The Forefront of DX on Construction Sites: How LRTK Is Transforming Layout Marking Work!

The Importance of Layout Marking and the Current Situation on Construction Sites

On construction sites, the task of indicating lines and reference marks at actual locations based on design drawings—known as layout marking (positioning)—is indispensable. In building construction, this includes locations of foundations and columns and lines for interior finishes; in civil engineering, it covers road centerlines and locations for installing structures. Accurate layout marking at every stage affects both the quality and efficiency of the work. Even today, many layout marking tasks are performed manually or with optical surveying instruments, where skilled technicians use tape measures, inklines, and laser devices to draw reference lines and points on site. While drawings have been digitized with CAD/BIM, the on-site positioning often still relies on analog methods, creating inefficiencies and risks of mistakes. In light of this, the movement to digitally transform construction processes (DX)—that is, to revolutionize on-site layout marking with digital technologies—is attracting attention.

Traditional Challenges (Labor, Accuracy, Time, Safety, Training)

Traditional layout marking methods have had the following challenges.

• Labor availability: Layout marking requires operating surveying equipment while performing marking tasks, so it has typically required teams of two or more. One person operates the instrument while another holds a staff (level rod) or prism, meaning multiple personnel are always needed; this is burdensome on sites facing labor shortages.

• Accuracy and risk of mistakes: Manual measurements with tape measures or mason lines can lead to small misreads or positional shifts. If dimensions transferred from control points are misapplied, significant rework can occur in later stages—such as columns not matching the drawings—causing schedule delays and quality degradation.

• Increased work time: Setting up surveying instruments like total stations or levels requires careful preparation such as mounting tripods, leveling instruments, and aligning coordinates, so it takes time before marking can begin on site. More complex layout marking demands more measurement and verification time, reducing overall efficiency.

• Safety concerns: Carrying heavy surveying equipment to heights or performing layout marking on busy roads poses danger to workers. During daytime outdoor work, laser layout lines can be hard to see in sunlight, and workers may spend extended time in traffic lanes confirming alignments, creating safety management issues.

• Skill transfer and training challenges: The number of experienced surveyors who can perform high-level layout marking accurately is declining and aging. Training newcomers has not kept pace, and human-dependent layout methods are reaching their limits. Such individualized methods also hinder productivity improvements and work-style reforms.

Thus, traditional layout marking has required substantial personnel and effort to maintain accuracy, and site conditions often severely constrain efficiency and safety.

How Digital Technologies (RTK, AR, Smartphone Integration) Change Things

To address these challenges, high-precision positioning (RTK) combined with AR (augmented reality) and smartphone integration has emerged as a new layout marking approach. Modern smartphones are equipped in some models with LiDAR sensors (infrared laser scanners), and by attaching a dedicated compact GNSS receiver and performing RTK (Real Time Kinematic) positioning, centimeter-level position information (half-inch accuracy) can be obtained easily on site. By combining the smartphone’s built-in LiDAR to capture floor and wall shapes with RTK-corrected self-position coordinates, digital design drawings and 3D models can be overlaid on real-world imagery with minimal misalignment. In other words, the combination of “smartphone + GNSS + AR” means that a palm-sized device can now function as a surveying instrument and layout marking tool on site.

So how does this digital technology concretely change layout marking tasks? The main benefits are as follows.

• Simplified preparation and immediate positioning: With just a smartphone and a small device, you can launch a dedicated app and immediately start positioning and AR display. There is no need to transport and set up heavy equipment or erect tripods and spend long preparation times, dramatically shortening the lead time even for small layout tasks.

• Single-person completion: Because workers only need to follow on-screen guides to place marks, layout marking that traditionally required two-person teams can now be performed by one person. Anyone can make accurate markings without a veteran assistant, reducing the burden of personnel allocation on site.

• High accuracy and reduced mistakes: Centimeter-level positioning accuracy from RTK-GNSS means that lines and points displayed in AR coincide with the exact coordinates in the design drawings. This prevents manual measurement errors and significantly reduces construction mistakes due to misplaced survey points. Demonstrations have shown average errors of less than 1 cm (<0.4 in) with smartphone + RTK, indicating positioning accuracy comparable to traditional optical surveying.

• Good visibility in any site condition: AR guides can be displayed on the smartphone screen as intuitive visuals like arrows or virtual stakes. Even in bright outdoor daylight, the guide is clearly visible on the screen, making it easier to confirm targets than laser layout lines that are hard to see in sunlight. Positions are less likely to be lost in scorching sun, and work proceeds smoothly without extra auxiliary equipment.

• Labor savings and improved safety: Digital guides are intuitive and easy to use, so even non-experts can operate them without confusion. The efficiency of single-person completion reduces labor burden, and shorter work times reduce exposure in high places or busy traffic areas. Since positions can be checked from a safe distance, non-contact layout marking is also possible, reducing physical strain on workers and minimizing near-miss incidents so layout work can proceed with greater peace of mind.

• Data utilization and DX promotion: Layout results (coordinates of marked points or point cloud data captured on site) can be saved and shared in the cloud as digital information. There is no need to record on paper drawings by hand, and by integrating with BIM/CIM models and construction management software, a continuous digital workflow from surveying to construction management can be realized. Digitizing the layout marking process streamlines subsequent deliverable inspections and quality control, contributing to improved productivity across the site.

In this way, combining RTK positioning with smartphone AR is resolving many of the constraints associated with traditional layout marking.

Typical Workflow (Surveying → AR Guidance → Layout Marking → Data Sharing)

Let’s look at the typical workflow when performing digital layout marking on site. The following is an example using an RTK-compatible smartphone device (for example, LRTK).

• Preparation and control point surveying: First, align the site coordinate system with the design data based on the construction drawings. If there are known control points, measure those coordinates with the device and match them to the coordinates in the design drawings. Even if control points are not available, obtaining absolute coordinates via GNSS and using them as site references allows alignment between drawing data and on-site positions.

• AR position guidance: Load design drawing data (CAD drawings or BIM models) into the surveying app on the smartphone. After linking control points, select the target data (lines or points) to be marked. Switching the app to AR mode overlays the design lines and marking positions on the smartphone or tablet screen together with the real-world view. The worker follows the on-screen guide to move to the specified position and identify the exact point.

• Performing layout marking: Place marks at positions indicated by AR. For example, when marking column positions on a foundation concrete surface, simply align the virtual column center shown on the screen and mark it with chalk or an inkline. For drawing lines on walls or floors, instead of measuring dimensions from drawings on site, follow the AR-displayed lines to mark quickly and accurately. By checking the smartphone as needed, a single person can proceed to mark multiple locations in succession.

• Data sharing and recording: Once layout marking is complete, record and share the results as digital data. For example, saving the coordinates of marked points in the app automatically uploads them to the cloud for immediate sharing with the site office or other teams. You can also photograph marked locations with geotagged images or save LiDAR scans as point cloud data after marking. In the cloud, distance and angle checks can be performed from the collected data, and stakeholders can view 3D representations in a web browser, enabling construction managers to confirm as-built status in real time and issue correction instructions immediately if deviations are found.

Through this flow, surveying to layout completion can be digitized end-to-end. Because importing design data, on-site guidance, and result recording are seamlessly connected, the separate tasks of “read drawing and measure,” “place marks,” and “record” are integrated, dramatically improving efficiency and reliability.

LRTK Solution and Technical Explanation

One high-precision positioning solution supporting smartphone-based layout marking is LRTK. LRTK is a system composed of an ultra-compact RTK-GNSS device that attaches to a smartphone, a dedicated app, and cloud services. By attaching a pocket-sized device (weighing approximately 165 g) to an iPhone or similar, it achieves positioning accuracy and diverse functions comparable to conventional surveying instruments.

With high-precision RTK positioning, LRTK enables smartphone-level horizontal accuracy of about 1-2 cm (0.4-0.8 in) and vertical accuracy of about 3 cm (1.2 in). While typical built-in smartphone GPS errors are about 5-10 m (16.4-32.8 ft), a dedicated GNSS receiver secures far greater accuracy by applying real-time corrections to satellite signal errors. LRTK supports Japan’s quasi-zenith satellite “Michibiki” centimeter-class positioning service (CLAS) and network RTK over the internet, and it is robust even on sites outside mobile coverage such as mountainous areas. This makes precise vertical measurements easier, which is useful for building leveling and elevation control in infrastructure works.

LRTK can also perform 3D measurement by integrating with the smartphone’s camera and LiDAR sensor. It can scan surrounding terrain and structures to collect point cloud data and tag that data with RTK-derived accurate position coordinates. The acquired point cloud is immediately saved to the cloud as 3D data with geodetic coordinates and can be overlaid with drawings and other survey data. This enables on-site management of complex as-built shapes and convenient earthwork volume calculations.

AR-based position guidance is another key feature of LRTK. It projects models and lines from design data to scale on the smartphone screen, intuitively supporting layout marking tasks (for example, marking pile positions or indicating piping routes). Tasks that previously required manual measurement with drawings and tape measures are now replaced by AR displays that clearly indicate “drive a pile here” or “route wiring along this wall,” preventing misalignment. Because the design model can be overlaid on the current conditions, it can also be used for clash detection during construction and for as-built verification, improving site understanding and preventing mistakes.

Additionally, the LRTK app automatically records positioning data and shares it to the cloud. Measured coordinates are recorded on the device with timestamps and measurement conditions and are converted in real time to Japan Geodetic System or plane rectangular coordinates. Point names and IDs are automatically assigned, eliminating the need for on-site manual calculations or handwritten records. Photos and notes can be attached to each survey point, and the app can output survey result reports with a single button. Uploaded data can be instantly viewed and shared via web-based maps and 3D viewers without installing special software, allowing clients and subcontractors to access the latest site information seamlessly. Smooth data linkage between site and office streamlines report and inspection document preparation.

In short, by introducing LRTK, a single smartphone can complete “high-precision positioning, measurement, layout marking, recording, and sharing” on site. As a multifunctional tool that requires no specialized skills, it provides an environment in which not only skilled workers but anyone on site can perform high-precision surveying and layout marking—a true technological innovation.

Case Studies and Use Cases for Site Implementation

Use Cases in Building Construction

On building sites, AR layout marking is useful across a wide range of stages from foundations to finishes. For example, consider marking column base positions on the top of a cast foundation in reinforced concrete construction. Traditionally, workers measured from drawings with tape measures and marked positions with chalk. Replacing that with smartphone + LRTK AR layout marking allows workers to simply align with virtual column position guidelines shown on the screen and mark, completing the task. There is no need to set up temporary batter boards or repeatedly remeasure with multiple people, enabling rapid and accurate placement of multiple column positions.

In interior finishing, AR can previsualize routing for piping, ducts, and locations for lights or equipment behind ceilings or inside walls. Without drawing lines on the wall or floor, pointing a tablet makes it instantly clear where piping routes will run, facilitating shared understanding among trades like HVAC and electrical contractors. Sharing the finished image via AR lets teams coordinate—“if piping comes here, we should open first,” or “adjust to avoid interference before finishing”—reducing construction mistakes and rework. Construction managers can also verify in real time that work is proceeding at the model-specified positions and instruct corrections on the spot if deviations are found, contributing to improved construction accuracy and reduced rework, leading to shorter schedules and better quality.

AR is also effective for confirming overall building layout. For example, projecting partition wall placements on an office floor in AR allows stakeholders to preview the completed space before construction. This reduces the risk of “it looks different” after installation and enables adjustments during pre-construction meetings, preventing costly rework. Thus, AR layout marking serves not only to streamline point marking but also as a communication tool on site.

Temporary structures such as scaffolding and temporary fencing are frequently assembled on building sites. AR layout marking is useful for planning these temporary installations as well. For instance, when erecting scaffolding around a building, the contact points of scaffold supports on the ground or wall must be marked accurately; AR can virtually display scaffold components on the building model and indicate support locations on the screen. Following the AR guidance to mark the ground is faster and more accurate than manually measuring regular intervals. High attachment points can also be checked from the ground via tablet, reducing climbs and improving safety. When installing long temporary fences, AR can display fence lines along site boundaries, eliminating the hassle of stringing lines or visually checking alignment. Applying digital guidance even to temporarily installed tasks that require precision accelerates preparation and improves assembly accuracy.

Use Cases in Civil Engineering

In civil infrastructure works, smartphone AR layout marking contributes to productivity gains. For example, in road construction, curvature lines and stake positions can be displayed directly on the pavement using AR so that heavy equipment operators can work while confirming alignment. Traditionally, many wooden stakes were driven at regular intervals to define a curve, but with AR only a few key points need marking, greatly reducing intermediate staking and batter board setups. Workers can complete earthworks and paving along on-screen lines without a surveyor present, enabling a new style where each worker handles surveying tasks with a smartphone in hand.

For large-scale earthworks, aerial photos from drones or terrestrial laser scans can be used to create terrain models with design data overlaid in AR. Machine operators can monitor tablet screens from the cab while excavating or filling, reducing the need for intermediate checks and additional layout marking. In a large solar panel installation, for example, accurately marking site leveling and pile positions in early stages allowed omission of many later detailed markings while still maintaining final accuracy. This is because AR layout marking dramatically reduced construction errors, eliminating the need for corrective work in later stages and increasing confidence in layout reliability.

Safety benefits in civil works are significant. Reducing the time people spend in traffic lanes for surveying and layout marking on road sites lowers the risk of traffic accidents. If sign erection positions and other points displayed in AR can be assessed remotely, there is no need to approach hazardous or densely vegetated areas or work at night. The ability to confirm positions non-contact contributes to preventing occupational accidents. There are reports of surveying tasks that previously required personnel to enter under bridge girders or steep slopes being completed from a safe distance using AR displays. In this way, AR layout marking in civil engineering delivers high impact in both large-scale work efficiency and worker safety.

The Future of Layout Marking and the Impact on Site DX

DX of layout marking using smartphone positioning and AR is revolutionizing position-setting work that has relied on craftsmen’s intuition and experience, opening the door to a future in which anyone can perform high-precision construction. Introducing solutions like LRTK turns a handheld smartphone into a precision surveying instrument and enables smooth digital transformation of layout marking procedures. Because you don’t need to procure especially expensive dedicated equipment, you can start with a relatively compact device and easy-to-use app, making adoption feasible even for small and medium-sized construction sites. Once used, you will realize positioning speed and accuracy that were unimaginable when lugging large surveying instruments, and information sharing among stakeholders will be markedly smoother. Layout marking DX offers the fourfold benefits of time savings, labor reduction, improved safety, and consistent quality—and is a technology well worth adopting now.

The benefits of digital technology extend beyond layout marking. With LRTK you can easily perform other simple surveys such as distance and area measurements or earthwork volume calculations from point cloud scans, enabling on-site teams to measure as needed, share results immediately, and connect findings to next actions. Tasks that previously required specialized surveying departments or external contractors can now be done rapidly in-house, accelerating decision-making and dramatically improving overall construction efficiency. By equipping everyone on site with tools to handle measuring and layout data, digital tools can breathe new life into construction sites that have relied heavily on a few veteran workers.

The construction industry is currently promoting ICT and DX under productivity-revolution initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction. Digitizing layout marking is at the forefront of this movement and has the potential to transform production processes across sites. The future of construction sites is already beginning with the smartphones in our hands. Now is the time to break away from conventional methods and proactively adopt the latest technologies to shift toward a safer, more efficient, and more resilient construction system. Why not use layout marking DX as a springboard to evolve your company’s sites to the next stage?