LRTK-changing layout marking work: Accurate positioning by one person made possible with GNSS high-precision positioning

Table of contents

• Challenges of conventional layout marking work

• Centimeter-level high-precision positioning with GNSS and RTK technology

• Layout marking tools anyone can use through smartphone integration

• Intuitive position guidance enabled by AR technology

• Cloud sharing and integration with smart construction

• New layout marking procedures (how far one person can go)

• Main benefits brought by high-precision layout marking

• Easy simple surveying starting with LRTK

• FAQ

Layout marking, an indispensable task on construction and civil engineering sites, is a critical process that influences the quality and progress of work. However, conventional layout marking has required advanced skills to read drawings, considerable manpower, and time, placing a heavy burden on sites. Recently, a new layout marking approach using GNSS (Global Navigation Satellite Systems) has attracted attention. By combining satellite positioning technology and digital tools, an era is approaching in which anyone can accurately set out positions alone.

This article first organizes the conventional challenges of layout marking and explains the use of GNSS as a solution. Next, we look in detail at centimeter-level high-precision positioning using RTK, the ease of operation enabled by smartphone integration, intuitive guidance via AR (augmented reality), and the benefits of data linking through cloud sharing. We also introduce the workflow for solo layout marking when these new technologies are introduced, and finally focus on the simple surveying tool “LRTK” that realizes these capabilities.

Challenges of conventional layout marking work

Layout marking is the process of accurately transferring the positions and reference lines from design drawings to the field in construction and civil engineering works. For example, the centerlines of building walls and the installation positions of equipment are marked on floors or the ground to serve as construction references. Traditionally this has been done using tools such as ink lines and chalk, tape measures, and even surveying instruments like laser markers and total stations. Because the accuracy of layout marking directly affects the overall quality of construction, even small errors are unacceptable, and the work requires the skilled techniques of experienced craftsmen.

However, conventional layout marking methods have the following challenges.

• Preparation of equipment is time-consuming: When using dedicated surveying instruments such as total stations or levels, the equipment must be mounted on tripods, leveled, and aligned with known points, requiring time and effort for setup before work can begin.

• Multiple people are required for the task: Surveying-based layout marking is usually performed by two or more people. Typically, one person operates the instrument while another holds a staff (rod) or prism at a distant point. Moving around the site is time-consuming, and in some cases three people including a recorder may be needed.

• Risk of errors due to human mistakes: Manual transfer of dimensions using tape measures or string lines is prone to small misreadings or mark placement shifts. Mistaking dimensions from a reference can lead to misaligned positions, potentially causing rework and having to redo construction.

• Laser is hard to see outdoors: Laser markers that project reference lines can be hard to see in bright outdoor conditions. Under direct sunlight, the projected line may not be visible to the naked eye, requiring the use of receivers to locate it, which adds work.

• Dependence on skilled workers and labor shortage: High-precision layout marking requires experienced technicians, but the number of such veterans is decreasing. Relying on a single veteran risks halting other work when that person is absent. The shortage of young skilled workers is also serious, and productivity improvements are limited if conventional methods are maintained.

As described, conventional layout marking requires substantial labor and specialist skills, posing issues for staffing and work efficiency. A promising approach to solve these problems is the use of GNSS terminals for layout marking.

Centimeter-level high-precision positioning with GNSS and RTK technology (cm level accuracy (half-inch accuracy))

A GNSS terminal is a device that receives signals from multiple satellite positioning systems such as GPS and GLONASS to determine its position. Smartphones also have GPS built in, but their usual positioning accuracy is on the order of several meters, which is insufficient for construction site layout marking. However, by using the RTK (Real Time Kinematic) method, positioning errors can be reduced to within a few centimeters.

In RTK positioning, correction information is obtained from a site-installed reference station (base station) or reference-point data delivered via the Internet, and the moving GNSS terminal’s position is corrected in real time. By correcting error factors in the satellite signals, horizontal positions can achieve accuracy on the order of ±1–2 cm (±0.4–0.8 in), and vertical accuracy can be on the order of a few centimeters. Precision positioning that once required expensive surveying instruments can now be easily accessed with a small GNSS receiver and a communication environment.

In Japan, infrastructure supporting RTK is also well established, such as the Ministry of Land, Infrastructure, Transport and Tourism’s network of electronic reference stations and the quasi-zenith satellite system “Michibiki” providing centimeter-level augmentation services (CLAS) (cm level accuracy (half-inch accuracy)). With a compatible GNSS receiver, it is possible to receive high-accuracy correction signals directly from satellites even at sites in mountainous areas where cellular communication is unavailable.

By using RTK-enabled GNSS equipment for layout marking, the coordinate values recorded in design drawings (for example, intersection points of building centerlines) can be specified directly as target points on site. The GNSS terminal continuously measures its position to the centimeter level while calculating and navigating the direction and distance to the specified coordinate. Therefore, it can directly guide you to the design location. There is no need to follow distance measures from a reference string with a tape measure or repeatedly re-measure positions. Because field positions are linked to drawings based on the global coordinate system obtained from GNSS satellites, cumulative errors between measurement points are eliminated. RTK’s precise positioning strongly supports the digitization and high-precision of layout marking work.

Layout marking tools anyone can use through smartphone integration

Recent GNSS terminals increasingly support integration with smartphones and tablets. By installing a dedicated app on a smartphone and connecting a small GNSS receiver, an everyday smartphone can quickly become a high-precision surveying instrument. In the past, surveyors had to operate specialized controllers and spend time on initial setup, but today, a simple interface on the smartphone screen allows starting and stopping positioning and saving data. Because it can be handled intuitively without special expertise, it can be said to be a surveying tool anyone on site can use.

Smartphone integration offers more than ease of operation. By leveraging the smartphone’s various functions, convenience and efficiency are greatly improved. For example, you can digitally record date/time, point names, and notes simultaneously with positioning, or take site photos with the smartphone camera and save them with location information on the app. There is no need to keep handwritten field books; all acquired data is digitized and automatically synchronized to the cloud, eliminating the need to transcribe values later. Measured coordinates are instantly converted and displayed in commonly used public coordinate systems (plane rectangular coordinates and elevations), so usable numbers can be checked immediately without manual calculations. These features allow site personnel to perform quick measurements and checks themselves on the spot, reducing the time spent “waiting for the survey team to deliver results.”

Moreover, the smartphone + GNSS terminal combination achieves high portability not found in large conventional surveying devices. The compact devices that fit in a pocket can be carried and used whenever needed, improving site mobility. Minor layout marking tasks that were previously deferred can be handled “while you’re there,” contributing to productivity improvements.

Intuitive position guidance enabled by AR technology

Combining GNSS terminals with smartphone apps also enables position guidance using AR (augmented reality) technology. AR overlays digital information on the camera view of a smartphone or tablet. Familiar examples include the game Pokémon GO and AR navigation in mapping apps, and similarly on construction sites it can visually indicate “please mark here.” If design coordinate data (target points and reference lines) are preloaded into the app, those points and lines can be overlaid as virtual objects on the live site view. Workers can understand at a glance where to mark simply by looking at the smartphone screen. Because there is no need to mentally match drawings and the site, even inexperienced personnel can accurately identify positions without hesitation.

Like an “in-site car navigation” for construction, AR guidance lets workers walk around the site with a smartphone to be guided to the target position. As you approach a target, the remaining distance, such as “X cm to go,” is displayed, and when you reach the target the marker on the screen perfectly aligns. In some cases, planned wall lines or piping routes can be visualized on the ground in AR, allowing layout marking along those virtual lines. This visual feedback enables accurate layout marking by anyone without relying on a veteran’s intuition.

Recently available smartphones with built-in LiDAR sensors further improve AR accuracy. LiDAR scans surrounding shapes with infrared lasers to create 3D data, and combining this with AR allows even bare lots without visible landmarks to have virtual objects precisely aligned in real space. Together with high-precision GNSS self-positioning, AR display drift is less likely even on large sites, enabling pinpoint position marking with minimal effort.

Cloud sharing and integration with smart construction

GNSS + smartphone layout marking is notable not only because it enables solo work, but also for its high compatibility with overall construction digitalization (smart construction). This is because surveying and layout marking processes can be seamlessly connected with other construction processes through data.

First, efficiency increases because digital data can be used consistently from the design stage through construction management. Whereas people used to read values from paper drawings and perform layout marking, AR layout marking allows CAD and BIM design data to be used directly on site. Eliminating the transcription process prevents copy errors and conveys the designer’s intent directly to the field.

Also, cloud integration enables real-time information sharing between the site and the office. Measured positioning data, photos, and notes captured on site can be uploaded to the cloud with one tap and plotted on a map instantly. Supervisors and designers in a remote office can immediately grasp the latest status and, if necessary, send additional instructions back to the site. The traditional hassle of bringing measured values back to the office and updating drawings or sharing them by email is unnecessary. Timely information sharing speeds up construction management and helps detect and correct errors early.

Furthermore, when site coordinates are unified by RTK positioning, it is easier to align with other smart construction technologies such as ICT construction machinery and drone surveying. For example, in road construction, machine guidance for heavy machinery can reduce the need for staking, while AR layout marking can be used for spot checks. Sharing the same 3D design data among people and machines reduces the need for marking and enables low-error construction.

Applying high-precision layout marking in a digital workflow aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of [i-Construction](https://www.mlit.go.jp/tec/i-construction/). *i-Construction* aims to improve productivity through ICT utilization across surveying, design, construction, and inspection, and labor-saving and upgrading of layout marking is an important theme. Solo layout marking using RTK and AR is expected to be a concrete solution that strongly supports on-site DX (digital transformation).

New layout marking procedures (how far one person can go)

So how is solo layout marking realized by high-precision positioning and AR actually performed? Below is a workflow that differs from traditional methods, outlined by main steps.

• Prepare design data and set up positioning: First, preload the design drawing data to be marked (foundation centerlines, equipment layout, etc.) into the smartphone app. At the same time, set the coordinate system to be used on site. If there are reference stakes with known coordinates, input their coordinate values into the app or measure them with GNSS to align the reference. Once ready, power on the GNSS receiver and start satellite positioning. Within tens of seconds the RTK “FIX solution” (centimeter-level solution) is obtained and high-precision positioning mode is entered.

• Position guidance with AR navigation: On the smartphone app, select the point or line to be marked and switch to AR display mode. Virtual markers or lines corresponding to the selected targets are overlaid on the camera view of the site. For example, selecting a point may show a virtual pin or stake on the ground, and selecting a line may draw a virtual line along the floor. The worker walks slowly while looking at the smartphone screen, moving toward the displayed AR marker. Arrows and distance information to the target are shown on the screen, so it is intuitive which direction and how many meters to move.

• Marking at the target position: Upon reaching the target point, the virtual marker on the smartphone screen aligns exactly with a point on the real ground. That spot is precisely the layout marking point indicated in the design. The worker confirms the position on the smartphone and marks the site with chalk or spray paint using one hand. For lines, the worker can snap a chalk line along the virtual line displayed in AR, completing the layout according to the drawing. Tasks that used to require a surveying team to string lines or measure with tape measures are now completed simply by following on-screen instructions.

• Recording and sharing measurement data: If necessary, the worker can measure and digitally record the coordinates of the marked points on the spot. With one tap in the smartphone app, current RTK positioning values can be saved, the point named and annotated, and uploaded to the cloud. Saved points and information are recorded on the cloud map immediately, creating a history of “which points were marked.” Taking a screenshot of the AR display also serves as evidence showing the virtual marker aligned with the real world. Being able to obtain survey records and reporting data simultaneously with layout marking is a major advantage of digital technology.

With this workflow, one person can carry out accurate layout marking without undue difficulty. There is no need to repeatedly set up heavy surveying equipment or coordinate with other workers, and you can quickly proceed from point to point.

Main benefits brought by high-precision layout marking

The new layout marking method using RTK positioning + AR guidance brings significant effects on site. The main benefits are summarized below.

• Solve labor shortages through reduced manpower: Layout and surveying tasks that previously required 2–3 people can now be completed by one person, enabling substantial labor reduction. Sites suffering chronic labor shortages can run more tasks in parallel with fewer personnel. The need to hire outside surveying contractors each time is also reduced, allowing more efficient use of human resources.

• Improved work efficiency and speed: Time spent setting up and dismantling heavy equipment, moving between measurement points, and checking drawings is greatly reduced. The time required for layout marking itself is dramatically shortened, which can shorten the overall construction schedule. Fewer measurement mistakes mean less rework, and instant cloud sharing of positioning data shortens waiting times for subsequent processes. Overall productivity and construction speed improve significantly.

• Improved accuracy and quality assurance: RTK centimeter-level positioning achieves an accuracy level not possible with tape measures or standalone GPS. Accurate first-time layout marking reduces re-measurement and corrections, stabilizing final construction outcomes. Because the work is based on digital data, anyone can reproduce the design results, contributing to standardized quality control.

• Enhanced safety: Solo completion of tasks reduces the risk of accidents caused by miscommunications or signaling errors between workers. Dangerous tasks such as transporting heavy surveying equipment to unstable scaffolding are reduced. AR guidance also helps workers keep situational awareness while marking, enabling both safety checks and work to be performed more easily. Thus the technology contributes not only to efficiency but also to on-site safety.

• Skills transfer and reduced training costs: Smartphone-centered operation is easy to understand, and workers can become proficient in a short period even without training on specialized surveying equipment. Because the app guides the user, reliance on veterans’ intuition is reduced and the work becomes less person-dependent. Newcomers can perform tasks to a certain accuracy, narrowing the skills gap. As a result, training costs and time decrease and the organization can maintain stable technical capabilities.

As described, solo layout marking using RTK positioning and AR guidance is an innovative method that greatly contributes to labor reduction, efficiency, and safety on site. This style, unconstrained by conventional norms, will play an increasingly important role in the digitalization of the construction industry.

In practice, adopting solutions such as LRTK technology, which combines a smartphone with an ultra-compact positioning device, makes your handheld device a high-precision surveying instrument so that anyone can easily perform layout marking and surveying. For construction sites facing labor shortages and productivity challenges, the solo layout marking workflow enabled by RTK and AR is a powerful ally for on-site DX.

Easy simple surveying starting with LRTK

A concrete example that embodies these latest technologies and has recently attracted attention is the LRTK GNSS positioning system. LRTK is a solution composed of an ultra-compact RTK-GNSS receiver and a smartphone app; attaching this receiver to a smartphone transforms a palm-sized device into a centimeter-level accurate all-purpose surveying instrument. It is very lightweight and compact—weighing on the order of a few hundred grams—making it easy to carry on site. Yet it achieves high precision comparable to surveying instruments using RTK positioning, and acquired data are automatically synced to the cloud. It includes coordinate navigation functions for layout marking and AR guidance, enabling even beginners to reach target points without confusion.

LRTK’s uses extend beyond basic control point surveying and layout marking: it supports 3D point cloud measurement of the surroundings using the smartphone camera or LiDAR, and AR-based on-site composite display of design models. It also has functions for measuring distance, area, and volume, covering most on-site digital measurement needs with a single versatile surveying tool.

Its greatest feature is that it is an easy-to-use surveying tool anyone can operate. It is relatively inexpensive as a specialized instrument and easy to introduce; with just a smartphone, one person per device can bring it to the site. Intuitive operation means that tasks previously handled by dedicated surveying departments or outsourced can now be performed by site staff whenever needed. As a result, the previously mentioned benefits of labor reduction and efficiency improvements can be realized quickly. LRTK is truly a device that accelerates on-site DX and transforms layout marking into a task anyone can do.

Why not update your layout marking practices with these new technologies rather than clinging to old methods? By using the high-precision, easy-to-use LRTK positioning tool, you can experience fast and accurate work that overturns conventional wisdom. Take this opportunity to introduce GNSS-based smart layout marking and experience the effects of precision position guidance on site. It will surely open a new door to improved productivity and quality.

FAQ

Q: What is LRTK? A: LRTK is a high-precision positioning system composed of an ultra-compact RTK-GNSS receiver and a smartphone app. Attaching the dedicated receiver to a smartphone enables easy centimeter-level positioning, which can be used for layout marking and surveying.

Q: What is the difference between GNSS and GPS? A: GPS is the name of the U.S. satellite positioning system, while GNSS is a general term that refers to all satellite positioning systems including GPS. Others include Russia’s GLONASS and Europe’s Galileo; GNSS terminals use signals from these systems to determine position. In general, a “GNSS surveying instrument” refers to equipment that can use multiple satellite systems, not just GPS.

Q: What is RTK? A: RTK (Real Time Kinematic) is a technique that improves GNSS positioning accuracy in real time. It receives correction information from a reference station and applies corrections to GNSS measurements to achieve centimeter-level accuracy. It reduces typical GPS errors of several meters down to a few centimeters, making it essential for precise layout marking and surveying.

Q: How accurate is the positioning? A: Under favorable conditions, when RTK positioning is established, horizontal accuracy is on the order of ±1–2 cm (±0.4–0.8 in) and vertical errors are on the order of a few centimeters. This is a level of accuracy not achievable with traditional manual methods or standalone GPS. However, positioning accuracy can temporarily degrade due to obstructions or atmospheric conditions.

Q: What do I need to use LRTK? A: Basically you need a smartphone (or tablet) and an LRTK receiver. Connect the smartphone and receiver, launch the dedicated app, and start positioning. To obtain RTK correction information, you also need a network connection (cellular or pocket Wi‑Fi) or the ability to receive the quasi-zenith satellite system “Michibiki” CLAS signals. Note that sufficient satellite reception is essential for high-precision GNSS positioning, so it is assumed the device will be used outdoors with an open sky.

Q: Are the benefits worth the implementation cost? A: Yes. Smartphone GNSS positioning like LRTK can significantly reduce the need for large traditional surveying equipment and two-person crews, lowering personnel costs. There is no longer a need to arrange specialist survey staff each time or purchase expensive total stations, so you can expect operational cost savings that exceed the initial investment. Indirect cost benefits from shortened construction schedules and improved quality are also substantial, making the overall value of implementation ample.