Zero Layout-Marking Errors: High-Precision LRTK and AR Guidance Make Anyone as Skilled as a Pro

Traditional Layout-Marking Processes and Their Challenges

Layout marking (sumi-dashi) is the process of drawing the dimensions and positional information from construction drawings onto floors and walls at actual size on building and civil engineering sites. As the step that indicates reference lines and points on site, this process plays a critical role in determining construction accuracy and quality. If layout marking is inaccurate, subsequent work can suffer from misalignment and errors, directly causing time and cost losses due to rework. For this reason, layout marking requires extreme care because mistakes are unacceptable.

Traditionally, layout marking has relied almost entirely on craftsmen performing manual work. Skilled workers check paper drawings and use tools such as chalk lines, measuring tapes, and laser layout instruments to draw reference lines and marks on site. For example, to draw a line on the floor indicating a building grid or wall position, the worker measures distances from reference points based on the drawings and marks them with chalk.

However, manual layout marking has many challenges. First, it takes significant time and effort. Marking hundreds of points or drawing numerous long layout lines across a large floor or site is extremely laborious. When marking at heights or in awkward scaffolding, workers must maintain careful postures while marking, which involves physical strain and safety risks.

Moreover, human errors are prone to occur. Wherever humans are involved, mistakes like misreading drawings, transcription errors, measurement errors, and calculation mistakes inevitably happen. On actual sites, it is not uncommon for layout marks to be misidentified or dimensions misread, with errors discovered later that require urgent re-marking. If layout-marking mistakes are found in subsequent steps, positions of columns or walls may need correcting, leading directly to schedule delays and higher costs.

The high dependence on skilled experience is also a problem. Accurate layout marking requires intuition and techniques backed by experience, and novice workers alone often find it difficult to maintain precision. Therefore, veteran craftsmen usually accompany the site work, and marking is commonly done by two or more people including an assistant. The quality and speed of layout marking depend on the skills of the responsible craftsmen—more experienced workers can work faster and more accurately. Conversely, even experienced workers cannot eliminate mistakes entirely, and variability between workers is unavoidable.

In addition, labor shortages and skill transfer issues have become serious. In the construction industry, an aging workforce and fewer young entrants make it difficult to secure personnel with advanced skills like layout marking. Sites try countermeasures such as implementing double-check systems to prevent mistakes, but these are inefficient because they require extra personnel. In fact, the Ministry of Land, Infrastructure, Transport and Tourism promotes construction DX (i-Construction) and encourages ICT use for surveying and measurement tasks like layout marking. Against this backdrop, there is a strong demand for new technologies that reduce human errors, lighten worker burden, and improve efficiency in layout marking.

Innovative Layout-Marking Method Using High-Precision Positioning (RTK) and AR Guidance

Recently, to solve these challenges, an innovative layout-marking method combining high-precision positioning technology RTK and AR (augmented reality) technology has emerged. RTK, short for Real Time Kinematic, is a high-precision positioning method using satellite navigation (GNSS) that can determine positions with errors down to a few centimeters. While traditional GPS has errors on the order of meters, RTK, by using dedicated reference stations and correction data, can determine horizontal and vertical coordinates with precision on the order of centimeters. LRTK brings this RTK technology into a compact device that is easy to use on-site. By using a small RTK receiver attachable to a smartphone or tablet, centimeter-level positioning is achieved in a palm-sized form factor.

AR technology overlays virtual information onto real-world scenes through a smartphone or tablet screen or via AR glasses. In construction, AR has already attracted attention for sharing finished-image overlays with clients and visually conveying instructions to workers. Applied to layout marking, AR becomes a game changer. Specifically, positional information from design drawings or BIM data is projected into the site space via AR, and workers simply follow the on-screen guides to place marks.

Because RTK continuously provides accurate worker positions, the lines and points displayed in AR precisely match real-world coordinates. For example, virtual lines can be displayed on the floor along the grid of walls or columns, or virtual markers can indicate positions where bolts or pipes should be installed. Workers need only follow the AR lines and marks shown on the screen and mark them with chalk or paint to complete layout marking according to the drawings.

The revolutionary point of this method is that anyone can intuitively perform accurate layout marking. Since AR guides are overlaid on the real site view, the cognitive load of interpreting drawings is greatly reduced. What used to require mentally calculating "a position XX mm ahead on the drawing" is now visually indicated by AR as "here," leaving little room for measurement or identification errors. Because RTK aligns positions, the cumbersome positional-transfer tasks of the past (establishing reference points, transferring levels) can be automated. Even height reference transfers (benchmarks), which were cumbersome on site, can be digitally presented when combined with high-precision GNSS altitude data.

AR guidance is also powerful in situations where direct marking is normally difficult. For example, if markers must be placed on a slope or an area out of reach of scaffolding, virtual stakes or lines displayed in AR from a distance make positions immediately identifiable. For marking high areas away from the ground or positioning within complex structures with many obstacles, AR eliminates the need to mentally extend unseen reference lines. RTK-based self-position correction ensures AR displays do not shift when the worker moves, maintaining consistently high-precision guidance. In short, combining RTK's precise "current location" information with AR's visual guidance fundamentally changes how layout marking is done, enabling anyone to achieve professional-level accuracy.

Benefits of Adoption: Solo Work, Skill Standardization, Labor Savings, and Error Prevention

Introducing a new layout-marking method using high-precision RTK and AR guidance brings a variety of benefits to the site. Here are the main effects.

• Enables solo work: Layout marking, which was often done by two people, can now be completed by a single worker holding the device. This reduces labor costs and simplifies staffing. Since AR acts like "another worker" by always indicating accurate positions, there is no need for an assistant to hold tapes or verify marks. This leads to more efficient personnel allocation and allows layout marking to proceed even on sites with labor shortages.

• Standardizes skills: With visual AR guides and precise RTK positioning, even less experienced workers can achieve the same accuracy as veterans. Consistent results are obtained regardless of who performs the task, making quality less dependent on individual skill and increasing confidence on site. Workers need only mark the displayed locations without deciphering complex drawings or using advanced measurement techniques. This is a significant advantage for skill transfer: even if specialist surveyors or veteran craftsmen are scarce, the team can maintain high-quality layout marking.

• Reduces labor and time: Digital guidance dramatically shortens the time required for layout marking. Reducing re-measurements and rework and simplifying setup processes accelerates tasks that used to take hours for a floor layout. Shortened task time contributes to compressing the overall schedule, and the freed time can be allocated to other construction activities to boost overall project productivity. Reduced physical burden also improves worker safety—there is less need to carry heavy surveying equipment or drag long tapes, decreasing fatigue and the likelihood of mistakes during long shifts.

• Prevents errors and raises quality: Digitizing and visualizing manual processes reduces the incidence of human error. AR displays based on RTK-backed coordinates are always accurate, minimizing mis-marking due to misunderstandings or assumptions. Careless mistakes—such as repeatedly comparing drawings and measuring—are greatly reduced, resulting in an overall improvement in layout-marking accuracy. Digitally recording the positions of layout marks makes later accuracy verification and information sharing easy, contributing to better quality control. Improved layout-marking accuracy stabilizes subsequent construction quality and contributes to smooth, rework-free progress.

Specific Use Cases and Effects in Building and Civil Engineering Sites

Building sites: Layout marking appears at many stages in building construction from structural work to finishing. Examples include formwork placement before concrete pouring, marking wall and column positions on each floor, indicating ceiling openings (for ducts and lighting), and marking equipment installation positions during finishing.

Previously, workers compared drawings and measured to mark locations, which required repeatedly checking drawings and remeasuring. With high-precision RTK and AR guidance, for example, floor marking is completed simply by tracing a virtual wall line projected on the floor. Ceiling opening positions can be indicated through AR goggles without spreading drawings on scaffolding—workers can simply drill where the AR indicates an opening. As a result, not only is work time shortened, but mistakes like "misplacing piping and redoing it" are reliably reduced. Because AR visually shares the design layout, stakeholders are less likely to have mismatched understandings, making post-construction complaints like "this wasn't what we expected" easier to avoid. On sites that introduced AR layout marking, reports indicate dramatic time reductions for positioning sleeves on a single floor and successful completion of layout marking even on days when veterans were absent.

Civil engineering: In civil engineering, layout marking (positioning) is also part of surveying tasks. Uses include establishing reference lines for roadwork, marking positions for structures in site development, and determining anchor bolt locations in bridge work.

Traditionally, surveyors used transits or electronic pile drivers to set stakes or chips, which craftsmen then used as references for layout marking. With high-precision RTK devices, digital reference points can be obtained without survey instruments and indicated in AR, allowing those without survey expertise to place stakes or marks at the correct positions. For instance, on a large development site where multiple foundation locations must be indicated, a worker can simply follow arrows and distance indicators on a tablet to reach the target points. As they approach a target, a "virtual stake" appears in AR, and they only need to drive a physical stake there. On asphalt or concrete where physical stakes cannot be driven, virtual markers in AR can substitute, and later crews can confirm positions via tablet. In this way, civil layout-marking tasks that once required survey expertise and multiple workers can be simplified and made more labor-efficient using digital technology.

Conclusion: The Potential of Simple Surveying Solutions with LRTK

The innovation in layout marking using high-precision RTK and AR guidance has the potential to dramatically improve productivity and quality at construction and civil engineering sites. If everyone can mark layouts accurately and rework due to mistakes approaches zero, site-wide efficiency will greatly improve. For example, if the time spent on layout marking in large projects is cut in half, this directly shortens schedules and reduces labor costs.

Today, simple surveying solutions that make this approach easy to implement are already appearing. For example, LRTK is a groundbreaking system that enables centimeter-level positioning and AR-based position guidance simply by combining a smartphone with a compact RTK-GNSS receiver.

These systems are designed to be operated mainly by touch on a tablet and require little difficult training, making them accessible to anyone. Compared with dedicated surveying instruments, they are often more affordable to introduce, making them suitable for small- to medium-sized sites. In addition to layout marking, they often include diverse functions such as high-resolution point-cloud scans or photogrammetry using an iPhone’s built-in LiDAR scanner and camera, so they can serve as an all-in-one surveying tool covering site measurement tasks.

Coordinate and mark data acquired by dedicated apps can be shared via the cloud immediately, smoothing communication between site and office.

By leveraging these modern technologies wisely, "zero errors" in layout marking need not be a pipe dream. For a construction industry struggling with shortages of skilled workers and rising labor costs, the RTK-and-AR-driven layout-marking revolution is a major step toward a future where anyone can work safely and efficiently. In the future, digital construction styles in which 3D design data created in BIM/CIM are projected directly onto the site during construction may become commonplace. It is expected that digital technologies will be used increasingly at many sites to contribute to improved productivity in building and civil engineering. The digital transformation of layout marking will be a key driver of productivity improvement in the construction industry going forward. We will continue to watch its evolution closely.