AR guidance so you won't get lost when driving piles! Visualize pile positions with the LRTK app

Driving piles that support columns and foundations at construction sites is a critical process that affects the safety of structures. However, the work of guiding pile placement, traditionally relies heavily on experience and intuition, making it difficult for beginners. On site, you need to determine positions from drawings, mark the ground, and drive piles at those marked positions—steps that are time-consuming, labor-intensive, and prone to mistakes.

In recent years, the construction industry has accelerated the adoption of digital technologies such as ICT and AR to streamline construction (so-called Construction DX). Within this trend, a new approach to pile driving guidance has emerged. To ensure you “won’t get lost when driving piles,” a system was needed that allows anyone to easily and accurately identify pile positions. Enter pile-driving navigation using an AR guidance app that combines a smartphone with high-precision GNSS. This article explains this innovative method and the LRTK app that makes it possible. With this new approach, pile-driving work will become significantly more efficient, enabling anyone to perform accurate work without getting lost.

Table of Contents

• Challenges of pile-driving guidance in foundation and temporary works

• Visualizing pile positions with AR display and coordinate navigation

• Workflow of pile-driving guidance using LRTK

• Frequently asked questions

Challenges of pile-driving guidance in foundation and temporary works

“Pile driving” refers to the work of driving piles into the ground to support buildings and civil structures, mainly as part of foundation work. When the ground’s bearing capacity is insufficient, concrete or steel piles are driven deep into the ground to transfer the building’s load to a firmer supporting layer and reinforce the foundation. Pile work includes methods such as driving factory-made piles (prefabricated pile method) or excavating on site and pouring concrete (cast-in-place pile method), but in any method it is important to execute at the design-specified positions and depths. Temporary works also sometimes require sheet piling or temporary pile driving for earth retention. For example, in excavations that are deep, steel sheet piles are driven to form a retaining wall (temporary earth-retaining structure) to prevent surrounding ground collapse; if the position or spacing of those sheet piles is off, the wall will not be effective. Even for temporary works, accurate pile installation is required.

In all cases, the correctness of pile positions according to the drawings directly affects the quality and safety of subsequent work. If the pile center is off, distortion can occur in the superstructure or the planned bearing capacity may not be achieved. Therefore, extremely high accuracy is required for guidance of pile positions. Since even small errors can affect the overall safety of a building, painstaking checks are performed before pile driving.

However, traditional pile-guidance work has been largely manual and required considerable effort and experience. The common method is to read coordinates and dimensions from design drawings, measure distances from site reference points using tape measures or surveying instruments, and mark the ground. On large sites, a temporary reference frame called “chouhari,” using wooden stakes and string lines, is set up to derive positions from those references. But in urban tight sites or areas with complex structures, there is often insufficient space to set up chouhari. When working below ground level or where there are many obstacles, poor visibility increases the effort required to re-establish measurement points.

Traditional surveying methods are also subject to human error. Mistakes reading a tape measure, transcription errors when copying calculated values, or marks being erased by passing heavy equipment are common on sites. Even a small error in pile position can necessitate extra excavation or repair work later, causing schedule delays and cost increases. For this reason, surveyors often perform double checks before pile driving, and construction managers carefully confirm markings. Still, under complex site conditions human error cannot be entirely eliminated, leading to ongoing concerns about how to make pile-guidance more accurate and efficient.

Against this backdrop, dedicated devices to streamline pile position layout have appeared in recent years. Examples include single-operator systems using total stations (TS) and prisms, and layout navigator devices for pile driving offered by various companies. TS can provide high-precision surveying, but require sufficient lines of sight and reference alignment at the site, and measurements must be redone as subterranean spaces or structures increase. TS surveying is also typically performed by two people (operator and prism holder), making it difficult and unsafe to position personnel in narrow excavation pits or at height. While dedicated devices can reduce surveying labor, they can be expensive and require time to master operation. For small to medium projects or sites lacking specialized surveyors, adopting such equipment can be a high hurdle.

“What if we could guide pile positions accurately and easily for anyone?”—to answer this request, attention has turned to a new approach using smartphones and apps. By combining the familiarity of smartphones with the latest technologies, efforts to dramatically streamline on-site layout work have begun.

Visualizing pile positions with AR display and coordinate navigation

A trump card for solving traditional problems is pile-guidance that leverages AR display and high-precision coordinate navigation. This is realized with a small GNSS device that attaches to a smartphone and a dedicated app. The key technology is RTK high-precision GNSS positioning. RTK (Real Time Kinematic) is a positioning technique that corrects satellite positioning errors in real time to determine location with centimeter-level accuracy. Traditionally, expensive GNSS receivers and radio equipment were required, but LRTK packages these into a palm-sized, all-in-one device that can be attached to a smartphone. The device itself is lightweight at about 200 g, and incorporates a high-performance antenna, battery, and communication module in a rugged design suitable for the field. Simply attaching it to a smartphone turns your everyday phone into a high-precision surveying instrument. The LRTK device also includes an inclination correction function, so even when a surveying pole cannot be held perfectly vertical, the tip position is automatically corrected to obtain accurate coordinates. This maintains accuracy in situations where the pole cannot be set straight due to obstacles, making it useful for surveying in confined sites or terrain with elevation differences.

The LRTK app offers various features to support on-site layout, the most notable of which is AR (augmented reality) guidance display. Based on pile position coordinate data registered in the cloud or the app beforehand, virtual markers and arrow navigation are overlaid on the smartphone camera view. For example, when you select the coordinates of the desired pile location and start navigation, the screen shows distance information such as “X m to target” and an arrow indicating the direction to proceed in real time. The worker simply holds the smartphone and walks in the direction the arrow points to approach the target. As the distance approaches zero, the discrepancy between the current location and the target coordinates is nearly eliminated, and eventually it becomes possible to stand on the pile center within a few centimeters (within a few inches) of error. The revolutionary aspect is that you can achieve accurate layout simply by following on-screen guidance without complicated surveying calculations or specialized knowledge.

Workflow of pile-driving guidance using LRTK

• Preparation of pile position data: Obtain the coordinates of the positions where piles should be installed from the construction drawings. Calculate latitude/longitude or planar coordinate values from drawing reference lines and design values, and compile them in Excel or CSV format.

• Importing data into the app: Import the prepared pile position coordinate data into the LRTK cloud or smartphone app. Multiple points can be registered in bulk and made readily available on site.

• Attach device on site and start navigation: Attach the LRTK device to the smartphone used for surveying and launch the app. Select the pile point to guide from the list and tap “Start Navigation.” Navigation begins while receiving GNSS correction information and performing high-precision positioning.

• Guidance to target point and pile driving: Move to the target point following the AR display on the smartphone screen. When you reach the indicated location, mark that point and drive the pile with a pile driver. If there are additional piles, select the next point and continue guiding sequentially.

Using the AR function, you can visualize pile positions even where physical marking is difficult. For example, on floors covered in concrete where marking is hard, or on steep slopes where footing is unsafe, you can place a virtual pile on the phone screen to indicate the location. This allows workers to identify points from a safe position without having to enter hazardous areas. Likewise, areas near operating heavy machinery that are unsafe to approach can be accurately indicated from a distance through the screen, improving construction safety.

For instance, in reinforcement work on a steep slope, you could virtually place an AR pile from a safe location above and then excavate vertically below that point to confirm the pile-driving location. Traditionally, a worker would have to descend the dangerous slope to set out marks, but AR guidance enables remote and safe specification of precise positions.

Implementing this smartphone × GNSS × AR pile-guidance system on site brings many benefits.

• Dramatic improvement in work efficiency: Pile position layout that used to require two people and half a day can be completed quickly by one person using LRTK navigation. Because multiple points can be guided sequentially while moving, the number of piles processed per day can increase significantly, shortening the overall schedule. In one comparative experiment, introducing RTK and AR guidance reduced the time required for position guidance to about 1/6 compared to traditional optical surveying staking-out.

• Improved surveying accuracy and reduced errors: In addition to high-precision RTK positioning, AR visual guidance reduces human reading and communication errors. Guiding pile drivers or workers according to on-screen instructions enables pile driving in accordance with design coordinates and dramatically reduces rework due to layout mistakes.

• Labor savings and improved safety: Tasks that previously required multiple people for surveying and guidance can be handled by one person, helping to address labor shortages and reduce labor costs. Because fewer people need to approach heavy equipment for surveying, the risk of contact or fall accidents is reduced. Dangerous staking-out tasks at heights or in deep excavations are minimized, reducing the physical burden on workers. Newcomers without surveying expertise can perform layout work simply by following the app’s screen guidance, greatly reducing the burden of training skilled personnel.

• Enhanced quality control through data utilization: During GNSS-guided layout, digital records such as positioning errors and arrival times for each point are automatically logged, allowing construction managers to review and use that data for quality control later. This eliminates the need for handwritten notes in paper field books, and if a mistake occurs, logs can be traced to identify causes. Visualization of the construction process with data contributes to improved site management.

With the advent of LRTK, pile-guidance—once reliant on the craftsmanship of experienced surveyors—is being transformed into a task anyone can perform with digital navigation. LRTK combines the ease of “smartphone surveying” with centimeter-level (half-inch accuracy) positioning accuracy comparable to dedicated instruments, making it a powerful tool to advance DX (digital transformation) in construction. These latest technologies align with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction policy and are expected to be solutions that achieve both productivity improvement and quality assurance.

LRTK, which realizes pile-driving without “getting lost,” can be applied not only to foundation work but to any layout task. In practice, AR navigation is being applied to various simple surveying tasks beyond pile driving, such as building layout and machine installation positioning, locating underground utilities, and as-built inspection. Furthermore, AR guidance technology is expected to be increasingly used in areas like heavy equipment automatic control and infrastructure inspection. If you feel uncertain or inefficient about on-site layout work, why not try smartphone surveying with LRTK for accurate and speedy pile-guidance? Experience the efficiency and peace of mind that cutting-edge technology can bring to your site.

Frequently asked questions

Q: What kind of product is LRTK?

A: LRTK is a positioning system composed of a palm-sized RTK-GNSS receiver that can be attached to a smartphone, a dedicated app, and a cloud service. By attaching the palm-sized device to your phone, it enables centimeter-level positioning (half-inch accuracy) and intuitive position guidance via AR.

Q: Can it be used without specialized surveying experience?

A: Yes. The LRTK app is designed to be user-friendly for beginners, and by following on-screen prompts you can navigate pile positions. No complex calculations or specialized knowledge are required, so even those with limited field experience can operate it after a short training period.

Q: Can it be used for tasks other than pile driving?

A: Absolutely. LRTK can be applied to layout of building foundations, setting out locations for temporary structures, establishing control points in roadworks, locating buried pipes, and all kinds of surveying and layout tasks. It helps visualize coordinate points from drawings on site, so one device can streamline many types of field surveying.

Q: What is the positioning accuracy?

A: It depends on environmental conditions, but typically horizontal positions are accurate to about ± a few centimeters (± a few inches), and vertical accuracy is a few centimeters to less than ten centimeters (a few inches to less than 3.9 in). This is dramatically more accurate than standalone GPS and is sufficient for pile driving and staking-out in construction sites.

Q: Does weather or surrounding environment affect positioning accuracy?

A: Because it relies on satellite signals, accuracy is generally only slightly affected by light rain or cloudy skies if the site is outdoors with open sky. However, in environments where the overhead view is obstructed—such as inside forests or surrounded by high-rise buildings—satellite reception can be poor and accuracy may degrade. In such cases, positioning may take longer or errors may increase, so consider changing observation points as needed. The LRTK device is dustproof and waterproof, so it operates fine in light rain.

Q: What do I need to use it?

A: All you need is the LRTK device and a compatible smartphone. The app is available for both Android and iPhone. RTK positioning requires receiving correction data from a reference station, but LRTK supports network RTK via mobile communications, so if your phone has cellular connectivity on site you can perform high-precision positioning. In Japan, LRTK is also compatible with the Quasi-Zenith Satellite System (QZSS) high-precision augmentation service (CLAS), which allows centimeter-level positioning without an internet connection within the supported coverage area.

Q: I'm worried about the cost of introduction—does it offer cost-effectiveness?

A: LRTK is generally more affordable than a full set of dedicated surveying instruments and makes use of existing smartphones, reducing waste. It can also reduce the need to hire external surveying contractors, lowering operating costs. Considering labor and time savings and resulting productivity improvements, adopting LRTK can be a cost-effective investment.

Q: I'm concerned the operation might be difficult. Is there support?

A: The LRTK provider offers initial device setup assistance and provides training materials and manuals on app usage. Support contact is available, so even those unfamiliar with device operation can introduce it with confidence. If you encounter problems on site, you can consult the support desk for advice.