Point Cloud Technology for Slope Greening to Streamline Infrastructure Maintenance

In infrastructure maintenance, slope greening—planting vegetation on slopes along roads, dams, and other structures—is an important measure from the perspectives of disaster prevention, landscape, and the environment. Covering slopes with vegetation prevents erosion of the topsoil, reduces the risk of sediment-related disasters, and also contributes to improved surrounding landscapes and ecosystem conservation.

That said, keeping vegetated slopes healthy over the long term requires regular inspections and maintenance. Traditionally, visual inspections by workers were the norm, but various issues have been pointed out, such as labor shortages, the personalization of records, and the need to inspect hazardous areas. In recent years, new technologies that leverage 3D point cloud data and AR (augmented reality) have attracted attention as solutions to these problems. This article explains the benefits and concrete applications of point cloud technology in slope greening maintenance and introduces the latest methods that streamline operations from routine inspections to disaster response.

The roles of slope greening in disaster prevention, landscape, and the environment

Slope greening involves planting vegetation or broadcasting seeds on slopes along roads or reclaimed land to cover the surface with greenery. The roots of the planted vegetation bind the soil firmly, preventing surface-layer collapse and soil runoff during rainfall, thereby enhancing slope stability. In addition, the transpiration of plants can remove excess moisture from within the slope, reducing the risk of slope failure due to water pressure. In other words, slope greening plays an important role in disaster prevention by helping to avert slope collapses and sediment-related disasters.

Moreover, greening slopes offers significant benefits for the surrounding landscape and environment. Bare slopes treated with concrete spraying or wire mesh have often been common, but covering slopes with plants makes them blend more naturally into the environment and improves visual quality. Slopes covered with seasonal flowers and trees provide people with a sense of comfort and soften the oppressive feel of inorganic structures. From an ecological standpoint, greened slopes provide habitats and corridors for insects and small animals, contributing to the conservation of local biodiversity. Thus, slope greening is indispensable in infrastructure maintenance not only for safety but also for landscape and environmental benefits.

Conventional slope maintenance and its challenges

In slope greening maintenance, regular patrols and inspections by specialized technicians or workers have been the norm. Inspectors check for abnormalities visually from the base or top of slopes, sometimes using binoculars for close views, or actually climb slopes to conduct detailed surveys. Inspection results are typically recorded in notebooks or on drawings, with simple sketches, and later compiled into reports at the office. While these methods have been passed down in the field for many years, recent times have revealed the following issues.

• Lacks quantitativeness: Visual inspections make it difficult to quantify changes in slopes, so small changes can be overlooked. For example, slight soil loss or subtle changes in slope gradient may be missed if evaluations rely on subjective judgment.

• Personalized records: Inspection content is often dependent on handwritten notes or an individual’s memory, making information sharing and historical comparison difficult. When personnel change, past inspection results may not be accurately handed over, and valuable insights can go unused.

• Workload and safety: Visual inspections on steep slopes and close-up checks at height impose a heavy burden on workers and come with safety risks such as falls and rockfalls. Inspecting hazardous areas may require multiple personnel and traffic closures, making the work onerous.

• Labor shortages: While demand for inspections rises due to aging infrastructure, the workforce is aging and manpower is lacking, expanding the responsibilities of individual staff. Consequently, maintaining inspection frequency and quality becomes increasingly challenging.

Recording and quantitative assessment of slope conditions using 3D point clouds

Advances in 3D measurement technologies have made it possible to record slope shapes in detail as point cloud data. Point cloud data is a 3D model representing countless points on a slope surface with X, Y, Z coordinates, obtainable via laser scanners or photogrammetry. It is like creating a digital replica of a slope, capturing its topography and vegetation bulges in high resolution.

Using this point cloud model, slope conditions can be understood and assessed quantitatively in a surface-based, three-dimensional manner. For example, slopes’ gradients and curvature—difficult to measure in the field—can be precisely calculated by slicing cross-sections on the point cloud. Total slope area, partially exposed soil extents, and volumes of collapsed sediment can be automatically computed and recorded as objective data rather than subjective impressions. Once captured, point cloud data provides an objective record of the entire slope at that time, making it easy to review details afterward. Unlike traditional flat photos or notes, point clouds allow comprehensive three-dimensional documentation in a single measurement, which is a major advantage.

Detecting abnormalities and tracking long-term changes with point cloud data

Regular acquisition and accumulation of point cloud data help track long-term changes and enable early detection of anomalies. For example, overlaying this year’s slope point cloud with last year’s allows detailed analysis of differences in slope geometry. Calculating differences between point clouds can visualize where soil has been lost (or accumulated) and quantify the change with color-coded heat maps. Even centimeter-scale topsoil loss or slight bulging or settlement—hard to notice with the naked eye—can be revealed by point cloud differencing, so small anomalies are not missed.

Specifically, if part of an embankment slope has been eroded by rain, the point cloud at that location will show subsidence relative to the previous measurement and indicate volume loss numerically. Conversely, if a bulge (deformation) appears on the slope, the point cloud will show a forward protrusion compared to the previous dataset. Surface depressions or crack-induced steps can also be quantified by comparing point cloud cross-sections. By comparing with past data, it becomes possible to quantitatively monitor long-term deterioration of slopes and more easily decide on repairs or countermeasures before damage worsens. Early detection through point cloud use can greatly contribute to disaster prevention and reduce maintenance costs.

Intuitive on-site information sharing with AR visualization

Point cloud data can be used not only for office analysis but also for on-site AR (augmented reality) visualization to dramatically improve information sharing among stakeholders. By holding up a tablet or smartphone, you can overlay the acquired 3D point cloud model or design data onto the actual slope, enabling intuitive confirmation of slope conditions on site. For example, displaying the current slope model created from a point cloud in AR and overlaying the original design shape makes it immediately obvious which parts are maintained as designed and which are deformed. Areas with large deviations can be highlighted in red on the AR screen so that where an abnormality exists is visually apparent—far easier to understand than verbal descriptions or drawings.

This AR visualization is effective not only for on-site workers but also for communication with clients and designers. If stakeholders accompany the team and view the AR display on site, they can discuss situations with a shared image. Sharing AR footage or screenshots with remote parties conveys subtle depressions or damage areas that are hard to express in textual reports. When information is shared in real space, consensus on response policies is easier to form and decision-making speeds up.

Safe and efficient measurement of difficult slopes

For slope inspections on steep terrain or cliff-adjacent areas, point cloud surveying excels in both labor reduction and safety improvement. Even slopes that are difficult or dangerous for people to enter can be assessed from a distance using lasers or cameras without approaching. For example, areas of slope collapse that once required workers to climb with ropes can now be captured in detail by drones collecting point cloud data from above, allowing comprehensive assessment from a safe location. The ability to gather data without exposing personnel to the risk of secondary disasters on unstable slopes is a major advantage.

Because point cloud surveys can cover wide areas at once, tasks that once took several workers many days can sometimes be completed with a scan lasting only minutes. Efficient on-site measurement with minimal staff makes it easier to maintain operations amid manpower shortages. Measurement equipment no longer necessarily requires heavy machinery or scaffolding; lightweight, portable devices increasingly enable on-site scanning, significantly improving field mobility. Point cloud technology, which allows less proximity to hazardous slopes, is thus a solution that contributes to both worker safety and operational efficiency.

Centralized patrol record management via cloud integration

Sharing and managing point cloud data and field records in the cloud enables centralized information management for maintenance operations. Previously, each inspection produced paper reports and photo albums stored in folders, but by accumulating digitized point clouds and photos in the cloud, slope information from past to present can be managed collectively. From a database organized by date and location, past inspection results and 3D models can be retrieved immediately, so reviewing “what was the condition of that slope years ago?” can be done instantly. Uploading point clouds acquired on site directly to the cloud allows all stakeholders to access the latest data by the time the team returns to the office, enabling near real-time sharing.

Cloud use allows multiple personnel to reference the latest and same information, reducing misunderstandings and transmission errors. Sharing automatically generated cross-sections or difference maps online simplifies report creation. Leaving comments and instructions on the cloud rather than exchanging paper records keeps interaction history intact and assists future inspection planning. By integrating point cloud data with the cloud, accumulation and utilization of patrol records become smooth, advancing digital transformation (DX) across maintenance operations.

A field case of point cloud measurement and AR using nothing but a smartphone

Recently, easy point cloud measurement solutions using smartphones have emerged. Here is one field case that demonstrates their effectiveness.

For a routine inspection of a road slope, an inspector went to the site with only a high-performance smartphone. A dedicated point cloud measurement app was installed on the phone; when activated and pointed at the slope, the phone’s built-in LiDAR sensor (or camera) captured surrounding 3D data. As the inspector walked along the slope base while pointing the phone, a point cloud model of the entire slope was generated on the device in just a few minutes. The captured data included GNSS position information, yielding an absolute-coordinate 3D model without post-processing.

Checking the point cloud model on the spot revealed a small depression in an embankment section mid-slope. The inspector switched the phone to AR mode and displayed a comparison of last year’s point cloud and the current data. Within the real scene, a red heat map appeared at the location in question, making it immediately clear that the terrain had retreated compared to the previous year. The inspector saved a screenshot of the AR display and shared it to the cloud with inspection comments. Supervisors and designers in the office could immediately view the data and begin discussing necessary repair work. Thus, with just a smartphone, the workflow—from point cloud measurement to on-site confirmation, recording, and sharing—was completed rapidly and accurately compared to traditional methods.

There are many advantages to using smartphone-based point cloud technology. The main points are summarized below.

• Mobility: With only a smartphone and a compact positioning device, there is no need to carry heavy equipment, allowing rapid movement around the site. Measurements can be taken on the spot, enabling quick response to urgent inspections.

• Immediacy: Scanning on site lets you confirm the 3D model and perform AR visualization instantly, so results are obtained during the inspection. There is no need to wait for office processing, allowing immediate consideration of countermeasures the same day.

• Improved accuracy: Combining GNSS (satellite positioning) and smartphone-integrated LiDAR can achieve centimeter-level accuracy that was previously difficult, enabling more reliable assessments and decisions based on high-precision data.

• Integrated records: Photos and notes can be recorded simultaneously on the phone with location tags. Observations can be annotated on the point cloud model, promoting centralized digital data accumulation instead of relying on paper notes.

• Cost reduction: Because affordable smartphones can substitute for expensive dedicated survey equipment, initial investment and maintenance costs are greatly reduced. Ease of use by individual technicians also lowers outsourcing expenses.

Streamlining routine inspections to disaster response with LRTK

Finally, as a concrete solution to implement the smartphone point cloud technologies discussed so far on site, we introduce [LRTK](https://www.lrtk.lefixea.com). LRTK is an integrated platform composed of a compact device equipped with high-precision GNSS and a smartphone app that enables centimeter-level surveying, 3D point cloud scanning, and AR visualization with just a smartphone. It requires no complex operations or specialized knowledge; its simple UI allows field personnel to use it intuitively while the acquired point cloud data meets the precision standards set by the Ministry of Land, Infrastructure, Transport and Tourism. When used for routine patrol inspections, it enables detailed records to be kept with less effort and prevents missing signs of anomalies. In the event of slope disasters caused by heavy rain or earthquakes, LRTK allows rapid scanning of affected areas to determine collapse volumes and immediately inform restoration planning.

By introducing LRTK, efficient and accurate responses become possible in all scenarios, from routine infrastructure inspections to emergency damage assessments. As an era approaches in which advanced spatial information can be handled with the familiar tool of a smartphone, slope greening maintenance methods are moving to a new stage. With the power of point cloud technology and AR, on-site safety and work efficiency dramatically improve. Why not incorporate these latest technologies into your daily infrastructure protection work? LRTK supports on-site DX and will strongly assist your maintenance operations.