Table of Contents

• Introduction

• The frequent problem of “rework” on construction sites

• What is RTK (Real Time Kinematic)?

• Why RTK implementation reduces rework

• Other benefits: shorter schedules and labor savings

• Case study: achieving zero rework in a mega-solar construction project

• Conclusion

Introduction

Nothing is more wasteful on site than when “rework” occurs. When work has to be redone, labor and material costs are incurred twice, and schedules are greatly disrupted. With rising construction material prices and a worsening labor shortage, it is more important than ever to complete work correctly the first time within limited budgets and personnel. However, in conventional construction sites, “rework” often occurs due to surveying errors and issues with construction accuracy.

In recent years, a technology attracting attention for these challenges is RTK (Real Time Kinematic) positioning. RTK is a high-precision positioning technique that uses satellites to determine positions in real time at a centimeter level. This allows construction points to be laid out accurately to prevent mistakes, and it is expected to dramatically reduce construction rework. This article organizes the problems of frequent “rework” on construction sites, explains the outline of RTK technology, and discusses the effects of its implementation. We focus especially on the largest benefit of RTK implementation—“reduction of rework”—and introduce concrete cases. Some advanced sites are already practicing construction management using RTK and reporting drastic reductions in rework and shorter schedules. We hope this helps you grasp the potential for site improvements through RTK implementation.

The frequent problem of “rework” on construction sites

First, let’s look at why “rework” occurs on construction sites. Construction and civil engineering sites require work to be carried out precisely according to drawings. In practice, however, errors in surveying and layout marking, human mistakes, or misreading of design drawings can cause positional or dimensional discrepancies. For example, many technicians have experienced situations where a foundation was off by a few centimeters (a few in) and steel column bolt holes no longer aligned, or where road lines differed from the plan and a section had to be reconstructed.

When such mistakes are discovered, the relevant portion of the work must be redone. Tasks such as breaking out and re-pouring already placed concrete, pulling out and re-installing piles installed in the wrong location, or refitting misaligned piping all involve significant time and cost for these rework operations. Rework under deadline pressure directly causes delays to the entire schedule. If rework requires additional materials, material costs increase, and there are disposal costs for wasted scrap. From a quality perspective, parts that have been removed and reconstructed inevitably may be less reliable than the initial work, and inspections may scrutinize them more strictly. In fact, it has been pointed out that rework due to construction defects can account for 5–10% of total project costs, a loss that cannot be ignored.

In particular, on large-scale projects, small surveying errors can become large deviations in later stages. If baseline lines or reference points are wrong at the initial stage, deviations accumulate in all subsequent work, potentially causing fatal inconsistencies at the final stage. As a result, large-scale rework or design changes may become necessary, leading to increased overall project costs and extended schedules.

Thus, “rework” on construction sites is a major headache for site managers. Traditionally, mistakes have been prevented by the intuition of experienced craftsmen and careful double-checking, but manual human work has limits. The countermeasure that has emerged is error prevention using the latest positioning technologies.

What is RTK (Real Time Kinematic)?

RTK (Real Time Kinematic) is a technology that uses satellite positioning systems (GNSS) to correct positioning errors in real time and obtain centimeter-level high-precision position information. Conventional GPS-based positioning typically incurs errors of several meters due to signal delays and satellite clock errors, making meter-level deviations unusable for construction layout. RTK uses two components—a fixed “base station” and a “rover” (the receiver carried by a worker)—and sends the error information received by the base station to the rover in real time to drastically improve positioning accuracy.

Using RTK positioning, horizontal accuracy can be pushed to approximately ±1–2 cm (±0.4–0.8 in), and vertical accuracy to approximately ±2–3 cm (±0.8–1.2 in) under good conditions. This is sufficiently reliable for establishing reference points and positioning structures on construction sites. As the name implies, RTK performs positioning in real time, so the rover-side (on-site worker) can confirm their current position to the centimeter on the spot while working. In other words, the worker can immediately verify “whether the point I’m about to mark right now is in the correct position according to the design” as they proceed.

RTK positioning can be implemented by transmitting correction information from a proprietary base station using dedicated radios, or by using network RTK that obtains correction data over the internet from electronic reference station networks. (In Japan, correction information services such as the Geospatial Information Authority’s electronic reference points and the Quasi-Zenith Satellite System Michibiki CLAS are also available.) Using the latter, correction data can be obtained without installing a base station on site, so centimeter-level positioning can be started easily in areas with mobile coverage. In any case, by using an RTK receiver, the site layout work that once relied on craftsmen’s intuition and experience can be carried out in a digital and high-precision manner.

Why RTK implementation reduces rework

So, why exactly does RTK implementation reduce “rework”? The main reason is that initial surveying and layout accuracy improve dramatically. If RTK can accurately determine the position of each construction point, work can be done according to the drawings from the start, eliminating the need for later corrections.

Let’s look at the effects of RTK implementation one by one. First, there is a drastic reduction in surveying and layout errors. With RTK receivers, errors that used to be several meters are reduced to a practically negligible range (a few centimeters or less). For example, parts that previously suffered from cumulative errors or misreads using manual tape measures or total stations are free from cumulative errors with RTK, since each point is measured directly against the satellite reference. Even if you mark out 100 points, each point is based on Earth coordinates, so there is less worry about point-to-point deviations becoming a problem later. As a result, human errors at the surveying and layout stage are greatly reduced, making it less likely that rework due to construction mistakes will occur.

Second, the ability to inspect and correct in real time is significant. With RTK, workers carry a receiver and can check the coordinates of their current position on the spot. If a position differs from the design, they notice it immediately and correct it on the spot. Previously, errors might have been discovered only after completing layout, but with RTK introduction, you can verify correctness at each step and correct course before major rework occurs.

Third, prevention of misunderstandings through digital data linkage should be noted. RTK devices can have design coordinate data preloaded and guide/display positions on site accordingly. The process of workers reading drawings and transferring them to the field is supported by the machine, preventing human mistakes such as “misreading dimensions.” Even non-experts can mark accurate points by following machine guidance, ensuring quality that is not dependent on individual skill, and thereby lowering the risk of rework.

In this way, RTK implementation suppresses on-site errors both in terms of accuracy and process, greatly increasing the probability of completing work correctly on the first attempt. The ideal of “zero rework” becomes more attainable by utilizing RTK.

Other benefits: shorter schedules and labor savings

The benefits of RTK introduction extend well beyond reduced “rework.” The main advantages are summarized below.

• Shorter schedules: Surveying and layout work becomes more efficient, enabling smoother progress according to construction plans. RTK positioning does not require line-of-sight constraints, so one person can continuously measure points across a large site. Tasks that previously required two people and half a day to complete can sometimes be finished in a few hours. Reducing rework removes wasted time and contributes to overall schedule compression.

• Reduced manpower (labor savings): Conventional total station surveying required two people as a team, but with RTK one person can basically perform positioning and marking. For example, without an assistant running with a prism, a single worker with a receiver can lay out each point. In construction sites chronically suffering from labor shortages, RTK is a precious asset. Accurate surveying with fewer personnel contributes to lower labor costs and site labor savings.

• Improved safety: RTK enables surveying in dangerous areas to be completed quickly. For example, layout on steep slopes or riverbank protection can be measured in a short time, minimizing the time workers are exposed to danger. On cliffs or bridges where long-term human entry is hazardous, measurement points can be finished quickly, reducing worker risk. Also, by reducing repeated heavy equipment entry and exit, the risk of machinery-related accidents and site confusion is suppressed.

• Easier consensus building: Combining visualization technologies that overlay 3D design data on site (AR, etc.) makes it easier to align understanding with clients and designers. Sharing the completed image in advance helps avoid later rework or design changes due to “this wasn’t what I expected.”

• Environmental benefits: Reducing unnecessary rework also saves resources and reduces environmental impact. Completing construction in one go eliminates extra material consumption and additional heavy equipment operation, reducing waste and CO2 emissions. With SDGs and environmental considerations increasingly emphasized in modern construction, RTK use that achieves both efficiency and sustainability is a valuable initiative.

Thus, RTK introduction brings revolutionary benefits in both construction quality and efficiency. Beyond achieving “zero rework” through improved accuracy, it boosts overall site productivity through faster work, reduced labor costs, strengthened safety management, and reduced environmental burden.

Case study: achieving zero rework in a mega-solar construction project

As an example of a site that has achieved significant results with RTK, consider mega-solar (large-scale solar power plant) construction. Mega-solar projects lay out thousands of solar panels across a site, and the positioning of the numerous foundation piles (supports) that hold them is extremely important. Over wide areas, even slight angular errors from reference points can result in large positional deviations far away. If piles are placed even a few centimeters (a few in) off in the initial survey, entire rows of panels can become distorted, causing interference between adjacent panels and equipment.

Conventional manual surveying required a surveyor to set pile positions one by one with a total station, which was time-consuming and still carried some risk of error. Sites with uneven terrain or dense vegetation have poor lines of sight, and slight errors can occur even from veteran surveyors. Moreover, surveying on steep slopes carried risks of slips or falling rocks, presenting safety challenges. As a result, piles sometimes had to be pulled out and reinstalled after being found misaligned, causing delays and cost increases.

However, conditions changed dramatically on mega-solar sites after RTK introduction. Workers carry RTK receivers across the wide site and mark pile positions sequentially. In open areas with good GNSS reception, positioning can be completed quickly even across several hectares. All pile coordinates can be set exactly according to the design, resulting in an almost perfect layout on the first installation. For example, on one site where several thousand piles were positioned using RTK, no rework due to positional deviation was detected in post-construction inspection. Assembly of panel racks proceeded smoothly, the schedule was shortened compared to plan, and additional costs were suppressed.

As this mega-solar example shows, RTK enables accuracy control approaching “zero construction errors.” In projects that combine many components, thorough precision management and getting it right on the first installation are keys to shortening schedules and ensuring quality. Eliminating construction mistakes also reduces material waste and extra machinery operation, contributing to reduced CO2 emissions—an environmental benefit. In renewable energy facility construction, it is especially desirable to proceed with efficient and sustainable construction processes.

Moreover, RTK’s effects are also notable in the building sector. For example, in reinforced concrete building foundation work, anchor bolt positions for columns and walls must be placed with millimeter-level precision (mm-level precision, hundredths to tenths of an in), but conventional manual layout sometimes resulted in occasional positional errors. After RTK introduction, anchor positions can be set according to design coordinates, and rework such as chiseling the foundation later to re-embed bolts has been almost eliminated.

RTK is also powerful in road construction, tunnel excavation, and various other fields. It is used to prevent centerline positioning mistakes on road alignments, minimize breakthrough errors in tunnel excavation, and generally reduce the risk of on-site rework to the utmost.

Conclusion

Through RTK technology implementation, you can see that the greatest waste on construction sites—“construction rework”—can be substantially reduced. Completing work accurately the first time not only reduces costs but also ensures quality and improves reliability. With initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* promoting ICT and digital technology to raise productivity, actively using digital tools is a major trend in the construction industry. High-precision positioning with RTK is one of the most powerful solutions that directly transforms the field. Of course, introducing high-precision equipment requires initial investment, but cost reductions from reduced rework and labor savings can more than recover it. In fact, many sites report achieving payback in about 3–5 years, and some projects have paid off within 2 years depending on scale. It is no exaggeration to say that whether a company embraces such digital innovation will determine its future competitiveness.

That said, introducing the latest surveying equipment to a site may seem daunting. One solution to watch is the easy RTK solutions that combine smartphones with compact GNSS receivers. For example, using systems like LRTK, centimeter-level positioning is possible with familiar devices such as smartphones even without specialized surveying instruments. Intuitive app operations allow point guidance and recording, so any site staff can handle it easily, and even non-experts can approach “zero-mistake construction.” With the barriers to enjoying RTK benefits greatly lowered, many companies are beginning to adopt these tools. Going forward, RTK positioning is expected to link with drone-based 3D surveying and AI-driven quality control to realize even more advanced smart construction. RTK-centered digital transformation is set to shape the future of the field, and this trend will only accelerate.

Sites troubled by rework should consider leveraging RTK’s benefits. It may be wise to start with small-scale processes. Once you experience the effects, standardizing RTK across sites can achieve substantial cost reductions and quality improvements. Please consider “getting it right the first time with RTK” for your next project. If you are interested in details of RTK solutions or case studies, you may also refer to LRTK’s [official site](https://www.lrtk.lefixea.com) as a resource to take the first step toward site reform.