 3D data with precise coordinates in the cloud; after backfilling, display that data in AR to intuitively grasp the route of pipes not visible from the surface. Because you can identify buried utilities by simply pointing a smartphone at the ground without marking surfaces, this prevents construction mistakes that come too close to existing pipes and improves efficiency when excavating for maintenance. For future works, you can immediately show locations on site without searching drawings.

• Machine guidance and construction navigation: RTK AR can assist heavy equipment operation. Display the work area and target heights or slope lines in AR on a smartphone or tablet, and operators or guides can follow those instructions to perform excavations and embankments to the specified shape. Previously, operators relied on lines indicated by survey teams with stakes or chalk; AR guidance provides a universal guide that everyone follows, ensuring uniform quality. For piling in tight sites, virtual piles (AR piles) can be displayed on a smartphone screen to indicate positions. Even on concrete floors where physical marking is not possible, using virtual piles on the screen can locate pile positions within a few centimeters (a few in). This navigation reduces time spent on surveying coordinate establishment and cuts waiting time for machines.

• Sharing the completion image before construction: Displaying AR-based predicted completion visuals on site before work begins eases communication with clients and local residents. The post-construction scenery that is hard to convey with drawings or perspective renderings becomes clear when viewers stand on site and see a life-sized AR model. Explanations like “a bridge of this height will be built here” are much more persuasive when a 3D model of the bridge overlaps the actual scenery. You can take questions and requests on the spot, revise the model, and reproject it quickly. Such AR use increases stakeholder acceptance and leads to faster consensus formation.

BIM/CIMデータとの連携による現場DX

To maximize the effect of RTK AR, smooth linkage with design data is important. Fortunately, many infrastructure and building projects now produce 3D models with BIM/CIM, and these can be used directly for AR display. Previously, 3D models were converted to 2D drawings for on-site checks, but with AR you can refer to the design model directly on site, eliminating the conversion work and the risk of information loss. It is also easy to compare design data and as-built data in the cloud and feed back differences in real time. In fact, some RTK AR systems can call BIM/CIM models uploaded to the cloud from the field and immediately project them in AR. This seamlessly connects design and construction data and promotes true digital twin–based site DX (digital transformation).

The Ministry of Land, Infrastructure, Transport and Tourism also promotes BIM/CIM and ICT construction, and has organized measurement methods such as those using drones and laser scanners in guidelines like the “Guidelines for As-Built Management Using Three-Dimensional Measurement Technology (draft).” AR is highly compatible with these trends and is expected to be a useful technology for future data consistency for electronic delivery.

RTK AR導入の流れと現場運用のポイント

To actually use RTK AR on site, several preparations and procedures are required. The basic components are 「RTK対応GNSS受信機 + スマートフォン/タブレット + ARアプリ + 設計データ」. First, to use high-precision GNSS you need to obtain RTK correction information from a reference station. In many cases, correction data are received over a network from public reference stations or private services, but in areas without mobile coverage such as mountainous regions, it is also possible to directly receive centimeter-level augmentation services (CLAS) from Japan’s quasi-zenith satellite “Michibiki” for corrections. When you connect the GNSS receiver to the smartphone and launch the app, satellite acquisition and correction data reception begin, and in a short time you reach an RTK fix (a solution with errors on the order of a few centimeters (a few in)).

Next is the step of loading the design 3D models and drawing data to be displayed in the AR app. If BIM/CIM models or as-built point clouds are prepared in the cloud in advance, they can be downloaded and used on site immediately. Alignment is automatically done by GNSS coordinates, but if necessary you can adjust model translations and rotations using known points on site to perfectly match the design coordinate system with the actual positioning coordinate system. Once set up, simply pointing the smartphone or tablet at the site will overlay the virtual model onto the real space. Users compare the model and the real object on screen to check positions, dimensions, slopes, and more. If you take photos on site, the images automatically record accurate coordinate values and timestamps and save them to the cloud. This enables real-time construction management, such as sharing on-site verification results with the office immediately.

As an operational note, ensure GNSS positioning accuracy. RTK is most effective outdoors with a clear view of the sky, but in canyons between high-rise buildings or under dense tree cover satellite signals can be interrupted and multipath errors can occur; therefore, place antennas in as open a location as possible and consider measures such as receiving Michibiki augmentation or using GLONASS satellites. To prevent initial offsets between the design data and site coordinates, it is reassuring to verify and fine-tune the AR display at a known point on site (for example, a distinct corner of an existing structure or a survey manhole) if possible. Because smartphone and tablet batteries drain quickly, carry spare batteries for long operations. Also, since focusing on the screen can make users less aware of surrounding hazards, pay close attention to safety management (especially when using AR at heights or near vehicles). With these points in mind, RTK AR is not an overly difficult technology. Recent systems have refined UIs and are designed so that even those unfamiliar with surveying or AR can master them after a short operational briefing. Even older technicians who are not used to using smartphones on site report that the apps are intuitive, and adoption on sites is expected to accelerate.

導入事例：RTK AR活用で生まれた成果

Success stories of construction management using RTK AR have already been reported domestically and internationally. Here are some examples.

• Pile-position accuracy management in urban building construction – At a redevelopment site in a city center with deep basements, RTK AR navigation was introduced for foundation works of a high-rise building. Despite the difficult condition of a tight site surrounded by tall structures, using a smartphone-mounted RTK device and AR app sped up the positioning of underground columns and piles. Compared with conventional methods where survey teams set pile centers from the ground, AR guidance reduced the time required to identify pile positions to about 1/6, and simplified double-checking tasks by hand. With centimeter-level RTK positioning and AR visual guidance, the construction accuracy of each pile was extremely high (positional errors were almost zero to a few millimeters), demonstrating a good example of balancing speed and quality in top-down construction methods.

• As-built confirmation and safety measures for buried pipe works – In a municipal water and sewer project, RTK AR was used before and after backfilling pipes. Pipes were scanned with a smartphone before burial and the data stored; after backfilling, displaying that data in AR on site allowed verification of the pipe route and slope before paving. This prevented poor pipe positions or connection mistakes that would have needed later pavement reopening. During excavation, sharing the positions of adjacent existing cables by AR visualization helped eliminate the risk of accidental damage. AR visualization of buried utilities contributed to both as-built inspection and safety management.

• Pavement thickness management and immediate correction – In road paving, thickness was traditionally checked by core samples, but at one site operators displayed an AR heat map of pavement thickness immediately after paving and adjusted compaction accordingly. Roller operators used color displays on tablets to identify areas with insufficient thickness and focused compaction or added material, enabling immediate correction of construction accuracy. As a result, there were no sections judged NG at inspection, eliminating rework and achieving uniform quality. Integrating RTK AR into in-process quality control thus reduced corrective work in later stages and facilitated smooth handover.

• Pre-verification of structural alignment in bridge works – AR is also being used in setting bridge girders and connecting new structures to existing ones. In one seismic reinforcement project, 3D models of additional stiffening ribs and brackets were displayed in AR and overlaid on existing girders to check bolt positions and dimensional consistency. This allowed much earlier detection of nonconformities than the traditional trial-fit method and prevented component processing errors and on-site rework. Similarly, when attaching a new structure to an adjacent old one, pre-validating the interface in AR enables high-precision installation. AR that visualizes misalignments between structures at site is highly valued as a tool that greatly simplifies the crucial task of alignment verification.

These cases show that RTK AR produces immediate and effective results across various work types and scenarios. Time spent on surveying and inspection is greatly reduced, construction accuracy improves, rework is minimized, and safety is enhanced—delivering outcomes that directly solve site-specific problems.

将来展望：RTK ARが拓く建設現場の未来

As RTK AR technology advances, the digitalization of construction sites will accelerate further. Currently smartphone and tablet use is central, but in the future more wearable AR glasses (smart glasses) may become widespread, allowing workers to view AR information continuously on displays attached to helmets. This would free both hands and enable safer and more efficient use of AR navigation. Combining AI could allow automatic detection of inconsistencies or defects from camera images and real-time AR warning displays—a move toward smart inspection. Improvements in GNSS satellites and sensor technology will further enhance positioning accuracy and AR display stability. For example, if multi-frequency, multi-constellation use of satellites such as Europe’s Galileo becomes commonplace, we can expect more stable RTK positioning even in urban canyons and mountainous areas.

From the perspective of promoting site DX, RTK AR could become a new standard tool. Within the i-Construction and CIM trends advocated by the Ministry of Land, Infrastructure, Transport and Tourism, AR is becoming indispensable as a means to fully utilize 3D design data. Facing industry challenges such as aging technicians and labor shortages, RTK AR offers a solution as a “digital work aid anyone can use.” Tasks that once relied on the intuition of specialist craftsmen may soon be handled by younger technicians using AR to achieve equal or better accuracy. This is not merely efficiency improvement but has the potential to transform how construction site work is done, creating new norms.

まとめ：LRTKによる簡易測量とAR表示機能で現場DXを加速

RTK AR makes on-site display of construction images and precise as-built checks easily achievable. This technology, which can reconcile quality assurance and productivity improvements, is beginning to be adopted widely from surveying firms to general contractors and municipalities. In particular, solutions like smartphone-based LRTK enable simple surveying and high-precision AR display without heavy, expensive equipment. By attaching an LRTK device to a smartphone, you can achieve centimeter-level positioning and 3D scanning and overlay design models for on-site verification. Embracing advanced technologies to drive site DX is an indispensable initiative for the future of construction. Why not take this opportunity to introduce RTK AR on your sites and experience its benefits? Intuitive AR functions enabled by LRTK could bring new value to your construction management on the next project.