The Future of Slope Greening Opened Up by Reduced-Personnel Construction

Introduction: Slope Greening Work and the Current Labor Shortage

Slope greening involves covering steep slopes (cut slopes) created by road construction or land development with vegetation to prevent soil erosion and improve the landscape. Slope greening work is an important task that supports safe social infrastructure, but much of it has relied on manual labor. In recent years the construction industry has faced serious labor shortages and an aging workforce, and on slope greening sites—where many tasks involve hazardous high-elevation work—the need for reduced-personnel construction has been rising. However, in the past it has not been easy to advance labor reduction in this field. This article reviews the background and challenges that made reduced-personnel approaches difficult in slope greening, introduces examples and effects of labor-saving measures made possible by the latest digital technologies and mechanization, and considers the future of slope greening opened up by these technologies. Finally, we suggest the adoption of the site-innovating tool "LRTK".

Traditional Methods Relying on High-Altitude Work and Craftsmen’s Intuition

On slope greening sites, dangerous high-altitude work on steep slopes is unavoidable. Tasks such as spraying a mixture of seed and fertilizer through a hose (hydroseeding) and installing vegetation mats often require workers to enter the slope directly, always facing the risk of falls or slips. For safety, a certain number of personnel are necessary, and each worker advances carefully while wearing lifelines.

Quality of work has also depended heavily on the intuition and experience of skilled technicians. For example, when spraying seed with a hose, techniques such as controlling spray pressure and achieving uniform seed adherence without streaks depended on veteran know-how, making mechanical standardization difficult. Because terrain and soil conditions vary from site to site, fine adjustments to the mix and spread quantities of greening materials have traditionally been left to the judgment of craftsmen. The combination of dangerous high-altitude work and dependence on craftsmen’s skills has made it hard to promote labor-saving and automation in slope greening work.

Human Costs Involved in Surveying and As-Built Management

Slope greening work requires substantial time and manpower not only for the construction itself but also for surrounding surveying and as-built management. Before construction, surveys to grasp the current slope shape and setting out of benchmarks (establishing reference heights and positions) based on design drawings are necessary. On steep slopes, if survey points cannot be reached on foot, staff must ascend and descend slopes or carry surveying equipment to set points, and multi-person teams were the norm. Scenes of experienced surveyors working with assistants to measure current terrain with total stations were commonplace.

After construction, there is the confirmation process known as as-built management. This verifies whether the finished slope meets the designed gradients and thicknesses, and it was traditionally dominated by manual measurement. For example, measuring heights on the slope at specified intervals and checking deviations from design values required surveyors to traverse steep slopes repeatedly. Analog methods remain, such as one person supporting a long staff (level rod) while another reads the telescope to record elevation differences. These surveying and inspection steps can take a long time per location depending on weather and terrain, imposing heavy burdens in terms of manpower and safety management.

In addition, joint inspections with site supervisors and clients require personnel and scheduling. The process of all stakeholders visiting the site after completion to visually check and measure the results—especially at sites with multiple slopes—becomes a considerable burden. In this way, surveying and as-built management associated with slope greening have incurred significant human and time costs, and improving their efficiency has been a long-standing challenge.

The Rise of Digital Technologies Supporting Reduced-Personnel Construction

Recently, the construction industry has rapidly advanced construction DX—the use of ICT and IoT (digital transformation, advocated by the Ministry of Land, Infrastructure, Transport and Tourism such as "i-Construction"). In slope greening as well, various digital technologies supporting reduced-personnel work have begun to appear. Representative technologies include 3D measurement, AR (augmented reality), and the ubiquity of smartphones that make these tools easy to use. These technologies are transforming processes before, during, and after construction, helping small teams deliver high-quality work.

For example, point cloud measurement using drones or terrestrial laser scanners makes it possible to convert wide-area terrain into 3D data in a short time. Where surveying an entire slope once took half a day, a drone flight of only tens of minutes can now complete it and provide detailed terrain models. Recently, it has also become possible to obtain point cloud data easily on-site using LiDAR sensors built into smartphones and tablets. Overlaying such on-site 3D data with design models before construction streamlines planning and quantity calculations.

Combining AR technology with high-precision positioning enables intuitive on-site construction management. By attaching an ultra-compact high-precision GNSS receiver (RTK-capable) to a smartphone, the device transforms into a surveying instrument capable of centimeter-level positioning. AR overlays of design data and measured points on the smartphone screen allow on-site operations to complete the cycle of "see, measure, and verify" in real time. Tasks that once required repeatedly checking drawings with tape measures and spirit levels are greatly simplified by leveraging digital data.

Visualizing Before-and-After with Point Cloud Data

One of the most notable labor-saving efforts in slope greening is the use of point cloud data. By comparing the point cloud captured before construction with the post-construction as-built point cloud, it becomes immediately apparent where and how much fill or sprayed material was applied, and differences from design. Information that was previously only roughly understood by craftsmen’s visual inspection or on paper drawings can now be evaluated quantitatively at centimeter-level accuracy using 3D point clouds.

For example, if the pre-construction slope is drone-photogrammetry scanned into a point cloud, accurate earthwork volume calculations and greening material quantity estimates can be made in advance. Risks such as ordering excess materials or running out of materials and halting work can be reduced. During construction, partial scans performed as needed to capture intermediate as-built conditions help prevent rework. Problems that used to be discovered only after completion—such as localized thickness deficiencies or gradient exceedances—can now be detected early and corrected using intermediate point cloud data.

After construction, scanning the entire finished slope to acquire the as-built point cloud allows automatic creation of as-built management diagrams and cross-sections by comparing with the design model’s point cloud or mesh data. Because the entire slope quality can be checked in data without people walking the slope, the days and personnel required for inspection can be greatly reduced. Furthermore, the obtained point cloud data can be used for future maintenance: re-scanning after several years and comparing point clouds quantitatively reveals erosion status and the establishment of vegetation, aiding timing decisions for repairs. In this way, point cloud technology contributes consistently to labor reduction and sophistication from preconstruction planning through post-construction maintenance in slope greening.

AR + Smartphone Enables One-Person Surveying and Layout

Another major ally of labor reduction is smartphone-based AR surveying. Surveying tasks that traditionally required two-person teams can now be completed by one person through a smartphone combined with a compact GNSS receiver. Attaching an RTK-GNSS–compatible receiver to a smartphone enables centimeter-level positioning for anyone without complex operation. Pressing a button on the phone at the point to be measured records coordinates, and the measured points are displayed as AR markers on the screen, allowing on-site location identification without poring over paper drawings.

A coordinate guidance (coordinate navigation) feature has also emerged, which navigates the user to pre-set coordinates on-site. When coordinates for points to be measured or locations to install structures are specified in the cloud in advance, arrows and guides appear on the smartphone screen to direct the user to the target spot. For example, if anchor positions to be installed on a slope are extracted from drawings as coordinates, the phone can display instructions like "50 cm east" or "a bit higher," enabling less experienced workers to mark precise positions. This not only allows one-person measurement but also enables accurate single-person layout.

AR’s advantage also includes on-the-spot confirmation of finished appearance during construction. Overlaying the design completion model on the smartphone camera view makes it visually clear "how much fill is needed to achieve the design gradient" or "where sprayed material is insufficient." Without relying on a veteran’s intuition, anyone can evaluate the finish against the same standard, reducing quality variation and preventing rework. The ability to verify the finish on-site thanks to AR technology provides significant reassurance to field personnel.

Experiencing the Effects of Labor Reduction: Efficiency and Safety Improvements

On sites that have adopted these digital construction methods, voices report feeling the labor-saving effects of "one-person measurement," "position guidance," and "on-site finish verification." The advantages of digitally enabled reduced-personnel construction are not limited to efficiency. Reducing the number of workers and lightening individual burdens also improves safety. Work time on slopes is shortened, reducing exposure to hazards, and fatigue reduction can help prevent human errors. With high-precision surveying equipment enabling accurate measurement in one go, unnecessary ascents and descents to re-measure are eliminated, lowering fall risk.

Also, standardizing work previously dependent on veterans through digital tools helps compensate for the lack of experienced personnel. Intuitive smartphone apps are easy for young or novice workers to use, enabling them to progress autonomously without veteran instructions. As a result, not only does overall site productivity increase, but veterans can focus on tasks requiring higher-level judgment while younger staff gain more opportunities to acquire skills through practice—creating a virtuous cycle. Reduced-personnel construction is expected to contribute to addressing Japan’s construction industry challenges of labor shortage and skills transfer.

New Site Management Enabled by Cloud and Remote Technologies

Another key to labor reduction is cloud integration and remote technologies. Managing and sharing digital data on the cloud allows construction management and inspections to proceed smoothly without everyone gathering on-site. For example, point cloud data and survey records can be shared instantly with office staff or remote stakeholders via the cloud. Uploading on-site 3D data lets clients and supervisors confirm as-built conditions from the office. This enables remote attendance and online inspections, reducing travel time and speeding decision-making.

In disaster recovery sites, for instance, one technician can survey a damaged area with a smartphone, send data in real time via the cloud, and head office staff can immediately generate drawings and consider countermeasures based on that data. Where previously everyone would travel to the site and the survey team would take data back for a meeting that might take days, cloud sharing allows on-site and office work to proceed simultaneously, significantly speeding initial responses in emergencies.

Storing data in the cloud also makes it easy to retrieve records when needed later. If additional planting work occurs months later, the previous point cloud model can be used to understand current conditions and respond flexibly. There is no need to hunt for paper documents or USB drives; digital data is becoming the common language of the site. Cloud and remote utilization enable flexible site management unconstrained by geographic limits.

Mobility Demonstrated in Small-Scale and Emergency Works

The benefits of labor-saving technologies apply not only to large-scale projects but also to small-scale works and emergency responses. Small slope repair jobs that formerly did not justify deploying large surveying equipment or many personnel—and were sometimes performed unsafely by hand—can now be handled accurately by a single site supervisor with a smartphone-based survey tool, including reliable as-built confirmation. Reduced manpower and less equipment transport shorten lead times from start to finish, contributing to earlier road reopening and quicker disaster recovery.

In emergency slope work, speed and ensuring safety are paramount. At landslide or slope-collapse sites where the risk of secondary disasters exists, rapid slope greening and temporary measures are required. Even in such situations, compact surveying devices and digital technologies show their effectiveness. A single person can carry a manageable set of equipment to a disaster site, measure terrain immediately, plan countermeasures, and begin work—enabling nimble responses once unimaginable. Reduced-personnel construction methods are a strong ally for doing what can be done right away with limited staff.

Conclusion: The Future of Slope Greening Opened by Digital Technology

Slope greening sites are now poised for major change through digital technology and mechanization. Robots and automation are approaching work that was once dangerous high-altitude labor, moving humans toward monitoring and management. At the same time, the spread of new methods such as point cloud measurement and AR construction management is creating environments where small teams can achieve high-quality work. In the future shaped by reduced-personnel construction, it will be possible to address challenges such as the decline of experienced craftsmen and harsh site conditions while enabling safer and more efficient slope greening.

One concrete solution supporting this future is the smart construction device LRTK. With LRTK, anyone on site can perform high-precision positioning and 3D scanning with just a smartphone, carry out intuitive AR-based construction checks, and achieve precise location guidance with coordinate navigation. From point cloud acquisition to as-built confirmation can be completed on-site, and cloud sharing enables smooth remote instruction and verification. It is literally making the era of "each person carrying a universal surveying instrument" a reality, and is being used across small repairs, large projects, and emergency responses. Why not introduce the benefits of reduced-personnel construction into your company’s slope greening work? Through fusion with digital technology, the future of slope greening is likely to become ever brighter.