In recent years, the civil engineering industry has been accelerating the digitalization of construction through *i-Construction*. Among these efforts, ICT construction (information-based construction) for slope works is attracting significant attention from the perspectives of productivity improvement and safety assurance.

However, slope work sites face many challenges specific to ICT utilization, such as as-built management, earthwork volume calculation, preparation of construction records, and handling 3D design data. This article organizes those issues and introduces solutions using 3D point cloud measurement with LRTK. LRTK, which enables anyone to easily acquire high-accuracy point cloud data with just a smartphone, is a powerful ally in promoting i-Construction for slope works. We explain in practical terms how to use it on-site and the benefits you can gain.

Challenges Faced in ICT Construction for Slope Works

When site managers and surveying/design personnel try to promote i-Construction for slope works, the first obstacle they encounter is the gap with traditional methods. Conventional slope as-built management commonly involved manually measuring slope gradients and lengths with tape measures, staffs, and levels, and checking them against drawings. Because measurements were taken point by point at key locations, the process was extremely time-consuming and the number of measurable points was limited. It is difficult to comprehensively measure an entire large slope, and as a result there is a risk that discrepancies with the design will remain in “unmeasured areas.” Even if major survey points meet standards, small deviations in unmeasured parts can be found during inspection and criticized as “not as designed.”

There is also the safety issue of surveying at height. Having people climb steep slopes to measure with a staff is hazardous and places a heavy burden on workers. With a shortage of experienced surveyors, manual two-person surveys are inefficient and cannot fully address labor shortages. Furthermore, there are challenges in earthwork volume calculation and creating construction records. Traditionally, earthwork volumes were calculated by comparing pre- and post-construction terrain with cross-sections, but the section method simplifies slope shapes and has accuracy limitations. Manual calculations or CAD-based quantity takeoffs are time-consuming, and if something was missed, additional surveying is required. Organizing construction photos and preparing reports also takes effort, and risks of human error—such as forgetting to take photos or record details—are inevitable.

In addition, handling 3D design data is another hurdle. Recently, it has become more common for clients to request delivery of CIM models or 3D drawings even for slope works. However, on small- and medium-sized sites, there are voices of confusion: “We don’t know how to use 3D design data” or “We don’t have compatible software.” Even if you are not using ICT-equipped construction machinery, it is recommended to use 3D data for as-built management and quantity calculations, and failing to follow this trend means falling behind in productivity improvements.

Thus, promoting ICT construction for slope works involves multiple challenges from surveying to data processing and record keeping. Is there a way to solve them all at once? One promising approach is 3D point cloud measurement technology.

Solved by 3D Point Cloud Measurement! Innovations Brought by LRTK

3D point cloud measurement is a method that acquires the shape of a site as a collection of many points (a point cloud) using laser scanning or photogrammetry. Because it can scan an entire slope in a short time and produce high-density 3D data, it enables a shift from conventional “point-based” surveying to “surface-based” as-built management. While drone photogrammetry and terrestrial laser scanners for point cloud acquisition have become more widespread, LRTK makes these approaches even more accessible.

LRTK is a cutting-edge surveying DX tool that uses smartphones, combining RTK-GNSS (real-time kinematic positioning) with the phone’s built-in LiDAR technology so that anyone can easily obtain high-accuracy point clouds with one hand. Without expensive dedicated surveying equipment or large drones, you can achieve a 3D scan of a slope simply by installing the LRTK app on a handheld smartphone. The high-accuracy GNSS positioning and the phone’s camera and LiDAR sensor provide point clouds that are assigned accurate coordinates in a global coordinate system. Therefore, it is easy to compare scanned slope point clouds with design drawings or other survey coordinates.

Let’s look concretely at the advantages of point cloud measurement with LRTK. First, it dramatically shortens measurement time and reduces labor. Even on large slopes, with LRTK the operator can walk around the base or perimeter holding up a smartphone and scan the whole shape in just a few minutes. For example, even for large slopes reaching tens of meters in height and 100 m (328.1 ft) in length, there are reports that as-built surveys that used to take half a day can be completed in minutes. Moreover, the work can be done by one person and the need to stop heavy equipment is minimized. The measurement results are visualized as point clouds on the smartphone screen on-site, allowing immediate confirmation of any omissions. Unlike drone photogrammetry, which may require hours of offline data processing, the immediacy of being able to move to the next action right away on site is a major benefit.

Second, it improves safety and accuracy. Even in dangerous steep slopes or areas at risk of collapse where people should not enter, LRTK can obtain detailed terrain data from a distance. There is less need to climb to heights or erect scaffolding, contributing to worker safety. The acquired point clouds are collections of high-density survey points with millimeter-to-centimeter accuracy (cm level accuracy (half-inch accuracy)), so even minute surface irregularities of the slope can be recorded. This allows detection of subtle bumps and hollows that were previously overlooked, improving construction quality and preventing rework. In fact, the Ministry of Land, Infrastructure, Transport and Tourism recommends surface-based as-built management using 3D measurement techniques in its as-built management guidelines, and point cloud measurement with LRTK is positioned as an approved method. Using point clouds, you can instantly identify which parts of the slope have been overcut or overfilled, greatly reducing the risk of being flagged by inspectors later.

Third, the range of data utilization is broad. Point cloud data obtained with LRTK can be used for much more than just capturing shapes. Various analyses and measurements can be performed on dedicated cloud services or in the app. For example, you can extract longitudinal or cross sections at arbitrary locations from the point cloud to check section shapes, or compare point clouds from multiple time points to calculate *出来形土量* (cut/fill volumes). With the press of a button you can obtain the slope surface area, which helps in quantity estimation for slope protection materials (such as erosion control mats or sprayed concrete). These measurements are performed automatically by the software, preventing manual calculation errors. Especially for earthwork volume calculations, which traditionally required cumbersome drafting and average cross-section methods, you can now obtain accurate figures instantly from differences between point clouds, greatly improving efficiency and accuracy. Of course, various dimensional checks required for as-built management (height and slope of the slope toe and shoulder, slope length, etc.) can also be freely performed on the point cloud.

LRTK also offers revolutionary use through AR (augmented reality) features. If you load design drawings or 3D model data created in CIM into the LRTK app, you can overlay them on live camera imagery of the site. In other words, when you hold up your smartphone, the designed finish lines or structure models appear superimposed on the slope. This “AR projection without offset” enables intuitive sharing of the finished image even during construction. For example, you can draw excavation lines in AR on the terrain to instruct an equipment operator, or compare the design model and the actual slope during as-built inspections to verify construction accuracy. By visualizing information that could previously only be checked on drawings in the context of the actual site, construction instruction and verification tasks are dramatically streamlined. You can also AR-display a “deviation heat map” generated from the point cloud to color-code where the surface is protruding or recessed relative to the design. This enables immediate identification of areas needing repair and quick incorporation of corrective work, speeding up the PDCA cycle.

Smart Construction Workflow for Slope Works Using LRTK

Now let’s follow the series of steps to see how LRTK can be specifically used on-site. Below we explain the ICT construction process for slope works using LRTK.

• Pre-construction on-site 3D measurement: Before starting work, scan the existing slope terrain with LRTK. Acquiring the current slope shape as 3D data helps with design comparisons and construction planning. For example, for improvement works you can understand current slope gradients and irregularities from the point cloud data and determine where and how much to cut or fill. Because LRTK can measure nimbly even in narrow sites, high-accuracy data can be used from the initial survey phase. The acquired as-is point cloud is stored in the cloud and shared with stakeholders, who can view it as a three-dimensional terrain model.

• Utilizing 3D design data: If 3D models or data are prepared at the design stage, import them into LRTK for on-site use. If you have CIM data or design BIM models derived from drawings, load them into the LRTK app and project them on-site with the AR feature mentioned earlier. Even if 3D design data are not available, contractors can use LRTK point clouds to create a simple completion image or set reference lines and surfaces to aid construction control. The important point is to enable a three-dimensional understanding of the finished form that previously could only be seen in plans and sections. ICT construction also promotes “ditch-and-batten-less” (eliminating traditional stakes for setting height and position), and AR visualization of finished lines precisely supports ditch-and-batten-less construction.

• Monitoring and construction management during work: While the work is in progress, LRTK supports the site in various ways. For example, machine operators and workers can use LRTK on their own smartphones to scan the slope as needed and immediately check deviations from the design surface. If you display a cross-section from the point cloud and compare it to the design section, you can detect overcutting or overfilling early. Also, using LRTK’s coordinate navigation function, you can direct someone on-site to a specified drawing point (for example the start point of the slope toe or anchor positions). This is useful for staking or setting anchor bolts, and the staking work that used to require the survey team and a total station can be performed easily by one person. For construction records, if you take geotagged photos with LRTK’s positioning photo function, you can later display the photo locations and orientations on the point cloud or drawings, and use them as explanatory materials for as-built conditions.

• As-built management (final shape measurement): After slope construction is complete, perform as-built measurement of the finished shape. LRTK is useful here as well. Scan the finished slope thoroughly and acquire the as-built point cloud. By comparing this with the design data point cloud, you can complete the slope as-built inspection at once. Specifically, compare point clouds to calculate height and slope differences at each location and evaluate whether they are within tolerances. On LRTK’s cloud service, noise removal and positional correction are automatically applied to the acquired slope point clouds to produce high-accuracy data. From that data you can generate necessary cross-sections and plans, or extract values required in inspection reports (for example slope shoulder heights and slope gradients) and organize them. As-built management using point cloud measurement is a method consistent with the Ministry of Land, Infrastructure, Transport and Tourism’s “As-Built Management Guidelines (Slope edition, etc.)” and results can be compiled in data formats compatible with electronic deliverables.

• Quantity calculation for progress payments and report preparation: Point cloud data are powerful not only for as-built management but also for tracking progress and volumes. By comparing pre- and post-construction point clouds, cut and fill volumes can be calculated accurately in three dimensions. Using the volume calculation feature in the LRTK system, the transport volume of fill material and the excavated soil volume can be automatically computed, yielding more reliable quantity data than conventional methods. This information can be directly reflected in progress payment reports and as-built dimensional control documents. Furthermore, LRTK allows online sharing of measured point clouds and photos, making it easy to report progress to clients and supervisors with 3D visualizations. Site conditions that were hard to convey with paper drawings or photos alone become clear through point cloud visualization, making inspections smoother. By leveraging LRTK in this way, measurement, records, and inspection document preparation can be fully digitized, greatly streamlining the as-built management process for slope works.

A Step Toward Site DX: Effects of Introducing LRTK and Future Outlook

As described above, 3D point cloud measurement with LRTK solves various challenges in slope works and strongly supports on-site implementation of ICT construction. Finally, we summarize the comprehensive benefits of adopting LRTK and consider its applicability, especially to small- and medium-sized sites.

Significant improvements in productivity and quality: By using point cloud technology to streamline surveying and as-built management, schedule shortening and cost reduction can be expected. LRTK has enabled cases where measurement, drafting, and quantity calculations that used to take several days are completed on the same day, with reported reductions in man-hours exceeding 50% in some cases. At the same time, measurement accuracy and management quality improve, so hidden cost savings from reduced rework and redoing tasks are also anticipated. Improved accuracy in quality assurance can raise client trust and contribute to better company evaluations.

Safety management and workstyle reform: Replacing hazardous slope surveying and reducing personnel on site is a major step forward in safety management. Reducing opportunities for workers to be injured while enabling sites to operate with fewer people also supports workstyle reforms. Because it is an intuitive smartphone tool that can be used by less experienced staff without relying on specialists, LRTK also offers benefits for skills transfer and human resource development. When everyone on site can participate in 3D measurement and AR use, the team’s overall digital literacy improves and supports broader DX initiatives.

Easy adoption even for small-to-medium sites: Traditionally, ICT construction has been seen as something for large projects or advanced firms. However, the arrival of LRTK is making it possible to introduce ICT techniques easily even on small- and medium-scale construction sites. Without purchasing expensive special equipment, you can access the latest point cloud and AR technologies with an everyday smartphone and an affordable subscription service. Because it can be started regardless of site size or budget, it lowers the barrier for companies thinking “it’s hard to digitize our site.” LRTK is already being used in small-scale slope repair and erosion control works, contributing to digitization of construction management.

A key to site DX: The i-Construction concept advocated by the Ministry of Land, Infrastructure, Transport and Tourism aims to improve site productivity and ensure the long-term sustainability of the construction industry. Achieving that requires raising the capabilities of not only large corporations but all construction sites. Easy-to-use yet powerful tools like LRTK will be key to supporting industry-wide digital transformation (DX). Even in the niche field of slope works, if a new construction management style combining 3D point clouds and AR becomes widespread, the fusion of accumulated know-how and cutting-edge technology could make “smart construction” the norm. Trying it out on a trial basis at a site and experiencing its effectiveness firsthand is the first step toward DX.

Construction managers and surveying technicians should give 3D point cloud measurement with LRTK a try. Promote i-Construction for slope works with LRTK—the future of your site will surely change dramatically.