What is RTK? Why is it Needed on Construction Sites?
RTK (Real-Time Kinematic) is a high-precision positioning technology that uses GNSS (Global Navigation Satellite System). It works by simultaneously performing satellite positioning at a base station (reference point) and a rover (moving station), and by sending real-time correction information of the base station’s position error to the rover, it achieves centimeter-level accuracy.

In traditional standalone GPS positioning, errors of several meters in location were common. However, RTK reduces this error to within a few centimeters. For example, in Japan's public surveying, network-based RTK surveying, which obtains correction information from the electronic reference point network, enables real-time centimeter-level positioning without the need to set up a base station on-site.

The reason RTK is needed on construction sites is primarily due to its accuracy and immediacy. In civil engineering projects, high precision is required for the positioning of structures and as-built management. Large errors can lead directly to rework and a decline in quality. With RTK, accurate coordinates can be obtained on-site, allowing the design and construction processes following surveying to proceed smoothly.

Furthermore, with the ongoing shortage of skilled surveyors, RTK allows for efficient surveying with fewer people, leading to reduced workload and labor savings on-site. In recent years, RTK-GNSS has also been utilized in machine guidance for heavy machinery as part of ICT construction, with initiatives expanding to include automatic precision construction using receivers installed on bulldozers and excavators. In this way, RTK has become an essential foundational technology for promoting construction DX.

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Benefits of Introducing LRTK (Time Savings, Cost Reduction, and Accuracy Improvement)
LRTK is a high-precision RTK positioning solution provided by our company. By implementing LRTK on construction sites, the following benefits can be achieved:

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Time Savings
By implementing RTK positioning, the time required for surveying tasks can be significantly reduced. Since correction data is received in real-time, positioning can be performed quickly, eliminating the time lag that used to occur with traditional methods (surveying on-site and then calculating at the office). For example, using network-based RTK eliminates the need to set up a base station, allowing surveying to be done with just one GNSS receiver.

For example, a construction company in Osaka reported that with the introduction of RTK, "the need to set up a base station was eliminated, and surveying that previously required multiple trips with a total station was completed in one trip." In this way, LRTK reduces on-site preparation and the number of observations, dramatically shortening the time required for surveying and construction management.

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Cost Reduction
The reduction in work time and improved workforce efficiency directly lead to cost savings. RTK allows for labor-saving in surveying tasks, enabling a single person to handle tasks that traditionally required two people, such as reference point surveying and the installation of stakes. The reduction in labor costs and the number of days required is significant, and by bringing outsourced surveying tasks in-house, cost reductions can be expected. For example, a small-scale general contractor introduced RTK equipment and started performing construction surveying in-house, resulting in lower outsourcing costs and improved on-site response capabilities. Additionally, while the initial cost of cutting-edge RTK devices like LRTK may be higher, the running costs during operation are kept low, leading to significant long-term cost benefits. If operating a base station in-house, communication line usage fees are required, but by using a network-based RTK service, multiple sites can share the service, further reducing equipment rental and relocation costs.

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Accuracy Improvement
The most significant benefit of implementing RTK is the dramatic improvement in positioning accuracy. With LRTK, horizontal accuracy is around 2–3 cm, and vertical accuracy is around 3–4 cm. This represents an accuracy improvement of up to 100 times compared to standalone positioning, making it well-suited for applications requiring millimeter-level precision, such as the installation of structures and as-built measurements. By obtaining high-precision data in real time, the accuracy of subsequent design and construction planning is also enhanced, helping to prevent rework and unnecessary delays.

For example, when RTK is combined with drone photogrammetry, it allows for reducing the number of reference points while still maintaining accuracy, enabling the collection of much more accurate terrain data in a shorter time compared to traditional methods. In this way, LRTK significantly enhances the data quality on-site, enabling "fast and reliable" surveying and construction.

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Practical Examples of LRTK Use on Construction Sites
LRTK and RTK technology are being increasingly utilized in various aspects of civil engineering and construction. Here are some key examples of their application:

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Example: Terrain Surveying on a Construction Site Using a GNSS Reference Station (Foreground) and an RTK Drone (Background)

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• Application to Construction Surveying (Topographic Surveying): In site development and the positioning of structures, surveyors traditionally used a total station to measure angles and distances and set up stakes. After the introduction of RTK, a GNSS receiver is set up to instantly acquire coordinates for each point, allowing for immediate pile driving or marking on-site. Since one person can measure multiple points, the initial surveying of large areas can be completed in a shorter period of time.

• Application to UAV Photogrammetry: By equipping a drone with an RTK receiver for aerial photography, GPS log errors can be corrected in real-time, reducing the need for reference point alignment during post-processing. Even in vast earthworks sites or steep mountainous areas, high-precision terrain models can be created without human intervention. In practice, maps and point cloud data generated from aerial photos obtained with RTK-equipped drones have shown significant improvements in accuracy compared to traditional methods, contributing to better design and as-built management.

• Machine Guidance for Heavy Machinery: In large-scale projects such as highway and dam construction, there has been an increase in the use of ICT-equipped construction machinery, where GNSS antennas are installed on bulldozers and power shovels. By accurately determining the machine's position using RTK, without relying on the operator's visual inspection or stakes, the height of the blade or bucket can be automatically controlled. This improves finishing accuracy while streamlining operations. An added benefit is that stable quality can be maintained during construction, even at night or in adverse weather conditions.

• Infrastructure Maintenance: RTK is also being utilized in the maintenance and inspection of railways and highways. For example, in monitoring rail distortions and road subsidence, RTK-GNSS allows for the rapid collection of a large number of measurement points. Traditionally, such work had to be carried out during short overnight intervals, but RTK is enabling extended maintenance hours and increased measurement frequency (as demonstrated in Ministry of Land, Infrastructure, Transport and Tourism pilot projects). Additionally, in disaster recovery work, RTK drones are deployed for 3D surveying of damaged areas, helping to quickly assess the situation and support recovery design.

In this way, LRTK contributes to improving efficiency and sophistication on-site across a wide range of scenarios, from surveying to construction and maintenance. In the future, the use of RTK will continue to expand across an increasingly broad spectrum of sites.

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Differences from Competing Technologies (Traditional Methods vs. RTK)
Surveying and positioning with RTK differs significantly from traditional methods (such as using total stations, levels, or standalone GNSS positioning) in terms of procedures and requirements. In sites with large elevation differences, traditional surveying methods were time-consuming. However, with RTK, even at points where visibility is obstructed, positioning can be achieved as long as satellite signals are accessible, making it more efficient. On the other hand, since RTK relies on GNSS signals, it has the limitation that positioning is not possible in areas where the sky is obstructed. Thus, while RTK is not万能 (all-powerful), its immediacy and efficiency make it a technology that can simplify many on-site tasks.

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The Process of Implementing LRTK and Key Considerations
This section explains the typical process of implementing LRTK and utilizing it on-site, along with the key points to keep in mind.

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Implementation Steps

1. Developing the Implementation Plan: First, identify the needs of the site and determine which tasks RTK will be applied to. Consider the required accuracy, coverage area, and compatibility with the existing surveying system (e.g., how to connect to existing reference points). Additionally, decide whether to use a network-based system or set up your own base station.

2. Selecting Equipment and Services: Based on the intended use, procure LRTK devices (rover receivers) and base station equipment. If using a network-based RTK system, preparation for VRS (Virtual Reference Station) services and SIM contracts will also be necessary. Our LRTK devices are compact, lightweight, and equipped with mobile communication functionality, allowing them to automatically acquire electronic reference point data for use as a base station, enabling immediate positioning on-site.

3. Initial Setup and Test Operation: Set up the equipment and perform accuracy verification at known points, as well as trial surveys. Check the coordinate system (such as WGS84/JGD2011) and positioning modes, and verify any discrepancies with existing drawings. If you are using RTK for the first time, it’s advisable to conduct test surveys in a small-scale area, combining this with training on operation.

4. Commencement of Application on Site:
   Begin using LRTK for surveying and construction in actual projects. During positioning, continuously monitor satellite reception and the status of correction data reception. If any issues arise, immediately perform re-surveys or use backup methods to supplement. Before and after daily tasks, perform accuracy checks (check surveys) at known points to ensure the system's accuracy is maintained.

5. Post-Deployment Evaluation and Expansion:
   Evaluate the implementation's effectiveness (such as time savings and accuracy improvements) and share knowledge within the company. If the benefits are significant, expand the use to other sites and, in the future, promote the digital transformation (DX) of positioning tasks as a company standard. Also, regularly check for software updates and new services provided by the manufacturer to continuously enhance the level of usage.

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Key Considerations During Implementation

• Ensuring Clear Sky Visibility: For RTK-GNSS surveying, it is essential that the sky above the antenna is wide and open. In urban areas with building shadows or in valleys in mountainous regions, satellites may not be adequately captured, leading to a decline in accuracy or a complete failure in positioning. When necessary, consider shifting the positioning points or temporarily supplementing with a total station to address these issues.

• Communication Environment: When using network-based RTK, a communication line is required on the rover side. In mountainous areas or underground locations, mobile communication may be unstable, so consider installing repeaters or implementing backup solutions for offline situations (such as switching to post-processing PPK).

• Initial Costs: The introduction of RTK equipment requires an initial investment. However, as mentioned earlier, the reduction in labor costs and improvements in productivity typically offset the costs. Take advantage of public support programs, such as subsidies for i-Construction compliant equipment provided by the Ministry of Land, Infrastructure, Transport and Tourism, to help reduce the financial burden.

• Accuracy Management: It is necessary to verify that the obtained positioning results consistently meet the required accuracy. Perform check surveys at known points on a daily or site-by-site basis to verify that there are no abnormal errors. Additionally, cross-checking the survey results with traditional methods can be effective during the initial stages of implementation.

By keeping these points in mind, the implementation of LRTK will proceed smoothly, and its performance will be fully realized on-site.

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If You Are Considering Implementing LRTK
LRTK is a solution that is being increasingly adopted across a wide range of sites, from small-scale civil engineering contractors to large general contractors. The technology for high-precision positioning is now accessible even to non-professionals, and the construction industry is entering a transformative phase.
If your company is looking to "streamline surveying" or "promote DX," we highly encourage you to consider implementing LRTK. We offer free materials detailing the LRTK products and use cases. Please feel free to request the free materials through the link below.

Additionally, for specific implementation inquiries or demo requests, please contact us through the inquiry form.
With automated and high-precision positioning technology, let’s elevate the productivity of your site. LRTK will strongly support you in taking that first step.

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A technician performing surveying on a construction site using an RTK-GNSS receiver. With our LRTK, which is compact and lightweight, it is easy to carry, allowing for quick on-site surveying by a single person.