How LRTK and AR Will Change Construction Management: The New Common Sense for Civil Engineering Construction Managers

The Role of Civil Engineering Construction Managers and the Need for On-site DX

Civil engineering construction managers are specialized technical professionals responsible for creating construction plans, managing progress, and overseeing quality and safety in the construction of civil structures such as bridges, roads, and riverbank revetments. Until now, many construction management tasks have been carried out using analog methods such as paper drawings, inspection reports, and on-site measurements. However, in recent years, labor shortages, demands for shorter construction periods, and the promotion of i-Construction have made digital transformation (DX) of civil works sites an urgent necessity. As up-to-date data utilization is required for on-site decision-making, new technologies such as smart surveying and AR (augmented reality) are attracting attention. In particular, with the spread of smartphone surveying tools equipped with high-precision positioning technology, an era in which “anyone can easily perform centimeter-level accuracy (cm level accuracy (half-inch accuracy)) surveying with a smartphone” is arriving. It is becoming the new norm for civil engineers to use these on-site DX tools to improve the accuracy and efficiency of construction.

Challenges of Conventional Construction Management Tasks (Surveying, Progress Confirmation, As-built Inspection, etc.)

In traditional civil construction, many control tasks such as establishing control points and as-built verification surveys have relied on manual labor. Manual measurements using tape measures, rods, and levels require multiple personnel, consume significant time and effort, and are limited in the number of measurement points, making it difficult to capture the overall shape of structures in a surface-based manner. For example, when verifying the finish of road paving, the conventional method was to manually measure pavement thickness and flatness at selected points after paving, and to measure longitudinal slope and lane width with tape measures. Because the inspection points were limited, there was always a risk of overlooking differences from the drawings or surface irregularities, and the work was time-consuming. On steep slopes and embankments, unstable footing and danger made detailed checks difficult with conventional methods, requiring surveying methods that ensured worker safety. Furthermore, organizing photo records taken during construction and reconciling them with design values was inefficient due to transcription onto paper forms. Thus, conventional construction management tasks had problems such as being “manual-centric with limited measurement points,” “high risk of safety and human error,” and “complex data organization,” all of which imposed burdens and risk factors on the construction site.

Basics of LRTK and Benefits of Introducing It to On-site Surveying

LRTK (smartphone RTK surveying) is a next-generation surveying technology that achieves centimeter-class high-precision positioning (cm level accuracy (half-inch accuracy)) using real-time kinematic (RTK) positioning simply by attaching a compact GNSS receiver to a smartphone. Normally, RTK positioning requires a base station or connection to an RTK network via the internet, but LRTK systems also support CLAS corrections from Japan’s quasi-zenith satellite system “Michibiki,” enabling high-precision positioning even in mountainous areas or disaster sites outside communication coverage. In urban areas with good communication conditions, conventional network RTK can be used, and in areas without coverage CLAS (positioning augmentation via quasi-zenith satellites) can be switched in, allowing high-precision positioning regardless of location.

As a result, the combination of “smartphone + LRTK” greatly reduces the effort and burden of surveying work. Control point surveys that previously required two-person teams operating total stations can now be performed by one person: by localizing at a known site, a single operator can carry a GNSS rover and instantly acquire coordinates of arbitrary points. For example, on large development sites, heavy equipment operators can use LRTK mounted on a tablet to measure the heights and positions of fills and excavations and check the depth of buried objects on the spot. With one device per person, smartphone surveying enables high-precision surveys to be carried out efficiently even at sites with labor shortages.

In addition, LRTK apps make staking and layout marking work easy. Traditionally, positions were set out using drawing coordinates with tape measures or total stations, but with LRTK you can set the target coordinates you want to position in the app and have the smartphone screen display the target direction and distance in real time. By following an arrow display similar to a car navigation destination guide, even inexperienced workers can intuitively and accurately locate positions, dramatically improving construction efficiency and accuracy. Furthermore, combining iPhone or Android smartphones’ LiDAR camera functions with LRTK makes high-density 3D point cloud terrain scanning simple. Each point in the acquired point cloud is tagged with centimeter-scale positional coordinates (cm level accuracy (half-inch accuracy)), allowing highly accurate and instantaneous calculation of cut-and-fill volumes and creation of cross-sections. In this way, introducing LRTK makes on-site surveying simpler, safer, and more accurate than before, realizing improved efficiency in construction management.

Innovation in Construction Management Through the Integration of AR Technology and LRTK (Overlaying Current Conditions, Progress Visualization, As-built Verification, etc.)

By using a smartphone camera and AR functions, design 3D models can be overlaid onto the real scene at civil works sites. For example, when viewing a structure under construction through a smartphone, the planned finished shape can be displayed in AR on the screen, allowing progress to be intuitively visualized. Comparing the finished model with the actual site makes it possible to instantly identify discrepancies in quantities of work completed, enabling adjustments to schedules and personnel allocation as needed and facilitating alignment of understanding among stakeholders. AR-based on-site visualization is therefore expected to contribute to shorter construction periods and cost reductions.

Using AR for construction verification enables early detection of construction errors through reconciliation of design data and current conditions. By displaying design 3D models on a smartphone while observing the actual construction area, discrepancies in the position and dimensions of rebar placement and buried pipes can be identified on the spot. For example, displaying rebar layout drawings in AR to check counts and spacing, or overlaying the planned finished structure to detect minute errors, allows construction to proceed while ensuring design-level accuracy. There have been reports of cases where AR-based on-site reconciliation enabled early correction of defects, reducing rework and material waste.

Moreover, combining LRTK’s high-precision positioning with AR can automate what used to be cumbersome alignment tasks. In AR systems linked to RTK positioning, design models can be displayed accurately on site without calibration using physical markers. Survey technicians can walk with a tablet and place virtual stakes at arbitrary points, accurately capturing target points even from a distance or across obstacles. Overlaying acquired point cloud data of current conditions with design 3D models makes it possible to verify in advance whether plans fit the terrain and structures. For example, LRTK cloud services automatically align current point clouds with BIM/CIM design data, enabling efficient confirmation of whether construction can proceed according to design.

Thus, the fusion of AR technology and high-precision positioning dramatically improves the efficiency of surveying work, enhances the accuracy of construction planning, and helps prevent rework. In practice, AR construction support using LRTK displays design models and buried object locations at full scale simply by pointing a smartphone, eliminating the need for conventional layout marking work and realizing intuitive visualization. Construction management using AR and LRTK offers new possibilities for solving on-site issues and improving communication.

Specific Use Scenarios with Examples for Slopes, Development Sites, Rivers, Bridges, etc.

• Slope (nori-men) management: 3D scanning with smartphone + LRTK is effective for capturing deformations before and after slope collapses on steep terrain. For example, if a slope is scanned and the point cloud data saved before heavy rain or an earthquake, re-scanning the same location after a disaster allows immediate calculation of the “collapsed area” and the “lost soil volume.” Volume calculations that used to take days can be shortened to minutes by point cloud differencing, which can be used for restoration planning and cause analysis. Moreover, using AR in combination allows the acquired slope 3D data to be overlaid on the actual site view, intuitively visualizing hazardous areas and locations for reinforcement anchors. Workers can confirm no-entry zones and reinforcement positions on their smartphone screens, preventing inadvertent approach to danger zones and allowing construction to proceed with enhanced safety.

• Roads and development sites: Mobile scanning is also effective for as-built control of paving and development sites. Right after paving is completed, capturing the road surface with a smartphone’s 3D scanner function can acquire a high-density 3D point cloud of the entire road surface. By overlaying the design 3D model on the acquired point cloud, an as-built heat map that color-codes elevation differences can be created on-site. This enables instant confirmation that pavement heights across the entire section are within design tolerances and ensures detection of any unevenness or insufficient thickness. Because paint markings on the road surface are reflected in the point cloud, lane widths can be directly measured and calculated in software, allowing safe and rapid completion of inspections. In this way, smartphone scanning and point cloud analysis advance the accuracy and labor-saving of as-built control beyond conventional manual methods.

• Riverbank revetments and bridge inspections: The smartphone + LRTK combination brings fresh approaches to bridge maintenance. Areas under girders and bearing components that previously required elevated work platforms or scaffolding can be scanned from the riverbed or sidewalk by photographing with a smartphone to build a point cloud model of the entire bridge. The acquired 3D point cloud is linked to photographic images, enabling office-based analysis of a digital twin model to grasp the size and location of deterioration cracks and delamination at actual scale. Parts that were difficult to access in the past, such as around piers and under girders, can be inspected without missing deterioration signs. For river works, similarly, changes in revetments and riverbed shapes can be recorded with a smartphone and captured in three-dimensional point clouds (a benefit unique to LRTK-enabled high-precision positioning). These data can be shared in the cloud, smoothing information flow between the office and the field and streamlining as-built inspections.

Effectiveness of Simple Surveying with LRTK and AR Construction Support

Finally, to summarize the advantages that smartphone surveying (LRTK) combined with AR support brings to construction management: with only a smartphone and a compact GNSS device, anyone can achieve centimeter-class positioning (cm level accuracy (half-inch accuracy)), enabling surveying tasks that previously required specialized equipment and skilled operators to be completed by on-site personnel using devices in the palm of their hand. Based on the acquired high-precision positional information, AR technology allows construction plans and hazard information to be overlaid onto the real world for intuitive confirmation, achieving construction accuracy and safety improvements that do not depend on experience. These technological innovations promote DX at civil works sites, directly contributing to reduced work time, suppression of human error, and smoother communication. One device per person for smart surveying tools and AR support will increasingly become the “new common sense” for construction managers.