Pile center marking made simple for one person: Streamline surveying and layout work with high-precision smartphone positioning

Table of contents

• What is pile center marking? Its importance in surveying and layout work

• Challenges of conventional pile center marking methods

• What is smartphone-based high-precision positioning (RTK)?

• Solo surveying realized by smartphone + RTK + AR

• Procedure for pile center marking using smartphone surveying

• Use cases for smartphone surveying (applications across various sites)

• Comparison with traditional methods: benefits in efficiency and accuracy

• Future prospects brought by smartphone high-precision surveying

• Summary

• Simple surveying realized by LRTK

• FAQ

What is pile center marking? Its importance in surveying and layout work

Pile center marking (kuishindashi) is the surveying and layout work in construction and civil engineering that accurately indicates the center position of piles on site. Simply put, it is the process of indicating on the actual site the points specified in the design drawings where “a pile should be driven here,” using piles or markings. Pile center marking is an indispensable step in foundation and bridge work and is a critically important task that affects the position and stability of the structure. For example, for building or bridge foundation piles, even a displacement of a few millimeters (a few mm (a few in)) in the pile center can affect the superstructure, so extremely high accuracy is required for pile center marking.

Generally, pile center marking is also called “pile positioning” or “layout marking”, and is carried out by surveyors or site technicians. Based on coordinates and dimensions read from drawings, positions are determined from site reference points using surveying instruments or tape measures, and marks are made on the ground with piles or markings. On open development sites, it is common to install reference frames called chohari and determine pile positions by measuring distances from their intersections with a tape measure. In contrast, in narrow urban lots or underground spaces where large reference frames cannot be installed, it may be necessary to measure precisely using nearby structures or temporary references. In any site, errors in pile center marking are unacceptable, and it is a task that requires skilled craftsmanship and carefulness.

Challenges of conventional pile center marking methods

However, carrying out pile center marking in the traditional way involves several challenges and inefficiencies. The problems of conventional methods can be summarized as follows.

• Requires manpower and is physically demanding: Surveying work to set out pile positions is usually done by a team of two or more people. For example, when using an optical surveying instrument called a total station (TS), one person operates the device while another holds the prism at the target point. Working with multiple people in confined spaces is difficult, and sites with labor shortages face the basic problem of securing personnel. Also, having multiple people work while heavy machinery is operating increases safety burdens.

• Often relies on experience and intuition: In sites with poor lines of sight or many obstacles, it is necessary to measure dimensions from reference points repeatedly to determine positions. Ultimately, there are many cases where one must rely on the experience and intuition of veterans, making the work dependent on individuals. As a result, there is a risk of variability in accuracy and finish quality depending on the skill of the person in charge.

• Time-consuming and labor-intensive: Setting up surveying instruments and establishing reference points each time incurs a large time cost. It is especially cumbersome to reposition a TS for each floor or basement and recalculate, and positioning even a single pile can require more steps than expected. On large sites where dozens of pile center markings are needed, it is not uncommon for layout work alone to take more than a full day.

• Risk of human error: Manual conventional work inherently carries the risk of human mistakes. For example, a tape measure may sag preventing accurate dimensions, numbers may be misread, or markings may be overlooked. Marks indicating pile centers that were painstakingly set may be erased during the course of construction, necessitating re-measurement. It is difficult to completely prevent mistakes or rework, and even with careful work, accumulation of errors may be unavoidable.

What is smartphone-based high-precision positioning (RTK)?

In recent years, high-precision positioning that combines smartphones and satellite positioning technology has been put into practical use to solve such surveying problems. A representative method is the GNSS positioning technique called RTK (Real-Time Kinematic). RTK works by having both a base station (reference point) and a rover (operator side) receive satellite signals simultaneously and correcting positioning errors in real time by using the observation differences from the base station. While standalone positioning (ordinary GPS) can yield errors of several meters, using RTK can determine positions to within a few centimeters, and under good conditions within a few millimeters.

Traditionally, RTK positioning on site required dedicated large GNSS receivers and one's own base station equipment. However, technological advances have produced solutions in which compact RTK-capable GNSS sensors can be connected to smartphones or tablets to perform centimeter-class positioning easily. In Japan, infrastructure such as the Geospatial Information Authority’s Continuously Operating Reference Stations network and the quasi-zenith satellite “Michibiki” provides services like CLAS (centimeter-level positioning augmentation service). Smartphones can obtain these correction data via the Internet or directly receive compatible satellite signals, enabling high-precision positioning in real time regardless of location. In other words, we have entered an era in which a single smartphone can determine a highly accurate current position from the global navigation system. It is revolutionary in that heavy surveying instruments or lengthy reference observations are not required and coordinate accuracy can be obtained in a short time.

Solo surveying realized by smartphone + RTK + AR

Along with smartphone-based high-precision positioning, the utilization of AR (augmented reality) technology is a major key to enabling “one-person pile center marking.” Dedicated surveying apps provide an AR navigation function that overlays target points from the design drawings and the direction to move on the smartphone camera view. For example, if you call up pre-registered pile coordinate data from the cloud and start navigation, the smartphone screen will display an arrow indicating the direction to the target point and the distance from your current position in real time. The operator simply walks in the direction the arrow points while looking at the smartphone, and the distance display decreases as you approach the target. Near the point, the arrow marker gives finer directional corrections, so by making small adjustments as instructed you can reach the target coordinate within a few centimeters (within a few in).

Because you are guided to the accurate pile position simply by following on-screen instructions, it is far more efficient than conventional methods where experienced workers repeatedly call out and confirm positions. Even inexperienced workers can reach precise points intuitively without difficult calculations or advanced surveying skills. It is like a real-world “car navigation” for the site, where the smartphone provides real-time guidance.

Furthermore, the smartphone AR display can visually indicate the target location itself as a visual marker. For example, in places where the surface is paved and marks cannot be made directly on the ground, or in hazardous areas, a virtual “AR pile” can be placed on the smartphone screen to indicate the position. Even on steep slopes or other places where physical approach is impossible, combining photogrammetry functions and later projecting a virtual marker at that point allows confirmation of the target from a safe location. Pile center marking and position guidance in environments that were previously difficult can thus be realized by combining smartphones and AR.

Procedure for pile center marking using smartphone surveying

With the new pile center marking method using smartphones and RTK, the workflow becomes very simple. A typical set of steps is as follows.

• Prepare and input coordinate data: First, obtain coordinate data for pile positions from the design drawings and load them into the surveying app on the smartphone. Enter drawing coordinates manually or upload CAD data or CSV files to the cloud in advance so that the target coordinate list can be called up on site immediately.

• Start positioning on site and begin guidance: On site, start the smartphone, switch to the high-precision positioning (RTK) mode, and measure the current position. Once positioning stabilizes, select the desired point in the app and start navigation. Follow the arrows and distance information displayed on the camera screen and move to the target location. High-precision real-time positioning greatly reduces the need for frequent distance measurements and fine adjustments.

• Mark the target location: When you reach the target coordinate, mark the spot with a stake or spray paint. Smartphones and RTK receivers are typically mounted on a pole (such as a single-leg pole) that can place the tip on the ground. Align the pole tip with the marker on the smartphone screen and make the actual mark at that location to complete the marking of the pile driving point. In addition to painting the ground, wood stakes or metal nails may be driven in to indicate the target point.

• Record and share surveying data: At the same time as marking, the measured coordinates are automatically recorded in the app. Point names, date and time, time taken for guidance, error on arrival, and other data are saved and can be uploaded to the cloud with a single button press. Because survey results can be shared instantly with staff in the office or other team members, the need to bring back paper records and enter data manually is eliminated.

Use cases for smartphone surveying (applications across various sites)

Smartphone high-precision surveying and solo pile center marking are expected to be used across a variety of sites. Here are some concrete examples.

• Residential land development and foundation work: In subdivision or residential development, many pile points need to be accurately set for lot boundaries, building layouts, and water/sewer pipe positions. Using smartphone RTK surveying, a single operator can advance pile positioning one after another across a large development site. Layout tasks that previously required surveying crews working half a day or more can be completed in a short time with just a smartphone, directly improving construction speed and reducing personnel.

• Slope works and surveying on inclined terrain: For slope (embankment) work along roads or hillside development, it is necessary to mark heights and positions on steep slopes according to design. Installing surveying equipment on a slope or having assistants enter the slope is hazardous, but with smartphone RTK a single operator can measure and guide points from a safe location. For example, one can measure coordinates of slope crest or toe from a distance and project virtual piles via AR to share positions with heavy equipment operators. This reduces work in dangerous areas while improving the accuracy control of slope shaping.

• Pile center marking in bridge construction: When constructing foundation piles for piers and abutments, each pile center must be set to the millimeter as per drawings. Even in cases where surveying crews repeatedly remeasure and confirm, smartphone RTK guidance enables rapid and high-precision pile center marking. GNSS surveying allows position guidance without relocating surveying instruments, so it is effective on wide sites such as riverbanks or reclaimed land. Construction managers themselves can check each point, reducing the need for double-checking and simplifying quality control.

• Disaster recovery and investigation: In sites affected by earthquakes or landslides, quick situation assessment and recovery planning are required. Smartphone high-precision positioning is highly mobile and allows a single person to survey sites where large surveying instruments cannot be brought in. Even if communications infrastructure is disrupted, centimeter-class positioning can be achieved by directly receiving augmentation signals from satellites, enabling mapping and recording of damage on the spot. Collected data can be synchronized to the cloud later and shared among multiple people, supporting efficient recovery efforts.

Comparison with traditional methods: benefits in efficiency and accuracy

One-person pile center marking using smartphone high-precision surveying offers many advantages over conventional methods. The main effects are summarized below.

• Significant reduction in work time: Using smartphone RTK coordinate navigation drastically shortens the time required for pile center marking. Time spent ensuring lines of sight or setting up survey instruments is eliminated, and the operator can walk and be guided to successive points. In practical trials, surveying time has been reduced by about 1/6 compared to conventional optical surveying. Tasks that previously took two people half a day can be completed by one person in a few hours, potentially shortening schedules and allowing earlier progress of subsequent work.

• Improved accuracy and reliability: In addition to RTK’s centimeter-level accuracy, AR visual guidance nearly eliminates human misreading and transmission errors. Because the operator is guided directly to the design coordinate point, conventional error sources such as misinterpretation of ground marks left by the surveyor are removed. Also, since guidance history and arrival error are all automatically recorded, root-cause analysis is easy if a mistake occurs. Quality control based on digital data becomes possible, greatly increasing the reliability of survey results.

• Labor reduction brings safety and cost benefits: Most importantly, because layout and pile positioning can be completed by one person, substantial labor savings are achieved. Reducing personnel directly cuts labor costs and is attracting attention as a countermeasure to chronic skilled worker shortages. More importantly, fewer personnel entering sites where heavy machinery is operating reduces the risk of contact accidents. Trips into dangerous excavation areas are minimized, and where AR allows confirmation from a distance, work at height or on unstable footing can be reduced. Reducing personnel thus directly contributes to improved safety.

Future prospects brought by smartphone high-precision surveying

Surveying technology using smartphones and RTK is expected to evolve further and accelerate digitalization on construction sites. Some future directions include:

• Further improvement in positioning accuracy using AI: The use of artificial intelligence (AI) may further enhance the accuracy and stability of GNSS positioning. For example, AI could analyze satellite signal reception conditions in real time and automatically correct error factors, or use machine learning on past positioning data to suggest optimal correction parameters, enabling stable centimeter accuracy even in challenging environments such as urban canyons or forests.

• Enhanced remote support and real-time sharing: Because smartphone surveying can maintain constant cloud connectivity, systems for real-time sharing of data and site conditions between field and office are likely to develop. Senior surveyors or designers could monitor field positioning remotely and provide advice or instructions via remote support. In the future, office staff might directly place markers or comments on an operator’s smartphone screen, or supervise multiple sites simultaneously.

• Integration with BIM and digital data: The construction industry is advancing the use of 3D digital models such as BIM/CIM, and integration with smartphone high-precision surveying is expected. For example, point cloud data (3D scanned terrain or structures) could be overlaid with design models on site to verify discrepancies. AR projection of the completed image on site for stakeholder sharing is another possibility. Combining with smart glasses could make hands-free surveying and pile guidance a practical option in the future.

• Alignment with national DX initiatives: Under initiatives promoted by the Ministry of Land, Infrastructure, Transport and Tourism such as *i-Construction* and site DX (digital transformation), smartphone-based high-precision surveying will occupy an important position. As a solution to digitalization and efficiency of operations, labor shortage countermeasures, and advanced quality control, technological innovation in this field is expected to receive increasing attention.

Summary

Surveying and layout tasks such as pile center marking have traditionally required multiple people. However, the advent of high-precision surveying technology that combines smartphones and RTK is set to change that norm significantly. As seen in this article, these technologies can overcome the personnel, time, and accuracy challenges unavoidable with conventional methods, making it possible for anyone to perform pile center marking and layout work safely and efficiently by themselves. These new technologies are not special—anyone can adopt them with a smartphone and a small device. In fact, using solutions like LRTK, it is now possible to enhance field surveying operations even without specialized surveying skills. Reducing the burden on surveyors and addressing chronic labor shortages and skills transfer issues make on-site adoption highly beneficial. Why not take this opportunity to experience the new standard for pile center marking using smartphone high-precision surveying?

Simple surveying realized by LRTK

One concrete solution that realizes the smartphone high-precision positioning and AR guidance introduced above is LRTK. The LRTK series consists of GNSS receiver devices and a dedicated app that, when paired with a smartphone, deliver centimeter-level positioning (cm level accuracy (half-inch accuracy)) and dramatically streamline on-site surveying work. Compared with conventional surveying equipment, it is compact and user-friendly and employs the latest technology compatible with the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*. It is designed so that advanced positioning technology can be easily used by anyone on site, and its introduction simultaneously improves surveying accuracy and achieves major labor savings. With LRTK, which lets you handle everything from pile center marking to as-built management with a single smartphone, you can bring your sites to the next stage. For details, please also visit the official LRTK website.

FAQ

Q: Can a smartphone really achieve the accuracy required for surveying? A: Yes, with the appropriate equipment and conditions, a smartphone can achieve the high precision required for surveying. Ordinary smartphone built-in GPS alone yields errors of several meters, but using an RTK-capable GNSS receiver can reduce errors to a few centimeters or less. In Japan, augmentation signals from the “Michibiki” satellites and a national network of reference stations are available, and smartphones that use these sources can achieve survey-grade accuracy. In clear outdoor conditions with good satellite reception, accuracy comparable to conventional surveying equipment can be expected.

Q: Do I need special or expensive equipment for high-precision positioning? A: Traditionally, high-precision positioning required dedicated large instruments and an in-house base station, but this is no longer necessary. Compact RTK-capable receivers that connect to smartphones are now available at relatively affordable prices, making centimeter accuracy possible without carrying heavy tripod equipment. By using correction data services provided via the Internet from reference stations (which may be paid), you can perform high-precision positioning without setting up your own base station. In short, smartphone + compact GNSS receiver alone can now achieve accuracy comparable to surveying equipment that used to cost hundreds of thousands of dollars.

Q: Does weather or the surrounding environment affect positioning accuracy? A: GNSS positioning performs best in open-sky environments. Therefore, in areas with dense buildings overhead, tunnels, or forests, satellite signals may weaken, causing reduced accuracy or unstable positioning. Extreme conditions such as heavy rain or solar flares can also affect satellite positioning. However, modern GNSS systems can use multiple satellite constellations (not only GPS but also GLONASS, Galileo, Michibiki, etc.), and RTK and satellite augmentation can correct many error factors, so accuracy degradation in adverse conditions has improved greatly compared to the past. In environments where signals absolutely cannot reach, combining conventional methods such as optical distance measurement or terrestrial laser scanning is advisable.

Q: Can people without special surveying knowledge or qualifications use it? A: Smartphone surveying systems are designed to be intuitive and easy to operate, so they are accessible even to those who are not professional surveyors. By following the app display and moving the smartphone, you can be guided to the target position without needing to understand complex calculations or advanced surveying theory. However, it is desirable to learn basic knowledge needed for accurate surveying (such as understanding coordinate systems and equipment handling). Also, on a regulatory level, when including survey results in as-built management or inspection documents, supervision or checking by a licensed surveyor may be required. On site, both the ease of use for anyone and the backing of surveying expertise are important.

Q: What is LRTK and what can it do? A: LRTK is a solution brand that makes smartphone high-precision positioning easy to use on site. It consists of a dedicated high-precision GNSS receiver device and a smartphone app, and uses RTK technology to achieve centimeter-level positioning and navigation. By introducing LRTK, one person can perform pile center marking and point guidance, greatly reducing time and labor. It is designed to minimize complex settings and operations, making it user-friendly even for those uncomfortable with technology, and supports site DX promotion and *i-Construction* compliance. LRTK is a reliable partner for making on-site surveying simpler and more precise.