A must-read for prospective adopters: Why LRTK makes cross-sectional drawing creation easy and its benefits

The importance and difficulty of creating cross-sectional drawings

In construction, civil engineering, and infrastructure sites, creating cross-sectional drawings of terrain and structures is indispensable. For example, in road and river maintenance, cross-sections are used to check slopes, and in embankment and slope works, as-built conditions are verified using cross-sections. Cross-sectional drawings also play an important role in locating underground utilities and planning land development. However, traditional cross-section creation requires careful field surveying and manual drafting, which in practice consumes a great deal of time and effort. When surveying by hand, survey point intervals tend to be coarse and there is a risk of overlooking small undulations, so accuracy is inherently limited. In particular, surveying steep slopes or rivers during high water can be hazardous and it can be difficult to efficiently capture current site conditions. If additional cross-section lines are needed later, the site must be remeasured, so conventional methods also lack flexibility. To eliminate these inefficiencies, recent years have seen a push to digitize surveying and as-built management under ICT construction and construction DX. Emerging to make cross-section creation simpler and more accurate is LRTK. As a new technology that supports on-site DX through ICT construction, it is currently attracting significant attention.

What is LRTK? A mobile surveying system using the latest technology

LRTK is a mobile surveying system consisting of a compact RTK-GNSS receiver that attaches to a smartphone and a dedicated app. It combines centimeter-level (half-inch accuracy) positioning accuracy from RTK with a smartphone camera and LiDAR sensor to allow anyone to easily perform 3D scanning and surveying on site. Without expensive laser scanners or drones, LRTK enables a single person to walk the site and capture the surrounding terrain and structures as high-density point cloud data. The captured point clouds are tagged with absolute coordinates and can be used for various measurements and drawing creation on the cloud services described below. This new technology has garnered attention within the construction DX and i-Construction movements and is expected to be a valuable tool for advancing on-site DX. With the advent of LRTK, surveying and cross-section creation—previously reliant on specialist technicians—are being transformed into far more efficient processes.

Why LRTK makes cross-sectional drawing creation easy

Using LRTK dramatically simplifies the process of creating cross-sectional drawings. Let’s look at the main features and characteristics that make this possible.

1. Record the entire site with point cloud scanning

The greatest feature of LRTK is that it can record site geometry completely through point cloud scanning. Simply walking around holding a smartphone and pointing the camera, you can capture surrounding terrain and structures as a high-density collection of points (a point cloud) that can number in the tens of millions. In fact, for typical road sections, a scan can be completed in about 5 minutes of walking, so even large sites can be digitized into 3D data in a short time. Traditionally, survey points were set at each location where a cross-section was needed, but with LRTK a single scan acquires 3D data for the entire site, allowing cross-sections to be generated later at arbitrary positions. Point cloud data are so high-density that they capture fine undulations and irregularities that manual surveying cannot, so the generated cross-sections faithfully reflect current conditions and accuracy improves dramatically. Moreover, RTK-GNSS positioning ensures centimeter-level (half-inch accuracy) precision is consistently maintained, so dimensions and elevations in cross-sections are highly reliable and can be compared rigorously with design drawings. In addition, point clouds obtained by LRTK meet the accuracy requirements of the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines, making them of sufficient quality for official as-built drawings and other deliverables.

2. Intuitive on-site verification and sharing with AR display

LRTK includes a feature to display captured 3D data and drawings in AR (augmented reality). By viewing the site through a smartphone or tablet screen and superimposing design drawings or cross-section lines at full scale, you can intuitively check for discrepancies between the site and the drawings. For example, AR display of planned lines or the expected finished appearance allows stakeholders to vividly imagine the completed state on site, facilitating shared understanding between clients and contractors. Because LRTK’s AR uses RTK for high-precision alignment, it is characterized by displays that do not drift no matter how much you move around. There are many use cases: overlaying as-built point clouds and design data in AR to spot as-built deviations on the spot, or visualizing the location of pre-scanned buried pipes. Information that was hard to convey with paper drawings can be shared immediately on site with AR, reducing communication loss. In short, the AR feature that visualizes designs directly on site greatly simplifies pre-construction checks and agreement formation, contributing to reductions in construction errors.

3. Instantly create and share cross-sections on the cloud

Data captured with LRTK can be managed and used on a cloud service. Point cloud data scanned on site can be uploaded to the LRTK cloud with a single tap, eliminating the need to transfer data to a PC back at the office. Using the cloud’s dedicated viewer, point clouds can be displayed via a browser and cross-sections can be cut and displayed instantly at any chosen line. The operation is simple: just draw the line where you want a cross-section on the point cloud and the corresponding cross-sectional shape can be checked immediately. Created cross-sections can be shared with internal and external stakeholders via the cloud, allowing remote designers or clients to view and review the same cross-section simultaneously. Recipients do not need to install dedicated software or have a high-performance PC; they can check 3D point clouds and cross-section views simply by accessing a shared link, greatly lowering the barriers to data sharing. Because the cloud always stores the latest data, there is no worry of people referring to different outdated drawings. Accumulated cross-section and point cloud data become a digital asset useful for future planning and maintenance, contributing to centralized site information management. Real-time information sharing enables rapid feedback and decision-making regarding cross-sections.

4. Unified coordinate management for high consistency with design drawings

LRTK assigns and records absolute coordinates (latitude, longitude, elevation) to all survey data. This ensures that captured point clouds and cross-section data are precisely positioned within a public coordinate system. Traditionally, aligning field-measured cross-sections with design drawings required correcting shifts relative to control points or adjusting scale, but LRTK data reside on a common coordinate basis, making overlay with CAD drawings straightforward. In other words, current cross-sections and design cross-sections can be compared without offset, allowing accurate determination of where and by how much differences occur. Centralized coordinate management smooths post-processing after cross-section creation and data linkage with other systems. For example, importing 3D data or cross-sections captured by LRTK into BIM/CIM models or GIS maps will automatically place them in the correct positional relationship for design review or analysis. Also, cross-sections based on absolute coordinates can include accurate elevation values and distance scales along each section line, eliminating the need to manually annotate numbers on drawings and improving the reliability of reports. Furthermore, LRTK includes a function to automatically compute earthwork volumes (fill/cut) from the difference between design data and as-built point clouds, allowing immediate grasp of shortages or excesses of earthwork. The ability to link data in a consistent coordinate system is a major advantage for site management.

5. DXF output makes use in CAD drawings easy

Cross-sections generated by LRTK can be exported as common CAD data such as DXF format. You can convert the cross-section lines displayed in the cloud to a DXF file with a single click and download it. This eliminates the laborious manual redrawing (tracing) of cross-sections and allows the automatically created cross-section lines to be used directly in CAD software. The resulting DXF cross-sections can be used directly in the creation of design documents and inspection reports, and can be smoothly integrated with other CAD drawings for report generation. Because DXF is a standard format supported by many CAD and surveying software packages, exchanging data with other departments and contractors is straightforward. The DXF output feature enables beyond just viewing LRTK-acquired site data; it allows secondary use as formal drawings, making it easy to incorporate into existing workflows.

Main benefits of introducing LRTK

By leveraging the functions described above, adopting LRTK provides the following benefits.

• Improved accuracy: High-density point cloud data capture terrain changes down to the millimeter level (0.04 in), dramatically improving the accuracy of cross-sections. Details that were previously overlooked can be identified and differences from design can be evaluated precisely. Higher accuracy reduces the risk of re-surveying and rework, contributing to quality assurance.

• Reduced labor: One-operation workflow completes surveying through to drawing, greatly reducing the heavy labor associated with cross-section surveying. Since operation does not require specialized skills, it prevents the concentration of surveying expertise in a few individuals. Fewer site visits are needed, enabling efficient work with a small team.

• Faster turnaround: With a few minutes of scanning and automatic processing, cross-sections are obtained instantly and results can be checked and shared on site. This significantly shortens lead times from surveying to completed drawings compared to traditional methods. Faster feedback improves decision-making speed across the project.

• Improved information sharing: Cross-sections and point cloud data can be viewed by all stakeholders via the cloud, allowing geographically dispersed teams to share site status in real time. Using AR also facilitates on-site consensus building. When everyone discusses the same information, misunderstandings decrease and design changes or corrective instructions are reliably communicated.

• Cost-effectiveness: Labor cost reductions and shorter construction schedules can lower overall costs. Additionally, because multiple specialized devices are not required and the system centers on smartphones, initial investment and maintenance costs are suppressed. Improved accuracy also prevents unnecessary rework, so returns on a modest investment are substantial.

Typical use cases for creating cross-sectional drawings

LRTK is useful for creating cross-sections in a wide variety of construction and civil engineering sites. Below are representative use cases and the advantages in each scenario.

• Slope faces (norimen): Situations where the cross-sectional shape of slopes beside roads or river levees needs to be understood. With LRTK you can scan from a safe distance without entering hazardous slopes and obtain detailed cross-sections. For example, you can measure the finished condition of a roadside cut slope from a safe location and check in cross-section whether the slope matches the design gradient. Accurately capturing as-built cross-sections in advance also provides margin for safety measures and quality control during slope construction.

• Embankments: As-built management for large embankments such as dams or road embankments. Scanning the entire embankment with LRTK allows accurate measurement of embankment height and width at each section and ties directly into earthwork volume calculations. Regularly checking cross-sections of dam crests or embankment shoulders ensures the required shape and volume are being achieved. It can also be applied to maintenance, such as regularly measuring cross-sections to monitor settlement or deformation after completion.

• Structures: Checking terrain cross-sections around structures such as bridge approaches, retaining walls, or culverts. LRTK point clouds allow arbitrary extraction of sections around structures to verify conformity with design plans in detail. For example, understanding the slope of backfill behind a retaining wall or the terrain around an elevated bridge abutment in cross-section confirms whether the structure is installed as planned. Showing interactions between the structure and surrounding terrain in cross-sections helps designers and contractors share a common understanding.

• Rivers: Regular surveys of river cross-sections and verification of bank protection works. With LRTK you can walk along riverbanks while recording river width and riverbed cross-sectional shapes, which helps calculate flow cross-sectional areas and supports flood inundation prediction. Riverbed shapes previously difficult to survey can be digitized, improving the accuracy of flood control planning datasets. LRTK is also effective for disaster response, such as rapidly measuring riverbed cross-sections after floods or earthquakes to assess deposited sediments.

• Land development: Checking differences between designed ground surfaces and current conditions for residential land development or site leveling. If you survey the entire development with LRTK, you can create longitudinal and transverse cross-sections at arbitrary points to check for excess or deficiency in cut-and-fill. Listing differences from design elevations in cross-sections during as-built inspections enables immediate decisions on whether additional earthworks are required, preventing rework. Acquired data can also be used during maintenance phases to periodically check for ground settlement by comparing cross-sections after completion.

In addition to these, LRTK is effective in any situation requiring cross-sectional measurement, such as tunnel cross-section surveys or roadway transverse surveys. Regardless of the type of site, LRTK’s major strength is the ability to quickly acquire and share necessary cross-sectional data.

Simple surveying with a smartphone, excellent usability makes adoption reassuring

As described above, LRTK achieves advanced simplified surveying while offering high usability tailored to field operations. When introducing new measurement equipment, field personnel often worry about whether they can operate it and whether it will fit into site routines. LRTK is a smartphone-based intuitive system; simply follow the app’s on-screen guidance to complete surveying and cross-section creation. Its operability is so high that no specialized training is required, and users familiar with smartphones can become proficient in a short time.

Moreover, the LRTK system can position itself using satellite augmentation signals even in mountainous areas without mobile reception, so it can be used confidently in offline field environments. High-spec PCs or special viewer software are not required; data can be viewed and used on commonly used laptops or tablets, adding to its convenience. Introducing LRTK will change the norms of cross-section creation and dramatically improve on-site productivity and safety. By leveraging LRTK— which combines accuracy, efficiency, and convenience—consider realizing significant labor savings and improvements in cross-section workflows. Why not consider adopting LRTK as a reliable on-site partner at this opportunity?