Point Cloud Technology for Slope Greening to Streamline Infrastructure Maintenance

In infrastructure maintenance, “slope greening,” which involves planting vegetation on slopes such as roadsides and dams, is an important initiative from the perspectives of disaster prevention, aesthetics, and the environment. Covering slopes with greenery helps prevent surface soil erosion and reduces the risk of landslides, while also improving the surrounding landscape and contributing to ecosystem preservation.

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

The role of slope greening in disaster prevention, aesthetics, and the environment

Slope greening involves planting vegetation or spraying seeds on slopes along roads or development sites to cover their surfaces with greenery. The roots of the vegetated cover bind the soil firmly, preventing surface collapse and sediment runoff during rainfall and improving slope stability. Also, plants’ transpiration helps remove excess moisture from within the slope, reducing the risk of slope collapse due to pore water pressure. In other words, slope greening plays an important role in preventing slope failures and landslides as part of disaster prevention measures.

Moreover, greening slopes offers significant benefits for the surrounding landscape and environment. Bare slopes covered with sprayed concrete or wire mesh were common in the past, but covering them with vegetation makes them blend into the natural surroundings and enhances the scenery. Slopes that flourish with seasonal grasses and trees provide people with comfort and relaxation and ease the sense of oppression from inorganic structures. From an ecological perspective, vegetated slopes become habitats and corridors for insects and small animals, contributing to the preservation of local biodiversity. Thus, slope greening is indispensable in infrastructure maintenance not only for safety but also for landscape and environmental reasons.

Traditional slope maintenance and its challenges

In slope greening maintenance, specialized technicians and workers have traditionally conducted regular patrols and inspections. Inspectors check visually from the foot or top of the slope, observe details with binoculars if necessary, or climb the slope for close-up surveys. Inspection results are typically recorded in notebooks or on drawings, or with simple sketches, and later compiled into reports in the office. While these methods have been passed down in the field for many years, the following issues have become apparent in recent times.

• Lack of quantification: Visual inspections make it difficult to quantitatively grasp slope changes, and small changes tend to be overlooked. For example, slight sediment runoff or subtle changes in slope angle can be missed if evaluations rely on subjective judgment.

• Personalization of records: Inspection contents often depend on personal handwritten notes or memory, making information sharing and comparison with past records difficult. When personnel change, past inspection results may not be accurately handed over, and valuable insights may go unused.

• Workload and safety: Visual inspections on steep slopes or close-up checks at height impose a heavy burden on workers and carry risks such as falls or rockfall. Inspecting hazardous areas may require multiple personnel and road closures, making the work highly burdensome.

• Labor shortages: While inspection demand rises due to aging infrastructure, the aging workforce and lack of successors have expanded each individual’s responsibilities. As a result, maintaining inspection frequency and accuracy becomes challenging.

Recording and quantitative evaluation of slope conditions with 3D point clouds

Advances in 3D measurement technology have made it possible to record slope shapes in detail as point cloud data. Point cloud data is a 3D model that represents countless points on a slope surface with X, Y, and Z coordinates and can be obtained by laser scanners or photogrammetry. It’s like creating a digital copy of the actual slope, faithfully capturing the slope’s shape at high resolution—from terrain undulations to vegetation mounds.

Using this point cloud model, you can grasp and quantitatively evaluate the slope’s condition in a surface-based, three-dimensional manner. For example, slope angles and curvature that are hard to measure in the field can be accurately calculated by slicing cross-sections on the point cloud. Total slope area, locally exposed soil extents, and volumes of collapsed sediment can also be automatically computed and recorded as objective data rather than subjective impressions. Moreover, once point cloud data are acquired, they remain an objective record of the entire slope at that time, regardless of date or season, making it easy to review and verify details later. Point clouds can perfectly record three-dimensional features in a single measurement—something that has been difficult with conventional planar photos or notes.

Grasping long-term changes and detecting anomalies with point cloud data

Regularly acquiring and storing point cloud data helps monitor long-term changes and detect anomalies early. For example, comparing the point cloud captured this year with last year’s by overlaying the datasets allows detailed analysis of differences in slope shape. Calculating differences between point clouds can visualize where soil has been lost (or deposited) and by what volume using colored heat maps. Even topsoil loss on the order of several centimeters (several in) or slight heaving or settlement that the naked eye would miss becomes apparent from point cloud differencing, so small anomalies are not overlooked.

Specifically, if part of an embankment slope has been eroded by rain and lowered, the point cloud there will show subsidence compared with previous data and appear as a numerical volume decrease. Conversely, if a bulge (deformation) forms on the slope, the point cloud will show a forward protrusion relative to the previous scan. Ground subsidence or step changes caused by cracks can also be quantitatively captured by comparing point cloud cross-sections. By comparing with past data in this way, you can quantitatively monitor long-term deterioration of slopes and more easily decide on repairs or countermeasures before deformations worsen. Early detection through point cloud use will greatly contribute to disaster prevention and to reducing maintenance costs.

Intuitive on-site information sharing with AR visualization

Point cloud data can be analyzed in the office, but displaying them on-site with AR (augmented reality) dramatically improves information sharing among stakeholders. By pointing a tablet or smartphone at the slope, you can overlay the acquired 3D point cloud model or design data onto the real slope, allowing intuitive on-site confirmation of slope conditions. For example, displaying the current slope model derived from point clouds in AR and overlaying the original design shape makes it immediately clear which parts are maintained to the design and which parts are deformed. Large discrepancies can be highlighted in red on the AR screen, so where anomalies exist can be visually identified far more easily than by verbal explanation or drawings.

This AR visualization is effective not only for on-site workers but also for communication with clients and designers. If they accompany you and view the AR display, everyone can share the same image and discuss the situation. Sharing AR footage or screenshots with remote stakeholders conveys subtle undulations and damage extents intuitively—details that are hard to express in text reports. Sharing information in real space smooths consensus building on response policies and speeds up decision-making.

Safe and efficient measurement of difficult slopes

For inspections of steep or cliff-adjacent slopes, point cloud surveying demonstrates strength in both reducing personnel and improving safety. Slopes that are difficult or dangerous to enter can be measured from a distance with lasers or cameras to grasp current conditions without approaching. For example, slope collapse areas that previously required workers to climb with ropes can now be captured in detail by acquiring point cloud data from the air with a drone, allowing safe assessment from a secure location. The ability to collect data without exposing personnel to the risk of secondary disasters on unstable slopes is a major advantage.

Also, because point cloud surveying can cover large areas at once, tasks that once took multiple people several days can be completed with just a few minutes of scanning. Efficient on-site measurement with minimal staff makes it easier to maintain operations even in labor-short environments. Measurement devices increasingly do not require heavy machinery or scaffolding; lightweight equipment can be carried and used on site, greatly improving field mobility. Point cloud technology, which keeps people away from dangerous slopes, is a solution that contributes to both worker safety and operational efficiency.

Centralized management of inspection records through cloud integration

By sharing and managing point cloud data and field records in the cloud, you can achieve centralized information for maintenance operations. Previously, inspections were stored as paper reports and photo albums in file folders, but if digitized point clouds and photos are accumulated in the cloud, slope information from past to present can be managed collectively. From a database organized by date and location, you can immediately retrieve past inspection results and view 3D models when needed, enabling instant retrospection like “what was the condition of that slope several years ago?” Uploading point clouds acquired in the field directly to the cloud means that by the time you return to the office, all stakeholders can already view the latest data—enabling real-time sharing.

Cloud usage allows multiple personnel to refer to the latest and same information, reducing misunderstandings and transmission errors. Sharing automatically generated cross-sections and difference maps online simplifies report creation. Leaving comments and instructions in the cloud rather than exchanging paper materials preserves the history of communications and assists future inspection planning. By integrating point cloud data with the cloud in this way, accumulation and utilization of patrol records become smooth and maintenance operations as a whole undergo DX (digital transformation).

Field case: point cloud measurement and AR use with just a smartphone

In recent years, easy point cloud measurement solutions using smartphones have emerged. Here is a field case that demonstrates their power.

At a routine inspection of a road slope, an inspector went to the site carrying only a high-performance smartphone. A dedicated point cloud measurement app was installed on the smartphone; by launching it and pointing it at the slope, the built-in LiDAR sensor (or camera) captured surrounding 3D data. As the inspector walked along the foot of the slope pointing the phone, a point cloud model of the entire slope was generated on the smartphone in just a few minutes. The acquired data also included position information from satellite positioning, providing an absolute-coordinate 3D model without post-processing.

On checking the point cloud model on the spot, a small depression was found in an embankment section on the mid-slope. The inspector switched the smartphone to AR mode and displayed this year’s data alongside last year’s. In the real landscape, a red heat map appeared over the relevant area, making it immediately obvious that the terrain had retreated since the previous year. The inspector saved a screenshot of the AR display and shared it to the cloud with inspection comments. Supervisors and design staff in the office could instantly view the data and begin considering necessary repairs. In this way, with just a smartphone you can complete point cloud measurement, on-site confirmation, recording, and sharing, achieving inspections that are far faster and more accurate than before.

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

• Mobility: With only a smartphone and a small positioning device, you don’t need to carry heavy equipment and can move quickly around the site. You can measure whenever needed and respond rapidly to unexpected inspections.

• Immediacy: Scanning on site allows you to confirm the 3D model and perform AR display immediately, so you obtain results at the same time as inspection. There’s no need to return to the office and wait for processing—you can move to considering measures on the same day.

• Improved accuracy: Combining GNSS (satellite positioning) and smartphone-built-in LiDAR technology enables capturing point clouds with centimeter-level accuracy (half-inch accuracy), which was difficult previously. High-accuracy data allow more reliable evaluations and decisions than before.

• Integrated records: Photos and notes can be taken on the smartphone and managed with position tags. You can annotate points of interest on the point cloud model, advancing unified data accumulation without relying on paper notes.

• Cost reduction: Because you can substitute familiar smartphones for expensive dedicated surveying equipment, initial investment and maintenance costs can be significantly reduced. Ease of use for each technician also reduces outsourcing costs.

Streamlining routine inspections to disaster response with LRTK

Finally, as a concrete solution to put the smartphone point cloud technology introduced so far into practice on site, we introduce [LRTK](https://www.lrtk.lefixea.com). LRTK is an integrated platform composed of a small terminal equipped with high-precision GNSS and a smartphone app, enabling everything from centimeter-level surveying (half-inch-level surveying) to 3D point cloud scanning and AR visualization with a single smartphone. It requires no complicated operations or specialized knowledge; the simple UI is intuitive for field personnel, while the acquired point cloud data meet the accuracy standards of the Ministry of Land, Infrastructure, Transport and Tourism. When used for routine patrol inspections, it allows detailed records to be kept with less effort than before and ensures that signs of anomalies are not overlooked. In the event of slope disasters caused by heavy rain or earthquakes, LRTK enables rapid scanning of affected areas to determine collapse volumes and immediately supports restoration planning.

By adopting LRTK in this way, efficient and accurate responses become possible in all situations, from routine infrastructure inspections to emergency damage surveys. As we enter an era 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 will improve dramatically. Why not incorporate these latest technologies into your daily infrastructure-preserving work? LRTK will assist your field DX and strongly support your maintenance operations.