In recent years, the civil engineering industry has accelerated the digitization of construction through *i-Construction*. Among the various applications, ICT construction (information and communication technology-enabled construction) for slope works is attracting strong attention for its potential to improve productivity and ensure safety.

However, on slope construction sites there are many challenges unique to ICT adoption, such as as-built management, earthwork volume calculation, creation of construction records, and handling 3D design data. This article organizes those challenges and introduces solutions using 3D point cloud measurement with LRTK. LRTK, which allows anyone to easily acquire high-precision point cloud data with just a smartphone, is a powerful ally for promoting i-Construction in slope works. From concrete ways to use it on site to the benefits gained, we explain everything in practical terms.

Challenges Faced in ICT Construction for Slope Works

When site managers, surveyors, and design personnel promote i-Construction for slope works, the first obstacle is the gap with conventional methods. Traditional as-built management for slopes typically involves measuring slope gradients and lengths manually with tape measures, leveling staffs, and spirit levels, then comparing those measurements with drawings. Because measurements are verified point by point, the process is very time-consuming and the number of measurable points is limited. It is difficult to comprehensively measure an entire large slope, and as a result there is a risk that inconsistencies with the design remain in "unmeasured areas." Even if the main measurement points meet the standards, small deviations in unmeasured areas can lead to findings at inspection that the work does not match the design.

There are also safety issues associated with surveying at height. Having people climb steep slopes and take readings with staffs is hazardous and places a heavy burden on workers. With a shortage of experienced surveyors, two-person manual surveys are inefficient and cannot keep up with labor shortages. Furthermore, there are challenges in calculating earthwork volumes and creating construction records. Traditionally, earthwork calculations were done by comparing cross-sections before and after construction, but the cross-section method simplifies slope shapes and has accuracy limits. Manual calculations or quantity extraction in CAD are time-consuming, and missed measurements require additional surveying. Organizing construction photos and preparing reports also take time, and human errors such as missed shots or recording mistakes are unavoidable.

In addition, handling 3D design data is another hurdle. Recently, it has become increasingly common for clients to request delivery of CIM models or 3D drawings even for slope works. However, at small and medium-sized sites there are often voices of confusion such as "we don't know how to use 3D design data" or "we don't have compatible software." Even if construction does not use ICT-equipped machines, it is recommended to use 3D data for as-built management and quantity calculations, and those who cannot follow this trend risk being left behind in productivity improvements.

Thus, promoting ICT construction for slope works involves multiple issues from surveying and data processing to record creation. Is there a way to solve these all at once? The technology drawing attention here is 3D point cloud measurement.

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

3D point cloud measurement is a method of capturing the site shape as a set 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 traditional point-based surveying to surface-based as-built management. In recent years, drone-based photogrammetry and ground-based laser scanners for point cloud capture have become more common, but LRTK is an innovative solution that makes these capabilities even more accessible.

LRTK is a cutting-edge surveying DX tool that uses a smartphone, combining RTK-GNSS (real-time kinematic positioning) with the phone's built-in LiDAR technology to make high-precision point cloud acquisition easy for anyone with one hand. Without dedicated expensive surveying instruments or large drones, you can achieve a 3D scan of slopes simply by installing the LRTK app on a smartphone you already have. High-precision GNSS position information combined with the phone camera and LiDAR sensor gives the acquired point cloud 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, there is a significant reduction in measurement time and labor. Even for wide slopes, with LRTK a person can walk along the base or around the slope while waving a smartphone to scan the entire shape in just a few minutes. For example, there are reports that as-built surveys that used to take half a day for large slopes dozens of meters high and 100 m long can be completed in minutes. Moreover, the work can be done by one person, and stopping heavy machinery is minimally required. Measurement results are visualized as point clouds on the smartphone screen on site, allowing immediate confirmation that nothing was missed. Unlike drone photogrammetry, which often requires hours of post-processing, the immediacy of being able to act on-site without long waits is a major advantage.

Second, it improves safety and accuracy. LRTK can capture detailed terrain data from a distance, even for hazardous steep slopes or areas at risk of collapse, reducing the need for people to climb to high places or set up scaffolding and thereby enhancing worker safety. The acquired point cloud data is a collection of high-density survey points with millimeter- to centimeter-level accuracy, so even fine surface irregularities can be recorded. This enables detection of small bumps or depressions that might have been overlooked before, contributing to improved construction quality and prevention of rework. In fact, the Ministry of Land, Infrastructure, Transport and Tourism recommends surface-based as-built management using 3D measurement technologies in its as-built management guidelines, and point cloud measurement with LRTK is positioned as an appropriate method. Using point clouds, you can instantly see which parts of the slope were overcut or overfilled, significantly reducing the risk of inspectors pointing out nonconformance later.

Third, there is a wide range of data applications. Point clouds acquired with LRTK are not just for measuring shapes. Various analyses and measurements can be performed on dedicated cloud services or apps. For example, you can extract longitudinal or cross sections from the point cloud to check cross-section shapes, compare point clouds from multiple time points to calculate *as-built earthwork volume* (cut and fill), or compute the slope surface area at the push of a button, which helps in quantifying slope protection materials (such as vegetation mats or sprayed concrete). Since these calculations are performed automatically by software, human calculation errors are prevented. In particular, earthwork calculation, which traditionally required drafting and averaging cross-sections, can be performed instantly and accurately from point cloud differences, leading to major efficiency gains and improved accuracy. Of course, various dimensional checks required for as-built management (e.g., heights and slopes at the slope crest and toe, slope length) can also be performed freely on the point cloud.

LRTK also offers a groundbreaking use case through its AR (Augmented Reality) feature. If design drawings or 3D model data created in CIM are loaded into the LRTK app, they can be overlaid on the live camera view of the site. In other words, when you point your smartphone, design finish lines or structure models appear superimposed on the slope. This "accurate AR projection" allows intuitive sharing of the completed-image during construction. For example, you can draw excavation lines on the terrain in AR to guide machine operators, or compare the design model with the actual slope during as-built inspections to verify construction accuracy. Information that could previously only be checked on drawings can now be visualized in the real site context, dramatically streamlining construction instruction and verification work. Additionally, you can AR-display a "deviation heat map" generated from point clouds to show in color which areas protrude or recess relative to the design. This makes it easy to identify areas needing repair and quickly reflect corrections in subsequent work, accelerating the PDCA cycle.

Smart Construction Workflow for Slope Works Using LRTK

Now let’s follow the concrete flow of how LRTK can be used on site. Below is the ICT construction process for slope works explained step by step when 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 in comparing with the design and planning construction. For example, in improvement works you can understand the current slope gradients and irregularities from the point cloud and determine where and how much to cut or fill. Because LRTK can measure nimbly even on confined sites, high-precision data can be used from the initial survey stage. The acquired as-built point cloud is stored in the cloud and shared with stakeholders for viewing as a 3D terrain model.

• Utilization of 3D design data: If 3D models or data are prepared in the design phase, they can be imported into LRTK for on-site use. CIM data or BIM models created from design drawings can be loaded into the LRTK app and projected on site using the AR feature mentioned above. Even if there is no 3D design data, contractors can use LRTK point clouds to create a simple completion image or set reference lines and planes to aid construction management. The important point is to enable on-site three-dimensional understanding of the final shape that could previously only be seen in plans or sections. ICT construction also promotes "batter-board-less" workflows (omitting traditional stakes for height/positioning), and AR visualization of finish lines directly supports batter-board-less methods.

• Monitoring and construction management during works: While construction is underway, LRTK supports the site in various ways. For example, machine operators or workers can use LRTK on their own smartphones to occasionally scan the slope and immediately check deviations from the design surface. If you display a cross section derived from the point cloud and compare it with the design cross section, you can quickly detect over-excavation or over-filling. Also, with LRTK's coordinate navigation feature, you can specify a point on the drawing (for example, a slope toe starting point or anchor position) and have the app guide you to that coordinate on site. This is effective for setting piles or anchor bolts, enabling tasks that used to require a surveying team with a total station to be done by one person. For construction records, using LRTK’s geotagged photo function stores photos with position information, allowing you to later display the photo location and orientation on the point cloud or drawings and use them as explanatory materials of as-built conditions.

• As-built management (final shape measurement): After slope construction is completed, perform as-built measurement of the finished shape. Again, LRTK comes into play. Scan the completed slope thoroughly to obtain an as-built point cloud. By aligning this with the design point cloud model, you can complete the entire as-built inspection of the slope at once. Specifically, compare point clouds to calculate height and slope differences for each section and evaluate whether they are within tolerances. On LRTK’s cloud service, noise removal and position correction are automatically performed on acquired slope point clouds to produce high-accuracy data. From this data, generate required cross sections or plans and extract values needed for inspection forms (for example, slope crest height or slope gradient) for documentation. As-built management using point clouds is a method compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s "As-Built Management Guidelines (Slope Edition, etc.)" and the results can be compiled in data formats suitable for electronic delivery.

• Quantity calculation and report preparation: Point cloud data is powerful not only for as-built management but also for grasping quantities (earthwork volumes). By comparing pre- and post-construction point clouds, you can accurately calculate cut and fill volumes in three dimensions. Using the volume calculation function within the LRTK system, transport quantities of fill or excavated volumes are automatically computed, providing more reliable quantity data than conventional methods. This information can be directly reflected in progress quantity reports and as-built dimensional management documents. Furthermore, because LRTK allows online sharing of measured point clouds and photos, it is easy to report to clients and inspectors in 3D. Site conditions that were difficult to convey with paper drawings or photos alone become immediately clear through point cloud visualization, facilitating smoother inspections. By leveraging LRTK, the entire process from surveying to record and inspection document creation can be digitized, greatly streamlining as-built management for slope works.

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

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

Dramatic improvements in productivity and quality: Leveraging point cloud technology to streamline surveying and as-built management can shorten construction periods and reduce costs. LRTK has enabled cases where measurement, drafting, and quantity calculation that used to take days are completed the same day, with reported labor reductions of over 50% in man-hours. At the same time, measurement accuracy and management quality improve, which reduces hidden costs from rework and corrections. Increased assurance of quality also enhances client trust and contributes to improved company reputation.

Safety management and workstyle reform: Replacing hazardous slope surveying and enabling labor reduction is a major advance for safety management. Reducing the opportunities for workers to be exposed to injury risk while enabling sites to operate with fewer personnel contributes to workstyle reform. As an intuitive smartphone tool that can be used by less experienced staff, LRTK also offers benefits in skills transfer and human resource development. When everyone on site can participate in 3D measurement and AR use, the overall digital literacy of the team improves, raising the floor for DX adoption.

Easier adoption at small and medium-sized sites: ICT construction has traditionally been seen as the domain of large projects or leading firms. However, with LRTK, even small- and medium-sized construction sites can easily adopt ICT technologies. Without purchasing special, expensive equipment, you can use modern point cloud and AR technologies with a regular smartphone and an affordable subscription service. Because it can be started regardless of site size or budget, barriers are low and it is easy to take the first step. In fact, LRTK is already being used in small-scale slope repair works and erosion control projects, contributing to DX in construction management.

As a key to on-site DX: The i-Construction concept advocated by the Ministry of Land, Infrastructure, Transport and Tourism aims to raise on-site productivity and ensure the sustainability of the construction industry. Achieving this requires raising performance across all construction sites, not just large companies. Tools like LRTK, which are simple yet powerful, can be a key to supporting industry-wide digital transformation (DX). Even in the niche field of slope works, if a new style of construction management combining 3D point clouds and AR becomes widespread, smart construction—where accumulated know-how and the latest technologies merge—may become commonplace. Starting with a trial on site to experience its effectiveness is the first step toward DX.

Construction managers and survey technicians are encouraged to try 3D point cloud measurement with LRTK. Promote i-Construction for slope works with LRTK—the future of the work site is sure to change dramatically.