Benefits of Using GNSS for Layout Marking: Improved Accuracy, Time Savings, and Reduced Manpower

Table of Contents

• Improved Accuracy: Making layout marking more precise with GNSS

• Time Savings: Speeding up layout marking with GNSS

• Reduced Manpower: Enabling single-person layout marking with GNSS

• Introducing simple surveying with LRTK

• FAQ

The essential layout marking work at construction and surveying sites is a critical process that affects project quality and schedule. Layout marking refers to transferring reference lines and positions from drawings to the field in construction and civil engineering. Because it is required at every stage—from foundation work to finishing and equipment installation—its accuracy and efficiency directly influence the overall quality and timeline of the project.

However, traditional layout marking has required skilled interpretation of drawings, significant manpower, and time, placing a heavy burden on sites. Specifically, the following issues have been pointed out:

• High manpower and time burden: Layout marking and surveying work are typically performed by two or more people, with one operator handling the surveying equipment and another person marking points at remote locations. Installing and moving large, heavy equipment (such as total stations on tripods) is time-consuming, and marking numerous points over a wide site can take a full day. Because layout marking is required at each stage, the total amount of time spent across a project is enormous.

• Dependence on skilled workers: Accurate layout marking requires the ability to read drawings and measurement skills, so much of the work depends on veteran craftsmen. If such personnel are lacking or absent, other work can be halted while waiting for layout marking. With the aging of skilled workers and a shortage of younger technicians in recent years, securing people with expert layout-marking skills has become a major challenge.

• Accuracy management and safety issues: Manual layout marking carries risks of dimensional errors and position deviations caused by human mistakes. In situations that require millimeter-level precision—such as setting foundation positions or pile driving—manual methods have limitations. In addition, marking work in areas where heavy machinery is operating requires careful attention to worker safety. These accuracy and safety concerns are also problems at sites.

As described above, conventional layout marking required tremendous effort and skilled technicians, posing major challenges in efficiency and human resources. A promising solution to these problems is the new approach of using GNSS (Global Navigation Satellite Systems, technologies that utilize multiple satellite positioning networks such as GPS and GLONASS) for layout marking. By using satellite positioning technology in RTK (real-time kinematic) mode, centimeter-level accuracy (half-inch accuracy) can be achieved, and by combining dedicated equipment with smartphones, intuitive AR (augmented reality) guidance display and cloud-based data sharing become possible. In short, the introduction of GNSS can simultaneously realize improved accuracy, time savings, and reduced manpower for layout marking. This article explains these benefits in detail. At the end, we introduce the latest simple surveying tool, LRTK, guiding you to an easy-to-adopt smart layout-marking method.

Improved Accuracy: Making layout marking more precise with GNSS

The most important factor in layout marking is accuracy. By using GNSS—especially RTK (real-time kinematic) positioning technology—you can achieve high accuracy that was difficult with traditional manual methods or standalone GPS. The error of standalone GPS positioning is said to be about 5-10 m (16.4-32.8 ft) under normal conditions, but with RTK, real-time correction information is communicated between a base station and a rover to reduce errors to about horizontal ±1-2 cm (±0.4-0.8 in) and vertical ±3-4 cm (±1.2-1.6 in). This allows positioning with precision sufficient for construction sites.

When RTK precise positioning is used for layout marking, coordinate values recorded in design drawings (for example, intersection points of building gridlines) can be used directly as site target points. A GNSS receiver continuously measures its position to centimeter accuracy and calculates the difference from the specified target coordinates to guide the operator. There is no need to repeatedly measure dimensions from reference marks or string lines; you can directly link design coordinates to the field for positioning. Because there are no intermediate calculations or cumulative errors, you can reliably mark points exactly as designed. In addition, GNSS-derived positions are inherently given in a global geodetic coordinate system, so you do not need to worry about accumulation of errors from coordinate transformations typical of traditional methods that transfer positions from local reference points.

However, it is necessary to choose the appropriate method depending on the required accuracy level. Optical instruments such as total stations can achieve millimeter accuracy at short distances, so for tasks that require strict millimeter-level precision—such as bridge alignment or precision machine centering—optical methods still have an advantage. For general civil engineering and building layout marking, however, RTK-GNSS is sufficient. GNSS positioning truly shines in wide-area surveys and cases requiring alignment to absolute coordinates. Recent GNSS receivers support multiple satellite systems and apply error-model corrections, allowing stable centimeter-level accuracy. The old assumption that “GPS has large errors and cannot be used for layout marking” is being overturned.

In Japan, infrastructure supporting RTK positioning has also matured, such as the Geospatial Information Authority of Japan’s reference station network and the quasi-zenith satellite “Michibiki,” which provides centimeter-level positioning augmentation services (CLAS) (half-inch accuracy). Therefore, if you have a compatible GNSS receiver, you can obtain centimeter-level positioning in real time nationwide without preparing a dedicated base station.

Time Savings: Speeding up layout marking with GNSS

Using GNSS dramatically shortens the time required for layout marking. Traditionally, much time was spent installing surveying equipment, ensuring line-of-sight, and moving gear. For example, surveying with a total station requires leveling and height adjustments each time the tripod is set up and repeated observations for backsight and foresight, so surveying a large site could take days. With GNSS, these tasks of fixed installation and securing line-of-sight are unnecessary. A worker carrying a high-precision GNSS receiver can walk the site and measure and guide point coordinates one after another. As long as satellites can be tracked, the theoretical coverage is unlimited, and a single antenna can cover a large area. After finishing observations at one location, the operator can immediately move to the next point and continue measuring, enabling continuous one-person operation.

In an actual comparative experiment, conventional optical surveying-based layout marking reportedly took about six times longer than a new method using GNSS and AR technology. That illustrates just how much faster GNSS-based methods can be.

By reducing personnel and procedural steps, the number of points that can be obtained on site increases dramatically. Even sites lacking experienced surveyors can have less-skilled staff use GNSS equipment to complete a substantial portion of layout marking, reducing wasted downtime caused by “waiting for surveying.” Measured data are digitally recorded on site and can be saved to the cloud, eliminating the need to return to the office to create drawings. It is also easy to share data immediately with stakeholders, reducing the waiting time for survey results. Speeding up the layout-marking process creates more flexibility for subsequent construction scheduling and can shorten the overall project timeline.

Thus, introducing GNSS significantly improves the productivity of layout marking. Because more work can be done in limited time, cost savings can also be expected. If you internalize layout-marking work that was previously outsourced by acquiring GNSS equipment, you can reduce outsourcing fees and the hassle of schedule coordination. Faster feedback of survey results enables quicker on-site decision-making, which in turn improves overall project efficiency.

Reduced Manpower: Enabling single-person layout marking with GNSS

The greatest impact of GNSS for layout marking is reduced manpower. As noted above, what used to require two to three people for surveying and layout marking can now be completed by one person. This has significant implications as a countermeasure against the serious labor shortage in the construction industry. Being able to accomplish more work with fewer people increases responsiveness even when staffing is limited.

Also, if site staff themselves can perform layout work using GNSS equipment even without a dedicated surveying technician on site, it helps break the dependency on skilled veterans. If anyone can perform accurate layout marking, concerns about skill transfer during generational change are reduced. Systems that link smartphones and GNSS terminals not only display positioning results on the screen in real time but can also use AR to overlay target positions on camera images. For example, the smartphone screen can display arrows or virtual lines indicating “mark here,” so even inexperienced workers can identify and mark positions accurately without hesitation. There is no need to mentally map points on drawings to the field; intuitive layout marking is possible without veteran intuition and experience.

This AR guidance is like a “car navigation system for construction sites.” Workers simply walk the site with a smartphone, and arrows or guide lines on the screen lead them to the target. As they approach the target, the remaining distance is displayed as “○ cm to go,” and when they reach the specified position a marker on the screen overlaps and aligns. These visual feedback cues allow accurate layout marking to be performed by anyone without relying on veteran intuition.

Alongside reduced manpower, digitization of work also improves overall efficiency and quality. Previously, manually recorded field notes had to be later transcribed into CAD drawings, but with GNSS you can acquire and share information as digital data from the beginning. Combining GNSS positioning with smartphones allows you to attach high-precision location information to photos to create geotagged survey photos or integrate with LiDAR scanners to obtain detailed 3D point clouds. Spatial data acquisition that once required separate equipment and specialized methods can now be realized with all-in-one digital tools. Furthermore, managing and sharing data through cloud platforms enables remote site monitoring and immediate checks of as-built conditions and earthwork volume calculations from acquired data. The large amount of location information obtained with GNSS is not only useful for drawing creation but also contributes to streamlining construction management and accumulating data for maintenance.

Reducing the number of people involved also decreases the number of personnel entering areas where heavy equipment is operating, contributing to improved safety. The reduction in manpower and digitization of layout marking align with the Ministry of Land, Infrastructure, Transport and Tourism’s “i-Construction” initiative and the broader construction DX movement, and their importance will continue to grow.

Introducing simple surveying with LRTK

As described above, using GNSS brings remarkable efficiency gains and high precision to layout marking. Still, some may feel that adopting it in-house is difficult. In the past, RTK-GNSS surveying equipment was often large and expensive, and operation required specialized knowledge. However, the recently introduced GNSS terminal called LRTK solves these challenges at once. LRTK is a system composed of an ultra-compact RTK-GNSS receiver and a smartphone app; by attaching this receiver to a smartphone and connecting via Bluetooth or wired connection, a palm-sized device quickly becomes a centimeter-level surveying instrument (centimeter-level accuracy (half-inch accuracy)). Weighing only a few hundred grams, it is extremely lightweight and easy to carry to the site. The era in which RTK surveying required fixed equipment weighing several kilograms is over; you can now carry it with your smartphone. Despite its compact size, it achieves the high precision associated with RTK typically used by surveyors, and the acquired data are automatically synchronized to the cloud. It includes coordinate navigation functions for layout marking and AR guidance, allowing even first-time users to mark target points without confusion.

By adopting advanced tools like LRTK, you can immediately enjoy the benefits of reduced manpower and increased efficiency described above. LRTK is exactly the kind of device that accelerates on-site DX (digital transformation) and transforms layout marking into a task anyone can perform. When introducing high-precision simple surveying to the field, consider adopting such advanced tools. You should be able to experience a speedy and accurate workflow that overturns conventional assumptions.

FAQ

Q. What level of accuracy can be achieved with GNSS for layout marking? A. Using RTK GNSS positioning, you can achieve approximately ±1-2 cm (±0.4-0.8 in) horizontally and ±3-4 cm (±1.2-1.6 in) vertically. This accuracy is generally sufficient for typical construction-site layout marking. However, for special cases that require millimeter-level precision, precise measurement with optical surveying instruments may still be necessary.

Q. Can GNSS surveying be performed in rainy weather or in environments with many obstructions? A. Rain or cloud cover has relatively little impact on GNSS positioning, but tall buildings or dense trees can block satellite signals and destabilize positioning. Modern high-performance GNSS receivers use multiple satellite systems and frequency bands and apply model corrections for errors such as ionospheric effects, so they can provide stable positioning even under somewhat adverse conditions. Ideally, use GNSS in open-sky locations, but if signal conditions are poor you can mitigate issues by placing a base station nearby or choosing times when satellite visibility is better.

Q. Can GNSS be used for indoor layout marking? A. Unfortunately, GNSS satellite signals do not reach indoors or underground, so GNSS cannot be used for interior building or tunnel layout marking. For indoor positioning work, you must continue to use other methods such as total stations or laser layout instruments.

Q. What do I need to start layout marking with GNSS? A. Fundamentally, you need an RTK-capable GNSS receiver and a device to display and operate the positioning results (recently, smartphones or tablets are commonly used). You also need a means to obtain correction information to achieve high accuracy. You can set up your own base station, but in Japan you can obtain correction data without a dedicated base station by using network RTK services that leverage the Geospatial Information Authority of Japan’s reference stations or augmentation signals provided by the Michibiki system (CLAS). For example, with LRTK, you can connect from a smartphone to RTK correction information (Ntrip service) via the internet and achieve centimeter-level positioning (centimeter-level accuracy (half-inch accuracy)) in real time anywhere in the country.

Q. Can people without specialized knowledge operate it? A. Yes. Modern GNSS surveying systems have refined user interfaces and are intuitive to operate. You do not need specialized qualifications to use them; on smartphone-linked apps you can start and stop positioning with button taps, and recording survey points and importing drawing data is simple. AR visual navigation features help first-time users identify points without getting lost. Some basic training is required, but these systems are far easier to learn than traditional surveying equipment.

Q. Aren't GNSS surveying instruments expensive and difficult to introduce? A. Indeed, RTK-capable surveying equipment used to cost several million yen, but now compact and affordable GNSS receivers like LRTK are available, and smartphones can be used as controllers, eliminating the need to invest in costly dedicated equipment. This lowers the initial investment barrier. By performing surveying in-house rather than outsourcing, you can achieve long-term cost savings. Considering time savings from efficiency gains and reduced labor costs, the return on investment for GNSS introduction can be very high.