Creating Cross Sections in the Era of On‑site DX: What Changes with High‑Precision Positioning × Point Cloud Scanning?

The wave of digitalization has reached the construction industry, accelerating on‑site DX (digital transformation). Among these changes, cross‑section creation (the task of converting terrain or structures into sectional drawings) has traditionally been an analogue process requiring significant time and effort, but it is now undergoing major transformation. By combining centimeter‑level high‑precision positioning with smartphone point cloud scanning, the flow from on‑site surveying to drawing creation is being dramatically streamlined. This article explains concretely what changes in cross‑section creation in the on‑site DX era thanks to these new technologies, comparing them with conventional methods and their issues.

Why cross sections are needed on construction sites and the problems with conventional methods

At construction sites, there are many occasions to create cross sections to check and record the shape of completed terrain and structures. For example, slope sections for roads or dams are needed to evaluate finished slope gradients and heights, and river or revetment works require sectional drawings to show fill thickness and revetment cross‑sections. Cross sections are essential deliverables in most civil engineering works because they serve as important documentation to verify design‑to‑construction consistency and to demonstrate the as‑built condition.

However, conventional methods for creating cross sections have many problems. Typically, surveying staff measure the cross‑sectional shape on site and create drawings from that data. Specifically, survey instruments such as total stations (TS) and levels are used to measure the heights and positions of multiple points along a section line, often with two people working together, and the point set is connected to draw the cross‑section. This work has had the following issues:

• Labor and equipment burden: Survey instruments like total stations are heavy and difficult to transport, and operation typically requires two or more personnel. Regular inspection and calibration of the instruments incur time and cost, making them burdensome for small sites.

• Accuracy and safety issues: General handheld GPS devices have positioning errors of about 5–10 m (16.4–32.8 ft), which is far too large for accurate cross sections. Therefore, TS surveying was indispensable for high‑precision surveying, but measuring on steep slopes required workers to enter dangerous areas, posing safety risks. Also, because drawings were created from a limited number of measured points, undetected irregularities between measured points might not appear on drawings, creating the risk of later disputes such as “part of the shape differs from the drawing.”

• Work time and accuracy limits: The conventional method of measuring one point at a time required vast amounts of time to capture wide‑area cross‑section shapes. When section lines are long or multiple, it could take days to finish all measurements. Additionally, it was necessary to sketch measurements by hand on site and then enter them into CAD software in the office to draw cross sections. This manual work required skill and was prone to omissions and transcription errors. In particular, re‑entering measured data from paper field notes into a computer was inefficient and burdensome for field technicians.

Conventional cross‑section creation thus demanded significant manpower and time and always carried the risk of missed measurements and drawing errors. Although there was high demand for more efficient and accurate cross‑sectioning, practical solutions were limited to expensive 3D laser scanners or outsourcing to specialist firms.

Easy on‑site surveying enabled by centimeter‑class high‑precision positioning

The key to solving these on‑site surveying issues is the use of RTK‑based high‑precision GNSS positioning. RTK (real‑time kinematic) is a positioning technology that corrects satellite positioning errors in real time using correction information from a base station, enabling extremely high accuracy within a few centimeters (within a few inches). Whereas RTK positioning once required specialized high‑end GPS equipment, small RTK‑enabled GNSS receivers paired with smartphones now provide solutions that allow centimeter‑level positioning on site with ease.

For example, with an LRTK system, you simply attach a compact GNSS device to your smartphone and launch an app to enable on‑the‑spot high‑precision satellite positioning. There is no need to carry heavy tripods or surveying instruments; a hand‑held device and a smartphone let you walk the site and survey. Positioning data obtained via RTK are provided as absolute coordinates based on the Geospatial Information Authority of Japan’s reference coordinate system, so measurement results can be directly overlaid onto drawings and maps. Device operation is very simple—intuitive steps like checking the current position and accuracy on the app screen and pressing a measurement button—so staff without specialized surveying knowledge can use it, enabling high‑precision positioning without lengthy prior training.

With high‑precision GNSS positioning available, tasks that previously required point‑by‑point TS measurements are greatly streamlined. For example, confirming ground elevations or staking out structure locations can be completed by one worker walking the site with a smartphone. Positioning data are plotted on the smartphone map in real time, making it easy to check for missed measurements on the spot or to add checks in suspicious areas. Now that “surveying by one person” is a reality, the on‑site surveying model that underpins cross‑section creation is beginning to change significantly.

Capture the entire site with point cloud scanning and automate section extraction

Once you have high‑precision position data, the next step is to digitize the entire surrounding shape. By using a smartphone’s built‑in LiDAR sensor or cameras to perform 3D measurement, terrain and structures can be recorded as a collection of points (point cloud data). With LRTK’s mobile scan function, simply holding a smartphone like a video camera and walking will scan the environment; for example, even a long slope of 100 m (328.1 ft) can be captured in three‑dimensional shape in a matter of minutes. The smartphone screen displays the point cloud in real time during capture, so you can proceed while confirming there are no unscanned blind spots, enabling zero measurement omissions.

High‑density point cloud data obtained in this way reflect all surface irregularities of the ground and structures in detail. While conventional methods only captured limited points along a section line, point cloud scans record the entire site comprehensively, eliminating worries like “I forgot to measure the required location.” With scan data, you can go back to the office and extract longitudinal or transverse sections at arbitrary positions, measure distances or slope angles between two points, and perform various analyses. The concept shifts from “measure everything” to “scan once and be confident,” with the intent of taking data that include all cross sections in a single site visit.

Moreover, LRTK point cloud scans attach the aforementioned RTK‑derived absolute coordinates to every captured point. This enables automatic alignment between point clouds and drawing data, producing a consistent, high‑accuracy 3D model even when scanning across wide areas. Even on sites with many trees or buildings, walking with a smartphone can capture point clouds into tight corners and cover details that traditional laser scanners might miss. Converting the entire site into a point cloud is itself a major step in DX, and the ability to automatically extract required cross sections from that data is the true value of this approach.

Display cross sections and export DXF from LRTK Cloud

Survey and point cloud data captured on site can be uploaded and utilized via the LRTK cloud service. With one tap from the LRTK app on your smartphone, data syncs to the cloud so you can immediately view and analyze site data in a PC browser in the office. No dedicated software installation is required; standard web browsers provide a 2D map and 3D viewer to review measurement results. In addition to basic functions such as distance, area, and volume measurement, the cloud offers robust cross‑section display capabilities.

For example, drawing an arbitrary line on uploaded point cloud data immediately displays the cross‑section profile at that location. You can generate either longitudinal or transverse sections with a single click, and the extracted section already has the acquisition absolute coordinates attached. The section shape can be exported as CAD data such as DXF format and downloaded with a single button. Cross sections that used to be drafted in the office after site surveying can now be used as deliverables with only minor adjustments when generated by LRTK Cloud.

In many construction projects, submission of cross sections as part of final documentation is required. For instance, riverbank or erosion control works commonly present pre‑ and post‑construction river cross sections. Using LRTK Cloud’s section display and export features, producing such deliverable cross sections becomes smooth. Extract sections at required locations from the acquired as‑is point cloud, overlay them with design section lines to confirm finished shapes, and output them as final drawings. Directly using point cloud data streamlines the creation of as‑built drawings and inspection documents, greatly improving quality and speed compared with manual drawing tracing. Because data reside in the cloud, stakeholders can easily collaborate by sharing URLs to view and discuss the same cross sections. Being able to complete the workflow digitally from on‑site data capture to drawing and reporting is a major benefit of on‑site DX.

Use cases where cross‑section creation adds value

LRTK‑based cross‑section creation contributes to operational efficiency across a variety of scenarios. Here are several examples.

• Slopes: Slope cross sections showing hillside or embankment shapes are essential for post‑construction gradient checks and stability evaluations. Previously, survey staff climbed dangerous steep slopes to measure a few heights, but LRTK point cloud scanning enables scanning the entire slope from a safe distance and obtaining continuous section shapes from crest to toe. Overlapping the resulting sections with design shapes allows detailed verification of whether fills or cuts were constructed according to design. Scanning slopes after heavy rain captures changes due to collapse or erosion, enabling cross‑section comparisons useful for maintenance and disaster response.

• Revetments: For riverbanks and coastal revetments, cross sections often show levee heights and berm shapes. Using LRTK, one person can walk across a wide riverbed and scan revetment shapes, producing river cross sections at arbitrary transects. Even when measuring near the waterline is difficult, oblique scans from land can cover almost the entire revetment surface, allowing safe and comprehensive data acquisition. Height and slope from point cloud cross sections let you verify conformity to design and store comparative data for future erosion monitoring.

• Embankments: When embankments are constructed for roads or development, cross sections are taken to check fill thickness and slopes. Because point cloud data allow extraction of arbitrary cross sections, you can, for example, create consecutive transverse sections every 10 m (32.8 ft) to check whether embankment height and width are uniform and whether there is any excess or deficiency compared with design. Comparing original ground and embankment point clouds enables one‑click calculation of fill volume, which is cumbersome from sectional area calculations. This provides more accurate volume estimation than traditional methods and is powerful for quantifying as‑built quantities.

• Structures: Large structures such as bridges, tunnels, and dams also benefit from 3D scanning and section creation. Scanning inside a tunnel lets you obtain tunnel sections at arbitrary positions to measure internal dimensions and detect deformation. Point cloud models of bridge piers or dam surfaces allow sectional analysis of crack depth during deterioration assessments and quantitative evaluation of deviations from design models. For renovation of existing structures, accurate as‑is section shapes are required for retrofit design; LRTK enables instant modeling of actual site dimensions, allowing designers to rapidly obtain the sections they need.

• Detached houses: In architecture, cross‑section creation is used for site surveys of detached houses and renovation planning. LRTK can scan houses and yards in a short time, producing 3D models of ground elevations and building outlines. Showing site elevation differences as cross sections aids consideration of earthworks and exterior design, and extracting building façades from point clouds enables before‑and‑after renovation comparisons. Measurements of detached house sites that used to be taken slowly with tape measures and levels can now be performed accurately with a single smartphone, offering both labor savings and improved presentation quality for homebuilders and landscaping contractors.

• Disaster sites: In disaster areas such as landslides or river breaches, rapid assessment of damage and planning for recovery are critical. Bringing LRTK to the site allows scanning of collapsed terrain from a safe distance to create detailed cross sections, estimate collapsed soil volume, and determine the extent of damage. Some municipalities have adopted smartphone surveying systems (LRTK Phone) for initial disaster surveys, balancing rapid situational recording with cost savings. The ability to measure immediately with a smartphone without waiting for specialized equipment is a major advantage in unpredictable disaster response situations.

Effects of DX on cross‑section creation work

As described above, high‑precision positioning, point cloud scanning, and cloud utilization significantly transform the cross‑section creation process. Here are the main effects of this on‑site DX.

• Efficiency gains: Capturing the entire site data in a single measurement and automatically generating multiple cross sections reduces duplication and waste. The previously separate steps of “on‑site surveying,” “drawing creation,” and “quantity calculation” are integrated on digital data, eliminating inefficient manual data entry and transcription. As a result, the same workload can be handled with far less effort.

• Quality improvement: Cross sections based on point clouds reflect many more measurement points and detailed shapes, improving the accuracy and reliability of the sections. Local deviations or changes that manual surveying missed can be captured in 3D data, eliminating gaps in as‑built control. Automated data processing reduces human errors, stabilizing report quality. From a safety perspective, reducing risky on‑site surveying lowers worker risk and thereby improves overall site quality.

• Labor savings: Surveys that used to require two people can now be completed by one, enabling substantial labor savings. In a construction industry facing severe labor shortages, this helps maintain site operations with fewer personnel. Because the tools are simple enough for less experienced technicians, operations are less dependent on specialists and easier to deploy across the organization. With fewer personnel needed on site, staff can be reallocated to other important tasks, directly improving productivity.

• Speed‑up: Lead times from data acquisition to drawing output are drastically shortened. With point cloud scanning and automatic processing, cross‑section creation that formerly took several days for surveying plus several days for drawing can sometimes be completed within the same day. Rapid preparation of inspection documents enables earlier reporting and delivery to clients. Decision‑making speeds up, and the construction schedule can proceed to subsequent processes without delay. Some sites report “inspection document preparation progressed more than three times faster” after DX adoption, demonstrating the clear time‑saving effects.

Conclusion

With the LRTK approach that leverages high‑precision RTK positioning and smartphone point cloud scanning, the previously cumbersome task of creating cross sections has become a realistic solution that can be completed “by one person” and “with a smartphone.” Without relying on expensive specialized equipment or expert technicians, anyone on site can intuitively handle surveying and drawing tasks, which is a major tailwind for DX promotion in construction.

Sites struggling with labor shortages or efficiency issues stand to gain the most from adopting these easy‑to‑use technologies. LRTK is designed to be usable even at small sites or at sites that have not traditionally implemented ICT construction methods, making it ideal as a first digital surveying tool. Once you experience creating cross sections immediately with just a smartphone, you will be impressed by the speed and simplicity. In the era of on‑site DX, cross‑section creation has evolved this far. If you feel your current approach is inefficient, consider trying this new method—you will likely see tangible improvements in productivity and work quality.