Smartphone-powered 3D Surveying for Slope Greening Anyone Can Do

Slope greening work involves planting vegetation on roadside slopes and dam faces to balance landscape and environmental conservation with prevention of soil erosion. In such projects, surveying the slope shape before construction for design, and inspecting the as-built (completed) shape after construction to verify conformity with the design, are indispensable tasks. However, surveying steep slopes poses many challenges in securing footing, personnel burden, and safety, so it has traditionally been handled by specialist surveyors.

In recent years, the construction field has faced labor shortages and demands for improved work styles, driving a need for labor-saving and efficiency improvements. One approach gaining attention is 3D surveying using smartphones. This article explains in detail how smartphone-based 3D surveying, which anyone can perform, brings benefits to surveying for slope greening projects.

The importance of surveying in slope greening work and traditional challenges

In slope greening projects, accurately understanding the on-site slope geometry can determine success or failure. If slope gradients (inclination angles), steps, and areas are not measured properly, it may be impossible to create a greening substrate according to the design, which can lead to problems with vegetation establishment and safety. Knowing the slope’s current condition before construction also allows accurate calculation of required seeds, imported soil (topsoil), and material areas (such as vegetation mats and nets), helping with cost control and scheduling. After construction, as part of as-built management, it is necessary to inspect whether the completed slope meets the designed shape and dimensions and to compile the results into a report for the client. In this way, surveying is a very important process in slope work.

However, surveying on slopes has long presented numerous challenges. On steep slopes, workers often must climb directly to operate tape measures or surveying instruments, increasing the risk of falls and other safety hazards. Preparations such as erecting scaffolding or wearing safety harnesses are time-consuming and labor-intensive. Manual measurement also limits the number of points that can be measured at once, making it difficult to capture the full detail of a wide slope. Even if only key points are measured and compared with drawings, unexpected depressions or discrepancies in unmeasured areas can remain and later be cited as nonconformance during inspections. In addition, manual methods are prone to human error, such as missed photos or transcription mistakes when recording measurements on paper, which added to on-site burden and stress.

Thus, traditional surveying for slope greening has been criticized for being “dangerous,” “labor-intensive,” and “limited in accuracy and coverage.” As a solution to these issues, smartphone-based 3D surveying is attracting attention, as described below.

Background driving demand for labor-saving and efficiency in surveying work

The construction industry as a whole is grappling with serious problems such as labor shortages and an aging population of skilled workers. It is especially difficult to secure survey personnel for works in mountainous or rural areas, so tasks must be handled efficiently with a limited workforce. At the same time, reforms in work styles are being demanded on sites, making the correction of long working hours and reduction of hazardous tasks important issues. Slope surveying often involves heavy labor under the sun and potentially dangerous high-place work, so reducing personnel and labor while improving safety has been strongly desired.

Against this backdrop, the Ministry of Land, Infrastructure, Transport and Tourism has promoted a productivity-improvement initiative for construction sites called *i-Construction*, encouraging the use of ICT and 3D surveying technologies. Efforts are underway nationwide to digitize and streamline surveying and as-built management processes that previously relied on manpower, enabling accurate measurements with fewer people in less time. As a low-cost option that even small contractors can adopt, smartphone-based 3D surveying methods have attracted attention. Even on sites where the latest ICT equipment or large drones cannot be introduced, using a handheld smartphone is expected to significantly improve surveying efficiency.

Basics of smartphone-based 3D surveying and what it can do

So what exactly is smartphone-based 3D surveying? At its core, it uses a smartphone’s camera and built-in sensors to scan the surrounding terrain and capture a large collection of 3D points called point cloud data. Some modern smartphones are even equipped with LiDAR sensors for distance measurement, and with a dedicated app you can simply move the phone while viewing the slope through the camera to record countless points that define the slope’s shape with XYZ coordinates. The resulting point cloud acts like a digital “copy” that faithfully captures the slope’s bumps and hollows. Where traditional methods measured one point at a time with tapes or total stations, smartphones can measure surfaces all at once, which is revolutionary.

With point cloud data obtained by smartphone, various measurements and analyses can be performed on site. For example, a dedicated app can easily measure the distance between any two points or determine height differences with a single button press. Being able to check slope angles and height differences in real time makes it quick to verify whether the required gradient is achieved or whether there are steps or unevenness. From scanned data, area and soil volumes (volumes) for specific zones can also be calculated. For instance, during embankment or excavation, you can scan the current condition and immediately compare it with design values to determine whether the target soil volume has been reached. In this way, a single smartphone serves as a versatile analysis tool that can cover most measurements needed on site.

Moreover, smartphone 3D surveying is a powerful tool for as-built inspections. By scanning the completed slope and converting it to a point cloud, you can record the finished shape in detail. The acquired data can be compared against 3D design data (BIM/CIM models, etc.) or design drawings to verify whether the designed gradients and thicknesses are met and to detect any missing fill or protruding areas. While traditional checks relied on a few measurement points, point clouds enable checking the entire slope, dramatically improving quality control accuracy. Some smartphone apps even display design deviations as color-coded overlays on site or automatically extract areas that exceed allowable tolerances. This allows objective pass/fail judgments based on data rather than relying on the intuition of veteran engineers.

Examples of point cloud data use: design verification, quantity calculation, and report preparation

Point cloud data captured with a smartphone can benefit construction management in various ways. Major use cases include the following:

• Design verification: By overlaying the scanned point cloud of current conditions on a prepared design model or cross-sections, it becomes immediately clear whether the as-built shape matches the design. For example, the app can display differences from design elevations as a color heatmap or extract areas outside specification. The “surface-based verification” possible with point clouds prevents even small misalignments from being overlooked.

• Quantity calculation (volume/area): Volumes of fill and cut or the surface area of slopes can be automatically calculated from point cloud data. Tasks that previously required manual soil-volume calculations based on drawings and measured points can now be computed accurately with a click. If a sudden design change requires additional imported soil, you can scan the site and instantly estimate the needed soil amount. Quantity calculation is essential for progress and as-built management in civil works, and point cloud use greatly streamlines this process.

• Report preparation: Acquired point clouds serve as a “3D record” of the site for later detailed analysis and drawing creation. For example, you can extract arbitrary cross-sections from point cloud data to produce before-and-after sectional comparison diagrams, or include a 3D view model of the slope in reports. Using a cloud-based point cloud viewer, you can share data with clients and internal stakeholders and have them verify measurements online. Information that is hard to convey through photos or paper drawings becomes far more persuasive when presented as 3D data.

Accelerating pre-construction checks and stakeholder agreement by combining AR

Data from smartphone 3D surveys and design models can be combined with AR (augmented reality) technology to greatly improve pre-construction checks. Using the AR capabilities of a smartphone or tablet, you can overlay 3D design models and drawing information onto the actual site view. For example, displaying the placement area of vegetation mats or the intended height of imported soil on the ground via AR helps intuitively share the finished appearance before construction. Finishes that are hard to imagine from drawings alone can be seen as life-sized CG models, preventing misunderstandings like “this isn’t what I expected.”

AR also helps build consensus with clients. Parts that used to rely on rendered images or verbal explanations can now be shown on-site through a smartphone, allowing clients and local residents to see and agree on the planned result before work begins. Since slope greening affects landscape, being able to preview the appearance after greening provides reassurance. If design changes occur during construction, a new model displayed in AR on site allows immediate sharing and agreement on the changes. Visual sharing via AR reduces time spent explaining and significantly speeds decision-making.

Additionally, by combining AR and the cloud, remote site checks become easy. If you upload photos taken during AR display or point cloud data to the cloud, clients can check progress and as-built status from the office. Because information can be shared in near real time without physically visiting the site, lead times for reaching consensus are greatly reduced. Combining smartphone surveying and AR dramatically improves the quality and speed of communication from pre-construction through post-construction.

Flexibility for small sites, steep terrain, and disaster recovery

Because of their ease of use, smartphone 3D surveys can flexibly adapt to varied site conditions. For small sites or short slope sections where deploying large drone surveys or expensive laser scanners is excessive, a smartphone can be taken out and used immediately for a solo survey, saving cost and setup time. The mobility of a smartphone allows data capture even in confined sites, enabling collection of details that conventional equipment might miss.

Smartphone surveying can also record terrain where other methods struggle, such as steep slopes or slopes surrounded by forest. Drones have difficulty flying in strong winds or under tree canopies, and laser scanners can be difficult to transport and set up in harsh conditions, but with a smartphone you can nimbly ascend and descend slopes and scan point by point within the area people can safely enter. Of course safety must be ensured, but the burden is far lower than carrying heavy equipment and working for long periods. Since smartphone surveys do not require special licenses or flight permissions, regulatory hurdles are lower and the method can be used flexibly regardless of terrain or environment.

Furthermore, smartphone surveying is useful for emergency response immediately after disasters. At sites where slopes have collapsed due to heavy rain or earthquakes, it is vital to quickly assess the affected area and the volume of collapsed soil to plan restoration. In such cases, site personnel can scan the collapse with a smartphone without waiting for specialists to arrive and rapidly analyze the damage from the data. It is possible to estimate collapsed soil volumes from point clouds or present hazardous areas as 3D models to share information with relevant agencies. With its flexibility and responsiveness, smartphone 3D surveying can support work from small-scale sites to urgent disaster recovery.

Improving on-site record accuracy through cloud sharing and automated reporting

Survey data captured by smartphone can be saved and shared directly to the cloud. Cloud connectivity allows scanned point clouds, photos, and measurement results to be viewed immediately from the office or remote locations, streamlining information transfer. Multiple stakeholders—site managers, designers, clients—can share up-to-date data, eliminating discrepancies such as “the site said this but HQ wasn’t informed.” Because data are stored in the cloud, past survey records can be easily retrieved when needed, aiding long-term record management.

Using digital data also enables automatic generation of various reports. Traditionally, as-built management documents and reports were created by manually inputting field measurements into drawings and tables. When point clouds and measurement results from smartphone surveys are linked to software via the cloud, difference lists from design values, cross-sectional diagrams, and quantity summaries can be generated automatically. This eliminates transcription errors and dramatically improves recording accuracy while reducing office workload. For example, surveys by the Ministry of Land, Infrastructure, Transport and Tourism report that creating as-built documentation in earthworks projects was greatly shortened where 3D surveying and ICT construction were implemented. Cloud and data integration make the cycle of “measure, summarize, communicate” seamless, boosting both on-site productivity and record accuracy.

An integrated solution: smartphone surveying + AR + point clouds + cloud with LRTK

As shown above, smartphone-based 3D surveying offers significant benefits for slope greening sites. However, realizing this on site requires not only a smartphone but also systems that support high-precision positioning and data processing. Enter the solution called LRTK. LRTK consists of a super-compact high-precision GNSS receiver that attaches to a smartphone and a dedicated app, providing centimeter-level RTK positioning information, smartphone 3D scanning capabilities, AR display, and cloud integration in one package. In short, it is a site DX tool that enables “measure, view, compare, and share” in a single workflow.

With LRTK, anyone can easily perform high-precision point cloud measurement and on-site analysis. Complex setup of survey coordinates and post-processing are automated, so even users without specialized knowledge can complete 3D surveying intuitively with a smartphone. Real-time positioning information is attached to the acquired point cloud, clarifying where each slope point lies in map coordinates. This allows immediate overlay and verification of site data with design drawings or CIM data, enabling as-built management, quantity calculation, and AR-based visualization of the finished image all within one platform. Measurement data can be saved to the cloud with one click, eliminating the need to copy via USB or send emails after returning to the office.

Systems like LRTK that can be started with just a smartphone are attractive because they are easy for small to mid-sized contractors and sites without dedicated surveying departments to adopt. In practice, sites that introduced LRTK reported that as-built surveying of slopes that previously required two to three people could be completed by one person in a short time, and that using point cloud measurement for routine progress checks eliminated waste. Reports also note improvements in safety and facilitation of young engineer training. Combining smartphone surveying, AR, point clouds, and cloud services into a unified solution can make surveying and management of slope greening projects markedly smarter.

Introducing advanced technology to the field may seem like a high hurdle, but with the arrival of LRTK, “3D surveying anyone can do” is already becoming a reality. If you are considering labor-saving measures or digital transformation for your sites, you may want to explore surveying solutions using LRTK that can be started with a single smartphone. Tasks like slope greening, which traditionally required significant effort, present an excellent opportunity to dramatically improve efficiency through cutting-edge technology.