Learning from LRTK Use Cases: The Effects and Benefits of 3D Construction

What is 3D construction?

In recent years, a method known as 3D construction has been attracting attention at construction and civil engineering sites. 3D construction involves capturing a site’s terrain and structures three-dimensionally as point cloud data or 3D models and using that data for construction planning and management. Site conditions that were difficult to grasp with traditional 2D drawings and numerical data can be visualized intuitively with 3D data. As a result, many benefits are gained, including early detection of gaps between design drawings and the construction site, more efficient post-construction as-built management, and easier alignment of understanding among stakeholders. The use of 3D data is also a key pillar of ICT construction (*i-Construction*) promoted by the Ministry of Land, Infrastructure, Transport and Tourism, and it is becoming common to apply detailed point clouds acquired by drone photogrammetry and laser scanner measurements to earthwork quantity (volume) calculations and progress/quantity management. 3D design data are also used in machine control (MC) and machine guidance (MG) for heavy equipment, and the trend toward consistently leveraging three-dimensional information from surveying through design and construction is accelerating across the industry.

Why 3D Construction Is Attracting Attention

So why is 3D construction drawing so much attention now? Behind this trend are challenges facing the construction industry, such as labor shortages and the aging of technical staff. As veteran surveyors and construction managers retire, the lack of younger personnel has revealed the limits of traditional labor-intensive approaches to construction management. At the same time, there is a growing demand for more advanced quality control and as-built management, increasing the need to perform accurate surveying and construction efficiently with limited personnel. In response to these circumstances, the government has promoted productivity improvements through ICT construction under the banner of *i-Construction*. In particular, digital technologies such as 3D surveying and AR are expected to be solutions that enable small teams to measure and manage wide areas in a short time, contributing to reduced human error and improved safety. For example, by leveraging the latest RTK-GNSS technology, even inexperienced workers can use smartphones to achieve centimeter-level positioning and point-cloud measurement, making it possible for a single person to achieve results equal to or better than conventional methods. In other words, 3D construction is being viewed as a trump card against the worsening shortage of on-site personnel and, at the same time, as the key to dramatically improving site efficiency and construction quality.

Features of LRTK

One of the new technologies supporting the kind of 3D construction described above is LRTK. LRTK (pronounced “El-Ar-Tee-Kay”) is an ultra-compact GNSS receiver for performing high-precision surveying using a smartphone; it is attached to and used with an iPhone or iPad. Precision positioning, which traditionally required specialized GPS surveying equipment and skilled operators, can now be performed easily by anyone at centimeter-level accuracy for positioning and 3D measurements using this device. The main features of LRTK are summarized as follows.

• Ease of use (smartphone-integrated): Preparation is complete simply by attaching a compact device weighing approximately 150 g to the back of your smartphone. After pairing via Bluetooth or connecting via Lightning, you can start surveying with the dedicated app at the push of a button. There is no need to carry tripods or heavy equipment, and the convenience of being able to handle everything from as-built measurements to staking out pile-driving coordinates with just a smartphone is a major benefit.

• High-precision positioning: It supports the RTK-GNSS method, improving accuracy from the several-meter errors typical of conventional smartphone GPS to roughly ±2–3 cm horizontally and ±3–4 cm vertically. It supports the Geospatial Information Authority of Japan’s electronic reference point network (Ntrip) and correction signals from Japan’s Quasi-Zenith Satellite System “Michibiki” (CLAS), enabling stable centimeter-level positioning depending on the site’s communication environment. Even in areas without mobile reception, using CLAS allows positioning to continue, making it effective in mountainous regions and disaster sites.

• Cloud-linked data sharing: Measured coordinate data, point cloud models, photos, and more are uploaded to the cloud in real time. Colleagues in the office or clients can instantly share the latest information acquired on site. Measurement results are plotted on maps and can be viewed by anyone via a web browser, enabling smooth reporting and work-quantity management. It also supports export to CSV and drawing data, greatly reducing the time previously required to organize and distribute surveying results.

• Versatile functions: LRTK is not just for measuring positions; it includes a wealth of features that support on-site digital transformation (DX). For example, a point-cloud measurement function combines with the iPhone’s LiDAR to scan surroundings while walking and acquire high-density point cloud data, and a photo positioning function automatically records the shooting position (coordinates) and orientation when a photo is taken with the smartphone. There is also a coordinate navigation (coordinate guidance) function that displays on-screen guidance when the smartphone approaches a pre-registered coordinate, and an AR function that overlays design 3D models and the positions of underground utilities onto the camera view. By leveraging these features, it can be used as an all-purpose surveying tool that allows one person to intuitively handle everything from surveying to construction verification.

Use Case at Land Development Sites

On earthwork sites involving site formation, embankment, and excavation, accurately determining soil quantities (volume) and verifying as-built conditions has traditionally been time-consuming. At a residential land development site, mobile scanning using LRTK greatly streamlined this process. The operator mounted an LRTK on an iPhone and walked the development site scanning the ground surface; even in an area roughly 50 m square, they were able to acquire high-density point cloud data comprising several hundred thousand points in about five minutes. Because the obtained point cloud already includes coordinate information, there is no need to align it with control points after measurement. By comparing before-and-after point cloud datasets on site, excavation and fill volumes can be calculated instantly and used for daily as-built and quantity management. This approach dramatically reduced the time required for traditional as-built measurements that were taken point by point by hand. In fact, at this site soil volume calculations that previously took several days were completed the same day, prompting surprised comments such as "it felt like one person did the work of two." By utilizing LRTK, even a small crew can grasp site progress in real time, making this a good example of how construction management efficiency can be improved and schedules shortened.

Use Cases in Road Construction

The benefits of 3D construction are evident even in projects involving the new construction or improvement of roads and bridges. At one road site, the existing terrain was 3D-scanned with LRTK before work began, and the design's 3D model was overlaid onto the point cloud data for preliminary review. By using AR functions to visualize the completed appearance of embankments and structures on site, they were able to detect discrepancies between the design and the actual conditions—discrepancies that would not have been noticed from drawings alone—early on, which helped in revising the construction plan.

During construction, the responsible technician used LRTK to measure excavation depths and shapes as work proceeded and immediately shared automatically calculated earthwork volume data via the cloud. This prevented over‑excavation and under‑excavation on the spot, resulting in high‑quality work with reduced variation in as‑built outcomes. Tasks that previously required a separate surveying team for inspection or later data analysis can be completed immediately by a single operator using LRTK. Real‑time measurement and data sharing reduced unnecessary rework and improved overall site efficiency and accuracy. Additionally, sharing the AR model of the finished design displayed on a tablet with the client and heavy equipment operators aligned everyone’s understanding and helped smooth communication.

Case Studies in the Water and Sewerage Sector

In infrastructure fields such as water supply and sewerage, 3D construction technology is contributing to solving on-site challenges. Accurately identifying the locations of buried water and sewer pipes is directly linked to maintenance and construction safety.

In one municipality, an initiative was undertaken to comprehensively compile location data for the city's water and sewerage facilities using LRTK. Staff patrolled points such as valves on buried pipes under roads and manhole covers, measured and recorded the coordinates of each point with LRTK, and consolidated the data in the cloud.

As a result, positional maps of all buried facilities were digitized with centimeter-level accuracy and are being used to support new construction and plans to replace aging pipes.

Also, LRTK’s AR functionality is highly effective for the “visualization” of buried pipes. For example, before excavation work, if you display the routes of underground water and gas pipes as AR overlays through a smartphone camera, workers can intuitively understand what lies beneath the surface. Compared with relying solely on drawings, being able to accurately locate buried assets in advance dramatically reduces the risk of accidentally damaging pipelines. Furthermore, by using LRTK’s coordinate navigation feature, you can reach the managed buried valve points on site without getting lost. In this way, if infrastructure assets are gradually measured digitally with a personal smartphone surveying tool, building a “digital twin” that reproduces an entire city’s underground buried utilities and structures is within reach in the future. The use of LRTK is thus a good example of how safe and efficient water and sewer infrastructure management can be achieved.

Use Cases in Disaster Response

LRTK has proven powerful even in situations that require emergency response, such as earthquakes and landslides. In the 2023 Noto Peninsula earthquake, with communications infrastructure down immediately after the disaster, municipal staff mounted smartphones on their helmets, walked through the rubble, and quickly surveyed damage using LRTK. By receiving augmentation signals (CLAS) from the Michibiki satellites, centimeter-level positioning was possible even outside network coverage, allowing damage locations in areas isolated by severed roads to be recorded with precise coordinates. Because measurements could be taken by a single, lightly equipped person moving around, surveys could be completed with the minimum necessary personnel even in hazardous areas with continuing aftershocks. The collected data were mapped at the field base, and the extent of the damage was shared immediately. As a result, lead time to develop recovery plans was greatly reduced, enabling earlier commencement of restoration work. Additionally, because staff themselves were able to measure the damage—work that had previously been outsourced to external surveying firms—this contributed to reduced emergency response costs and the internalization of technical expertise.

Even at landslide sites caused by intense torrential rains, the advantages of one-person surveying are evident. In one such storm disaster, a responder conducted LRTK measurements alone from a safe position overlooking a mountainside where collapsed debris had accumulated. By using the continuous positioning mode and simply walking around the perimeter of the hazardous area, they recorded coordinates in succession and were able to accurately grasp the spread of the collapsed material in a short time. Because the on-site data allowed immediate calculation of the volume of the collapsed earth, they could accurately determine the heavy equipment and number of dump trucks required, making the recovery operation planning smoother. Compared with the conventional method—where multiple people risked surveying the site and then calculated volumes later back at the office—LRTK, which completes “measure and immediately calculate” on-site, dramatically accelerates the speed of initial response. Since one person can perform the measurements, there is no time needed to arrange additional personnel and no unnecessary site entry, greatly enhancing safety. These disaster-response cases also demonstrate that mobile 3D surveying technology is a valuable tool in crisis management.

Effects and Benefits of 3D Construction

The main effects that 3D construction and the introduction of LRTK bring to construction sites can be summarized as follows.

• Significant increase in work efficiency: The labor and time required for surveying and as-built measurements are dramatically reduced. Surveying tasks that previously took a full day with two to three people have in some cases been completed by one person within a few hours. By leveraging point cloud data to reduce manual work, there have been reports of reducing labor input by 50–60% on small to medium-sized sites.

• Shortened schedules and real-time management: Data measured on-site can be shared to the cloud immediately, allowing on-the-spot as-built checks and earthwork quantity calculations, which greatly speeds up decision-making. Timely daily progress management enables rapid revisions to construction plans and adjustments to sequencing. In practice, some projects have been able to shorten the overall construction period compared to the original plan through the introduction of 3D construction.

• Improved quality and accuracy: Centimeter-level survey data and AR visualization enhance construction precision and the level of quality control. Discrepancies between the design model and the field can be detected and corrected in advance, reducing variability in as-built results and construction errors. Using 3D data in as-built inspections enables objective evaluations that do not rely on subjective judgment, increasing the reliability of quality verification.

• Enhanced safety: Enabling one-person surveying minimizes the number of personnel who need to enter hazardous slopes or disaster-affected areas. Pile-driving operations in locations with poor footing can be completed quickly and safely with AR guidance, and surveying at heights or in confined spaces can be carried out with reduced risk. Accurately identifying the positions of buried utilities helps prevent excavation accidents, contributing to a reduction in occupational injuries and construction incidents.

• Cost reduction: The synergistic effect of improved efficiency and fewer mistakes also yields cost benefits. Reduced outsourcing of surveying cuts labor costs, and preventing excessive excavation and material waste curbs unnecessary spending. Additionally, cloud-based information sharing reduces rework, cutting extra costs associated with redo construction. 3D construction, which secures quality while reducing manpower, can be seen as an excellent initiative in terms of cost performance.

Tips and Considerations When Introducing LRTK

LRTK is convenient, but to maximize its effectiveness on-site, there are several tips and precautions to be aware of.

• Coordinate alignment with existing data: When matching surveyed points with drawings or design data, verifying the coordinate system is important. LRTK supports automatic conversion to systems such as plane rectangular coordinate systems, but it’s reassuring to verify accuracy using known points on site beforehand. If necessary, configure conversion to local coordinates and take care to ensure the acquired data matches existing drawings without any offset.

• Check communication environment and correction mode: Within smartphone coverage, using network RTK provides stable high accuracy, but in mountainous areas, tunnels, or other locations without signal, switching to Michibiki (CLAS) corrections is essential—choose the mode appropriate to the situation. Familiarize yourself with the positioning mode in advance, and if needed attach an external antenna or take other measures adapted to the environment.

• Equipment handling and battery management: LRTK devices have an internal battery that lasts about six hours. This is usually sufficient for normal working periods, but for long continuous surveys prepare spare batteries or charging options to be safe. Using a monopod or tripod to secure your smartphone reduces camera shake and enables more stable positioning and photography. For measurements at height, extend the monopod to bring the sensor closer and make effective use of included accessories.

• Points when using AR features: When guiding staking positions or visualizing the finished form with AR, you must register design data accurately in the LRTK cloud beforehand. LRTK aligns models automatically, but pay attention to calibrating the smartphone’s orientation sensor and to awareness of the surroundings, and check each time that markers are displayed without drift. Since weather and brightness affect screen visibility, consider using a sunshade or other accommodations as needed for the field environment.

• Safety considerations: Just because a task can be done alone doesn’t mean you should let safety management lapse in hazardous areas. Continue to enforce basic safety measures such as surrounding monitoring and vocal communication, and deploy assistants when necessary. Especially when working while focused on a smartphone screen, be careful to watch your footing and prevent contact with heavy machinery. While mastering the latest technology, remember that the principle of safety-first on site remains unchanged.

Summary

The era when anyone can perform high-precision 3D construction without relying on experienced specialists is becoming a reality. By leveraging smartphone surveying devices like LRTK, even limited personnel can drive on-site DX while achieving both higher productivity and improved quality. LRTK incorporates a variety of features that support simple surveying on site, such as photo positioning, which records locations simply by taking a photo; coordinate recording, which logs coordinates with the push of a button; a mechanism to sync data to the cloud on the spot; stable measurements using a monopod; and a volume calculation function that automatically computes embankment and excavation volumes from acquired point clouds.

By leveraging these functions, staff without surveying expertise can smoothly handle everything from acquiring the necessary data to sharing it, which in turn will lead to greater efficiency in overall construction management. It is a solution that truly embodies the concept of completing high-precision surveys with a single handheld iPhone—"iPhone surveying"—and LRTK’s simplified surveying features are sure to become a reliable ally on many job sites moving forward.