The New Standard in As-Built Management Using Point Cloud Data:
What Are the Key Points for Efficiency?

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Published February 28, 2025

What is Point Cloud Data?

Point cloud data is a collection of numerous measurement points in 3D space that represents the shape of objects or terrain. Each point contains coordinates (X, Y, Z) that indicate its position, and can also include information such as color or intensity. By collecting these points, the shape of the object can be recorded in detail and three-dimensionally. The higher the density of the point cloud, the more realistic and photo-like the 3D model representation can be.

In recent years, point cloud data has been increasingly used in the civil engineering industry. This is partly due to government initiatives, such as the Ministry of Land, Infrastructure, Transport and Tourism's promotion of "i-Construction," and the growing use of measurement technologies like 3D laser scanners on-site. Point cloud data enables highly accurate surveying, and its use has expanded in various fields, including infrastructure inspection and aging diagnostics. In civil engineering, incorporating 3D point cloud surveying for as-built management is becoming the "new standard."

What is As-Built Management?

As-built management refers to the process of ensuring that the shape and dimensions of a constructed structure comply with the design specifications intended by the client. In simpler terms, it is the process of verifying that completed (or partially completed) civil structures align with the design drawings, ensuring quality assurance. As-built management is an important element of construction management, alongside schedule management and quality control, as it is responsible for checking construction accuracy against contract conditions and specifications.

As-built management is crucial because many construction processes are difficult or impossible to reverse once completed. In civil construction, as-built measurements are taken at various stages to confirm that the project is proceeding correctly. For example, measurements taken after concrete pouring or before backfilling must be carefully documented, as they can only be measured during construction. Particularly for parts that will become invisible later (such as underground sections), evidence is left behind, such as photographs, to ensure proper verification after completion. In this way, as-built management plays a key role in quality assurance and preventing rework. It has been strictly implemented in public works projects following detailed standards. However, traditional methods have been criticized for requiring a lot of manpower and time, and for the difficulty of fully understanding the entire scope due to the limited number of measurement points.

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Benefits of Using Point Cloud Data in As-Built Management

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By incorporating point cloud data into traditional as-built management, the work efficiency and accuracy on-site are dramatically improved. Below are the main benefits:

• High-Precision Surveying:
  Point clouds obtained through 3D laser scanning or photogrammetry are highly precise. When measured correctly, they allow for capturing as-built conditions with millimeter-level accuracy, enabling much more detailed as-built management compared to traditional methods. Since point cloud data itself is a high-precision 3D information source, it can detect discrepancies with design values in great detail. Even small bumps or depressions that are easily overlooked in manual surveying can be detected using point clouds.

• Increased Efficiency in Surveying and Management Tasks:
  The introduction of point cloud measurement is expected to significantly simplify tasks such as measuring as-built dimensions and recording photos. Since large areas can be measured non-contact in a short amount of time, the collection of measurement points that previously required many personnel and effort can now be completed in one go. Additionally, by analyzing the point cloud, differences from the design can be automatically calculated, and pass/fail assessments can be made, reducing manual calculations and the need for writing on drawings. As a result, the time spent on as-built inspections on-site is shortened, leading to reduced workload for inspectors and improved productivity.

• Storage and Use as a Record:
  Point cloud data can be stored as digital information, becoming a valuable record asset for the future. The acquired 3D data can be viewed from any angle on a computer, and it is possible to extract cross-sections or remeasure dimensions as needed. By saving the point cloud at the time of completion, it can be used in future maintenance to check for deformations or in design considerations for expansions or renovations. Furthermore, point cloud data itself can serve as evidence (proof) for as-built management charts and reports, making it a more reliable record compared to relying on paper photo logs.

Another associated benefit is the improvement in safety, as hazardous areas can also be surveyed non-contact. With point cloud data, measurements can be taken remotely in areas that are inaccessible to people, such as steep slopes or zones with active heavy machinery, reducing the risks during measurement. In this way, point cloud as-built management significantly surpasses traditional methods in terms of accuracy, efficiency, and safety, bringing about advantages that can truly be considered the "new standard."

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Specific Steps for Utilizing Point Cloud Data

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Now, let’s look at the general steps involved in utilizing point cloud data for as-built management. The key stages are "Data Acquisition," "Data Processing and Analysis," and "As-Built Evaluation."

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1. Methods of Acquiring Point Cloud Data:

Point cloud data of the target object is measured on-site. There are several methods for data acquisition. For example, a ground-based 3D laser scanner can be set up to scan structures and terrain. When a large area, such as a bridge or embankment, needs to be quickly surveyed, using a drone (unmanned aerial vehicle) equipped with a laser scanner or camera for aerial surveying is also effective. For long stretches of roads or large sites, mobile mapping systems (MMS) with laser scanners mounted on vehicles are used to collect data while driving. In addition, handheld 3D scanners and underwater scanners are also used depending on the target and site conditions.

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2. Data Processing and Analysis Flow:

The point cloud data obtained on-site is raw coordinate data, so it must be processed and organized into a usable form for as-built management. First, if there are point clouds obtained from multiple measurement locations, these must be integrated (aligned) into a single coordinate system. By using reference points or known benchmark coordinates, the point clouds are georeferenced (converted to absolute coordinates), which provides accurate location data. Next, unnecessary noise points or duplicate points are filtered out, and only the surface or structures are extracted. In some cases, a mesh or contour lines are generated from the point cloud and converted into surface data. The processed 3D point cloud data is then compared with the design data, and differences at various points are analyzed. For example, the height deviation between the design surface and the as-built point cloud can be calculated, or cross-sectional shapes can be compared to determine if they meet the required specifications. In earthworks, the as-built conditions of excavation or embankment can be measured from the point cloud by cross-section, checking whether the prescribed width and height are maintained. For paving works, flatness and thickness can also be calculated from the point cloud data. The analysis results are visualized as numerical tables or heatmaps (as explained below) for the inspection team to review.

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3. Use Cases and Applications:

The use of point clouds in as-built management is expanding. As mentioned above, point clouds are useful not only for quality management during construction but also for post-completion maintenance. In the case of bridges or tunnels, point cloud data from completion is saved as baseline data and can be compared with newly acquired point clouds during periodic inspections to detect displacement or damage. In earthworks, point clouds are also used to calculate quantities (embankment and excavation volumes) alongside as-built measurements. For example, comparing the terrain point clouds before and after construction and automatically calculating the volume can streamline the creation of progress reports. Additionally, point clouds acquired during as-built management can be combined with 3D design data to create a CIM model, which can be used in discussions with the client and pre-inspection consultations. In this way, the use of point cloud data spans a wide range, from construction management to maintenance and even future planning, and is becoming the foundation of digital construction.

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Key Points for Streamlining As-Built Management Using Point Cloud Data

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To maximize the use of point cloud data and streamline as-built management, here are the key points to focus on at the construction site.

• Smooth Point Cloud Acquisition on Site:To ensure smooth measurement work, proper preparation and planning are crucial. Make sure the equipment’s battery is charged and calibration is completed, and set up reference points (known coordinate points) as necessary. If the measurement area is large, using both drones and ground-based laser scanners is ideal to select the best measurement method. For areas that are outside of view or could be in shadow, increase the number of measurement positions to reduce missing areas in the point cloud. Pay attention to weather conditions as well; for example, during rain, lasers can scatter, so it may be necessary to avoid scanning in such conditions. To enhance on-site mobility, using lightweight handheld scanners or smartphone-mounted measurement devices is another approach.

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• Minimizing Errors:To maintain high precision in point cloud measurements, minimizing positioning errors is essential. The use of survey reference points is key. By initializing the equipment using known points before measurement or aligning the point cloud to reference points after measurement, you can ensure that the obtained point cloud has absolute accuracy. Combining coordinates obtained from RTK-GNSS or total stations allows for local point clouds to be unified with geodetic coordinates. During measurement, avoid scanning from excessive distances or sharp angles, and set appropriate resolution and scan speed to reduce noise. During analysis, apply filtering and smoothing to reduce the impact of measurement errors. If multiple measurements can be taken, improving accuracy through averaging or overlay validation is beneficial. For instance, scanning the same location multiple times and merging the point clouds can enhance the reliability of the accuracy.

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• Using Analysis and Management Tools:To efficiently utilize point cloud data in as-built management, it’s effective to use specialized software and tools. Recently, various companies have released as-built management software compatible with point cloud processing, and some tools automatically perform as-built evaluations by simply loading the design data and point cloud. For example, comparing point clouds with design surfaces generates heat maps (deviation maps in color), which visually shows excess or deficit compared to the specification values. The error statistics for each measurement point (average, maximum, minimum) and the evaluation area are automatically displayed, and the values required by the as-built management guidelines can be instantly calculated. Additionally, the results of the as-built pass/fail evaluation can be output into the required format (PDF or Excel) with a single click. Using such tools significantly reduces the time spent on complex calculations and report generation. Moreover, systems have been developed that link 3D point clouds and heat maps to on-site tablets, allowing inspectors to verify the as-built conditions directly at the site. By utilizing IT, smart as-built management enables seamless handling of data from the office to the site.

By focusing on the above points, you can maximize the effectiveness of as-built management using point cloud data, achieving both further efficiency in surveying and inspection tasks and high-quality construction.​

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Introduction to LRTK – Easy High-Precision Point Cloud Measurement with a Smartphone

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RTK-GNSS Device "LRTK Phone" for Smartphones

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Finally, we introduce LRTK as a new solution that greatly contributes to the efficiency of point cloud measurement. The LRTK Phone is a tiny RTK-GNSS receiver that attaches to the back of a smartphone (iPhone/iPad). By simply attaching this device, the smartphone transforms into a "universal surveying tool" capable of centimeter-level precision. Traditionally, absolute coordinate-based point cloud measurements required stationary equipment or large drones, but with LRTK, this is easily achievable using a palm-sized device and smartphone app.

For example, with LRTK, on-site technicians can walk around the area on their own, measure the surrounding point clouds, and compare them with design data to verify the as-built conditions in real time. The high-precision data acquired can be instantly shared via the cloud, allowing supervisors and clients in the office to receive real-time updates. If each worker has a pocket-sized device, surveying and inspection can be conducted immediately when needed, leading to a significant increase in on-site productivity.

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LRTK is a groundbreaking tool that paves the way for smartphone-based surveying. Its high convenience contributes to as-built management in the following ways:

• Instant Acquisition of Absolute Coordinates:LRTK uses RTK-GNSS technology to constantly obtain high-precision self-positioning on global coordinates (the world geodetic system). This eliminates the need to convert point cloud data to reference points afterward, as the point clouds measured on-site are instantly available in the design coordinate system. It reduces the time spent on coordinate transformations and setting up reference points in as-built management, enabling immediate evaluation and decision-making.

• High Portability and Ease of Use:Weighing only about 125g and with a thickness of 13mm, the compact design of LRTK allows it to be attached to a smartphone case and carried around at all times. It can be easily pulled out for surveying when needed, without requiring setup time. With the dedicated app, positioning can be started or stopped with a single touch, and data can be recorded easily. This makes it user-friendly even for workers without specialized surveying skills, enabling them to perform as-built measurements independently.

• Multifunctional On-Site Use:LRTK is not only used for point cloud measurement but also supports layout marking and AR functionality. It can show positions on-site based on design coordinates or visually check the deviation from the as-built conditions by displaying the completed model in AR. These features allow for immediate on-site verification and correction of as-built conditions, helping prevent rework. When attached to an optional monopod (pole), it can easily adjust height offsets, and the smartphone and receiver can be separated to be used like a standalone GNSS surveying device.

• High-Precision Positioning Even Outside of Communication Coverage:In civil engineering projects, there are often areas, such as mountainous regions, where mobile communication is out of coverage. LRTK offers a model that supports the centimeter-level augmentation service (CLAS) provided by Japan’s quasi-zenith satellite system "Michibiki," allowing for high-precision positioning even in areas without internet connection. Even if correction data from RTK networks cannot be received, the system can obtain high-precision data directly from the satellites, ensuring reliable use in sites where signals are unavailable. This feature is particularly effective in remote island projects, mountainous construction, and areas where communication infrastructure is unstable after a disaster.

In this way, LRTK makes as-built management using point cloud data more accessible and convenient. The era has arrived where you can perform as-built surveying anytime, anywhere, by utilizing your existing smartphone, without relying on expensive specialized equipment. As a tool driving the digital transformation (DX) of construction sites, LRTK will greatly contribute to the efficiency of construction management and as-built management.

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By combining the new standard of point cloud data utilization with the latest technologies like LRTK, as-built management in civil engineering will continue to evolve into a smarter and more reliable process. We encourage you to implement this technology on your own sites and experience the improvements in quality and productivity.