In the construction industry, there is a serious labor shortage, and concerns are rising about project delays and worsened labor shortages due to the strengthening of overtime regulations starting in April 2024, referred to as the "2024 problem." In response to this situation, the Ministry of Land, Infrastructure, Transport, and Tourism is promoting labor-saving measures using ICT through "i-Construction 2.0," with the goal of increasing on-site productivity by 1.5 times and achieving over 30% labor reduction by 2040. In other words, the introduction of digital technologies, through construction DX (Digital Transformation), is essential to supplement the labor shortage and improve operational efficiency.

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One of the key technologies drawing attention is the use of point cloud data. Point cloud data, obtained through laser surveying or photogrammetry, is a collection of numerous 3D coordinates that can accurately represent the surface shape of objects. This article will provide a comprehensive explanation of point cloud data, from its basics to specific use cases on construction sites, and explore labor-saving methods using the latest technology, LRTK. In construction sites struggling with labor shortages, utilizing point cloud data is a crucial factor in improving construction efficiency and reducing labor.

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2. What is Point Cloud Data?
Basic Concepts and Expanding Applications

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Point cloud data refers to 3D coordinate data consisting of numerous points that represent the surfaces of objects in the environment. Each point contains location (X, Y, Z) information, and in some cases, additional information such as color or intensity. This allows for the accurate three-dimensional recording of buildings, terrain, and other objects. Point clouds are acquired through measurements with laser scanners (LiDAR) or by analyzing drone aerial photographs (SfM: Structure from Motion). In traditional surveying methods (such as total stations or GPS surveying), coordinates are observed point by point, but with point cloud measurement, an enormous number of points can be captured in a short amount of time, enabling high-density digital representation of the entire object. This is one of the key features of point cloud measurement.

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With the evolution of surveying technology, the scope of point cloud data utilization has also expanded. Looking back at history, total stations became widespread around the 1980s, and the first 3D measurement device (3D laser scanner) was introduced to Japan in 1998. Later, in 2008, Japan’s first domestic 3D laser scanner was released, and by 2016, major construction company Kajima Corporation introduced drone-based 3D surveying. Within about 20 years, the digitalization of surveying advanced rapidly. Today, point clouds can be captured using a variety of methods, including ground-based laser scanners (TLS), mobile mapping, and UAV (drone) surveying, and are applied in a wide range of fields, from infrastructure inspections and urban planning to civil construction management.

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Compared to traditional surveying methods, point cloud measurement excels in efficiency and comprehensiveness. For example, while total stations and GPS surveying measure only a limited number of points, point clouds allow the entire area to be scanned, enabling the detailed digital modeling of terrain and structures. This, in turn, facilitates various analyses that contribute to the advancement and efficiency of construction management, as discussed later.

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3. Use Cases of Point Cloud Data in Improving Construction Efficiency

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Labor-saving in Surveying Tasks

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By utilizing point cloud data, labor-saving in surveying tasks is achieved. Even for large-scale terrain surveys, the work can now be completed in significantly less time and with fewer people compared to traditional methods. For example, when surveying a land development area of several hectares, a total station would take about 3 days, and a ground-based laser scanner would take about 2 days. However, using drone photogrammetry, the same task can be completed in about half a day. This is a great example of how a single operator can manage the drone’s automatic flight and capture and analyze data, dramatically reducing both personnel and time requirements.

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Additionally, when using a ground-based laser scanner, data can be acquired at a rate of tens of thousands of points per second, so measurements that would traditionally require multiple points for complex structures can now be completed in a single scan. This reduces the time spent on-site for surveying, contributing to improved safety. Naturally, this also lightens the load on workers, leading to further labor-saving benefits.

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Improving As-Built Management Accuracy

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Point cloud data is also highly effective in as-built management during construction. Traditionally, after construction, measurements were taken to verify the as-built conditions, primarily using sectional checks or verifying on 2D drawings. In contrast, with point cloud measurement, 3D data can be captured in real-time during construction, allowing for immediate and three-dimensional verification of the as-built conditions. For example, using the latest total station-integrated scanners or mobile LiDAR, the scanned point cloud can be immediately overlaid with the design 3D model to visually compare whether the embankment or structure matches the design. This enables the visual detection of construction errors, minimizing the need for rework or corrections. Quality management, which used to rely on the intuition of experienced professionals, is now enhanced in accuracy and reliability with point cloud data as objective information.

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Additionally, in tunnel construction, there are emerging examples of using four-legged robots equipped with LiDAR for autonomous inspection. The acquired point cloud data is compared in real-time with design BIM data at a remote office to check the as-built conditions. With the ability to instantly share and compare point cloud data, construction accuracy can be monitored from distant locations, achieving both efficiency and improved accuracy in quality management.

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Streamlining Soil Volume Calculation

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Soil volume management in earthworks can be significantly streamlined with point cloud data. Traditionally, calculating volumes required the use of string lines and cross-sectional drawings, or measuring the volume after completion, which was time-consuming. However, with point clouds, simply scanning the site can instantly calculate embankment and excavation volumes. For example, by scanning the terrain before and after construction with drones or ground-based LiDAR, the volume of material moved in and out can be automatically calculated from the differences. In fact, with the LRTK system, it is claimed that "simply scanning the embankment will easily generate soil volume calculations," and there is functionality to calculate the volume directly on the acquired point cloud data. This digital soil volume management enables immediate tracking of daily earthwork progress, allowing for flexible adjustments to the construction plan.

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Additionally, by utilizing point cloud data, comparing it with design quantities becomes more efficient. For example, comparing the current point cloud with the design earthworks model and calculating the quantity from the differences can drastically reduce the time needed for reviewing soil distribution plans or considering design changes. In this way, point cloud data enables rapid quantity calculations and plan revisions, contributing to waste-free construction and labor savings.

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4. Labor-saving through Integration of Point Cloud Data with BIM/CIM

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In recent years, the combination of point cloud data with BIM/CIM (3D models) has increasingly been used to further promote the efficiency and labor-saving in construction management. By overlaying point clouds obtained on-site with the BIM models from the design phase, a digital twin of the site can be created, enabling the streamlining of various management tasks.

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For example, by integrating point clouds with BIM models, as-built management and quality control can be carried out remotely from an office, even in distant locations. In experiments conducted by Shimizu Corporation and others, point cloud data sent from robots was compared with design BIM data at the head office, successfully allowing for remote checks of as-built conditions, reinforcement, and pouring status. This allows construction status to be monitored on the data itself without visiting the site, enabling quality control even on sites with fewer specialized technicians, and contributing to the efficient allocation of personnel. Additionally, by creating a digital twin of the entire site with accumulated point cloud data and tracking progress and as-built conditions over time, significant labor savings in construction management are also expected.

The integration of point clouds and BIM also contributes to flexible responses to design changes. Even if design modifications arise during construction, by comparing the latest point cloud data with the BIM model, it is possible to immediately understand which parts need to be changed and by how much. For example, by comparing the current point cloud data with the earthworks model and recalculating the soil volume, the time required for earthwork planning or design modifications can be reduced. By using integrated data from point clouds and BIM, inconsistencies between design and construction can be detected and addressed early, leading to a reduction in rework and shortening of project timelines.

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Furthermore, by combining BIM/CIM models and point cloud data for AR (augmented reality) displays, new uses for facilitating explanations and building consensus on-site are emerging. For example, by displaying the design model and point cloud data simultaneously on tablet screens over live camera footage, it becomes easy to intuitively compare the completed design with the current construction status. This makes it easier to explain to clients or nearby residents, reducing the time and effort required for confirmation tasks. Moving forward, point cloud data will not only be utilized on its own but also play a crucial role in advancing the digital transformation (DX) of the entire construction process through its integration with BIM/CIM.

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5. Methods for Acquiring Point Cloud Data and Latest Technologies

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There are several methods for acquiring point cloud data, each suited to specific applications and site conditions. With the advent of the latest technologies, the accuracy and convenience of these methods have significantly improved.

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• Ground-based Laser Scanners (TLS): These are tripod-mounted laser scanners that perform high-precision scanning of the surroundings from a fixed point. They can measure distances ranging from several meters to several hundred meters with millimeter to centimeter-level accuracy, and are used in environments such as building interiors and tunnels. The range of data that can be captured is limited to the device's line of sight, so scanning from multiple locations is required for large sites, though recent advances in automatic registration technology have simplified this process.

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• Aerial Surveying by Drones (UAV-SfM and UAV LiDAR): This method involves equipping drones with cameras or LiDAR to measure terrain and structures from the air. In photogrammetry, point clouds are reconstructed from aerial images using software. Drones excel at quickly capturing wide-area 3D point clouds, even in areas that are difficult for humans to access, such as mountainous regions or large land developments. UAV-LiDAR drones can also measure terrain beneath tree canopies, enabling the collection of ground surface data that cannot be captured by aerial photos.

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• Mobile Scanning Technology (SLAM LiDAR): This method involves using handheld or vehicle-mounted devices to perform measurements while moving. The SLAM (Simultaneous Localization and Mapping) algorithm, which estimates position and creates maps simultaneously, allows real-time point cloud generation even in indoor or underground spaces where GPS signals are unavailable. Handheld LiDAR scanners have been developed and are used for measuring complex plant facilities or long tunnels. The ease of scanning surroundings simply by walking makes this method particularly effective for narrow inspections and understanding the current state of structures.

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• GNSS and RTK Precision Positioning: RTK (Real-Time Kinematic) is a technology that uses satellite positioning (e.g., GPS) to obtain centimeter-level precision coordinates. While RTK does not directly generate point cloud data, it is essential for the georeferencing of drone photogrammetry points or point cloud data alignment. Recently, solutions that combine smartphones with compact GNSS receivers for RTK surveying have emerged, allowing anyone to easily acquire high-precision reference point coordinates. This makes it easier to assign global coordinates to point cloud data and use it as base data for civil surveying.

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With these various acquisition methods, it is now possible to collect point cloud data using the optimal method depending on the site conditions and objectives, contributing to labor savings. Moreover, new solutions combining these technologies, such as LRTK, are being developed, further enhancing the efficiency of on-site surveying and measurements.

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6. Innovation on Construction Sites with LRTK

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In this chapter, we will explain in detail LRTK, a cutting-edge technology for utilizing point cloud data that is gaining attention. LRTK is a solution developed by Lefixea, consisting of a compact RTK-GNSS receiver and cloud services, which, when combined with a smartphone, creates a high-precision surveying and point cloud measurement tool that anyone can use.

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The ultra-small RTK-GNSS receiver "LRTK Phone" attaches to the back of a smartphone. It is pocket-sized, portable, and enables immediate high-precision positioning and point cloud measurement whenever needed.

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Features of LRTK Phone
(Easy Scanning with iPhone + RTK)

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The core device of LRTK, the LRTK Phone, is an ultra-compact RTK receiver weighing about 125g that attaches to an iPhone or iPad. By attaching it, the smartphone transforms into a versatile surveying tool that can handle global coordinate systems with centimeter-level precision. With this single device, you can perform standalone positioning, point cloud measurement, staking (positioning), and even composite displays with AR. Measurement data can be instantly shared to the cloud. Its price is significantly more affordable compared to traditional surveying equipment, and the ability to deploy one device per person makes it a practical tool for improving overall on-site productivity.

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Notably, by combining the LiDAR sensor built into the latest iPhone with RTK positioning, it enables easy and high-precision point cloud scanning. While iPhone LiDAR allows for quick 3D scanning, it previously had the issue of not attaching coordinates to the captured point cloud data, and distortion occurred when walking while scanning. However, by using LRTK, all point clouds are assigned global coordinates with centimeter-level precision, and scanning is performed with accurate self-positioning, preventing any distortion in the point cloud. This makes it possible for anyone, even without specialized knowledge, to easily capture point clouds with location information.

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On-site, with this pocket-sized device, you can easily perform point cloud scanning and measure distances between any two points or the volume of embankment right on the spot. There’s no need to carry heavy laser scanners or laptops, and you can literally "measure and scan with one hand." This is a groundbreaking system that fulfills the wishes of construction managers and workers who want to be light on their feet and easily conduct measurements themselves. For example, by scanning the entire site first thing in the morning, you can immediately track daily progress and soil volumes, or after construction, you can upload and share the as-built point cloud of important structures to the cloud on-site. This makes it possible for on-site personnel to handle measurement tasks that were traditionally outsourced to specialists. As a result, wasted waiting time for surveying is reduced, leading to faster decision-making and labor-saving.

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Utilization of LRTK LiDAR
(Long-Distance Scanning and Precise Point Cloud Acquisition)

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LRTK also offers a high-performance scanning unit called LRTK LiDAR. This system combines GNSS-RTK technology with high-resolution laser scanning, allowing for the precise scanning of structures up to 200 meters away to obtain accurate point cloud data. It is suitable for wide-area surveying and measuring complex terrain and structures, and it excels in providing a more agile approach to long-distance measurements that traditionally required large stationary equipment.

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The biggest feature of LRTK LiDAR is its ability to perform revolutionary 3D measurements without the need for markers. Typically, when scanning large structures from multiple locations and integrating the data, it is necessary to install targets (marker plates) on-site for alignment. However, with LRTK LiDAR, this is not required. Thanks to GNSS-RTK, high-precision coordinates are automatically assigned to each point during scanning, eliminating the need for cumbersome target placement and post-processing, which significantly reduces preparation time on-site. This reduction in setup time also reduces the need for manual labor, greatly improving efficiency.

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The large volume of point cloud data acquired is centrally managed on the cloud, and can be quickly reviewed on a smartphone within minutes. For instance, even with large-scale point clouds consisting of up to 15 million points, they can be quickly checked on-site and, if necessary, resampled immediately, ensuring that data is collected reliably and without error. Distance, area, and volume measurements, as well as coordinate verification, can be completed on the cloud without the need for specialized software, making it easy to share results with remote stakeholders and smoothly utilize the measurement data.

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Benefits of Implementation and Comparison with Traditional Technologies

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The introduction of LRTK Phone and LRTK LiDAR provides the following advantages compared to traditional technologies:

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• Surveying Possible with One Device per Person: Traditionally, expensive GPS equipment and laser scanners were handled by a limited number of measurement teams, but with LRTK, each on-site worker can carry a low-cost, compact device and immediately conduct surveying or point cloud acquisition when needed. This enables measurements to be taken without any waiting time, significantly improving productivity.

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• All-in-One for Task Consolidation: Multiple tasks such as surveying (for current conditions and as-built), staking, photo recording, and volume measurement can all be handled with a single smartphone + LRTK device. For example, there was traditionally a time lag in information transmission from the surveying team to the construction manager, but with LRTK, point cloud and coordinate data are instantly shared via the cloud, enabling real-time on-site decision-making.

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• High Precision and Simplicity: Despite its user-friendly operation that requires no specialized knowledge, LRTK achieves centimeter-level positioning accuracy. Previously, accurate point clouds and distance measurements that could not be obtained with simple iPhone scans can now be easily realized by anyone, compensating for the shortage of skilled surveyors.

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• Reduced Initial Costs and Effort: As mentioned earlier, LRTK LiDAR does not require the installation of markers, and there is no need for large tripods or generators. It reduces the manpower and time needed for setup while offering performance comparable to traditional stationary scanners, capable of measuring up to 200 meters. Additionally, cloud integration reduces the time and effort needed for data organization.

 

Overall, the introduction of LRTK brings an impact to the field that could be described as "the democratization of high-precision surveying." Tasks that were once handled by a select group of specialists can now be shared across the entire site, enabling efficient construction while maintaining quality, even in the face of labor shortages. By lowering the barriers to utilizing point cloud data, LRTK is rapidly becoming a key technology that accelerates construction DX, driving transformation in the industry.

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7. Conclusion and Future Outlook

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We have discussed the use of point cloud data to address labor shortages, covering everything from the basics to the latest examples. Point cloud data strongly supports the "visualization" and "automation" of construction sites, enabling efficiency and labor-saving in many tasks, including surveying, as-built management, and volume management. New technologies, such as LRTK, are particularly transformative, making advanced measurements accessible to anyone and greatly contributing to the improvement of on-site productivity. In the future, the scope of these digital technologies will continue to expand. Point cloud data, integrated with BIM/CIM, IoT devices, and AI analysis, will lead to even smarter construction management. For example, experiments on remote construction management through real-time point cloud transmission are showing success, and in the future, "construction management without being on-site" may become a reality. Further promotion of construction DX will transform the construction industry into a sustainable industry that can be managed with a limited workforce.

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Finally, I want to emphasize that technology only creates value when it is used on-site. Even powerful tools like point cloud data can only reach their true potential when on-site engineers understand their importance and actively implement and utilize them. I hope this article has helped you appreciate the benefits and potential of point cloud data. The key to construction in an era of labor shortages lies in the smart use of digital technologies. By leveraging point cloud data and LRTK, we can transform construction sites into more efficient and smarter environments.

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Thank you for reading. Let’s continue to shape the future of the construction industry with the latest technologies through construction DX.