Make cross-sections from point cloud scans easy – How LRTK revolutionizes construction management

The importance of creating cross-sections

In construction sites and surveying work, creating cross-sections is an indispensable process. Cross-sections that visualize terrain elevations and internal shapes of structures are used to check consistency with designs and to verify as-built conditions. For example, in civil engineering, cross-section drawings are attached to road and embankment as-built reports to show whether heights and slopes match the design. Cross-sections are also used for quantity calculations, playing an important role in computing excavation and fill volumes and evaluating slope stability. In other words, cross-sections are reliable records that “cut” the site, and they are widely used from construction management and quality control to considering design changes.

Traditional methods for creating cross-sections and their challenges

Until now, creating cross-sections has relied on conventional surveying methods and faced many challenges. Typically, surveying staff measure elevations at points along a survey line using levels or total stations, and draw cross-section lines based on that point cloud (point set). However, this method has presented the following problems:

• Labor- and time-intensive: Creating one cross-section typically requires at least two surveyors (one to measure and one to record), and for long transverse surveys, tripods must be repeatedly repositioned. On large sites, cross-section surveying alone can take several days to weeks.

• Hazardous work: On steep slopes or riverbank revetments, surveyors must descend to the site to plant poles, increasing the risk of slips and falls. Having multiple people work in hazardous areas itself raises the risk of labor accidents.

• Limitations in accuracy and coverage: Manual surveying typically samples points every several meters, so subtle undulations between points may not be captured. Because only the minimum required survey points are taken, if you later realize you needed more detail, you must return to the site.

• Work involved in drafting: Entering field measurement data into CAD software and drawing cross-section lines in the office is also cumbersome. When multiple cross-sections are required, the work essentially becomes repetitive and near-manual, increasing the chance of human error.

• Equipment and cost burden: High-precision cross-sections may require expensive surveying instruments or, in some cases, 3D laser scanners, making adoption difficult on small- to medium-sized sites due to cost.

As described above, traditional cross-section creation has faced issues such as “large personnel and time burdens” and “partial or missing data,” indicating room for improvement in both efficiency and accuracy.

Workflow for creating cross-sections with LRTK

By leveraging the latest digital technologies, creating cross-sections becomes astonishingly simple and fast. A notable solution is LRTK, a versatile surveying system that combines smartphones and GNSS for high-precision positioning. Let’s look at the workflow for creating cross-sections using LRTK.

• Acquiring point cloud data: Using an LRTK device attached to a smartphone, scan the site to acquire 3D point cloud data. Simply walk while pointing the smartphone camera to record the shapes of objects and terrain as a collection of countless points (a point cloud). Because LRTK supports RTK-GNSS centimeter-level positioning (cm level accuracy) (half-inch accuracy), the acquired point cloud is assigned absolute coordinates of latitude, longitude, and elevation. This makes it easy to align the site with the design coordinate system for later comparisons.

• Automatic processing in the cloud: The acquired point cloud data is synchronized to the LRTK cloud service for analysis (there is also a mode that processes on the smartphone itself when there is no internet connection). On the cloud, unnecessary points are removed and colorization is applied automatically to generate a 3D model of the site. No dedicated software installation is required; you can view and manipulate point clouds from a web browser. Because large-point-cloud processing is handled on the cloud side, data can be checked on-site within minutes of starting the scan.

• Extracting cross-sections: From the point cloud model uploaded to the cloud, extract cross-sections at any desired locations. By specifying two points on the screen for the line where you want the cross-section, a cross-section along that line is generated automatically. You can create cross-sections at any angle or segment, such as vertical sections of slopes or transverse sections perpendicular to a road. Because the point cloud includes fine details of ground surfaces and structures, minute undulations and shapes are accurately reflected in the cross-sections.

• Output as drawings: The extracted cross-sections can be viewed on-screen and exported as CAD data such as DXF format for saving. This lets you obtain the cross-section lines that used to be redrawn manually as digital data immediately. The generated cross-sections can be incorporated into design documents or as-built materials and shared with stakeholders with one click. Of course, you can also print them on paper to attach to reports.

Through these steps, you can create high-precision cross-sections from on-site scans in a short time. Cross-section creation that used to take days can be completed on the spot with LRTK, dramatically shortening the lead time to produce drawings.

LRTK features (smartphone-compatible, single-operator, high precision, cloud integration, AR use)

Using LRTK provides many advantages not only for creating cross-sections but for surveying and construction management as a whole. The key features of LRTK compared to traditional methods are summarized below.

• Usable with a smartphone: LRTK uses a small GNSS device attached to a smartphone or tablet, so you don’t need to carry special surveying equipment. It is operated on an intuitive smartphone app, eliminating the need to transport heavy tripods or stationary laser scanners. The entire kit fits in one hand, allowing quick response to any site.

• Surveying completed by a single person: Survey tasks that traditionally required a team can be done by one person with LRTK. By attaching the device to a smartphone and walking around, surveying is completed, reducing personnel requirements. This removes the need to arrange staff and enables agile surveying and recording even on sites with labor shortages.

• Centimeter-level high precision (half-inch accuracy): LRTK supports RTK-GNSS technology and can obtain position information with errors on the order of a few centimeters (a few inches). By using satellite augmentation signals provided by the Geospatial Information Authority of Japan (CLAS) or network-based reference station services for real-time error correction, surveying at smartphone level achieves extraordinary precision. This allows cross-sections to reflect reliable measured values.

• Cloud integration and data sharing: Measured data is synchronized to the cloud on-site for secure storage and analysis. Point cloud data on the cloud can be viewed from office PCs or tablets, enabling real-time information sharing with supervisors or clients in remote locations. Because 3D point clouds can be manipulated in a browser without a dedicated viewer or high-performance PC, all stakeholders can intuitively grasp the latest site conditions.

• Use combined with AR: Absolute-coordinate point clouds and design data obtained with LRTK can be overlaid on the site using a smartphone’s AR (augmented reality) features. For example, you can AR-display a design model over the finished terrain to confirm the completion image with no positional offset. Thanks to LRTK’s high-precision positioning, virtual objects remain fixed in the correct location no matter how much you walk around, eliminating the positional drift that plagued conventional AR. Also, if you AR-project a recorded point cloud model of buried pipes scanned once, anyone can easily avoid unseen underground utilities during subsequent excavation work, improving safety.

Given these features, LRTK can be called a versatile surveying tool that enables “anyone, anywhere, and with high precision” to perform surveying and create cross-sections. By simply carrying a smartphone and walking the site, measurements that were previously limited to specialists become feasible, accelerating site digitization.

Diverse use cases (slopes, revetments, buried pipes, embankments, residential exterior work)

Point cloud scanning and cross-section utilization with LRTK are powerful in various site scenarios. Below are some primary use cases.

• Slope surveying and as-built verification: For steep slope works, cross-sections are used to verify final slopes and the shapes of cut or fill. With LRTK, you can obtain point cloud data of an entire slope by scanning from below without climbing with an aerial work platform or by hand. For example, even a slope tens of meters high and extending 100 m (328.1 ft) can be captured in detail with a scan lasting just a few minutes, and cross-sections can be generated at arbitrary locations. You can check slope cross-sections at an accuracy that meets as-built management guidelines, allowing early detection of construction defects and easy preparation of as-built reports.

• Use in riverbank revetment works: For river embankment or revetment block installation, cross-sections or transverse surveys are needed to confirm there is no deviation between the planned line and the actual installed position. LRTK records the completed revetment geometry in a point cloud without omission, and cross-section profiles can be extracted immediately. Presenting maps that overlay the design and as-built cross-sections to clients makes it easy to explain completion status at a glance. By scanning continuously during construction, you can manage as-built progress with data and make necessary construction adjustments to assist quality assurance.

• Recording and visualizing buried pipe locations: In underground utility works such as water, sewer, or gas pipes, it can be difficult to know exact positions after backfilling. LRTK can 3D-scan trenches during excavation and record the positions and depths of buried pipes with high precision. From the acquired point cloud, pipe diameters and separations from other equipment can be measured later. If the underground pipe point cloud is stored in the cloud, you can project the pipe positions onto the ground with smartphone AR during future maintenance to visualize “the pipe runs ○ m below here.” This reduces the risk of accidentally damaging pipes and enables safer excavation.

• Volume measurement of fill and cross-section management: For embankment and excavation on roads or development sites, accurately knowing as-built volumes is important. By measuring terrain with point clouds before and after filling using LRTK, earthwork volumes can be automatically calculated from the differences. For example, scanning the terrain after fill and comparing it to the design elevation to draw cross-sections clearly shows where soil is lacking and where there is excess. The cloud can instantly calculate required or excess soil volumes, aiding decisions on additional delivery or cutting. Earthwork quantity management that used to require multiple people for surveying and calculation can be completed on-site by one person with LRTK, enabling rapid as-built quantity control.

• Exterior surveying for detached houses: LRTK is also effective for yard and driveway works on private homes. Even on small lots, surveyors can perform measurements with a smartphone without setting up a tripod, so a single craftsman can conduct a quick on-site mini-survey. For example, by recording pre-renovation site elevations as a point cloud and creating cross-sections, you can accurately plan how much to excavate or fill to level the ground. Scanning the entire site after exterior works are completed generates a “3D record of the residential exterior” including buried utility layouts, walls, and gate positions, which can be stored as an asset and used for future maintenance or extensions.

As shown above, point cloud scanning and cross-section creation with LRTK are effective across a wide range of scenes from large infrastructure to familiar residential sites. Point cloud data once acquired can be reused for various analyses, and the digital information obtained in each use case feeds into future construction planning and maintenance.

Innovation in as-built management by comparing design with point cloud cross-sections

Creating cross-sections from point clouds obtained by LRTK makes it easy to overlay and compare with design drawings. This is a major point of innovation in as-built management. Traditionally, verifying whether the constructed shape matches the design involved visually comparing the design line and measured line on a cross-section. The LRTK cloud refines this process further by overlaying design data (design cross-section lines or 3D models) on the acquired point cloud to intuitively visualize the differences between the as-built and the design.

For example, when inspecting the as-built of a road slope, you overlay the design cross-section line and the cross-section created from the current point cloud on the same screen. The system can automatically color-code areas: sections within design tolerance in green or blue, and those deviating from the design in red, so you can immediately see where rework is needed. The amount of deviation can also be shown numerically, allowing you to instantly derive specific corrective instructions such as “add ◯ cm (◯ in) of fill” or “cut ◯ cm (◯ in).” There is also a function to instantly calculate surplus or deficit soil volumes from the differences, enabling accurate knowledge of how much soil to bring in or remove.

This kind of visualization, essentially an as-built heat map, makes it easy to share quality information not only with inspectors but also with site workers and clients. Data-driven as-built management replaces subjective “inspection by intuition and experience” and achieves objective, persuasive quality assurance. LRTK is not just a tool for measurement efficiency; it is an innovative solution that transforms the construction management process itself into a data-driven workflow.

Benefits from the perspective of on-site DX (labor saving, speed improvement, quality improvement)

Digitizing point cloud measurement and cross-section creation with LRTK directly advances on-site DX (digital transformation). Finally, here are the main benefits from the DX perspective.

• Increased productivity through labor saving (reduced personnel): As mentioned, LRTK can achieve greater surveying results with fewer people and in less time. Tasks that used to involve people measuring point by point are now handled collectively by machines, dramatically improving surveying efficiency. In practice, there are reports like “a transverse survey that took two days was completed in half a day” and “as-built measurements that used to take four people a week were finished in a few hours by one person.” This is great news for the construction industry, which struggles with labor shortages and overtime reduction. Replacing measurements in hazardous areas with remote scans also reduces worker burden and improves safety. LRTK is a tool that immediately realizes the DX goal of productivity gains through reduced personnel.

• Speed-up and real-time responsiveness: Faster data acquisition to drawing generation speeds up on-site decisions and responses. For example, it becomes possible to perform multiple as-built checks on earthworks in a single day and make iterative construction adjustments—a real-time PDCA. Previously, converting survey data to CAD and performing calculations took days, delaying corrective actions. With LRTK, results are available the same day, contributing to schedule shortening and process flexibility. Reports to stakeholders can also be done immediately via the cloud, enabling fast remote instruction and consensus-building. DX promotes seamless circulation of information between site and office, accelerating the overall workflow.

• Quality improvement and data accumulation: Using detailed point cloud data contributes to improved construction quality. Full-data cross-sections with no omissions reduce oversights and make early correction of construction errors possible. Acquired data is accumulated in the cloud and can be reused for future maintenance and analysis. For example, if point cloud data is retained after construction, you can rescan the same area during annual inspections and compare differences to quantitatively evaluate aging or deterioration. Long-term data utilization that was difficult with paper drawings can now be practiced at the site level through DX. In short, introducing LRTK does not only provide one-off efficiency improvements but enables continuous data-driven quality management.

Taken together, the benefits of using LRTK for cross-section creation are not merely a single operational improvement but a DX solution that can transform how the entire site works. Achieving the trio of labor saving, speed, and quality will lead to cost reductions and enhanced competitiveness, making LRTK adoption highly meaningful in the construction and surveying industries.

Conclusion: Start new cross-section creation with LRTK

Cross-section creation, which used to require skilled techniques and much effort, can now be performed easily by anyone with LRTK. Being able to “easily create cross-sections from point cloud scans” directly links to innovations in construction management and DX promotion. Why not try LRTK on your site first to experience its ease and accuracy?

LRTK can be introduced with just a smartphone and requires no special training. As a first step, it is recommended to use LRTK’s simple surveying function to quickly measure current site conditions. You can record coordinates and elevations of arbitrary points as easily as taking photos, allowing you to experience high-precision surveying in your daily work. From there, move on to point cloud scanning and you’ll quickly obtain a 3D model of the entire site and cross-sections. This step-by-step approach makes it easy to start digital surveying without strain, which is another appeal of LRTK.

On-site DX starts with small initiatives. Try the effects of LRTK’s simple surveying, and eventually step up to full point cloud utilization for efficient cross-section creation and construction management. Cutting-edge smartphone surveying technology will bring new productivity and peace of mind to your sites.