The Future of Slope Greening Opened Up by Labor-saving Construction

Introduction: Slope Greening Works and the Current Labor Shortage

Slope greening is the work of covering steep slopes (cut-and-fill slopes) created by road construction or land development with vegetation to prevent soil erosion and improve the landscape. Slope greening works are important tasks that support a safe social infrastructure, but much of the work has relied on manual labor. In recent years, the construction industry has faced a severe labor shortage and an aging workforce, and the demand for labor-saving construction (construction with reduced personnel) has grown, especially on slope greening sites where many high-altitude, hazardous tasks are performed. However, advancing labor-saving measures in this field has not been easy. This article looks back at the background and challenges that made labor-saving difficult in slope greening works, introduces examples and effects of labor-saving measures being realized through the latest digital technologies and mechanization, considers the future of slope greening these technologies are opening up, and finally suggests the use of the on-site innovation tool "LRTK".

Traditional Construction Relying on High-altitude Work and Craftsmen’s Intuition

On slope greening sites, dangerous high-altitude work on inclined ground is unavoidable. Tasks such as blowing a greening mixture of seeds and fertilizer through hoses (hydroseeding) or installing vegetation mats often require workers to enter the slopes directly, always facing the risk of falling or slipping. Consequently, a certain number of personnel are necessary to ensure safety, and each worker proceeds cautiously while wearing life lines.

Moreover, construction quality has largely depended on the intuition and experience of skilled workers. For example, in hose-based seed spraying, the tricks for setting the spraying pressure and uniformly applying seeds without streaks depended on veteran know-how, making mechanical standardization difficult. Because each site has different terrain and soil conditions, adjustments to the greening material mix and application rates were left to the discretion of craftsmen. In this way, the combination of dangerous high-altitude work and reliance on artisanal skill made it hard to advance labor-saving and automation in slope greening works.

Personnel Costs for Surveying and As-built Management

In slope greening works, not only the construction itself but also surrounding surveying and as-built management require considerable time and manpower. Before construction, surveying to grasp the current slope shape and setting up batter boards (marking reference heights and positions based on design drawings) are necessary. When surveying steep slopes, if people cannot walk to survey points, staff must climb and descend the slope or carry surveying equipment to set points, making multi-person operations the norm. It was common to see experienced surveyors teaming with assistants to measure the current terrain with total stations.

After construction, there is also inspection work called as-built management. This is the process of measuring whether the finished slope has the design gradient and thickness, and traditionally this has also been centered on manual measurement. For example, measuring heights on the slope at prescribed intervals and checking errors against design values requires surveyors to go back and forth across steep slopes many times. Analog methods remain, such as one person supporting a long staff (grade rod) while another reads the level with a telescope to record elevation differences. These surveying and inspection processes can take a long time per location depending on weather and terrain conditions, imposing significant burdens in securing personnel and managing safety.

Furthermore, joint inspections with site supervisors and clients also require people and scheduling. The process of having all responsible parties visit the site after completion to visually check the finishing with measuring tapes can be a major burden, especially on sites with multiple slope locations. Thus, the surveying and as-built management associated with slope greening has incurred substantial human and time costs, and how to make these processes more efficient has long been a challenge.

The Rise of Digital Technologies Supporting Labor-saving Construction

Recently, the construction industry has rapidly advanced construction DX (digital transformation, such as the Ministry of Land, Infrastructure, Transport and Tourism’s proposal of "i-Construction") utilizing ICT and IoT. In the field of slope greening, various digital technologies that support labor-saving construction have begun to emerge. Representative technologies include 3D measurement technologies, AR (augmented reality), and the ubiquitous smartphone that enables easy use of these tools. These technologies are transforming processes before, during, and after construction and helping small crews deliver high-quality work.

For example, point cloud measurement by drones or terrestrial laser scanners has made it possible to convert large terrain areas into 3D data in a short time. What used to take half a day to survey an entire slope can now be completed by flying a drone for tens of minutes from above, yielding detailed terrain models. Recently, it has also become possible to easily acquire point cloud data on-site using LiDAR (light detection and ranging) sensors built into smartphones and tablets. If the current 3D data obtained by these technologies before construction is overlaid with the design, planning and quantity calculation become more efficient.

At the same time, combining AR technology with high-precision positioning is enabling intuitive on-site construction management. By attaching an ultra-compact high-precision GNSS receiver (RTK-capable) to a smartphone, the smartphone can transform into a surveying device capable of centimeter-level accuracy (half-inch accuracy) in positioning. Moreover, because design data and measured points can be visualized overlaid on the smartphone screen using AR, “see, measure, and verify” can be completed on-site in real time. Tasks that once required repeatedly checking drawings with tapes and levels have been greatly simplified by the use of digital data.

Visualizing Before and After Construction with Point Cloud Data

One of the most notable labor-saving approaches in slope greening is the use of point cloud data. By comparing the point cloud of the existing condition acquired before construction with the as-built point cloud obtained after construction, it is immediately apparent where and how much fill or sprayed material has been applied and what the differences from the design are. Information that used to be roughly grasped by craftsmen’s visual inspection or paper drawings can be quantitatively evaluated to an accuracy of a few centimeters (a few inches) using 3D point clouds.

For example, if the pre-construction slope is photographed by drone and converted into a point cloud, pre-calculations of earthwork volumes and the required amount of greening materials can be performed accurately. This reduces the risk of ordering excess materials or, conversely, running out and interrupting the work. During construction, partial scans can be performed as needed to understand interim as-built conditions and prevent rework. Problems such as “partial thickness deficiency” or “excess gradient,” which used to be discovered only after completion, can now be detected early and corrected using interim point cloud data.

After construction, the entire finished slope is scanned to obtain an as-built point cloud. By comparing this with the design model point cloud or mesh data, it is possible to automatically create as-built management maps and cross sections. Because the quality of the entire slope can be checked in the 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. Acquiring point clouds again after several years and comparing them allows quantitative assessment of slope erosion and vegetation establishment, helping to determine the timing for repairs. In this way, point cloud technology contributes consistently to labor-saving and sophistication from pre-construction planning to post-construction maintenance of slope greening works.

AR + Smartphone Enables One-person Surveying and Layout

Another major ally of labor-saving is smartphone-based AR surveying. Survey tasks that used to be done by teams of two can now be completed by one person using a smartphone combined with a small GNSS receiver. Attaching an RTK-GNSS-compatible device to a smartphone enables anyone to achieve centimeter-level accuracy (half-inch accuracy) without complicated operations. By simply pressing a button on the smartphone at the point to be measured, coordinates can be recorded, and the measured points appear on the screen as AR markers, allowing on-site location awareness without poring over paper drawings.

There is also a coordinate guidance (coordinate navigation) function that guides the user to pre-set coordinates on-site. If coordinates for points to be measured or positions where structures should be installed are specified in the cloud in advance, arrows and guides are displayed on the smartphone screen on-site to direct the user to the target location. For example, if anchor positions on the slope are extracted from drawings as coordinates, the smartphone can display instructions such as “50 cm (19.7 in) east” or “a little higher,” enabling even less experienced workers to mark the correct positions. This enables not only one-person surveying but also accurate one-person layout.

A further advantage of AR is that it allows the finishing image to be checked on the spot during construction. Overlaying the design’s finished model on the smartphone camera view makes it easy to visually understand “how much fill is required to achieve the design gradient” or “where the sprayed material is insufficient.” Because anyone can evaluate the finish against the same standard without relying on a veteran’s “intuition,” quality variation is reduced and rework is prevented. The fact that AR technology enables on-the-spot verification of the finish offers significant reassurance to site personnel.

Feeling the Effects of Labor-saving: Improved Efficiency and Safety

On sites that have adopted such digital construction techniques, voices report experiencing the labor-saving effects of “being able to measure alone,” “being guided to positions,” and “being able to verify the finish.” The benefits of labor-saving construction using digital technology are not only efficiency. Reducing the number of workers and the burden on each person also improves safety. Work time on slopes is shortened, reducing exposure to hazards, and fatigue-reduction helps prevent human error. With high-precision surveying devices enabling accurate measurement in a single attempt, the waste of climbing up and down slopes to “measure again” disappears, lowering the risk of falls.

In addition, standardizing tasks previously reliant on veterans using digital tools helps compensate for a lack of experienced personnel. Intuitive smartphone apps are easy for young or inexperienced workers to use, allowing them to work autonomously without veteran instruction. As a result, not only does overall site productivity increase, but veterans can concentrate on tasks requiring higher-level judgment while young workers gain opportunities to acquire skills through practice—a virtuous cycle. Labor-saving construction is expected to contribute to addressing Japan’s construction industry challenges of labor shortages and skill succession.

Expanded Site Management via Cloud and Remote Technologies

Another key to labor-saving is cloud integration and remote technologies. With digital data managed and shared in the cloud, more construction management and inspections can be conducted smoothly without everyone gathering on site. For example, the aforementioned point cloud data and surveying records can be shared immediately with office staff or distant stakeholders via the cloud. Uploading the 3D data acquired on-site allows clients and supervisors to check the as-built condition from their offices. This enables remote attendance and online inspections, reducing travel time and enabling quicker decision-making.

In practice, in disaster recovery sites, one technician may survey the damaged area with a smartphone and transmit the data in real time via the cloud, while head office engineers immediately create drawings and consider countermeasures based on that data. What used to take days—everyone visiting the site, the survey team bringing data back, then holding review meetings—can now proceed concurrently on-site and in the office thanks to data sharing. Easier information sharing with remote locations has dramatically sped up initial responses in emergencies.

Also, storing data in the cloud allows immediate retrieval when needed later. For example, if additional planting work occurs several months later, previous point cloud models let you grasp the current condition 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. With cloud and remote utilization, flexible site management unconstrained by geography is becoming possible.

Mobility Demonstrated in Small-scale and Emergency Works

The benefits of labor-saving technologies are seen not only in large projects but also in small-scale works and emergency response sites. Traditionally, small slope repair jobs that did not warrant arranging large surveying equipment or personnel were sometimes carried out by “making do” with manual methods that were not entirely safe. However, with smartphone-based simple surveying tools, a single site supervisor can perform sufficient surveying and even accurate as-built confirmation. Reduced personnel arrangements and heavy equipment transport shorten lead times from start to finish, contributing to earlier road reopening and faster disaster recovery.

In emergency construction after disasters, speed and safety are top priorities. At landslide or slope-collapse sites, where there is a risk of secondary disasters, rapid slope greening and temporary measures are required. In such situations, compact surveying devices and digital technologies prove powerful. One person can carry the necessary equipment to the damaged site, quickly measure the terrain, plan countermeasures, and proceed with work—an agile response previously unthinkable. Labor-saving construction methods are a reliable ally for achieving “doing what can be done immediately” even with limited personnel.

Conclusion: The Future of Slope Greening Opened by Digital Technology

Slope greening sites are now on the verge of major change through digital technologies and mechanization. Robots and automation are beginning to address dangerous high-altitude work, bringing an era closer in which humans focus on monitoring and management. At the same time, the spread of new methods such as point cloud measurement and AR-based construction management is creating an environment where high-quality work can be achieved by small crews. In the future opened by labor-saving construction, it will be possible to realize safer and more efficient slope greening while addressing issues such as the decline of experienced craftsmen and harsh working conditions.

One concrete solution supporting this future is the smart construction device LRTK. By using LRTK, anyone on site can perform high-precision positioning and 3D scanning with just a smartphone, realize intuitive construction checks via AR, and achieve accurate position guidance with coordinate navigation. From point cloud acquisition to as-built confirmation can be completed on the spot, and cloud sharing enables smooth remote instruction and verification. It truly makes the era of “everyone carrying a universal surveying instrument” a reality, and it is being applied across small-scale works, large projects, and emergency responses. Why not incorporate the benefits of labor-saving construction into your company’s slope greening works? Through the fusion with digital technology, the future of slope greening will only become brighter.