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Table of Contents

• Introduction

• What pile-driving guidance is

• Issues with traditional pile-driving guidance

• Pile-driving guidance evolving with ICT construction and GNSS

• Achieving labor savings using smartphones

• Benefits of introducing GNSS guidance

• Simple surveying enabled by LRTK

• FAQ

Introduction

In pile-driving work performed on construction sites, it is extremely important to drive piles into exact positions quickly and safely. An indispensable part of this is the work known as "pile-driving guidance," in which experienced workers normally give signals and directions to heavy equipment operators to fine-tune pile positions. However, traditional pile-driving guidance has relied heavily on manual labor and presented challenges in terms of work efficiency and safety. In recent years, the construction industry has been promoting ICT construction (construction using information and communication technology), and initiatives to upgrade pile-driving guidance using satellite positioning technologies (GNSS) and smartphones have been attracting attention. ICT utilization targets include improving on-site productivity by about 20% compared with conventional methods, and streamlining pile-driving guidance plays a part in that. This article explains how cutting-edge ICT construction can improve efficiency and reduce manpower in pile-driving guidance.

What pile-driving guidance is

Pile-driving guidance is the guidance work performed in building and civil engineering to install foundation piles, bridge piers, and the like at prescribed positions and angles. Specifically, it involves site workers sending instructions by hand signals or radio so that heavy equipment operators of pile drivers or hydraulic excavators can move and position the machinery exactly at the pile locations specified on drawings. The guidance personnel check the pile center position and orientation and provide fine directional instructions, such as "50 cm (19.7 in) forward" or "a little to the right," relying on ground markers that are hard to see from the operator’s cab. Through this pile-driving guidance work, piles are installed according to design drawings and the stability of structures is ensured. If a pile’s position deviates significantly, it can affect the overall structural strength or require remedial work later, so pile-driving guidance is an extremely important process.

Issues with traditional pile-driving guidance

Traditional methods require multiple personnel for pile-driving guidance, and communication errors or inaccuracies due to poor visibility frequently occur. For example, when a surveyor measures pile positions with a total station and another worker guides the heavy equipment operator so that the pile tip is aligned at that position, at least two people are always required. In addition, because guidance personnel work close to heavy equipment, there is a risk of contact accidents, and safety concerns are particularly acute on cramped sites or in low-visibility conditions. Weather and time-of-day constraints are also issues. Optical surveying instruments can see their accuracy reduced or work interrupted in rain or at night. These factors have long suggested that traditional pile-driving guidance has room for improvement in both efficiency and safety.

Another problem is the heavy dependence on skilled personnel. If staff with advanced surveying skills and extensive experience are lacking, securing accurate pile positions can take more time and increase the likelihood of mistakes. The construction industry faces chronic labor shortages and an aging workforce, and demand for labor-saving measures is increasing year by year. Therefore, new technologies that can reliably place piles at prescribed positions while reducing site burdens have been sought.

Pile-driving guidance evolving with ICT construction and GNSS

One solution to these issues is to incorporate GNSS positioning technology into pile-driving guidance as part of ICT construction. GNSS is a general term for global navigation satellite systems including GPS, and in recent years high-precision technologies such as RTK (Real-Time Kinematic) that can reduce positioning errors to the order of centimeters have been put into practical use. In construction, the Ministry of Land, Infrastructure, Transport and Tourism is promoting *i-Construction*, encouraging machine guidance and machine control using GNSS-equipped construction machines, drone surveying, and utilization of three-dimensional design data. Systems that use ICT in construction are also being supported with evaluation points from clients and financial assistance, which helps drive the introduction of these new technologies on-site.

If GNSS is used for pile-driving guidance, it becomes possible to guide heavy equipment to prescribed coordinates by comparing the current position obtained from satellites with the pile positions on the design drawings. For example, if a system that mounts a GNSS antenna on the machine and displays coordinates in real time is used, the operator can view the deviation from the target position on a monitor in the cab and maneuver the machine to the correct coordinates. This enables high-precision alignment without the intermediary of traditional guidance personnel. GNSS-based positioning guidance can be used during daytime or nighttime and in somewhat adverse weather as long as satellite signals can be received from an open sky, so line-of-sight is not required. Overall, GNSS utilization greatly advances methods of pile-driving guidance and contributes to on-site digitalization and automation.

Achieving labor savings using smartphones

A key to using GNSS on-site is an easy-to-use interface and a mechanism for utilizing data. This has led to increased attention on methods that use smartphones for pile-driving guidance. Smartphones offer intuitive operation and are familiar devices to many site staff. By combining a smartphone with a high-precision GNSS receiver, position-setting work that previously required specialized surveying instruments can now be conducted easily.

Concretely, pile position coordinate data from design drawings are loaded into a smartphone app, and when a worker approaches the target location on-site, the smartphone screen displays the distance and direction to the target. To perform coordinate guidance, the pile position coordinates must be prepared in advance. If the design drawings are digital, coordinate values obtained from CAD software can be registered in the app; if only paper drawings are available, on-site surveying must be carried out to measure pile coordinates. Such preparation ensures that the correct target coordinates are available on-site. A worker walks the site holding a smartphone and follows on-screen directions to reach the target pile location. For example, the app can display real-time guidance such as "5 cm (2.0 in) to the target" or "current position is 10 cm (3.9 in) east of the target," allowing the user to fine-tune the position until the error is minimized. Once the exact point is reached, the worker marks the pile-driving location or places the pile temporarily to inform the heavy equipment. This entire flow can be completed by one person without complicated manual work or reliance on experienced intuition.

Moreover, technologies that overlay the design pile position onto live site video using the smartphone camera or AR (augmented reality) are emerging. Because a virtual pile marker can be seen through the screen, users can intuitively share an image of "drive the pile here," enabling clearer guidance. The advantages of using smartphones are labor savings and simplicity. Specialized expensive surveying instruments and long training periods are not required; anyone can participate in guidance work using a familiar smartphone and app. This not only improves overall site productivity but also reduces individual worker burden and helps standardize work quality independent of skill level. Even as the number of skilled workers declines, maintaining a certain level of quality is feasible, aiding skills transfer.

Benefits of introducing GNSS guidance

There are many benefits to introducing GNSS-based pile-driving guidance. First, improved efficiency through reduced manpower. Because pile surveying and guidance work that previously required two people can be completed by one person, pile-driving work can proceed smoothly even on sites with labor shortages. For example, layout marking that traditionally took two workers one hour might be reduced to about 30 minutes with GNSS guidance performed by one person, representing a significant efficiency gain. This can lead to reductions in labor costs and shorter schedules.

Second, improved construction accuracy. The centimeter-level accuracy (half-inch accuracy) provided by RTK-GNSS is more consistently precise than relying on skilled intuition or visual checks. This reduces pile displacement and construction errors, lowering the need for rework and the risk of structural defects in later stages. Digital guidance systems can also automatically record pile position deviations, allowing them to be retained as data in post-construction reports, which is useful for quality control.

Third, improved safety. If guidance personnel no longer need to signal from close to heavy equipment, the risk of contact or entanglement accidents is reduced. Near-miss incidents where workers are almost struck by machinery during guidance are frequently reported on sites, but digital GNSS guidance can avoid such dangers altogether. Also, because machines can be guided using coordinates even at night or in low-visibility conditions, workers are not forced to operate in unsafe situations. Overall, GNSS guidance greatly contributes to reducing human error and ensuring safety.

In addition, a digitalized guidance process supports enhanced construction management. By sharing progress and positioning data via the cloud, real-time information coordination between the site and office becomes possible. Managers can immediately grasp the progress and as-built conditions of pile-driving work and issue prompt instructions as needed. Implementing guidance systems that combine GNSS and ICT therefore promotes not only labor savings but also the digital transformation of the entire construction process.

Simple surveying enabled by LRTK

A solution that makes GNSS- and smartphone-based pile-driving guidance even easier to implement is LRTK. LRTK combines a compact high-precision GNSS receiver with a smartphone to drastically simplify on-site positioning and guidance. A single dedicated device that attaches to a smartphone houses the antenna and battery, eliminating complex equipment setup and cable connections. By launching a dedicated app, users can easily perform everything from loading design coordinate data to starting positioning with the push of a button.

LRTK supports network RTK (correction information via the internet) and, even in areas outside mobile coverage, can use the centimeter-class augmentation service provided by Japan’s quasi-zenith satellite system (QZSS) — CLAS — to achieve high-precision positioning. In other words, stable positioning accuracy can be maintained even in mountainous areas or sites with poor communication environments. It also includes easy-to-use guidance functions that anyone can operate: after inputting pile coordinate points, the app guides users to the destination with on-screen arrows and distance displays as described above. Even when grass or snow cover hides visual markers, following LRTK guidance on foot will lead users to buried reference points or pile locations.

By utilizing LRTK, on-site staff who are not surveying specialists can measure and guide pile positions themselves. Because expensive surveying instruments or large equipment are unnecessary, LRTK is easy to introduce even on small-scale construction sites, contributing to overall labor savings and efficiency gains. LRTK-based simple surveying supports the site DX (digital transformation) in many scenarios beyond pile-driving guidance, such as various layout tasks and as-built control. Above is an overview of pile-driving guidance using ICT. Next, please refer to the following Q&A for related frequently asked questions.

FAQ

Q: How many workers are required for traditional pile-driving guidance? A: Generally at least two people are required. One operates the surveying instrument and confirms pile positions, while another acts as the guidance person signaling the heavy equipment operator. In some cases, additional personnel for safety monitoring may be assigned, increasing manpower further. New methods using GNSS and smartphones can complete this work with one person, enabling substantial labor savings.

Q: How accurate can pile-driving positions be when using GNSS? A: By using RTK-GNSS technology, theoretical horizontal accuracy on the order of a few centimeters can be achieved. With proper equipment operation in actual field conditions, pile position errors can be kept within a few centimeters. This is far more precise than standalone GPS and more stable than visual checks or tape-measure positioning.

Q: Can smartphone positioning and guidance be used without specialized knowledge? A: Yes, basically. Smartphone apps display intuitive guidance, so even those without surveying expertise can reach the target point by following the instructions. Unlike traditional surveying instruments, complex operations are unnecessary, and with prepared coordinate data, anyone can master the system after a short training session.

Q: Can GNSS guidance be used at sites with poor radio or satellite reception? A: An open sky is preferable for stable satellite signal reception, but modern high-performance GNSS receivers that support multi-GNSS and multi-frequency operation can maintain accuracy even when visibility is partially obstructed. Satellite augmentation services usable without mobile coverage (for example, QZSS’s CLAS) also enable high-precision positioning in mountainous areas. However, GNSS cannot be used inside tunnels or buildings where the sky is completely blocked, so in those cases it must be used in combination with traditional surveying methods.

Q: What is LRTK? A: LRTK is the name for a smartphone-linked surveying system that makes high-precision GNSS positioning easy to achieve. By attaching a small GNSS receiver to a smartphone and using a dedicated app, RTK centimeter-precision positioning, guidance, and point-cloud measurements can be performed. Because specialized instruments are unnecessary and anyone can obtain high-precision location information on-site, LRTK is attracting attention as a modern ICT construction tool.

Q: Isn’t the cost of introducing a new GNSS guidance system high? A: Costs depend on the chosen equipment configuration and scale, but prices for high-precision GNSS receivers have fallen in recent years, making them considerably more affordable than before. Considering labor cost reductions and efficiency gains, the investment often pays off compared with conventional surveying equipment. In some cases, national or local government subsidy programs for promoting ICT construction may also be available, which can help reduce initial costs.

Q: Can GNSS be mounted on pile drivers to automatically position them? A: Some large construction machines already incorporate GNSS-based machine guidance or machine control functions, and there are advanced examples where the machine itself is guided to specified positions. However, such systems require dedicated equipment and software and are limited to compatible machines, making initial costs and preparation time relatively large. By contrast, guidance using a smartphone and GNSS terminal can be easily applied to existing machinery and is flexible and easy to introduce regardless of site scale.

Q: What preparations are needed to introduce GNSS guidance on-site? A: First, procure a GNSS receiver that supports centimeter-class accuracy and a compatible smartphone or tablet. In addition, set up an RTK base station or ensure connection to a service that provides correction information via the internet (such as regional electronic reference points or CLAS). Then obtain pile position coordinates from the design drawings and load them into the system, and carry out on-site trials to become familiar with operations. The operations themselves are not difficult, but it is advisable to perform sufficient pre-checks and practice to understand equipment characteristics and positioning environments.

Q: How will pile-driving guidance using ICT develop in the future? A: It is expected to keep advancing toward higher precision and efficiency. Further improvements in GNSS satellites and correction technologies will enable even more stable positioning. The introduction of AR and AI may make on-site guidance more visual and automated. In the future, automatic operation of pile drivers themselves and coordination with other machine tasks may become feasible, approaching fully smart construction. At the same time, the spread of small, inexpensive devices is expected to make ICT-based pile-driving guidance commonplace even on small-scale sites.