Improved Construction Efficiency with Coordinate Guidance:
The Role of Compact RTK in Advancing Civil Engineering DX

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Published March 14, 2025

In recent years, the importance of coordinate guidance in construction has been increasing in the industry. This is due to factors such as the aging of skilled workers, labor shortages, and the need to address infrastructure deterioration, which have driven the strong demand for improvements in construction accuracy and efficiency. Traditionally, surveyors would set up benchmarks and plumb lines on-site, and workers would rely on these for their work. However, this method is time-consuming and prone to errors, leading to rework due to misplacement. As a result, coordinate guidance using RTK positioning has garnered attention. By utilizing compact RTK-GNSS devices, accurate position coordinates can be obtained in real-time on-site, enabling the digital transformation (DX) of construction. For example, ultra-compact RTK devices that can be attached to smartphones have been developed, allowing anyone to perform surveying and positioning with centimeter-level accuracy. The widespread adoption of such compact RTKs is bringing about significant changes in civil engineering and construction sites.

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Coordinate Guidance and RTK Technology

First, let’s understand what RTK positioning is. RTK (Real-Time Kinematic) positioning is a technology that uses two GNSS receivers, a reference station and a rover, to provide high-precision real-time positioning. While the error in typical GPS positioning is around several meters, RTK can achieve positioning with an accuracy of just a few centimeters.

This is achieved by sending the error correction data received by the reference station from satellite signals to the rover, and then correcting the error based on the observation differences between the two. In Japan, devices that support network-based RTK, such as VRS (Virtual Reference Station) using the Geospatial Information Authority of Japan’s electronic reference point network, and those that support centimeter-level augmentation services (CLAS) from the quasi-zenith satellite Michibiki, have emerged. These technologies now make high-precision GNSS positioning possible without the need to set up local reference stations, which was previously necessary.

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On the other hand, coordinate guidance is a method of guiding work positions and construction machinery based on digital coordinate data. Specifically, the coordinates of structures or excavation positions indicated on design drawings are received by on-site workers or heavy machinery operators using GNSS devices, allowing them to progress with their work while checking the difference between their current position and the target position on the screen. It's like a "GPS for the construction site," where GNSS-derived current coordinates guide workers to the desired location.

Traditionally, survey markers and chalk lines were used to indicate positions, but with coordinate guidance, workers can simply follow the device's directions to reach the target location. Thanks to RTK-GNSS's centimeter-level positioning accuracy, such coordinate-guided construction has become practical. For example, if a guidance display on a smartphone app shows "5 cm to the east, 2 cm to the north," workers can accurately drive stakes or perform installation tasks at the prescribed location without the need for benchmarks, even without specialized surveying knowledge. In this way, combining RTK technology with coordinate guidance is starting to significantly change the procedures for surveying and construction.

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Specific Examples of Improved Construction Efficiency Using RTK
By incorporating coordinate guidance through RTK, improvements in efficiency and accuracy can be expected in various on-site tasks. Let's take a look at some specific use cases.

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Simplification and Automation of Benchmark Setup

In civil engineering projects, benchmarks, which serve as the reference for level and position, were traditionally set by surveying teams who would measure multiple times and install them. This required skilled craftsmanship and effort. However, by using RTK surveying equipment, coordinates obtained from the design drawings can be entered into field terminals, allowing workers to simply go to the location to identify the stake position. For example, the current position and target stake location are displayed on the tablet or smartphone screen, and as they approach the target, the system notifies them with sound or visual indicators, enabling workers to pinpoint the location accurately without confusion, even by themselves. In fact, reports indicate that using coordinate guidance apps for staking tasks has improved work speed by 1.5 to 2 times compared to traditional methods.

In many cases, the number of benchmarks that need to be set can also be reduced, directly contributing to labor savings and faster surveying. Moreover, more recently, AR (augmented reality) technology has been used on-site, enabling workers to directly project "structural lines" onto the live smartphone display for layout tasks. With AR layout combined with RTK’s high-precision positioning, accurate positioning can be intuitively shared without the need to draw lines on the ground, further advancing the digitalization of construction.

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Machine Guidance with GNSS Excavators

By equipping heavy machinery such as hydraulic excavators (backhoes) with RTK-GNSS, machine guidance (machine control) can be realized. By attaching angle sensors to the boom and arm of the backhoe and using GNSS to position the machine body, the current height and location of the bucket (shovel) tip can be calculated in real-time. On the operator's monitor, the difference between the target slope or excavation depth of the design surface and the current bucket position is displayed, allowing the operator to work as if moving the machine within a 3D design. This makes it possible to carry out excavation work to the required shape even without the need for benchmarks.

This allows anyone, not just skilled operators, to perform excavation and embankment tasks with consistent accuracy, improving both productivity and finishing quality. For example, with a GNSS-guided backhoe, the operator can always monitor the discrepancy from the correct design surface, eliminating the need for an assistant to verify height, thereby enhancing safety. In fact, reports have shown that the "3D backhoe guidance" system has significantly reduced the need for benchmark setup during excavation, contributing to the digital transformation (DX) of heavy equipment operations and the reduction of personnel on-site.

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Improvement of Precision in Piping and Foundation Work and Optimization of Construction Management
RTK coordinate guidance is effective for tasks that require precise positioning and height accuracy, such as piping work for water, sewage, and gas lines, as well as foundation work for buildings. For example, in sewer pipe installation, traditional methods used string lines and levels to check the slope while laying pipes. With RTK equipment, the desired height and position can be known from the excavation stage, allowing pipes to be laid at the correct slope. By managing the starting and ending points of the pipes and joint positions with coordinates, future re-digging or investigation is made easier.

For foundation layout in building construction, using RTK and a tablet to measure the corners and center points of the foundation allows for accurate marking in a short amount of time. From a construction management perspective, the ability to digitally record the actual positions of structures and buried objects on-site enhances the efficiency of as-built management. The measured point cloud data and coordinate information can be instantly shared and stored on the cloud, allowing site supervisors and designers to check progress and quality in real-time.

In this way, by utilizing RTK, not only the construction itself but also the digital transformation (DX) of management is advanced, leading to the optimal and efficient operation of projects with less waste.

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Real-World Use Cases of LRTK

To leverage high-precision RTK coordinate guidance on-site, the key is to introduce easy-to-use equipment. A prime example is the pocket-sized RTK-GNSS receiver "LRTK" series. LRTK is an ultra-compact RTK device that works in conjunction with smartphones and tablets, offering centimeter-level positioning precision in a device weighing only 125g and 13mm thick. By simply attaching it to a smartphone with the dedicated app, users can instantly measure the current position in the global coordinate system. Designed with the goal of allowing each on-site worker to carry their own device, it offers the convenience of pulling it out from a pocket and immediately using it for surveying or positioning tasks.

By using a dedicated monopod, it is also possible to perform stable positioning, similar to traditional surveying equipment. The smartphone screen displays real-time coordinate values, height, and measurement mode (such as "Fix" status), making it intuitive for anyone to operate. The coordinate guidance function is also comprehensive: once you input the coordinates of a point to measure, the screen shows arrows or distance displays to guide you to the target location. For example, when setting the foundation position for a building, by loading the coordinates obtained from the drawing into the LRTK app, guidance displays can help workers identify the exact position for staking. Tasks that were traditionally done with a total station by a specialized surveyor, such as marking, can now be done by on-site staff with LRTK, leading to successful in-house surveying and labor-saving efforts. There are reports that small general contractors have successfully completed construction surveying with RTK, praising the ability to perform surveying tasks alone. Furthermore, LRTK supports continuous positioning (surveying while moving), in addition to point measurements. It can continuously capture up to 10 high-precision coordinates per second and plot the trajectory, allowing for large-scale surveying of existing conditions or the quick recording of as-built shapes.

In actual field applications, what used to take a full day for surveying existing conditions was completed in about half a day using LRTK, and the measurement data was instantly uploaded to the cloud, allowing for immediate sharing and discussion with design personnel. With cloud integration, coordinates and point cloud data obtained on-site can be shared with internal stakeholders in real-time, facilitating instant feedback on surveying results and design changes.

In highway and railway maintenance, LRTK’s coordinate guidance is also expected to be utilized. For example, in highway inspections, high-precision measurements of surface and structural displacements can be taken, and the data transmitted immediately, reducing nighttime work hours and traffic control time. In railways, GNSS positioning is being applied for measuring track and catenary pole displacements and managing tunnel progress (in areas where GPS signals are unavailable, LRTK's indoor positioning feature and integration with other sensors prove powerful). In fact, LRTK’s usefulness was demonstrated in a disaster site. During the Noto Peninsula earthquake, LRTK was used for on-site surveys in a situation where large equipment couldn't be brought in and communication infrastructure was down. Even in mountainous areas without internet coverage, LRTK was able to receive CLAS correction data from Japan’s quasi-zenith satellite Michibiki, allowing for centimeter-level positioning. This enabled the rapid recording of disaster site coordinates and helped with recovery planning. In this way, LRTK is gaining attention as a key tool for on-site DX in various civil engineering and construction scenarios.

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Introduction to LRTK
As we have seen, coordinate guidance using RTK significantly enhances both productivity and accuracy on construction sites. So, how should you go about implementing it? If you are considering the introduction of the compact RTK device, LRTK, it is recommended to first obtain detailed information from the official website. Free material requests are also available, allowing you to review product specifications, use cases, and data on implementation benefits. Additionally, consultations for live demos are available, so you can try out the device's usability on-site.

The official LRTK website also provides comparison information with other RTK devices. Compared to traditional RTK surveying equipment (such as stationary GNSS receivers or total stations), LRTK offers the following advantages:

• Portability and Ease of Use: LRTK is compact enough to fit in your pocket and can be integrated with a mobile device, whereas traditional RTK surveying equipment required tripods and large controllers. With LRTK, anyone can carry it daily, allowing for immediate surveying and positioning whenever needed.

• Initial Investment Cost: High-performance RTK-GNSS receivers traditionally cost several million yen, but LRTK is offered at a significantly lower and more affordable price (for specific pricing, please refer to the official website). With its low cost, it is possible to equip each employee, making it easier for small and medium-sized businesses to implement.

• Ease of Use: With traditional equipment, surveying technicians with specialized knowledge were often required for setup and operation. However, LRTK performs automatic coordinate system conversion and correction calculations through a simple UI on the app. The intuitive operability, which can be mastered by on-site staff with short training, is a significant advantage.

• Scalability of Features: LRTK excels not only in surveying but also in software scalability, including integration with cloud services and AR-based navigation. It is designed to connect with new DX tools (e.g., real-time as-built management or remote presence*) that were difficult to integrate with traditional equipment.

(*Remote Presence: An initiative recommended by the Ministry of Land, Infrastructure, Transport and Tourism, where data from cameras and positioning devices installed on-site is used to conduct remote site inspections.)

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From these comparisons, it would be wise to determine whether the solution fits your company’s needs. Of course, in some cases, combining it with traditional methods like total stations can also be effective. For example, optical instruments can be used for finishing measurements in construction that require millimeter-level accuracy, while RTK can be used for general surveying or earthworks. The key is to effectively incorporate the latest RTK technology to drive construction DX and contribute to a productivity revolution on-site.

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Coordinate guidance using RTK is becoming an essential technology in the construction industry. By shifting from traditional construction methods relying on experience and intuition to precision construction based on digital data, both quality assurance and efficiency can be achieved simultaneously. The advent of compact RTK devices has made high-precision positioning accessible not only on large-scale sites but also on smaller construction and maintenance projects. In practice, on-site surveying and construction times have been dramatically reduced, and there have been reports of this leading to the resolution of labor shortages and cost reductions.

As satellite positioning technology and IoT continue to evolve, the possibility of fully autonomous construction machinery and real-time construction management will become increasingly realistic. In this context, accessible RTK solutions such as LRTK will become key tools for civil engineering DX. The benefits gained from their implementation are immeasurable. Take this opportunity to explore the latest RTK coordinate guidance technology and take the first step towards integrating it into your construction site. This will lead to enhanced future competitiveness and the realization of safe, high-quality construction.