Achieving Coordinate Guidance with cm level accuracy (half-inch accuracy) and Improving Piling Work Efficiency

Table of Contents

• Introduction

• Challenges of Conventional Piling (Positioning) Work

• Improving Piling Coordinate Guidance with GNSS and AR

• Accuracy Improvement and Human Error Reduction through AR Piling Guidance

• Centimeter Accuracy (cm level accuracy (half-inch accuracy)) Supported by RTK Technology

• The Potential of Smartphone Surveying for Site DX

• Conclusion: A New Era of Simple Surveying Opened by LRTK

• FAQ

Introduction

In the construction industry, the push for ICT and DX (digital transformation) in recent years has strongly demanded improvements in site efficiency. However, on actual sites, surveying and piling—i.e., positioning work—still take considerable time and manpower, and issues such as labor shortages and the aging of skilled workers are becoming more serious.

For example, when placing numerous piles accurately for the foundation work of a structure, careful positioning and piling by surveyors were indispensable in the past. To drive each pile into the coordinates specified on the drawings, survey instruments such as total stations had to be set up to measure distances and angles from a reference point, and multiple workers were required to mark and install piles. When driving many piles across a large site, it was not uncommon for the surveying and piling alone to take more than a full day.

Moreover, conventional manual methods relying on human work cannot avoid the risk of human error. Even a small reading mistake or marking error that shifts a pile position by a few centimeters can cause misalignment of structures or rework in later stages. Re-driving piles or correcting positions reduces overall site productivity and directly increases costs. Previously, inexpensive GPS devices had errors too large for precise piling, forcing reliance on expensive surveying equipment and skilled personnel. As a result, positioning work incurred significant cost and time, posing a large burden especially for small- and medium-scale projects.

A promising new solution to overcome these issues is the fusion of the smartphone, GNSS (Global Navigation Satellite System) positioning technology, and AR (augmented reality) site guidance. By using centimeter-class (cm level accuracy (half-inch accuracy)) position information obtained through high-precision GNSS positioning (such as RTK) on a smartphone and overlaying guidance onto the real-world video, intuitive and accurate piling support becomes possible. Combining a smartphone with a compact high-precision GNSS receiver makes it increasingly feasible to guide pile coordinates to centimeter-level accuracy—previously requiring dedicated equipment and multiple-person teams—so that a single worker can perform the task easily.

This article focuses on coordinate guidance for piling work in the context of site DX and explains in detail the latest construction support methods that utilize GNSS positioning and AR technology. It clearly summarizes the problems of conventional methods, the innovations brought by new technologies, the resulting benefits, and finally touches on solutions that enable practical “simple surveying” on-site.

Challenges of Conventional Piling (Positioning) Work

Conventional methods for piling (positioning) on construction sites involved various inefficiencies. To mark pile positions on the ground based on design drawings, survey instruments such as total stations are typically mounted on tripods, and work is commonly carried out by a team of two people—a surveyor and an assistant. Even to locate a single point, laborious steps were required: measuring distance from a reference point with a tape measure, marking, and the assistant fine-tuning the pile position under the surveyor’s instructions. When piles are numerous on a vast site, this surveying and piling work alone can take more than a day.

Relying on analog manual labor also meant a high risk of human error. Small calculation mistakes or marking errors that shift pile positions can lead to rework during subsequent construction or compromise the overall accuracy of the structure. In practice, re-driving piles or performing additional corrective work due to position deviations has severely reduced site productivity. Furthermore, inexpensive GPS devices used to have errors of 5-10 m (16.4-32.8 ft), making them unsuitable for precise piling, and forcing reliance on expensive surveying equipment and skilled technicians. Consequently, positioning work including surveying required significant costs and time, creating a major burden on sites amid worsening staff and technician shortages.

Improving Piling Coordinate Guidance with GNSS and AR

The key to solving the above problems is the digitalization of piling coordinate guidance by combining GNSS positioning data with AR display. If the coordinates of pile positions from the construction drawings are preloaded into a surveying app on a smartphone, the app can compare the high-precision GNSS-derived current position with the target and display the remaining distance and direction to the target in real time. For example, the screen can show numerical guidance like “10 cm north and 5 cm east to the target point,” allowing the worker to reach the design-specified location by simply moving a few steps as instructed. Tasks that previously required multiple people using tape measures can now be completed by one person holding a smartphone.

Using this GNSS + AR navigation dramatically reduces the effort and time required for piling work. Preparation of dedicated equipment and waiting for the surveying team become unnecessary, and workers can perform surveying and piling on the spot whenever needed. Because a single worker can complete the task, no complex manpower adjustments are required, enabling smooth positioning even on sites facing labor shortages. In practice, sites that introduced the latest digital piling systems report substantial reductions in piling time. Cases have been reported where survey-and-pile tasks that previously required two people and a full day were completed by one person in about half a day after introducing digital tools—demonstrating clear efficiency gains.

Accuracy Improvement and Human Error Reduction through AR Piling Guidance

The true value of GNSS and AR combined for piling guidance lies in the high accuracy and error-reduction effects. By overlaying virtual markers or indicators of the design pile positions onto the smartphone camera view, workers can intuitively identify the exact point where “the pile should be driven” through the screen. Even without advanced surveying skills, workers can place piles following the visual guide, significantly reducing human errors such as misidentification of positions or marking mistakes. Naturally, pile rework is greatly reduced, and corrective rework for position deviations in later stages becomes largely unnecessary.

Sites that have implemented GNSS×AR piling guidance report feedback such as “pile position variation decreased and all points fell within the plan in as-built inspections” and “we no longer have to redo piling and can confidently proceed to the next stage.” The combination of AR visualization and high-precision positioning has propelled piling work to a leap in accuracy. Positioning tasks that used to be worrisome can now be performed accurately by anyone with the support of digital technology.

As described above, introducing GNSS positioning and AR guidance dramatically improves both the efficiency and accuracy of piling work. The main benefits are as follows:

• Labor reduction: Tasks can be performed by one person, significantly reducing manpower

• Time savings: Greatly reduces time required for surveying and piling

• Improved accuracy: Enhances positional accuracy and reduces variability in construction quality

• Cost reduction: Lowers overall costs by reducing rework and outsourcing expenses

• Improved safety: Reduces work around heavy machinery and the need to transport heavy equipment, lowering safety risks

• Elimination of reliance on individuals: Enables accurate work without depending on specialized skills

Centimeter Accuracy (cm level accuracy (half-inch accuracy)) Supported by RTK Technology

So why is such high-precision positioning possible with a smartphone? The key is RTK (Real Time Kinematic), a representative method of high-precision GNSS positioning. RTK dramatically improves satellite positioning accuracy by using correction information from a base station: both a fixed base station at a reference point and a mobile station (rover) perform GNSS positioning simultaneously. By transmitting correction information obtained at the fixed station to the mobile station in real time, positioning errors that are normally on the order of several meters can be reduced to below a few centimeters. In Japan, use of the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations (CORS) network and the quasi-zenith satellite system “Michibiki” centimeter-class positioning augmentation service (CLAS) is advancing, making RTK positioning possible without placing a private base station on site. Recent smartphones are equipped with high-performance multi-band GNSS chips, and by combining them with small antenna-integrated receivers, centimeter-level positioning comparable to dedicated surveying equipment can be achieved. The emergence of such “smartphone RTK” enables anyone to easily obtain high-precision position information, forming the foundation for improving accuracy and efficiency in tasks such as piling coordinate guidance and various construction management operations.

The Potential of Smartphone Surveying for Site DX

Smartphone surveying—the combination of smartphones, RTK-GNSS, and AR—holds much potential to promote site DX beyond piling guidance. For example, in infrastructure inspections and post-construction as-built management, the “coordinate photo” function that tags photos taken on a smartphone with accurate capture coordinates and camera orientation is useful. If photo data with position information are stored in the cloud, it becomes clear later “from which point what was photographed,” greatly improving efficiency for comparing changes over time and preparing reports. Combined with AR functionality, it is possible to display an icon in the real world at the location of a previously taken inspection photo and capture the latest photo from the same angle.

Additionally, 3D design data can be overlaid onto on-site video to verify as-built conditions on the spot, or invisible structures such as underground piping can be visualized in AR to safely proceed with excavation. In fact, a major construction company has begun combining BIM data and AR to visualize internal piping routes before construction, preventing construction mistakes in advance. This AR “visualization” makes on-site information sharing smoother, greatly contributing to reduced communication loss and human error prevention.

Thus, the fusion of smartphone + RTK + AR technologies is becoming a powerful tool supporting DX across surveying and construction management, not limited to piling guidance.

Conclusion: A New Era of Simple Surveying Opened by LRTK

The smartphone surveying tool LRTK, which fuses RTK positioning and AR, is accelerating site DX in a way that overturns conventional wisdom. Everyone can easily handle centimeter accuracy (cm level accuracy (half-inch accuracy)) position information and overlay 3D design data onto the real world—what was a dream a few years ago has already become reality. The new approach of “simple surveying” brought by LRTK opens the door to an era in which high-precision surveying, once performed only by specialists such as surveyors, can be used routinely by anyone on site.

AR × RTK fusion technology is rapidly becoming the new standard in construction management and surveying, including piling guidance. Actively introducing digital tools instead of clinging to traditional methods will be the key to maintaining competitiveness in the construction industry going forward. By leveraging smartphone surveying solutions such as the LRTK series, which also support the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, you can achieve smart site operations that balance accuracy and efficiency. The future of site DX has already begun. Take this opportunity to adopt next-generation solutions on your site and experience the transformative construction management enabled by AR × RTK.

FAQ

Q1. How accurate is RTK surveying? A. Under favorable conditions, common RTK-GNSS can achieve planar positioning errors on the order of a few centimeters and similar accuracy in height. Smartphone-based RTK positioning can also be expected to match dedicated surveying equipment accuracy if appropriate correction information is used. In practice, LRTK often achieves standalone positioning errors of about 1-2 cm (0.4-0.8 in), and averaging data over a certain period can reach accuracies below 1 cm (0.4 in). However, accuracy varies with satellite geometry and radio conditions, so for critical measurements it is safe to confirm that a stable Fix solution is obtained before proceeding.

Q2. Is RTK surveying possible in areas with tall buildings or trees nearby? A. Poor satellite signal reception can make it difficult to maintain RTK accuracy or keep a Fix solution. In urban areas surrounded by high-rise buildings or in forests, signals may be blocked and positioning can become unstable. Increasing the number of visible satellites using multi-GNSS and multi-band receivers can mitigate accuracy degradation to some extent. Also effective are strategies such as moving briefly to an open area for initial positioning and then continuing work while supplementing with the smartphone’s inertial sensors or AR markers. However, if satellites cannot be detected at all, RTK surveying is not applicable and switching to conventional methods like total stations may be necessary.

Q3. Does LRTK support Japan’s Michibiki CLAS? A. Yes, LRTK offers models that can directly receive CLAS (centimeter-class positioning augmentation service) signals provided by the quasi-zenith satellite Michibiki. With a CLAS-compatible model, centimeter-class positioning is possible using Michibiki’s correction information without relying on the Geospatial Information Authority’s CORS network or internet connections. This makes it especially reliable in mountainous or offshore areas outside mobile coverage, as long as Michibiki signals reach the sky above. Note, however, that CLAS availability is essentially limited to within Japan.

Q4. What should be done in tunnels or underground spaces where GNSS signals cannot reach? A. Unfortunately, RTK positioning cannot be performed where satellite signals are completely blocked. For tunnel construction or underground facilities, other technologies must be used for positioning. Examples include systems that install transmitters in tunnels to measure short-range distances via wireless signals, IMU-based dead reckoning, or SLAM techniques using image analysis—these are under research and in practical use. LRTK is primarily a GNSS-based tool and demonstrates its strengths outdoors where satellites can be received. However, in some cases it is possible to capture satellites near a tunnel entrance to establish a reference, then perform short-duration tasks inside using AR markers or known points to maintain relative position. It is important to combine RTK with other methods depending on the situation.

Q5. What changes on-site after introducing LRTK? A. Before introducing LRTK, positioning and as-built checks often required requests to specialized departments or external surveying companies, and waiting for results. Aligning plans with actual site conditions frequently relied on visual judgments and experience, leaving constant risks of rework and mistakes. After introduction, site staff can perform positioning and measurement on the spot and immediately confirm and share results via AR, significantly changing workflows. Real-time construction management improves decision speed, and any mistakes can be detected and corrected early. Tasks that previously required two to three people can often be done by one person, allowing more flexible personnel planning. In short, many report that LRTK has dramatically reduced “waiting time” and “rework,” enabling more efficient overall site operations.

Q6. Are special skills or preparations required to use smartphone surveying? A. No—beyond basic smartphone operation skills, no special expertise is required. Smartphone surveying systems, including LRTK, are designed to be intuitive, and site staff can operate them effectively after simple app training. Preparation typically involves loading point coordinate data from design drawings into the app; complex settings and calculations are handled automatically by the system. Required equipment is minimal—just a smartphone, a compact GNSS receiver, and a pole—eliminating the need to prepare large equipment or a surveying team as in the past.

Q7. If we want to advance site DX, where should we start? A. First, review current work processes and identify tasks that consume significant time and effort. If you find issues in surveying or positioning stages, consider pilot-testing digital technologies like smartphone surveying to validate their effects. Start with small sites or a portion of the workflow, gather feedback from site staff, and gradually expand for smooth adoption. Gaining understanding from management and site personnel is also essential; share cost-effectiveness and success stories from other companies to build consensus. Additionally, leveraging examples and subsidy programs related to the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative can help advance DX in stages. Begin with achievable digitalization steps on-site, accumulate small successes, and DX will steadily take root. Please take a proactive approach.