LRTK Technology Enabling One-Person Layout Marking: Promoting Labor Savings with AR and High-Precision Positioning

Basics of Layout Marking and Challenges with Traditional Methods

“Layout marking” (墨出し) refers to the work on construction and civil engineering sites where reference lines and position marks are indicated on the site based on the design drawings. In building construction, this includes marking the positions of foundations and the centerlines of columns and walls; in civil engineering, it includes indicating the centerline of a road or the installation position of a structure on the ground. This is an extremely important process for ensuring constructed elements are placed in 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 project.

However, traditional layout marking work has had various challenges. The main points are as follows:

• Equipment setup is time-consuming: Layout marking has commonly relied on specialized surveying instruments such as total stations and levels. Using these requires setting up tripods, installing equipment, and aligning level and reference points, so a considerable amount of time and effort is needed before work can even begin.

• Multiple people are required: When using surveying equipment, at least two people or more are usually necessary. For example, with a total station one person operates the instrument while another stands at a distant position holding a prism or staff as the target. If there are many marking points, traveling around the site becomes a major burden, and in some cases a team of three including a recorder was required.

• Risk of measurement errors and rework: Traditional manual methods using tapes and string lines can lead to small reading mistakes or misaligned markings. If dimensions from the reference are recorded incorrectly, it can cause position mismatches in later stages and lead to rework. This can result in schedule delays and quality degradation.

• Outdoor visibility problems: Laser line projectors are sometimes used to project lines or points, but laser light can be hard to see outdoors on sunny days. On bright sites, projected reference lines may not be visible, and extra steps such as using a receiver to locate the position may be necessary.

• Labor shortage and skill transfer: A major problem is the steadily declining number of skilled technicians capable of accurate layout marking and surveying. Operating advanced surveying equipment and the experience-based judgment that comes with it cannot be acquired overnight; relying on a few veterans risks halting work when they are absent. It is also difficult to attract young talent industry-wide, and relying on manpower-intensive traditional methods limits productivity improvements and workstyle reforms.

Thus, traditional layout marking requires significant time and personnel to maintain high accuracy, and efficiency can drop depending on conditions. Recently, a new approach that leverages modern technologies to solve these issues has attracted attention.

Elements That Enable One-Person Layout Marking (RTK Positioning, AR Guidance, etc.)

With recent advances in digital technology, accurate layout marking by a single person is becoming achievable. The key is the combination of RTK technology, which delivers centimeter-level high-precision positioning, and AR (augmented reality) guidance, which can intuitively indicate 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.). While a typical smartphone GPS can have errors of several meters, connecting an RTK-capable compact GNSS receiver to a smartphone and receiving correction information from a base station enables positioning accurate to a few centimeters. For example, in Japan, using Michibiki (QZSS)’s centimeter-level augmentation signals or GNSS reference station networks via the internet (VRS method) allows stable outdoor positioning with horizontal accuracy of about 1–2 cm.

• Intuitive position guidance with AR: AR (Augmented Reality) technology can overlay digital design data onto the real-world view. When viewing the site through a smartphone or tablet camera, lines and points from the design drawings appear as virtual markers overlaid on the live image. For instance, if a point indicates “place a column at this foundation position,” an AR display can show a virtual stake or line on the screen. The worker can then align the real ground or structure with these virtual markers, eliminating the need to compare paper drawings with the site and rely on intuition.

• Utilizing smartphone-built LiDAR sensors: Some modern smartphones are equipped with LiDAR sensors that measure distances using infrared lasers. By scanning the surrounding floor and walls to create 3D data, LiDAR improves the accuracy of AR displays. Combined with RTK for highly accurate self-positioning, virtual objects in AR are less likely to drift even across wide outdoor areas, enabling precise projection of virtual lines with minimal alignment steps. Because models can be placed based on GNSS coordinates even in open land with few reference points, it becomes possible to achieve pinpoint location marking that was difficult using conventional methods.

By combining these technical elements, layout marking tasks that used to rely on multiple people can be supported digitally so that one person can efficiently and accurately perform layout marking. In particular, linking a smartphone with an ultra-compact RTK-GNSS receiver (such as solutions called “LRTK”) makes centimeter-level positioning possible with palm-sized equipment. Site staff can perform simple surveying themselves and use AR to confirm marking positions based on that data.

Practical Workflow Supported by High-Precision Positioning

So, what does the actual workflow on site look like when using high-precision positioning and AR for layout marking? Below is a main-step outline of a one-person workflow that differs from traditional methods.

• Data preparation and positioning setup: First, import the design data for the layout target (e.g., foundation centerlines or structure placement drawings) into an app on the smartphone. At the same time, set up the site’s reference coordinate system. If there are known reference stakes, input those coordinates into the app or measure them with the RTK receiver to align the reference. After preparation, power on the RTK-GNSS receiver and begin acquiring satellite positioning. Within several tens of seconds you can obtain an RTK “FIX” solution (positioning accurate to 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. The chosen virtual objects (markers or lines corresponding to the selected locations) are overlaid on the site view through the camera. For example, a point may appear as a virtual pin or stake on the ground, and a line may appear drawn along the floor. The worker walks slowly while watching the smartphone screen and is guided to approach the displayed AR marker. The screen can also show arrows and distance information from the current location to the target, 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 display is aligned with an actual point on the ground. That point is exactly the layout position indicated by the design. While confirming the position on the smartphone, the worker marks the site using chalk or spray paint with one hand. For lines, the worker can snap a chalk line along the AR virtual line to mark according to the drawings. Tasks that previously required survey staff to stretch strings or measure with tapes are now completed simply by following the on-screen guidance.

• Recording and sharing survey data: If needed, the coordinates of marked points can be measured on the spot and saved as digital records. By pressing a button in the smartphone app, the current RTK coordinates can be stored, annotated with a name or note, and uploaded to the cloud, leaving a history of what was marked where. Taking screenshots or photos of the AR display also preserves images showing the virtual stake aligned with the real ground, which can be reviewed later in the office to reconfirm positions. In this way, the worker can handle layout marking, surveying records, and reporting data all by themselves, which is another advantage of using digital technology.

This sequence enables one person to perform accurate layout marking without undue strain. There is no need to repeatedly carry and set up heavy equipment or coordinate calls with others for measurements, and many points can be marked in a short time.

A New Workflow of Layout Marking Integrated with Smart Construction

High-precision positioning plus AR layout marking not only enables one-person operation, but also has high compatibility with the digitalization of overall construction (smart construction). A new workflow that consistently uses data connects previously separate surveying, layout marking, and other construction processes seamlessly.

First, efficiency improves when digital data is integrated from the design stage through construction management. Traditionally, numbers from paper drawings were read and manually transferred during layout marking, but AR layout marking allows CAD and BIM design data to be used directly on site. Because there is no manual transcription of drawing information, transcription errors are eliminated and the design intent is conveyed directly to the field.

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

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

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

Concrete Benefits for Labor Reduction, Efficiency, and Safety

Finally, let’s summarize the concrete benefits that this new layout marking method brings to the site. One-person, high-precision layout marking delivers significant advantages compared to traditional methods in the following ways:

• Solving labor shortages through reduced manpower: Layout marking and surveying that used to require 2–3 people can now be completed by one person, enabling substantial staff reductions. Sites suffering from chronic labor shortages can proceed with multiple tasks in parallel with fewer workers. It also reduces the need to hire external surveying specialists for each job, leading to more efficient use of human resources.

• Improved work efficiency and speed: Time spent setting up and packing heavy equipment, traveling between measurement points, and preparing and checking drawings is drastically reduced. Positioning data is shared to the cloud from the site, shortening wait times for subsequent processes. As a result, the time required for layout marking is greatly shortened compared to conventional methods, which can compress the overall construction lead time.

• Improved accuracy and quality assurance: Centimeter-level layout marking enabled by RTK achieves accuracy levels unattainable with tape measures or standalone GPS. Smaller errors mean fewer re-measurements and corrections, leading to more consistent final construction quality. Because the work is based on digital data, the design quality can be reproduced by anyone, standardizing and leveling quality control.

• Enhanced safety: Since tasks can be completed by one person, the risk of accidents caused by miscommunication or incorrect signals between workers is reduced. Reducing the need to carry heavy surveying equipment also lowers the risk associated with moving gear across unstable ground. AR guidance helps workers monitor their surroundings while they work, making it easier to balance marking tasks with surrounding safety checks. Overall, this technology contributes to both efficiency and safety on site.

• Skill transfer and reduced training costs: Smartphone app operation is intuitive, enabling people without formal surveying training to learn how to use the system in a short time. The app’s guidance allows anyone to perform layout marking without relying on the experience or intuition of veteran surveyors, reducing task dependence on individuals. New workers can achieve a consistent level of accuracy, helping to close skill gaps in succession. As a result, organizations can cut costs and time for education and training while maintaining stable technical capability.

In summary, one-person layout marking using RTK positioning and AR guidance is an innovative approach that greatly contributes to labor reduction, efficiency improvements, and safety management on site. This nontraditional style is expected to play an increasingly important role in the ongoing digitalization of construction sites. Indeed, adopting solutions such as LRTK technology, which combines a smartphone with a compact positioning device, turns a handheld device into a high-precision surveying tool, allowing anyone to easily perform layout marking and surveying. For construction sites facing labor shortages and seeking productivity gains, the one-person layout marking workflow enabled by AR and high-precision positioning is a powerful ally for realizing on-site DX.