1. Introduction

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In recent years, DX (Digital Transformation) has rapidly advanced in the construction industry, and the introduction of ICT technologies on civil engineering construction sites is progressing. As exemplified by the Ministry of Land, Infrastructure, Transport and Tourism's "i-Construction," efforts are being made to use digital technologies across all processes, from surveying to maintenance, with the aim of improving productivity and creating more attractive sites. In this context, point cloud data, which enables the high-precision 3D digitization of site terrain and structures, is gaining increasing importance and is being widely applied across design, construction, and maintenance. The use of point cloud data for 3D modeling is relatively easy to implement and has a wide range of applications, making it a technology that every civil engineering professional should be familiar with.

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2. Real-Time Utilization of Point Cloud Data on Construction Sites

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By utilizing point cloud data in real time on-site, situations that were previously difficult to understand using only 2D drawings can now be intuitively grasped. Recently, it has become easier to confirm the 3D current conditions of terrain and structures by using tablet devices (such as LiDAR-equipped iPads), scanning the surroundings on-site, and displaying 3D models of the current site. By overlaying design data onto the actual terrain on the tablet screen, discrepancies between the design and the current state can be immediately visually identified, which is useful for reviewing construction plans and ensuring safety.

Additionally, point cloud data is being used in the creation of design drawings. For example, in the repair design of aging infrastructure, there has been an increase in the practice of scanning existing structures to create design drawings or restoration diagrams. In the past, when design drawings were not available for old bridges, it was a labor-intensive process to conduct on-site measurements and generate drawings. However, by using laser scanners to measure the entire bridge and create a highly accurate 3D model, the necessary dimensions and shapes for repair design can be precisely determined. In fact, point cloud data is playing a key role in creating 3D models for many of the approximately 700,000 bridges across the country, significantly contributing to the creation of damage record diagrams and restoration diagrams that serve as the foundation for reinforcement designs.

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Point cloud data is also effective in as-built management during construction. For example, if you need to measure the volume of embankment on-site in real time, you can calculate the embankment volume from point clouds obtained with drones or ground-based LiDAR, or perform the soil volume calculation directly on a tablet. Recently, services have emerged that integrate BIM/CIM models and point cloud data in the cloud, enabling anyone on-site to easily measure embankment and excavation volumes using just a tablet. In practice, it is possible to instantly calculate the difference in soil volume by comparing two sets of point cloud data (before and after construction) on the cloud, allowing immediate insight into how much soil has been added or removed.

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For example, if a slope collapse occurs, the lost soil volume can be measured from point clouds before and after the collapse, allowing for rapid planning of recovery efforts. In this way, by using point cloud data, changes in as-built conditions that occur on-site can be quantified in real-time, drastically improving the efficiency of soil volume calculations and as-built management, which previously took a considerable amount of time.

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3. Benefits of Utilizing Point Cloud Data

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By utilizing point cloud data, several benefits can be achieved in various aspects of civil construction. The main advantages are as follows:

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• Improved Surveying and Construction Management Accuracy: Point cloud data records the shape of the site with a high density of points, allowing for more detailed and accurate site assessments compared to traditional surveying methods. This enables accurate volume calculations during the design phase and provides a quantitative evaluation of as-built conditions, eliminating reliance on human judgment or experience. For example, by capturing the terrain as point cloud data, comparing the design with the post-construction shape can help identify even minor discrepancies, contributing to the prevention of rework and ensuring quality.

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• Optimization of Construction Planning: By utilizing 3D site data, potential conflicts with terrain or structures can be evaluated during the planning stage. When point cloud data is combined with design models, tasks such as confirming heavy machinery access routes or planning the layout of temporary scaffolding can be done more efficiently. Additionally, by integrating point cloud data with BIM/CIM data and managing information centrally, optimal decisions can be made throughout the entire process, from design and construction to maintenance. This ultimately leads to well-structured plans that eliminate waste and unnecessary effort.

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• Cost Reduction and Time Savings: Introducing point cloud data enables a reduction in the number of surveys and streamlines tasks. By minimizing repetitive tasks that relied on the intuition of seasoned professionals and preventing unnecessary rework, overall construction costs are directly reduced. For instance, on a certain site, conducting crack surveys of structures with a LiDAR-equipped tablet reduced the time for tasks like photo composition and diagramming from 1–3 days to just about 5 minutes. It also reduced the amount of work outsourced to partner companies by 30-40%. In this way, automating and streamlining labor-intensive tasks with point cloud data leads to significant improvements in both project timelines and labor cost reduction.

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4. Future Outlook and Challenges

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The use of point cloud data is expected to expand into even broader fields in the future. With the introduction of new measurement methods such as LiDAR-equipped drones and mobile mapping systems (MMS), efficient 3D measurement is becoming possible even in areas that were previously difficult to measure (such as steep slopes in mountainous regions or inside long tunnels). Going forward, the potential of point cloud data is vast, including applications such as deformation detection through automated analysis using AI and real-time construction automation linked to construction machinery.

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However, there are also specific challenges associated with point cloud data. One of the key issues is the efficiency of data sharing. Compared to photos or videos, point cloud data contains much more information and has much larger file sizes. As a result, sharing point cloud data acquired on-site with stakeholders has traditionally required bringing physical media back to the office or taking time to upload to the cloud, making immediate information sharing difficult. However, this challenge is gradually being addressed. With the development of high-speed communication environments and cloud services, efforts to share 3D data from the site in real time with remote locations are underway. For example, one construction site successfully used satellite communication (Starlink) to transmit point cloud data from a tunnel construction site in real time, allowing immediate confirmation of construction progress and the alignment of supports from a remote office. In another example, a game engine was used to overlay BIM models and point cloud measurement data, enabling remote participation from multiple locations on PCs, tablets, and VR platforms. This system allows for the comparison and verification of design data with the actual construction conditions in 3D without the need to visit the site, contributing to improved accuracy in information sharing and progress management. In the future, point cloud data from the site will be shared in real time on the cloud, further enhancing collaboration among clients, designers, and contractors.

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5. Utilization of Point Cloud Data with LRTK

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In the final section of this article, we will discuss LRTK (developed by Lefixea), a solution gaining attention for its ease of use in applying point cloud data on-site. LRTK is a unique platform that combines GNSS (Global Navigation Satellite System) real-time positioning (RTK) technology with LiDAR measurement, providing strong support for high-precision point cloud acquisition and sharing on construction sites. Here are some of its key features.

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• High-Precision Point Cloud Acquisition with LRTK Phone: The LRTK Phone is an ultra-compact RTK-GNSS receiver that can be attached to an iPhone/iPad. By using this device, the smartphone transforms into a surveying tool with centimeter-level positioning accuracy. When combined with the built-in LiDAR on the smartphone, it allows for easy 3D point cloud scanning while walking around the site. Typically, smartphone LiDAR scans do not include coordinates, and long-distance walking can cause accuracy distortion. However, by using LRTK in conjunction, every point obtained is assigned a global coordinate, and the device continuously corrects its position with centimeter-level accuracy while scanning, eliminating the risk of terrain distortion. With just one pocket-sized device, anyone can easily acquire coordinate-tagged point clouds and perform tasks such as measuring distances between two points or calculating embankment volumes directly on-site. This ease of use is revolutionary.

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• Wide-Range 3D Scanning with LRTK LiDAR: LRTK LiDAR is a measurement device that integrates GNSS-RTK with a high-precision laser scanner. It eliminates the need for complex target (reference point) setup, automatically acquiring centimeter-level coordinate values simultaneously with the scan, which significantly reduces preparation time. Additionally, the device is equipped with laser technology that allows for precise measurements up to 200 meters away, making it suitable for large-scale terrain surveys and measurements of complex structures. It can acquire massive point cloud data with up to 15 million points in a short time, allowing for immediate verification of preliminary measurement results on a smartphone screen. If any gaps are found, rescanning can be done right away. This feature ensures that anyone can efficiently capture complete and accurate measurements.

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• LRTK’s Advantage in Real-Time Utilization: The LRTK platform is equipped with robust mechanisms for uploading and immediately sharing the acquired data to the cloud for practical use. For example, point cloud data obtained via the LRTK app can be sent to the LRTK cloud with the push of a button. Without needing dedicated software, users can view the point cloud through a web browser, measure distances, areas, and volumes at selected locations, and more. Photos taken on-site are automatically linked to the point cloud on the cloud along with high-precision coordinates, enabling users to view photos on the point cloud and check details of cracks or deformations. This cloud integration allows the latest 3D data captured on-site to be instantly shared both internally and externally, enabling remote instructions and consultations. This makes real-time construction management a practical reality.
  
  As shown above, the real-time utilization of point cloud data is bringing significant transformation to construction sites in civil engineering. Being able to accurately understand and share the "current" 3D data bridges the gap between design and construction, leading to more efficient and safer site operations.
  
  With the ongoing evolution of measurement and communication technologies, the use of point cloud data will continue to expand. In an era where those who control data control the site, point cloud data will undoubtedly become an essential tool in construction management in the DX era.