Enabling Single-Person Layout with LRTK Technology: Promoting Labor Reduction with AR and High-Precision Positioning

Basics of Layout Marking and Challenges of Conventional Methods

"Layout marking" refers to the work on construction and civil engineering sites of marking reference lines and positions on site based on design drawings. In building construction, this includes marking the foundation positions and the center lines of columns and walls on site; in civil engineering, it includes indicating the road centerline or the installation positions of structures on the ground. It is an extremely important process for constructing works at the correct positions and dimensions, and it is not an exaggeration to say that the accuracy of layout marking determines the overall quality of the work.

However, conventional layout marking work has various challenges. The main points are as follows.

• Time-consuming equipment preparation: Layout marking has commonly used dedicated surveying instruments such as total stations or levels. Using these requires setting up a tripod and installing the instrument, performing leveling and alignment with reference points, and thus preparing to start work takes time and effort.

• Requires multiple personnel: When using surveying instruments, at least two people were required. For example, with a total station one person operates the instrument while another holds the prism or staff at a distant position as the target. When there are many marking points, moving around the site becomes burdensome, and in some cases a three-person team including a recorder was employed.

• Risk of measurement errors and rework: In conventional manual methods using tape measures or mason's line, small reading mistakes or marking misplacements can occur. If dimensions from the reference are recorded incorrectly, later stages will face "misaligned positions" leading to rework. This often causes schedule delays and reduced quality.

• Visibility issues outdoors: Laser line projectors can be used to project lines or points, but laser light can be hard to see outdoors on bright sunny days. On bright sites, projected reference lines may not be visible, requiring extra steps such as searching with a receiver, increasing workload.

• Labor shortage and skill transfer: A major problem is the decreasing number of skilled workers who can accurately perform layout marking and surveying. Mastery of advanced surveying instruments and experience-based judgment cannot be acquired overnight, and relying on specific veterans risks stopping work when they are absent. Also, the industry-wide difficulty in securing young talent means that continuing to rely on manpower-intensive conventional methods limits productivity improvements and workstyle reforms.

Thus, conventional layout marking requires considerable effort and personnel to maintain high accuracy, and efficiency can fall under some conditions. Recently, new approaches using the latest technologies to solve these issues have attracted attention.

Elements that Enable Single-Person Layout (RTK Positioning, AR Guidance, etc.)

With recent advances in digital technology, performing accurate layout marking by a single person is no longer a dream. The key is the combination of RTK technology that achieves centimeter-level high-precision positioning and AR (augmented reality) guidance that intuitively indicates positions on site.

• High-precision positioning with RTK: RTK (Real Time Kinematic) is a technology that dramatically improves positioning accuracy by applying real-time corrections to satellite positioning (GPS, GLONASS, etc.). Built-in smartphone GPS typically has errors of several meters (several ft), but by connecting a compact RTK-capable GNSS receiver to a smartphone and receiving correction information from a base station, positioning with errors of several centimeters (several in) becomes possible. For example in Japan, using the centimeter-level (inch-level) augmentation signals of Michibiki (QZSS) or GNSS reference-station networks via the internet (VRS method) allows you to obtain stable positioning outdoors with horizontal accuracy on the order of about 1-2 cm (0.4-0.8 in).

• Intuitive position guidance with AR: AR (Augmented Reality) technology can overlay digital design data onto real-world imagery. By viewing the site through a smartphone or tablet camera, lines and points drawn in the design appear as virtual markings over the real scene. For example, AR display can show a virtual stake or line on the screen for "place a column at this foundation position." The worker can align physical marking with these virtual markers while looking at the actual ground or structure, eliminating the need to compare paper drawings with the site and rely on intuition.

• Use of smartphone-integrated LiDAR sensors: Some latest smartphones include LiDAR sensors that measure distances around them with infrared lasers. By scanning floors and walls and converting them into 3D data, LiDAR further improves AR display accuracy. Combined with RTK for accurate self-positioning, AR virtual objects are less likely to drift even in wide outdoor spaces, enabling precise projection of virtual lines with minimal alignment steps. Because models can be placed based on GNSS coordinates even in featureless sites such as bare lots, pinpoint positioning that was difficult with traditional methods becomes possible.

Combining these technical elements allows digital support for layout work that previously relied on manpower, enabling accurate and efficient single-person layout. In particular, solutions that link smartphones with ultra-compact RTK-GNSS receivers (for example systems called "LRTK") enable centimeter-level positioning with palm-sized devices. Site personnel can perform simple surveying themselves and use AR to confirm layout positions based on that data.

Workflow Supported by High-Precision Positioning Technology

So what are the specific steps on site when using high-precision positioning and AR? Here is a workflow for single-person operation that differs from conventional practice.

• Data preparation and positioning setup: First, import the design data for the layout (e.g., foundation center lines or structure layout drawings) into the smartphone app. At the same time, set up the coordinate system to be used as the site reference. If known control points exist, enter their coordinates into the app or measure them with the RTK receiver to align references. Once ready, power on the RTK-GNSS receiver and start satellite positioning. In several tens of seconds you can obtain an RTK "FIX solution" (a solution with errors of a few centimeters), and the high-precision positioning mode starts.

• Start position guidance (AR navigation): On the smartphone app, select the points or lines you want to mark and switch to AR display mode. Virtual objects (markers or lines corresponding to the selected locations) are overlaid on the live camera view of the site. A point will appear as a virtual pin or stake on the ground, and a line will be drawn along the floor surface. The worker walks slowly while viewing the smartphone screen and is guided to approach the displayed AR marker. The screen can show arrows and distance information from the current location to the target point, making it intuitive which direction and how many meters to move.

• Marking the point: When you reach the target position, the virtual marker on the smartphone screen is displayed exactly overlapping a point on the actual ground. That is the layout position specified in the design. While checking the position on the smartphone, the worker marks the site with chalk or spray paint using one hand. For lines, the worker can snap a chalk line along the AR virtual line to mark according to the drawing. Tasks that traditionally required survey staff to stretch lines or measure with tape can be completed simply by following the on-screen guidance.

• Recording and sharing survey data: If necessary, you can measure and digitally record the coordinates of the marked points on site. With the smartphone app, pressing a button saves the current RTK positioning coordinates and uploads the point with a name or note to the cloud, leaving a history of where markings were made. Capturing screenshots or photos of the AR view preserves images showing virtual stakes aligned with the actual ground, which can later be reviewed in the office. Thus, a single person can simultaneously perform layout marking and obtain survey records or reporting data—another benefit of digital technology.

This sequence enables a single worker to perform accurate layout marking without difficulty. There is no need to repeatedly transport and set up heavy equipment or coordinate calls with others, and multiple points can be marked quickly.

New Workflow of Layout Marking Integrated with Smart Construction

High-precision positioning plus AR layout marking is not only about enabling single-person operation; it is also notable for its high affinity with overall construction digitalization (smart construction). A workflow that consistently uses data connects formerly separate surveying/layout tasks with other construction processes.

By linking digital data from design through construction management, efficiency improves. Traditionally, workers read values from paper drawings and transcribed them for layout, but AR layout uses design CAD or BIM data directly on site. Because there is no manual transcription of drawing information, clerical errors are eliminated and design intent is conveyed directly to the site.

Moreover, real-time cloud sharing of site information including layout results strengthens coordination between site and office. For example, once layout marking for the day is finished, recorded coordinate data and site photos can be uploaded to the cloud immediately. Supervisors and designers in remote offices can check them right away and, if necessary, send additional instructions to the site. This timely information sharing speeds up construction management and enables early detection and correction of rework.

Coordination with ICT-equipped machinery and other smart construction technologies is another advantage. Today, various smart construction technologies such as machine guidance/control for heavy equipment and drone surveying are being introduced on sites. Under a unified coordinate system provided by RTK, digitally managing layout marking on the same standard ensures consistency between machine-used 3D design data and human work. For example, in road construction where stakes and batter boards were traditionally installed at intervals to indicate height and width, the number of stakes may be reduced with machine guidance; humans can still verify key points using AR layout. This enables minimal necessary marking while achieving low-error construction by both people and machines.

Applying high-precision layout marking to a digital workflow aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative (https://www.mlit.go.jp/tec/i-construction/). i-Construction aims to improve productivity by using ICT across processes from survey and design to construction and inspection, and reducing labor for layout marking is an important theme. Single-person layout using RTK and AR is expected to strongly support on-site DX (digital transformation) as a concrete solution.

Concrete Benefits in Labor Reduction, Efficiency, and Work Safety

Finally, summarize the concrete benefits this new layout method brings to the site. High-precision single-person layout yields significant advantages compared to conventional methods in the following ways.

• Solving labor shortages through workforce reduction: Layout and surveying that previously required 2–3 people can be completed by one person, enabling significant personnel reductions. On sites suffering chronic labor shortages, fewer people can handle multiple tasks in parallel. The need to arrange external surveying contractors for each job is also reduced, enabling more efficient use of human resources.

• Improved work efficiency and speed: Time spent setting up and dismantling heavy equipment, traveling between survey points, and producing and checking drawings is drastically reduced. Positioning data are shared to the cloud on site, shortening waiting times for later processes. As a result, the time required for layout marking is greatly reduced compared to conventional methods, compressing overall construction lead time.

• Improved accuracy and quality assurance: Centimeter-level accuracy achieved by RTK is a higher precision level than tape measures or standalone GPS can deliver. Smaller errors mean fewer remeasurements and touch-ups, stabilizing the final form quality of constructed works. Because work is based on digital data, anyone can reproduce the design quality, contributing to flattening and standardizing quality control.

• Enhanced safety: Because the work can be completed by one person, the risk of accidents caused by incorrect signals or communication mistakes between workers is reduced. Reducing the need to carry heavy surveying equipment also decreases hazardous tasks such as transporting gear across unstable scaffolding. AR guidance allows workers to check surrounding conditions while working, making it easier to combine marking tasks with situational safety checks. Overall, this technology contributes to site safety alongside efficiency improvements.

• Skill transfer and reduced training costs: Smartphone app operation is intuitive and can be learned quickly by those without specialized surveying instrument training. Without relying on veteran surveyors’ experience and intuition, anyone can perform the same layout work by following app guidance, reducing task dependence on individuals. Newcomers can achieve a certain level of accuracy, closing skill-transfer gaps. Consequently, training costs and time are reduced and the organization can maintain stable technical capability.

As described above, single-person layout using RTK positioning and AR guidance is an innovative method that significantly contributes to labor reduction, efficiency, and safety on site. This style, unconstrained by conventional thinking, is expected to play an increasingly important role in the ongoing digitalization of construction sites. In fact, introducing solutions such as LRTK technology that combine smartphones and compact positioning devices turns a handheld device into a high-precision surveying instrument, enabling anyone to easily perform layout marking and surveying. For construction sites facing labor shortages and productivity challenges, the workflow that AR and high-precision positioning enable for single-person layout will be a powerful ally for achieving on-site DX.