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

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

On construction sites, the task of indicating lines and reference points in real locations based on design drawings—known as layout marking (setting out)—is indispensable. In building construction, this includes positions of foundations and columns and interior finishing lines; in civil engineering, it includes road centerlines and locations for structures. Accurate layout marking influences both quality and efficiency across all phases of work. Even today, many layout marking tasks are performed manually or with optical surveying instruments, where experienced technicians use tape measures, ink lines, and laser devices to draw reference lines and points on site. While drawings have been increasingly digitized with CAD/BIM, position transfer to the field often still relies on analog methods, leaving room for inefficiency and error risk. Against this backdrop, the movement to digitally transform construction processes (DX)—that is, to innovate on-site layout marking using digital technologies—has attracted attention.

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

Traditional layout marking methods have faced the following challenges:

• Securing manpower: Layout marking requires both operating surveying equipment and making markings, so it typically involved teams of two or more. One person operates the equipment while another holds a staff rod or prism, so multiple personnel are constantly required. This becomes a burden on sites with labor shortages.

• Accuracy and risk of mistakes: Manual measurements with tape measures or mason’s lines can lead to slight reading errors or misalignments. If dimensions transferred from reference points are incorrect, significant rework can occur in later stages—e.g., “column positions don’t match the drawings”—causing schedule delays and reduced quality.

• Increased work time: Setting up surveying instruments like total stations or levels requires careful preparation—tripod setup, leveling, and coordinate alignment—so it can take time before layout marking can even begin. The more complex the marking, the longer measurements and checks take, lowering overall efficiency.

• Safety concerns: Carrying heavy surveying gear to heights or performing layout marking on busy roads exposes workers to danger. During daytime outdoor work, laser layout lines can be hard to see under sunlight, and workers may need to spend extended time in traffic lanes to check alignment—raising safety-management issues.

• Skills transfer and training issues: The number of skilled surveyors who can perform precise layout marking is decreasing and aging. Skill transfer to newcomers is lagging, and methods that depend on individual expertise are reaching their limits. Such reliance on personal skills also hampers productivity improvements and work-style reforms.

Thus, traditional layout marking has required significant manpower and effort to maintain accuracy, and site conditions often impose large constraints on efficiency and safety.

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

To address these challenges, approaches using high-precision positioning (RTK) and AR (augmented reality) combined with smartphone integration have emerged. Recent smartphones include LiDAR sensors (infrared laser scanners), and by attaching a dedicated compact GNSS receiver and using RTK (Real Time Kinematic) positioning, centimeter-level location information can be obtained on site with ease. By combining the smartphone’s LiDAR-based scanning of floors and walls with RTK-corrected self-position coordinates, digital design drawings or 3D models can be overlaid on real-world video with minimal offset. In other words, the combination of “smartphone + GNSS + AR” enables a palm-sized device to function on-site as a surveying instrument and layout-marking tool.

So how exactly does layout marking change with these digital technologies? 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 start positioning and AR display immediately. There’s no need to transport and set up heavy equipment or erect tripods and spend a long time preparing; even small layout tasks can begin much faster.

• Work completed by one person: Since you only need to follow guides shown on the smartphone screen to make marks, layout marking that traditionally required two people can now be performed by one person. Anyone can make precise markings without a veteran assistant, reducing the burden of site staffing while progressing work.

• High accuracy and fewer mistakes: Centimeter-class positioning from RTK-GNSS ensures that lines and points shown in AR match the design coordinates. This prevents manual measurement errors and greatly reduces construction mistakes from mislocated survey points. Demonstrations have confirmed average errors under 1 cm with smartphone + RTK, showing that positioning accuracy can rival conventional optical surveying.

• Good visibility in any site conditions: AR guides can be displayed on the smartphone screen as arrows or virtual pegs that are visually easy to understand. Even in bright outdoor daylight, guides are clearly visible on the screen, making it easier to identify targets than laser layout lines that fade in sunlight. Positions are harder to lose even in scorching sun, enabling smooth work without additional aids.

• Labor savings and improved safety: Digital guides are intuitive and easy to use, so even non-experts won’t be confused. Single-person workflows reduce labor burdens, and shorter task times reduce exposure on heights or busy roads. Because positions can be checked from a safe distance, non-contact layout marking becomes possible around heavy machinery or during night work. This leads to reduced physical strain for workers and fewer near-miss incidents, allowing layout marking to proceed with greater peace of mind.

• Data utilization and DX promotion: Layout results (coordinates of marked points or point-cloud data acquired on site) can be saved and shared in the cloud as digital information. There’s no need to record on paper drawings by hand; by linking with BIM/CIM models and construction-management software, an integrated digital flow from surveying to construction management becomes possible. Digitizing layout marking streamlines subsequent quantity checks and quality control and contributes to productivity improvements across the site.

In these ways, RTK positioning combined with smartphone AR is resolving many of the constraints that came with traditional layout marking.

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

Let’s look at a typical flow for performing digital layout marking on site. The following is an example when using an RTK-capable device for smartphones (such as LRTK).

• Preparation and reference-point surveying: First, align the site coordinate system with the design data based on construction drawings. If known reference points exist, measure their coordinates with the device and compare them with the coordinates on the design drawings. If there are no reference points, you can use GNSS to obtain absolute coordinates and use those as the site reference, enabling alignment between drawing data and field positions.

• AR-based position guidance: Load the design data (CAD drawings or BIM models) into the smartphone surveying app. After matching to reference points, select the targets (lines or points) you want to mark. Switch the app to AR mode to display the design lines and marking positions overlaid on the real-world view on the smartphone or tablet screen. The worker follows the on-screen guidance to move to the specified position and identify the exact point.

• Performing the layout marking: Make marks at the positions indicated by AR. For example, to mark column positions on a cast foundation top, simply align to the virtual column center displayed on screen and draw a mark with chalk or an ink line. For wall or floor lines, instead of measuring from drawings on site, mark along the lines displayed in AR for quick and accurate work. By checking the smartphone as needed, one person can sequentially mark multiple locations.

• Data sharing and recording: After marking is complete, record and share the results as digital data. For example, save the coordinates of marked points in the app to automatically upload to the cloud for immediate sharing with the site office or other teams. You can also take photos with location information of the marked spots, or LiDAR-scan the as-marked condition into point-cloud data. Uploaded cloud data can be used to check distances and angles or viewed in a browser-based 3D viewer, allowing construction managers to verify as-built conditions on the spot and issue correction instructions immediately if deviations are found.

With this flow, surveying through to completed marking is handled digitally end to end. From importing design data and on-site guidance to recording results, the process is seamlessly connected, integrating tasks that used to be separate—"read drawings and measure," "make marks," "record"—and dramatically improving efficiency and reliability.

LRTK Solutions and Technical Explanation

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

Through high-precision RTK positioning, LRTK enables horizontal accuracy of about 1–2 cm and vertical accuracy around 3 cm even on a smartphone. While typical built-in smartphone GPS errors are on the order of 5–10 m, a dedicated GNSS receiver achieves dramatically higher accuracy by real-time correction of satellite signal errors. LRTK supports centimeter-class services such as Japan’s quasi-zenith satellite "Michibiki" CLAS and network RTK via the internet, making it strong even on sites without cellular coverage in mountainous areas. This makes precise vertical measurements easier as well, which is useful for leveling in buildings or height control in infrastructure work.

LRTK also enables 3D measurement by integrating with smartphone cameras and LiDAR sensors. It can scan surrounding terrain and structures into point-cloud data and tag them with accurate RTK-derived coordinates. The acquired point cloud is immediately stored in the cloud as georeferenced 3D data and can be overlaid with drawings and other survey data. This allows tasks like on-site management of complex shapes and earthwork volume calculations to be performed easily.

AR-guided positioning is another important LRTK feature. The app projects models and lines from design data to scale on the smartphone screen to intuitively support layout tasks—such as marking pile-driving locations or indicating pipe routes. Tasks that used to require measuring from drawings with a tape measure are now resolved by AR displays that clearly indicate "drive a stake here" or "route wiring along this wall," preventing misalignment. Because design models can be overlaid on the current site condition, AR also supports interference checks and as-built verification during construction, helping improve site understanding and prevent mistakes.

Furthermore, the LRTK app automatically records positioning data and shares it to the cloud. Measured coordinates are automatically saved on the device with timestamps and measurement conditions and converted in real time to national geodetic systems or plane rectangular coordinate systems. Point names and IDs are auto-assigned, eliminating the need for manual calculations or handwritten notes on site. You can attach photos and notes to each survey point, and the app can output survey reports with a single button. Uploaded cloud data can be immediately reviewed and shared in map or 3D views via a web browser, allowing internal and external stakeholders to access the latest site information without installing specialized software. Smooth data linkage between site and office streamlines report and inspection-document creation.

In short, by adopting LRTK, a single smartphone can complete "high-precision positioning, measurement, layout marking, recording, and sharing" on site. As a multifunctional tool that requires no special skills, it allows not only veterans but anyone on site to perform high-precision surveying and layout marking—an important technological innovation.

On-Site Implementation Examples and Use Cases

Examples in Building Construction

In building construction, AR layout marking is useful across a wide range of processes from foundations to finishes. For example, consider marking column locations on the top of foundation concrete after casting in a reinforced concrete building. Traditionally, workers would use tape measures from drawings to measure positions and mark with chalk. Replacing that with smartphone + LRTK AR layout marking means workers can simply align to the virtual column center shown on the screen and mark accordingly. There’s no need to set up batter boards or repeatedly measure with multiple people; multiple column positions can be laid out quickly and accurately.

In interior work, AR can show planned pipe and duct routes or fixture and lighting locations behind ceilings and inside walls before installation. Even without pre-drawing lines on the wall or floor, contractors can point a tablet to immediately share where pipes will run, making it easier for trades—plumbing, electrical, etc.—to coordinate. When teams share the completed model in AR, they can make adjustments in advance—"if the pipe comes here, leave an opening" or "adjust to avoid interference before finishing"—which smooths collaboration and reduces construction mistakes and rework. Construction managers can also verify progress against the model in real time and issue corrective instructions on the spot if deviations occur, contributing to improved construction accuracy and reduced rework, shortening schedules and improving quality.

AR is also effective for overall building layout confirmation. For instance, projecting partition-wall layouts on the floor of an office with AR lets stakeholders preview the finished space before partitions are built, reducing the risk of "the finished layout isn’t what we expected" and enabling adjustments during pre-construction meetings to avoid later rework. Thus, AR layout marking serves not only to improve marking efficiency but also as a communication tool on site.

Additionally, temporary works like scaffolding and temporary fencing are frequently erected on building sites. AR layout marking helps plan these installations too. For example, when erecting scaffolding around a building, you need to accurately mark footing positions on the ground or walls; AR can virtually display scaffold member placement on the building model and indicate post positions on the screen. Workers can mark the ground accordingly, which is faster and more accurate than manually spacing and marking. High attachment points can be checked from the ground through a tablet, reducing climbs and improving safety. For long temporary fences, displaying the fence line along the site boundary with AR eliminates the need for stringing lines or visual checks. Using digital guidance for temporary works that still require precision accelerates setup and improves assembly accuracy.

Examples in Civil Engineering

In civil infrastructure work, smartphone AR layout marking also contributes to productivity gains. For example, in road construction, curves and positions for width stakes can be displayed directly on the pavement using AR so heavy equipment operators can work while confirming positions. Traditionally, establishing curve shapes required driving many wooden stakes at regular intervals, but with AR you may only need to mark a few key points, greatly reducing intermediate stake-driving and batter-board setups. Without a surveying specialist constantly guiding work, site personnel can follow on-screen lines for grading and paving, realizing a new style where each worker carries out surveying tasks with a smartphone in hand.

In large-scale earthworks, drone aerial photos or terrestrial laser scans can generate terrain models onto which design data is AR-projected for use on site. Heavy-equipment operators can check tablet screens from the cab while excavating or filling, reducing the need for frequent intermediate surveys and additional layout marking. For large solar-panel installations, accurately laying out site grading and pile-driving positions at an early stage can eliminate many intermediate layout tasks while maintaining final precision. This improvement is driven by the fact that AR layout marking significantly reduces construction mistakes, to the point where corrective positioning in later stages is unnecessary and layout reliability is greatly improved.

Civil works also see major safety benefits. Reducing the time personnel spend stepping into traffic lanes for surveying and marking lowers the risk of traffic accidents. If AR displays signage or mounting positions remotely, workers need not approach hazardous areas like dense vegetation or night-time sites. This non-contact position verification capability helps prevent industrial accidents. There have been cases where surveying tasks that used to require personnel under bridge girders or on steep slopes were completed via AR from a safe distance. Thus, AR layout marking in civil works yields high effects on both large-scale work efficiency and worker safety.

The Future of Layout Marking and the Impact on Site DX

Layout-marking DX using smartphone positioning and AR technology is transforming position transfer tasks that once relied on craftsmen’s intuition and experience, opening the door to a future where anyone can perform high-precision construction. Introducing solutions like LRTK makes a smartphone into a precise surveying instrument and enables smooth digital transformation of layout marking. Because you don’t need very expensive specialized equipment—only a relatively compact device and an easy-to-use app—the adoption barrier is low even for small and medium construction sites. Once used, you’ll realize layout marking can be finished with speed and accuracy unimaginable when carrying large surveying machines, and information sharing among stakeholders becomes far more seamless. Layout-marking DX offers quadruple benefits—time savings, labor savings, improved safety, and stable quality—which makes it a technology worth adopting now.

The benefits of digital technologies extend beyond layout marking. With LRTK, you can easily perform other basic surveys such as distance and area measurements or earthwork volume calculations from point-cloud scans, carrying out necessary measurements on demand, sharing results immediately, and linking outcomes to the next actions all on site. Tasks that used to be outsourced to surveying departments or external vendors can be performed in-house quickly, accelerating decision-making and dramatically improving overall construction efficiency. In this way, as digital tools enable everyone on site to handle measurement and layout data, they can bring new life to construction sites that were short on younger workers and overly reliant on veterans.

The construction industry is currently promoting ICT/DX under productivity-revolution projects such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction. Digitizing layout marking is one of the frontlines of this movement and has the potential to transform the entire production process from the site. The future of the construction site already begins with the smartphone in our hands. Now is the time to move beyond conventional methods and proactively adopt the latest technologies to shift toward safer, more efficient, and more resilient construction. Why not let layout-marking DX be the catalyst that evolves your company’s sites to the next level?