How Cross-Section Drawing Is Evolving with 3D Surveying – How Does LRTK Achieve Higher Accuracy and Efficiency?

In recent years, 3D surveying technology that captures site geometry in three dimensions has rapidly spread in the civil engineering and construction sectors. Within this trend, the process of creating cross-section drawings that show the cross-sectional shape of land and structures is also undergoing significant evolution. Cross-section drawings are indispensable in many situations—checking slope gradients, calculating earthfill and excavation volumes for site formation, and maintaining infrastructure structures. However, conventional methods have required considerable effort and time from surveying to drawing, and they have faced challenges in terms of accuracy and efficiency. This article organizes the importance of creating cross-section drawings and the problems of traditional methods, and explains how cross-section creation changes with the latest 3D point cloud surveying. Furthermore, we introduce an integrated workflow that quickly generates cross-sections through point cloud acquisition by LRTK, an innovative surveying system using smartphones, and cloud processing, and explore benefits such as reduced work time, improved accuracy, and consensus building through visualization. Finally, we touch on how LRTK’s simplified surveying and cross-section processing functions enable anyone to easily create high-accuracy cross-sections, offering hints for considering on-site introduction.

The Importance of Creating Cross-Section Drawings and Main Use Cases

A cross-section drawing represents the shape of a cut through the terrain or a structure in the vertical direction. Alongside plan views (top-down views) and longitudinal profiles (profiles in the direction of travel), cross-sections are one of the basic elements of civil engineering drawings. For example, in road work they show the road cross-section (roadway width, slope of embankments, shapes of fills and cuts); for rivers and dams they show cross-sections of embankments and berms. Because cross-sections capture on-site height information and internal structure, they are extremely important in the following use cases:

• Design and management of slopes: For road cut slopes and site formations, cross-sections are used to check gradients and heights and to evaluate whether the slope matches the design and is stable. Cross-sections serve as standards for designing preventive measures against collapse and for post-construction slope inspections.

• Site formation and earthwork volume calculation: In land development and excavation work, cross-sections are used to obtain cross-sectional areas of fills and cuts, which combined with length are used to calculate earthwork volumes. The average cross-section method, which estimates volume from the average cross-sectional area of multiple sections, is a typical technique; cross-sections serve as the basis for construction planning and progress control.

• Maintenance of structures: For infrastructure such as tunnels, bridges, and dams, recording and comparing cross-sectional shapes during periodic inspections helps detect deformation or deterioration. For example, monitoring lining deflection from tunnel cross-sections or checking section loss from bridge girder cross-sections utilizes cross-sections for structural health assessment. Even when drawings for old structures are missing, creating as-built cross-sections aids in renovation planning and strengthening design.

Thus, cross-sections are important documents that present site geometry intuitively and quantitatively. From pre-construction planning to construction management and post-completion maintenance, properly created and used cross-sections facilitate safety assurance, accurate quantity assessment, and smooth alignment of understanding among stakeholders.

Workflow and Challenges of Conventional Methods

Traditional cross-section creation centered on manual surveying and hand-drawn drafting. A representative example is surveying with total stations or levels. For instance, when measuring slopes or road cross-sections, surveyors observe the height and position of points at set intervals (or at change points) in the field, then connect those points to draw the cross-sectional outline. When measuring multiple cross-sections to calculate earthwork, each cross-sectional area is computed and averaged later in the office. Drawing was once done by hand on drawing boards or graph paper based on field-recorded numbers, and even today requires manual input into CAD software to draw lines.

The primary challenges of conventional methods are the large amount of labor and time. Precise measurement with an optical total station, including setup and post-processing, often requires multiple people and can take a full day or more. For example, to create cross-sections for a 100 m (328.1 ft) road section measured at 10 m (32.8 ft) intervals, selecting and observing survey points might take half a day and drafting another half day, so total man-hours easily reach several days. Dangerous steep slopes or restricted-access areas also involve risk when measured manually. On small sites without a dedicated surveyor, outsourcing is often unavoidable, creating issues of outsourcing costs and scheduling.

There are also problems with accuracy and coverage. Manual surveying tends to capture only representative points, so small undulations between points may be overlooked. Resulting cross-sections can differ slightly from reality, leading to unexpected additional fill or over-excavation. If some areas were missed during measurement, returning to the site is necessary, which is inefficient. Especially when checking as-built shapes, drawings may appear acceptable while parts of the slope remain too flat in reality—such oversights can occur.

Moreover, information sharing is difficult with traditional methods. Cross-sections are hard to interpret for non-specialists, and paper drawings or tables take time to align understanding among owners and other departments. Even with photographs, 2D information cannot fully convey surface irregularities or depth, making it hard to share the completed image.

Thus, conventional cross-section creation faced problems of being labor-intensive, having uncertain accuracy, and being hard to share, creating demand for more efficient and accurate methods.

How 3D Surveying and Point Cloud Use Change Cross-Section Creation

Emerging in this context is the use of point cloud data from 3D surveying technology. Laser scanners and drone photogrammetry can measure an entire site and generate point cloud data—collections of countless points that record shape. Because point clouds consist of a vast number of points covering object surfaces, they contain high-density shape information that is on a different level from representative-point surveys. Applying point cloud technology to cross-section creation has produced the following major changes:

• No missed data: Point cloud measurement scans the entire site at once, so measurement omissions are rare. The acquired 3D data records on-site details, allowing cross-sections to be cut and analyzed at any location afterward. The assurance that “if you capture the data, you can measure it later as much as you want” greatly reduces the need for additional surveys.

• Automation of cross-section creation: Point cloud processing software can automatically generate cross-sections along arbitrary section lines from point cloud data. Without tedious drafting, specifying a cross-section location in the software immediately displays and outputs the section shape. Multiple sections can be processed in batch—10 or 20 sections can be created quickly—greatly reducing manual drafting workload.

• Capturing previously unseen shapes: Complex shapes and curved surfaces difficult to measure manually can be accurately drawn from point clouds. For example, irregularities in vegetation mats or shotcrete on slopes, or curvature of tunnel interior walls, can be reproduced in detail in point cloud sections. Parts that were previously approximated by average shapes can now be precisely captured, enabling detection of subtle differences between design and as-built conditions.

• Advanced earthwork calculation: By comparing pre- and post-construction terrain point clouds, fill and cut volumes can be calculated directly in three dimensions without relying on cross-sections. Localized surpluses or shortages that the average cross-section method could not capture can be accurately computed by differencing point clouds, dramatically improving progress management accuracy. Cross-sections themselves can also be auto-generated from point clouds, so as-built drawings can be produced quickly.

3D surveying with point clouds brings “no-miss data capture,” “efficiency through automation,” and “precise shape understanding” to cross-section creation. Since point clouds can also be handled as visually rich 3D models akin to photographs, it has become easier for all stakeholders to share a three-dimensional image of the site. The process of creating cross-sections is being digitally transformed, and these new high-accuracy, labor-saving methods are gaining attention on-site.

Workflow from Point Cloud Acquisition with LRTK to Cloud-Based Cross-Section Extraction

Making point cloud use even more accessible is LRTK, a mobile surveying system using smartphones. LRTK is a solution that mounts a small RTK-GNSS receiver to a smartphone or tablet and combines high-precision positioning and built-in sensors for 3D scanning to acquire point cloud data. By enabling 3D surveying—previously requiring expensive laser scanners or specialized equipment—on everyday smartphone devices, LRTK significantly lowers the barrier to on-site measurement.

The flow from point cloud acquisition with LRTK to cross-section extraction proceeds as follows:

• Smartphone-based high-precision point cloud scanning: Walk around the site with a smartphone equipped with an LRTK receiver, scanning the surroundings with the camera or LiDAR. With RTK position correction, each point receives world coordinates at the cm level accuracy (half-inch accuracy) in real time, so the acquired point cloud is immediately placed in an accurate coordinate system. In just a few minutes of scanning, point cloud data of the terrain and structures can be obtained on-site.

• Upload data to the cloud: The acquired point cloud can be uploaded to the LRTK cloud from the smartphone with a single tap. If there is no network, data can be sent later when connected, aggregating data in the cloud.

• Cloud processing for cross-section extraction: Without specialized software, you can access the LRTK cloud via a web browser to view and analyze uploaded point clouds. In the browser’s 3D viewer you can rotate and zoom the point cloud and slice cross-sections at arbitrary positions to display the cross-sectional shape. Specifying a section line auto-generates a point cloud cross-section image, and you can download the cross-section image or export CAD data with one click. You can also overlay design data to check comparisons against reference sections.

• Share and utilize results: Cross-sections and point cloud models generated in the cloud can be shared with stakeholders immediately. Issuing a shareable URL lets recipients view the 3D point cloud and arbitrary cross-sections in a dedicated viewer. Data added from the field syncs to the cloud immediately, so managers in the office or owners can grasp cross-section shapes in real time. Generated cross-sections and point clouds can be stored as records and used in reports or CAD drawing creation.

Thus, with LRTK the process from on-site point cloud measurement to cloud-based automatic cross-section generation is seamlessly connected. The workflow minimizes data conversion and manual processing, allowing required cross-sections to be retrieved whenever needed.

An Integrated Cross-Section Processing Workflow from Field to Cloud

Traditionally, cross-section creation involved many steps—bringing measured numbers back from the field and creating CAD drawings on office PCs. Using LRTK replaces this with a unified digital flow of “measure, digitize on the spot, and share/draw in the cloud.” A continuous workflow from the field to the cloud offers the following advantages:

• Real-time capability: Since cross-section data are digitized on-site and shared in the cloud immediately, stakeholders can check the data by the time the surveyor returns to the office. There is no need to wait for the surveyor to produce drawings before making decisions or moving to the next task.

• Reduced rework: Because you can cut cross-sections freely later in the cloud, you don’t need to return to the field just because “I want to check this section too.” As long as the point cloud data exists, subsequent processing can be done as many times as needed, minimizing rework caused by missed measurements or drafting mistakes.

• Centralized information management: With cross-sections, point clouds, and coordinate data consolidated in the cloud, access to the latest data is easy for everyone. The risk of missing drawing revisions or using outdated versions decreases, and the latest information can be shared among the field, design team, and owner. Centralized data management streamlines communication toward consensus.

This field-to-cloud connected workflow represents surveying and drawing creation in the DX (digital transformation) era. Even for the single task of cross-section creation, digitizing the entire process from data collection to utilization provides unprecedented speed, accuracy, and flexibility.

Benefits: Reduced Work Time, Stable Accuracy, and Consensus Building through Visualization

Cross-section creation using 3D surveying and LRTK brings dramatic efficiency and quality improvements over traditional methods. Below are the main benefits in terms of “work time,” “accuracy,” and “visualization.”

• Reduced work time: Point cloud scanning and automated processing significantly cut the time needed to create cross-sections. For example, where a slope cross-section measurement and earthwork calculation once took a surveying team half a day, LRTK can complete the on-site measurement in 10 minutes and automatic computation in seconds in some cases. One person can measure a wide area quickly, eliminating the need to arrange personnel and enabling quick cross-section checks alongside other tasks. Overall, this accelerates construction management cycles and contributes to shorter schedules.

• Stable accuracy: RTK-GNSS position correction and high-density point clouds improve the accuracy and reliability of generated cross-sections. There is no human observation error or subjective bias in point selection, so consistently high-quality data can be obtained. In particular, with LRTK each point has absolute coordinates at the cm level accuracy (half-inch accuracy), so measurements taken over multiple days do not conflict. Cross-sections generated from point clouds faithfully reflect site reality, ensuring accurate shapes down to the details.

• Easier visualization and consensus building: Point clouds and cross-sections provide rich visual information, facilitating smooth information sharing among stakeholders. By displaying deviations in as-built conditions with color maps on the 3D point cloud or overlaying design and measured lines on cross-sections, differences become apparent at a glance. Even non-specialist owners or local residents can be given intuitive explanations using photo-like point cloud models and clear cross-sections. LRTK’s AR function can overlay virtual design drawings onto the real scene, accelerating consensus building with a “seeing is believing” effect.

These new cross-section creation methods outperform traditional approaches in speed, accuracy, and clarity. As a result, they reduce on-site burdens and streamline inspections, and they are highly effective for explaining conditions to owners and coordinating with other departments.

Why It’s Easy to Adopt Even on Small Sites

Hearing “latest 3D surveying” might suggest a need for advanced specialists and expensive equipment. However, lightweight systems like LRTK are designed to be easily adopted by small and medium-sized contractors. Reasons include:

First, low initial investment cost: LRTK leverages commercially available smartphones or tablets, making it far less expensive than purchasing dedicated large equipment. A compact GNSS receiver and an app are sufficient, so the multi-million-yen-scale cost of traditional 3D measurement equipment is replaced by a much lower investment. Compact equipment is easy to store and transport, making it practical to bring to sites of any size. Second, usability for anyone: The system is designed so that non-specialist staff can perform high-precision surveying by following smartphone app guidance. The UI is intuitive, and short training enables site personnel to operate it themselves. This means small sites do not need dedicated operators; regular construction supervisors can handle surveying and cross-section creation, reducing labor costs and avoiding reliance on specialized individuals. Third, reduced outsourcing costs and improved responsiveness: Tasks that previously required requesting a survey company—even for small cross-sections—can be handled in-house with LRTK. This eliminates delays from outsourcing and allows immediate response to urgent measurement needs. For small projects with limited schedules and personnel juggling multiple tasks, LRTK is cost-effective enough that a one-person-one-device setup becomes realistic. As a result, site flexibility and productivity improve, and the benefits of digital surveying become accessible regardless of scale.

Thus, new measurement technologies like LRTK break the constraint that “surveying must be left to specialists,” especially felt on small sites. The ability to produce high-accuracy cross-sections on demand enables finer management that was previously overlooked, leading to improved quality and safety.

Make Cross-Section Creation Easier with LRTK

We have introduced the importance of cross-section creation, the evolution brought by 3D surveying, and the many efficiency gains enabled by LRTK. By using LRTK’s simplified surveying and cross-section processing functions, even less-experienced technicians can quickly perform 3D measurements on-site and obtain accurate cross-sections the same day. Complex surveying tasks can be completed with a single smartphone, and the acquired point cloud data can be freely utilized in the cloud. Quickly sharing high-accuracy cross-sections accelerates the PDCA cycle of construction and directly contributes to efficient, safe, and reliable site operations.

With LRTK overturning conventional wisdom, cross-section creation is becoming an accessible, easy task for everyone. If you currently face challenges with cross-section measurement or as-built management, consider trying smart surveying with LRTK. You will likely be surprised at its efficiency and accuracy. For more details, please also visit the [LRTK official site](https://www.lefixea.com/) and consider adopting next-generation cross-section creation methods on your sites.