Layout marking with smartphones and AR?! What next-generation construction management enabled by LRTK looks like

Layout marking ("sumidashi") is an indispensable task on construction and civil engineering sites. However, layout marking faces many challenges: a decline in skilled workers and labor shortages, as well as work errors and waiting times due to checks, among others. This task—transferring the dimensions from drawings faithfully to the site—plays a critical role in determining the overall quality and efficiency of a project. At the same time, crews are required to complete layout marking quickly while maintaining high accuracy with limited personnel, placing a heavy burden on the site.

To address these issues, a new approach using smartphones and AR (augmented reality) technology for layout marking has been attracting attention in recent years. Furthermore, with the emergence of "LRTK" technology that enables centimeter-level high-precision positioning with a smartphone, layout marking is undergoing a dramatic change. This article explains how next-generation construction management using smartphones and AR is transforming the field, describing concrete problems and solutions and showing where these technologies can be applied.

On-site challenges faced by layout marking

Layout marking is the key task that shows building positions and dimensions on site, but there are several barriers. First is the problem of labor shortages and skills transfer. As veteran surveyors and layout specialists decline in number and fewer young workers enter the trade, tasks must be handled by fewer people. Especially on large sites or for complex layouts, procedures that should ideally be done by multiple people are increasingly being handled by a single person.

Next is the risk of rework due to mistakes. Even small errors in baseline lines or reference points can cause downstream issues—"positions not aligning" or "structures not fitting"—requiring rework. If layout marking proceeds with poor accuracy, it directly leads to schedule delays and increased costs. Therefore, double-checking at critical points is essential, but on sites with constrained personnel, even the verification work itself becomes burdensome.

Additionally, idle time and inefficient sequencing are problems. For example, workers often wait for surveying specialists or equipment to arrive, or for instructions or drawing updates; such waits are common on site. Time is wasted traveling back and forth to reconfirm due to drawing errors or communication mistakes, which lowers productivity. These wasted hours are especially damaging under labor shortages, and to run a site with a small crew requires innovations to "not search, not wait, not return."

Thus, layout marking faces a threefold challenge of personnel constraints, maintaining accuracy, and communication mismatches. How can these be solved? The key is digital technology—particularly next-generation layout marking that combines smartphones and AR.

How smartphone + AR changes positioning and verification

In conventional layout marking, positions are measured with surveying equipment and guidelines are drawn on floors and walls with chalk or ink to indicate references. By contrast, using a smartphone and AR technology allows digital reference lines and markers to be overlaid directly onto the real-world space. Through a smartphone’s camera view, lines and points from drawing data or 3D models are projected to match the physical scene.

For example, if the finished wall position or equipment installation points are displayed in AR, workers can visually confirm positions without drawing physical lines on floors or walls. What used to require measuring dimensions from drawings and marking the site with tapes or lasers can now be intuitively understood on the smartphone screen—"a line should be here," "the center of the column should be at this position." Because real-world scenes and drawing information can be matched on the spot, you can instantly check whether measurement points and layout marks align.

The mechanism behind AR-based positioning relies on the smartphone’s built-in camera, sensors, and positioning information. The smartphone overlays virtual objects at the proper angle and distance by detecting orientation and motion with accelerometers and gyros. However, traditional consumer AR required manual initial alignment and could drift when users moved, because a smartphone’s standalone GPS accuracy is on the order of meters and AR depends on relative motion tracking.

This is where integrating high-precision positioning technology into smartphones comes in. A typical example is RTK-GNSS, a satellite positioning technology in which a small dedicated receiver attached to a smartphone uses correction signals to achieve centimeter-level accuracy. Systems like "LRTK," which combine a smartphone with high-precision positioning, minimize the discrepancy between design coordinates and real space, so AR-displayed lines and points always indicate accurate positions. There’s no need for painstaking initial alignment, and virtual markers won’t shift when the user moves.

With this smartphone × AR × high-precision positioning setup, positioning and verification in layout marking can be done simultaneously. Site staff can hold a smartphone to confirm required positions, mark directly on the spot, and fine-tune construction locations. It’s like projecting a digital plumb line or layout line onto the real world, greatly reducing misidentification and communication errors.

Site transformation driven by fusing high-precision positioning and AR display

Combining centimeter-level smartphone positioning with AR display brings major changes to site workflows. Enabling precise digital layout marking produces benefits such as:

• Improved efficiency and reduced waiting time: Tasks that once waited for surveying teams or verifications can now be carried out by site staff themselves using smartphones, reducing idle time. With a "one-person, one-device" surveying tool that lets individuals measure whenever needed, scheduling becomes more flexible and delays from waiting are eliminated.

• Labor saving and multi-skilled workers: Since positioning and layout marking can be completed by one person, tasks that previously required two or more people can be handled solo. Even without experienced surveyors, intuitive AR displays enable many people to perform a certain level of surveying and positioning. As a result, dependence on specialists decreases and a small crew can take on multiple roles.

• Quality improvement and prevention of rework: AR allows immediate comparison of design positions and the actual installed item, making early detection and correction of errors easy. For example, if piping or anchor bolt locations are off from the drawings, they can be noticed and corrected immediately after installation. Preventing the deviations that used to be discovered later reduces rework and stabilizes quality.

• Smoother communication: 3D models and lines shown in AR become tools for on-site communication. During meetings with clients or other trades, the projected completed form can be shared on the spot, reducing "mismatched understanding." Spatial interfaces that were hard to convey with drawings alone can be confirmed by overlaying them on reality, facilitating consensus building.

In this way, the fusion of high-precision positioning data and AR strongly accelerates on-site DX (digital transformation). Moving to data-driven construction management makes previously experience- and intuition-based tasks visible and enables reproducible quality control. Measured data can be shared and stored in the cloud in real time, streamlining subsequent as-built management and reporting. Waiting time for information from site to office and between people is reduced, enabling a faster, leaner construction management cycle.

Use cases spanning surveying, construction, as-built management, and maintenance

Smartphones with high-precision AR are useful across every phase of the construction process. Here are representative applications in four areas: surveying, construction, as-built management, and maintenance.

Surveying use cases

Using smartphone AR for pre-construction condition surveys and setting reference points greatly simplifies surveying work. For example, topographic surveys that once required setting up equipment and multiple personnel can be done by walking with a smartphone to acquire point cloud data and measure coordinates where needed. Combining smartphone LiDAR or photogrammetry using the camera with high-precision GNSS correction allows quick generation of a local 3D model. In addition, RTK-GNSS can instantly establish reference points tied to global coordinates, providing a speedy basis for subsequent layout marking or machine guidance. Being able to perform adequate surveying alone reduces survey wait times and cuts costs of outsourcing to survey contractors.

Construction site use cases

During construction, a smartphone with AR effectively becomes a layout marking tool. Visualizing building grid lines and finish lines in AR lets even non-experts carry out accurate marking while checking positions. Applications to machine guidance are also expected: for example, in earthwork, AR can be used to confirm fill volumes or project excavation boundaries onto the ground so operators can work accurately without relying on intuition. Moreover, in places where people cannot enter or where physical marking is impossible, AR can place virtual stakes or markers. You can set "invisible stakes" on key points on slopes or on extension lines from off-site, and identify those positions remotely. This capability makes previously difficult positioning tasks much easier and contributes to improved safety.

As-built management use cases

Smartphone AR also shines in as-built management (post-construction verification). Immediately after constructing a structure, you can scan the as-built with a smartphone and compare it to design data to check deviations. For instance, measuring finished concrete elevation on the spot and comparing it with the required height in AR allows quick judgment on whether corrective action is needed. Systems are emerging that automatically generate 3D models with global coordinates from smartphone photos and save them to the cloud. This enables as-built records to be retained as digital data rather than photo plans or handwritten sketches. Cloud-based 3D data can be shared among stakeholders instantly, allowing remote quality inspections. Prompt, objective as-built management helps prevent rework and streamlines recordkeeping.

Maintenance use cases

After completion, smartphone + AR combinations are also useful for maintenance and inspections. A major advantage is the ability to visualize invisible infrastructure buried underground or inside structures. For example, technologies now allow AR to display buried water/sewer pipes and cables even after backfilling. If you scanned and created a 3D model during construction and saved it to the cloud, you can later confirm exact buried locations on a smartphone when excavation is needed. Without relying on markers or drawings, you can view an unalterable virtual cross-section on site, preventing accidental damage to pipes and enabling precise maintenance. In bridge and tunnel inspections, displaying past inspection data in AR alongside the current condition makes it easy to intuitively identify deterioration. Thus, digital construction data produced during works can be leveraged for long-term maintenance, improving efficiency and safety across the lifecycle.

How layout marking and guidance can be done accurately by one person

So, can smartphone and AR-based layout marking really be done by a single person? The answer is yes. In sites where this new technology has already been adopted, one-person surveying and one-person layout marking have produced reliable results.

Traditionally, establishing references required two or more people—for example, one person looking through surveying equipment and another holding a staff rod at the point. With systems combining a smartphone and high-precision GNSS, you can confirm the measured point on the smartphone screen yourself and mark the location simultaneously. In other words, the measurer and the marker become the same person. For example, one site supervisor used a smartphone with a GNSS antenna temporarily fixed to a pipe scaffold, established reference points solo, and immediately marked them. The results were comparable to conventional two-person work, and setup time was reduced.

Machine guidance can sometimes also be handled by one person depending on the situation. AR can visualize instructions like "dig to this depth" or "excavate along this line," so operators and the guide can share the same screen. This is especially valuable in low-visibility sites or night work, where precise positional and directional guidance can be given without relying on verbal communication.

Feedback from the field supports this one-person approach. Engineers who adopted smartphone RTK report being "surprised by the high positioning accuracy even in mountainous areas," and that the lightweight, portable equipment made forest surveying much easier. On social media, voices of excitement such as "I was moved when the device arrived" and "It’s amazing that you can do this with your own smartphone now" indicate real momentum in field implementation. As these examples show, smartphone and AR layout marking technologies are already in the practical implementation stage, and they are drawing attention as a means to perform accurate and speedy surveying and positioning even by one person.

Construction management DX that supports labor saving, efficiency, and quality improvement

Introducing smartphone × AR for layout marking is a powerful solution to the three major on-site challenges of labor saving, efficiency, and quality improvement. Utilizing such digital technologies is part of "construction management DX," and the industry is promoting adoption.

On the labor-saving front, as mentioned earlier, the range of tasks that can be completed by a single person is expanding, helping organizations operate with fewer workers despite labor shortages. Digital tools reduce dependence on veteran specialists, lowering person-dependence and making it easier to maintain stable construction quality with a small crew.

In terms of efficiency, digitizing operations leads to significant time savings. As surveying, layout marking, inspection, and recording shift from paper- and person-centered processes to digital-data-centered workflows, redundant work is reduced and real-time information sharing becomes possible. The result is fewer unnecessary waits and rework, letting you complete more tasks in limited time.

DX also brings measurable quality improvements. With data-driven management, decisions are made objectively rather than relying solely on intuition and experience, raising construction accuracy. Preventive measures against mistakes become easier, and if a problem does occur, digital records let you trace causes and take corrective actions quickly. Accumulated quality data can be used to drive future improvements.

Construction management DX is not just about IT; it transforms how work is actually carried out on site. Smartphone and AR based layout marking is a representative example. Combining this with IoT sensors, AI analysis, and cloud integration can realize safe, resilient site operations. A digital, smart construction site is also an attractive proposition for workstyle reform and recruiting younger talent. In advancing construction complexity, sites that adopt DX will be able to balance productivity and quality.

Start next-generation construction management with smartphone RTK "LRTK"

Finally, as a concrete example of a solution for implementing DX using smartphones and AR, we introduce "LRTK." LRTK is a system consisting of a compact device that attaches to a smartphone and a dedicated app, enabling RTK-GNSS positioning and AR functionality with ease. No complex setup or bulky equipment is required—your everyday smartphone becomes a centimeter-accurate surveying instrument.

For example, by attaching LRTK to a smartphone, you can use the high-precision positioning service provided by Japan’s quasi-zenith satellite "Michibiki" (via CLAS) to obtain high-accuracy coordinates in real time. With a dedicated app, a single button press can record measurement points or project layout positions, and the acquired data can be uploaded to the cloud for sharing. Tasks that previously required specialized knowledge are simplified by LRTK into operations that anyone can intuitively perform. New users on site can pick up the technique in a matter of tens of minutes and feel the benefit from day one.

An attractive point is its portability and cost-effectiveness. LRTK devices are compact enough to fit in a pocket and include a built-in battery, so you can carry them around the site all day. Pricing is set so that adoption is far easier than with traditional surveying equipment, making it realistic to provide one device per person within a department. You can easily bring them to small construction or renovation sites and quickly take them out for surveying and layout marking when needed—this convenience is a major strength.

Use these simple surveying and positioning tools as an entry point to start your company’s construction management DX. We recommend piloting them on a few sites first to experience the effects and usability. If site staff start saying, "This is useful," or "We’d be uneasy without this," then your first step in DX has succeeded. By digitizing the familiar task of layout marking and leveraging accumulated data horizontally, you can drive improvements in other business processes as well.

Next-generation construction management can start with just a smartphone. Why not embrace technologies like LRTK and bring innovation to your future site operations?