The Future of Slope Greening Construction with AR

Slope greening works are an important construction type that covers slopes along roads, embankments, and development sites with vegetation to improve scenery, prevent landslides, and conserve the environment. However, because work often takes place on steep slopes and terrain can be complex, there are many challenges from design through construction to post-completion management. Recently, digital transformation (DX) in construction sites has created new approaches to solving these challenges. In particular, the use of AR (augmented reality) technology available on smartphones and similar devices has attracted attention. This article reviews the on-site challenges of slope greening works and introduces how AR is changing the future of construction.

What slope greening works are

Slope greening works involve covering artificially formed or natural slopes with vegetation. Specifically, methods vary according to terrain and soil conditions, such as vegetation substrate spraying—mixing seed and nutrients into topsoil and spraying it as a slurry (commonly called seed spraying)—laying and securing vegetation mats in which seeds are woven into fiber mats, planting works that plant nursery stock at set intervals, and seeding methods that broadcast seed. These techniques introduce green vegetation to otherwise inorganic concrete or cut slopes, improving scenery, preventing erosion from rainwater, and restoring ecosystems. While slope greening plays an important role in environmental consideration and disaster prevention for social infrastructure, its design and construction require a high level of expertise.

Challenges in slope greening works

First, let us organize representative challenges field engineers face in the design, construction, and management of slope greening. Because this work deals with steep slopes, each phase presents difficulties not found in other trades. The main points are listed below.

• Design stage challenges: It is not easy to grasp the shape of a slope and its surrounding environment from drawings alone. Traditionally, slope and greening extents are considered based on plan and section drawings, but with complex terrain it can be difficult to share a completed-image among stakeholders, causing delays in conveying the design intent. Also, planned drawings sometimes do not match the actual terrain, forcing changes during construction. Features easy to overlook on drawings—such as slope undulations and interfaces with the surrounding environment—often appear later and necessitate plan revisions.

• Construction stage challenges: Working on steep slopes involves many physical constraints, making it difficult to construct exactly as designed. Attention must be paid to worker safety and the transport and securing of materials and equipment, and errors are likely in tasks such as staking out reference points or placing materials. On large slopes it is also difficult to accurately know on-site “what to install where,” increasing the risk of omissions or duplications due to human error. Many tasks must rely on on-site judgment, which raises concerns that quality can be influenced by the experience and intuition of the responsible personnel.

• Construction management (as-built verification) challenges: Verifying whether the work has been completed as designed—known as as-built management—is also a major burden. Inspecting the slope’s overall gradient and covered area requires many measurement points, and traditionally measuring heights point by point with surveying instruments took considerable time. Moreover, high-elevation measurements are dangerous, so you cannot arbitrarily increase the number of measurement points, which tends to result in inspections that lack comprehensiveness. Because measurement locations are limited, oversights can occur, and bringing measured data back to the office to compare with drawings adds extra effort. Problems are not always noticed immediately on site, and delayed rework can create additional costs.

Sharing design imagery and reaching agreement before construction

To address these challenges, visualizing the completed image with AR before construction is effective. By creating a 3D design model of the slope greening in advance and pointing a smartphone or tablet at the site, you can overlay the post-completion greened state on the actual slope through the camera view. For example, you can intuitively confirm on-site which positions the planned vegetation mats will cover, or how extensive the sprayed areas will be. This lets all stakeholders on site share the completed-image of slope greening, which previously had to be imagined from drawings or perspectives. Preventing mismatched expectations, and aligning understanding among the owner, designer, and construction team early on, enables smooth agreement formation without backtracking. Because the finished image is easier to share, it also aids external consensus-building such as explanations to local residents.

In one real case, showing a greening plan model overlaid on the slope using smartphone AR earned praise from the owner who said, “I could understand the finished form at a glance in ways the drawings couldn't convey.” A veteran construction manager was also impressed, saying, “This allows confirmation without relying on experience,” and pre-construction meetings became smoother. AR-based information sharing has revitalized on-site communication and ultimately contributed to improved quality and efficiency.

The significance of experiencing elevation differences and positional relationships with AR

One advantage of AR visualization is that it lets you sense height and distance on site. Slopes are shown as two-dimensional lines and numbers on plan drawings, but on site they have absolute heights and gradients that far exceed human height. By viewing a design model overlaid through AR, you can intuitively perceive elevation differences that are hard to grasp from drawings. For instance, you can confirm in real scale “how many meters up the vegetation mat will be laid” or “how much higher is the upper edge of the vegetated area compared to where I am standing,” which helps in considering safety measures and construction methods.

AR also makes the positional relationships among design elements immediately clear. Boundaries between multiple greening methods (such as seed spraying and planting zones) and clearance distances from nearby structures can be checked on site, allowing you to verify in advance whether each work can be placed as planned without interference.

Improving as-built verification accuracy with point cloud scanning × AR

AR is also powerful for as-built management that verifies post-construction quality. Recently, drones, laser scanners, and high-performance smartphones have made it easy to capture an entire slope’s shape as point cloud data and create 3D models. After constructing a slope, scanning it with a smartphone’s LiDAR or photogrammetry records the finished surface’s undulations as a collection of millions of points (a point cloud). For a slope about 100 meters long, you can scan the entire surface in minutes while walking with a smartphone—an efficiency vastly superior to traditional point-by-point surveying. Because point cloud data contains real X, Y, Z coordinates (positional information), you can overlay it with the 3D design model (or a terrain model created from design drawings) and analyze the differences. For example, creating a color-coded heat map that shows excesses and shortages in height by comparing the design model and the as-built point cloud makes it immediately clear where the slope is higher or lower than designed. Displaying this heat map or the point cloud model in AR on site allows you to accurately identify the locations of deviations on the actual slope. With centimeter-level precision AR overlay, you can detect construction defects without overlooking them and promptly start corrective work on the spot. Where previously an as-built inspection—from measuring each point to report generation—could take several days, this workflow lets you understand results immediately on site and dramatically streamlines the inspection process. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the spread of as-built management using such 3D utilization, and point cloud measurement combined with AR is likely to become a new standard.

For example, in one slope project, AR heat maps immediately revealed areas with insufficient spray thickness, and additional spraying completed the correction the same day. Under traditional methods, defects might have been discovered after inspection and required reassembly of scaffolding for rework, but immediate point cloud + AR checks prevented unnecessary loss. In this way, combining AR with point cloud measurement brings a rapid PDCA cycle to the field.

Smooth information sharing through cloud integration

To fully leverage AR and point cloud data, data integration via cloud platforms is essential. Traditionally, drawings and survey data were exchanged on paper or by email and managed separately at the site and the office, which often caused issues such as the latest drawings not reaching the site or site changes not being communicated to the designer. Through the cloud, 3D models and construction conditions created during the design stage can be uploaded and shared with the site in advance. Construction personnel can call up the latest data on their smartphones and display it in AR at any time, enabling construction based on the most current information. Conversely, point cloud scans and as-built records obtained on site can be saved to the cloud immediately, allowing owners and designers to check progress or provide advice from the office. For example, a heat map automatically generated from as-built point clouds can be shared via the cloud so stakeholders can issue real-time instructions such as, “This area has too much fill—let’s cut it back.” With centralized data management in the cloud, the information gap between owners, designers, and construction sites is bridged, reducing rework and disputes caused by misunderstandings. Some cloud systems also automatically generate forms from acquired data, further reducing the burden of producing inspection documents and reports. Accumulated 3D data can also be used for future maintenance and improvement works. Comparing past as-built data with current conditions makes it easier to detect aging-related changes and repair locations, aiding long-term infrastructure management.

Lightweight and fast: useful for small sites and disaster recovery

AR construction support tools are not only valuable for large-scale projects. Because smartphone-based systems are lightweight, they are especially effective for small-scale sites and disaster recovery that require rapid response. Traditionally, introducing ICT into small projects in areas where arranging 3D surveying equipment and specialized operators is difficult has been challenging. But with a smartphone + AR, anyone can quickly deploy the system, making it easy for local governments to adopt for simple repairs of roadside slopes or small private development site greening. In disaster recovery sites—such as slope collapses caused by heavy rain or earthquakes—rapid situation assessment and countermeasure planning are essential. For example, one could measure a collapsed slope on site with a smartphone, calculate the volume of collapsed soil from the point cloud model, and immediately share a post-restoration greening plan in AR with stakeholders. High mobility and on-site completeness make such solutions especially useful where it is not feasible to deploy large machinery or many personnel. Indeed, some local governments and contractors have begun using smartphone AR in disaster recovery, contributing to faster initial response.

Start AR construction management with your smartphone: the potential of LRTK

Finally, as a concrete solution for realizing AR on site, we introduce LRTK. LRTK is a positioning device that attaches a small high-precision GNSS antenna to a smartphone, transforming the phone into a centimeter-class surveying instrument. Compared with traditional dedicated surveying equipment, it can be introduced at lower cost and it is realistic for site staff to carry one unit per person. This single device supports a wide range of functions from position measurement and 3D point cloud scanning to AR overlay of design models. It requires no complicated setup or specialized skills—just attach it to the smartphone and launch the dedicated app—and it is designed so anyone on site can use it intuitively, allowing even veteran technicians who are not used to IT to operate it without difficulty.

• High-precision positioning and point cloud acquisition: Using LRTK, you can obtain high-precision point cloud data with absolute coordinates simply by scanning the surroundings with the smartphone camera or LiDAR. Measuring slope shapes is completed by walking the site and capturing images with the phone instead of relying on labor-intensive hand surveying by skilled personnel. From the acquired point cloud, calculations such as earthwork volumes and cross-section generation can be automatically executed on site, greatly shortening the time from surveying to design review.

• AR overlay display: Using the precise positioning information from LRTK as a base, design drawings and 3D models can be accurately overlaid on the real landscape. For the slope greening construction discussed here, projecting a model uploaded to the cloud on site allows you to visualize the finished image accurately. It is also possible to display an AR heat map that visualizes differences between the as-built point cloud data and the design model, directly preventing oversight of defective areas.

• Construction navigation (staking-out support): LRTK also offers an AR navigation function that shows points and lines defined in the design drawings on site. For example, you can virtually draw contour lines or construction range lines on the slope, or place virtual markers where stakes should be driven. This enables one person to accurately and quickly perform staking-out and reference marking that previously required a surveying team. Even on steep slopes that are difficult to access directly, AR allows remote pointing and confirmation of points, contributing to improved safety.

By leveraging LRTK in this way, plan creation, as-built management, and surveying for slope greening can be performed seamlessly with just a smartphone. Site DX can begin from familiar tools without major capital investment. Trials of smartphone AR are already progressing at small and medium-sized construction sites, and the use of digital technology in the slope greening field is steadily expanding. Try a simple 3D survey and AR display using a smartphone and LRTK—communication and quality control on slope greening sites should improve dramatically, delivering unprecedented efficiency and peace of mind. The future of slope greening construction is steadily being opened up by these digital technologies. If smartphone AR devices become the norm on sites, the way slope greening is carried out will be radically transformed. Enabling what was previously “invisible” to be seen through AR is, in essence, the future form of slope greening construction.