Easily Survey Steep Slope Greening with a Smartphone

Why steep slope greening is required

A steep slope refers to a hillside with a sharp incline that has a high risk of landslides and other soil failures. Conducting slope greening in such locations plays an important role for both safety and the environment. From a safety perspective, planting vegetation on a slope helps stabilize the soil, preventing surface soil washout and slope collapse caused by heavy rain or strong winds. Grass and tree roots firmly grip the ground, reducing the risk of sudden landslides and thereby mitigating damage to homes and roads. From an environmental perspective, compared to inorganic measures that merely cover slopes with concrete, greening preserves a pleasing landscape and creates slopes that harmonize with the surrounding natural environment. Vegetation not only prevents surface erosion but is also expected to improve soil water retention and provide habitat for insects, small birds, and other wildlife. Greening steep slopes is thus an indispensable effort for balancing disaster prevention and environmental conservation.

That said, work on steep slopes is inherently more hazardous than on flat ground. Therefore, to carry out slope greening work safely, it is essential to accurately grasp the slope geometry and select appropriate construction methods and revegetation techniques. Traditionally, specialized surveying teams measured slope heights and gradients and then planned earthworks and planting based on those measurements. However, the very task of surveying steep slopes has long posed significant challenges.

Issues with conventional slope surveying

In conventional methods of surveying steep slopes, the foremost problem was ensuring the safety of workers. For a person to enter a slope to measure angles and heights, scaffolding must be erected or safety ropes used. The work must be performed with constant vigilance against slipping or falling. Especially on slopes loosened by recent rain or on unstable slopes at risk of collapse, simply approaching for surveying posed a risk.

Additionally, labor and time requirements were major issues. Typical surveys use total stations (optical surveying instruments) or levels to measure key points on the slope one by one. But on steep, irregular slopes, measurable points tend to be limited. Many locations are not visible (line-of-sight) from the surveying instrument, and even moving a person to the desired measurement position can be difficult. As a result, multiple survey plans and repositioning of instruments are often required to grasp the overall shape of the slope, making the process very inefficient. For example, it was not uncommon to be able to measure only a few points at the top, bottom, and mid-slope, leaving fine undulations and curve shapes to be inferred from the craftsmen’s intuition and experience.

When work must be done quickly with limited personnel, variations in measurement accuracy are also unavoidable. Manual measurements using tape measures or leveling rods can introduce small deviations that accumulate into significant errors across an entire slope. Conventional methods sometimes failed to accurately measure slope angles or uniformly confirm the thickness of fill, making it difficult to ascertain the as-built (final) shape. In this way, surveying steep slopes historically faced a dual challenge of safety risks and limitations in work efficiency and accuracy.

High accuracy and labor savings brought by smartphone surveying

In recent years, one technology attracting attention for transforming this situation is smartphone surveying. Modern smartphones are increasingly equipped with advanced sensors that instantly capture surrounding shapes and technologies that enable high-precision positioning. A representative example is the combination of LiDAR sensors and RTK-GNSS.

LiDAR is a sensor that uses laser light to measure the distance to an object, and by simply pointing a smartphone you can acquire the surrounding three-dimensional shape as a collection of points. With a high-performance smartphone, you can obtain countless measurement points covering an entire steep slope by merely moving the device while pointing it at the slope a short distance away. This capability is revolutionary—recording on-site 3D data with the same ease as shooting a video.

On the other hand, RTK-GNSS is a technology that corrects satellite positioning errors in real time, which previously required expensive dedicated equipment. Today, small RTK receivers can be attached to smartphones, enabling anyone to use centimeter-level positioning (half-inch accuracy). By leveraging RTK (Real Time Kinematic) positioning, the position error that would be several meters with a smartphone’s built-in GPS can be reduced to a few centimeters, allowing highly accurate coordinates to be appended to the acquired data. In other words, combining “smartphone + LiDAR” with “RTK high-precision positioning” turns a palm-sized smartphone into a high-performance surveying instrument.

Smartphone surveying has tremendous benefits even on steep slopes. First, worker safety is dramatically improved. Because data can be obtained by scanning a slope from a distance with a smartphone, there is less need to enter hazardous areas for surveying. While some movement is still required to thoroughly scan an entire slope, there is no longer a need to carry heavy equipment or repeatedly relocate scaffolding. The work can be performed by a single person, reducing the need to station supporting staff around the site. The convenience of being able to survey anytime with just a smartphone and a small device directly translates into labor savings for surveying tasks. Because data acquisition completes in a short time, situations that were once abandoned as “difficult to measure right now” can now be handled quickly.

In addition, the accuracy of smartphone surveying is practically sufficient. Each point in the LiDAR-derived point cloud is assigned coordinates corrected by RTK, ensuring high reliability in distance, area, and angle measurements on the slope. The accuracy is now comparable to that of professional instruments, enabling digital capture of slope geometry. Thus, surveying steep slopes is shifting from being a “dangerous and arduous task” to a “safe and quick task.”

Advantages of slope management using point cloud data

The enormous collection of measurement points obtainable by smartphone—i.e., point cloud data—offers various advantages that conventional surveying could not provide. The greatest feature is that point cloud data can capture the current state of a slope as a surface (entire area). For example, scanning an entire steep slope records visible features from surface irregularities to subtle changes in slope angle. Complex terrain that cannot be fully understood from planar drawings or a few measured points can be captured in detail by point clouds, almost like copying the slope itself.

Utilizing this high-density 3D data can revolutionize planning and as-built management for slope greening. Gradients that were previously calculated as averages from a few cross sections can be measured at any location on the point cloud. Visualizing the distribution of slope angles and curvature across the entire slope makes it possible to identify dangerous steep sections without omission. If fill or topsoil is applied to the slope, the thickness can be verified from the point cloud. Overlaying original terrain data with post-construction point clouds enables easy analysis—such as color-coding areas that are too thin or excessively filled. These analysis results from point clouds also serve as compelling documentation for quality control.

Moreover, point cloud-based as-built records contain far more information than photos or paper records and retain their value over time. For example, if the completed slope is stored as point cloud data in the cloud, you can recreate the terrain in 3D years later when planning maintenance and compare it with the current conditions. You can quantitatively assess vegetation growth and erosion progress, and easily identify areas that need repair. Sharing the data with other contractors or government agencies allows the as-built condition to be explained with objective evidence. Digital records that preserve the entire slope strongly complement traditional partial drawings and photographic records.

Once point cloud data have been acquired, they can be reused in many ways. If you later want a cross-section of a particular area or a measurement from a different angle, there is no need to return to the site. Additional measurements and drawing generation can be done on the data, reducing human error. In slope greening, once vegetation mats cover the surface after construction, it becomes difficult to check the substrate, but if the terrain was recorded beforehand as a point cloud, the hidden parts are preserved in the data. In this way, leveraging point cloud data obtained with a smartphone significantly improves the quality of slope management.

Rapid assessment and AR utilization useful at difficult sites and disaster scenes

Steep slopes include difficult sites where it is hard for people to approach and disaster sites where slopes have collapsed due to heavy rain, earthquakes, or other hazards. In such locations, rapid assessment and immediate countermeasures are required, but there may be no time to bring in large surveying equipment or erect scaffolding. Smartphone surveying is powerful in these emergency situations. Because only a small, lightweight smartphone and a positioning device are needed, teams can respond to unstable slopes immediately after a disaster with mobility. For example, if part of a slope collapses after heavy rain, as soon as surrounding safety is assured, a worker can scan the slope with a smartphone and obtain terrain data of the collapse area in minutes. Calculating the volume of displaced soil from that data immediately allows quick estimation of the temporary sandbags or the amount of fill needed for restoration. Emergency responses that previously relied on visual inspection and experience can now be conducted quickly and accurately based on data.

Also, 3D data acquired by smartphone surveying can be shared instantly with internal and external parties via the cloud, making it easy to seek expert advice remotely. In disaster response, visualizing the situation is crucial; by having all stakeholders simultaneously review a point cloud model, discussions and decision-making—including by technicians not on site—can proceed swiftly.

Furthermore, the smartphone’s AR (augmented reality) functionality becomes a reliable support tool on steep-slope sites. With AR, point cloud data or design models can be overlaid onto real-world scenery. For example, overlaying a post-restoration design model on a collapsed slope via AR lets you intuitively see the terrain that should be present compared to the collapsed area in front of you. This helps quickly grasp where and how much fill is needed for restoration, simplifying recovery planning. During construction, it is also possible to directly compare the current slope point cloud with the design on site. By viewing the planned finish line and the current condition through the smartphone screen, you can check deviations at a glance. Using heatmap coloring to visualize thickness excesses and shortages makes it possible to detect on the spot where revegetation material thickness is insufficient or where fill volume is lacking.

AR visual aids also contribute to safety. For example, by predefining hazardous zones or work areas and displaying their boundaries through the smartphone, AR can serve as a warning tool for workers. Even inexperienced staff can more easily understand spatial instructions—such as “do not proceed beyond this point” or “fill to this height”—through AR displays. In environments where on-the-spot decisions are difficult, like on steep slopes, AR’s ability to share digital information visually is a powerful advantage.

Effects of completing surveys with a single smartphone: reduced personnel, increased efficiency, and lower training costs

Introducing smartphone surveying greatly contributes to on-site labor reduction and efficiency. Previously, surveying a slope required multiple people and highly skilled surveyors. Now, field supervisors or workers can complete the task with an intuitive smartphone interface that can be operated by one person. This helps alleviate labor shortages and optimize staff deployment. If several people no longer need to cling to a hazardous slope to perform measurements, personnel can be reassigned to other important tasks.

In terms of work efficiency, smartphone surveying offers a dramatic time savings over traditional methods. Time losses from transporting and setting up surveying equipment, waiting for suitable weather, or waiting to perform measurements are reduced, allowing immediate measurement whenever needed. Since the flow from data acquisition to analysis is automated, volume calculations and drawing generation can begin as soon as scanning is finished on site. Where previously survey results had to be brought back to the office to create CAD drawings before as-built checks could be performed, everything can now be completed on the spot with a single smartphone. This shortens the construction management cycle and helps ensure schedule compliance and early implementation of safety measures.

An equally important benefit is reduced training costs. Smartphone surveying is designed to be simple to operate, so it can be handled without special certifications or years of experience. Intuitive app interfaces suitable for novice to veteran users and automatic error correction mechanisms enable even surveying beginners to achieve a certain level of accuracy. This offers a solution to knowledge transfer challenges arising from the retirement of veteran technicians. Because digital tools provide objective data instead of relying solely on seasoned intuition, the overall technical capability of the field is lifted. Moreover, completing work with the familiar device of a smartphone lowers psychological barriers to digital tools and positively impacts human-resource development for promoting on-site DX.

Unified management of surveying, point clouds, AR, and cloud with LRTK

To fully leverage the benefits of smartphone surveying, it is important to have a system that seamlessly covers everything from surveying to data utilization. Enter the solution called LRTK. LRTK is a comprehensive platform that combines a compact RTK-GNSS receiver that attaches to a smartphone, a dedicated app, and cloud services. With a single implementation, you can centrally manage surveying, point clouds, AR, and cloud services.

Specifically, you attach the LRTK device to the smartphone at the site, launch the app, and start surveying. Real-time, high-precision corrected positions are obtained, and coordinates are automatically assigned to the point cloud captured by the smartphone’s LiDAR. Simply walking along the slope you want to measure while scanning produces a high-density point cloud in a matter of minutes. Remarkably, the subsequent processing is also simple. The acquired point cloud is immediately converted into the designated coordinate system (such as public coordinate systems), so you won’t struggle later with coordinate alignment. With the press of a button, you can upload to the cloud, and the data can be viewed and shared from office PCs or tablets. In other words, the entire sequence that formerly required outsourcing to specialized contractors or complex equipment is designed to be completed with only a smartphone and LRTK.

LRTK also includes functionality to overlay point clouds captured on the smartphone with design data for AR display. For example, you can easily overlay the designed finish line on a scanned 3D model of a steep slope and check discrepancies on site. Because point cloud data accumulated in the cloud are centrally managed within the company, progress and as-built conditions can be shared in real time, making it easy to manage construction remotely from distant locations. A major advantage is that data do not become scattered by project site and can be integrated with safety information and construction history for unified management.

In this way, LRTK completes the processes of measuring, recording, comparing, and sharing on a single platform. For complex and hazardous sites such as steep-slope greening, the smooth data integration enabled by LRTK’s unified management will prove highly effective. When data remain continuously connected, the boundary between field and office blurs, accelerating DX across the entire project.

The future of DX expanding in steep slope greening

With technological advances, a wave of digital transformation (DX) is undeniably sweeping into steep-slope greening. By combining smartphone surveying, point cloud data, and AR utilization, tasks that once relied on manual labor and experience will become data-driven, enabling safe and efficient construction that satisfies everyone. From slope safety evaluation to quality management of greening construction, a future in which everything is governed by digital data is already within reach.

Adopting cutting-edge smartphone surveying solutions like LRTK will especially transform steep-slope greening operations. There will be no need to fear surveying in dangerous locations, and real-time 3D measurement will enable consistently optimal decisions. Data-driven construction eliminates waste and minimizes environmental impact. Above all, when everyone on site can use digital tools, an organization’s ability to promote DX improves. This aligns with industry-wide initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*, enabling implementation of modern smart construction.

Greening steep slopes is a noble task that contributes to public safety and the creation of a richer environment. Bringing DX into these sites can create a better future for both workers and local communities. LRTK, which enables easy surveying with a smartphone, should be a reliable partner supporting the first steps toward that future. Break free from conventional assumptions and actively adopt new technologies to innovate steep-slope greening operations. By making digital technology your ally, you can achieve future-oriented construction that improves safety, quality, and efficiency. Take this opportunity to realize DX in steep-slope greening through LRTK and step forward in building the next-generation worksite.