Solar Power Plant Elevation Surveying Made Easy｜Safe Design on Slopes with LRTK

Introduction: Practical challenges that "elevation differences" bring in solar power plant construction

When constructing solar power plants, dealing with elevation differences (undulations and slopes) on the site becomes a major challenge. In Japan, where many mega-solar installations are located in mountainous or sloped areas, it is necessary to confront non-flat terrain. If there are elevation differences of several meters within a site, large-scale earthworks (cut-and-fill) may be required, directly impacting schedule and cost. On steep slopes there are also safety concerns such as landslide risk and the stability of mounting structures. "Elevation differences" are a practical factor that can determine plant layout and construction planning, so they must be properly understood and addressed.

However, in practice, projects sometimes proceed without fully grasping the terrain’s undulations during the planning stage, leading to unforeseen issues during construction like "I didn’t realize the valley was this deep" or "the excavation volume turned out to be greater than expected." If the rows of racking supporting the solar panels interfere with the ground or, conversely, float too far above it, additional adjustments or rework will be required. To prevent such problems, it is important to accurately survey the site elevation differences in advance and incorporate them into the design. This article explains the challenges of acquiring elevation information on slopes and introduces a new technology, LRTK, which enables easy elevation surveying.

Required quality and quantity of surveying for solar design on slopes

When designing a solar power plant on sloped terrain, more detailed topographic information is required than for flat land. Even on gentle slopes there can be locally severe undulations such as hollows and ridge-like rises when looking at the entire site. There are subtle elevation differences on site that cannot be read from plan views or existing topographic maps, and overlooking them can lead to design discrepancies. On slopes, slight height differences affect shadowing between adjacent panels and the design of racking leg lengths, so vertical accuracy is extremely important.

In addition, the density (quantity) of survey points must also be secured. On a vast slope, measuring only a few representative elevations is not sufficient. For example, while measuring the four corners might roughly capture the shape of a flat 50 m square site, on an undulating slope you won’t know how much the elevation changes between those points. To capture the overall shape of a slope, it is necessary to place many survey points in a fine mesh pattern or measure heights continuously along cross sections. Only with surveying that is substantial in both quality and quantity can design on sloped land be undertaken with confidence.

Limitations of conventional elevation surveying (total station / contour interpretation / drone surveying)

Several conventional methods have long been used to understand terrain elevation differences. However, from the viewpoint of quick and detailed surveying on slopes, each has limitations. Let’s look at representative methods and their challenges.

• Surveying with a total station: This optical surveying instrument measures the elevation of each point using a staff with a prism. While accuracy is high, observations are time-consuming point by point and the number of measurable points is limited. On highly undulating sites, more survey points are needed to ensure lines of sight, increasing the workload including manpower as the survey area expands. Setting up a tripod on an active construction site with heavy machinery is cumbersome, and it is not suitable for applications requiring real-time understanding of current conditions.

• Reading existing topographic maps and contour lines: This method estimates elevation differences from topographic maps by the Geospatial Information Authority or from existing construction drawings. While you can capture broad trends, the contour interval (resolution of elevation data) is coarse, so fine undulations cannot be identified. Reading from paper drawings leaves room for interpretation, which can produce discrepancies from the actual terrain. For past developed sites, drawings may be old and differ from the current conditions, so they cannot be fully relied on for design accuracy.

• Aerial surveying using drones: A recently popular method where a drone equipped with a camera or LiDAR measures the terrain from above to generate point clouds and orthophotos. Its major advantage is the ability to measure large areas densely in a short time, but there are challenges in terms of immediacy and operational constraints. Drone flights depend on weather and aviation law approvals; in forested mountain areas the ground surface may not be visible from above (covered by trees), preventing adequate data acquisition. Also, post-processing of captured data requires specialized software and time, making it difficult to meet needs such as "we want to know the elevation difference of this area right now" in the field.

As above, traditional methods involve a trade-off: highly precise elevation data can be obtained but at the cost of time and effort, while convenient methods lack precision or detail. For solar power plants on slopes, a new surveying approach that fills the gap between these conventional methods has been needed.

Immediate grasp of elevation differences with LRTK (cross-section display / elevation-attached point clouds / one-handed surveying)

That is where the new positioning technology called LRTK comes in. With LRTK, you can quickly understand the site’s elevation differences while on site. Specifically, it offers the following features:

• Instant on-site terrain cross-section display: When surveying with an LRTK unit linked to a smartphone, vertical differences between points and continuous terrain cross-sections can be drawn on the screen in real time. For example, measuring directly from point A to point B on a slope produces an immediate profile (longitudinal section) of the undulation between them. This visualizes, in numbers and graphs on the spot, subtle changes in gradient that are hard to perceive with the naked eye.

• Acquisition of point cloud data with elevation information: LRTK leverages centimeter-level accuracy of satellite positioning (RTK-GNSS) to attach precise latitude, longitude, and elevation to each measured point. By recording points at high density, you can obtain detailed point cloud data in the field and create terrain models similar to those from laser scanners. The acquired point clouds can be transferred to a PC via the cloud and imported into CAD software for design use, making it easy to reflect the measured data in design studies on the same day.

• Easy one-handed surveying: LRTK devices are compact and designed to attach to a smartphone for one-handed operation. No heavy tripods or complicated initial setup are required, so you can start measuring whenever needed. Surveying that used to require two people can be conducted by one person walking the site and collecting data with LRTK. It shows mobility even in narrow forests and on uneven slopes and eliminates the need to repeatedly set up equipment at each point. With intuitive operation that anyone can use without specialized knowledge, anyone can quickly obtain elevation information when needed.

Using LRTK in this way makes it possible to grasp elevation differences on slopes both immediately and at high density. In the next sections we will look at how this data can be concretely applied to earthworks planning and racking layout design.

Ease of volume calculation and slope measurement in earthworks planning on slopes

Detailed height data obtained with LRTK is powerful for earthworks planning (cut-and-fill design) on slopes. First, because cross-section data can be obtained immediately, rough calculations of earthwork volume are possible on the spot. For example, if you want to know how much of a slope needs to be cut to create a flat pad, you can measure the current ground cross-section with LRTK and compare it to the horizontal line representing the desired elevation to instantly determine the cross-sectional area to be excavated. Trying this for several cross sections across the site gives a handle on the overall earthwork balance, allowing you to estimate rough cut-and-fill volumes on the same day. Earthwork volume calculations that used to be performed after returning with survey data can now be done in a way that is close to real-time on site.

Also, slope (gradient) measurement is simple with LRTK. For example, evaluating slope stability or confirming the gradient of a work road requires knowing the average gradient or elevation difference over a certain section. If you measure the elevations at the endpoints of a section with LRTK, you immediately obtain the elevation difference numerically and can easily calculate the gradient (in percent or degrees) by combining it with distance information. Since smartphone apps can display elevation differences between two points and read section gradients from profile displays, you can measure slopes far more efficiently and accurately than with manual tools like spirit levels or tapes. These easy analyses allow you to repeatedly refine earthworks plans on site and create balanced cut-and-fill strategies.

High-precision terrain models useful for racking layout planning

High-precision terrain models obtained by LRTK bring major benefits to racking layout design for solar panels. On slopes, ground elevation varies by row, so adjusting each racking height and optimizing row spacing is important. In the past, designs were often based on only simple terrain models and then tweaked in the field during construction to match actual undulations. With the detailed terrain data acquired by LRTK, you can conduct layout studies that reflect the existing terrain from the design stage.

Specifically, by importing point cloud or survey point data into CAD or layout design tools, you can accurately determine the elevation at each racking placement location. As a result, you can estimate the support leg lengths for each rack appropriately, plan terraced configurations where needed, and make such decisions in advance. For example, even if a central part of a row has a ground depression, knowing the amount of sag from the model allows you to prepare height adjustment components in advance or shift the layout to a flatter area to avoid problems.

Furthermore, in areas with steep slopes it is also necessary to carefully consider row spacing and tilt angles to avoid mutual shading. By simulating this on the terrain model, you can check whether rows will cast shadows on each other. Terrain models built with LRTK can also be used for generation-impact evaluations (shadow analysis) and load assessments on racking foundations, improving design reliability. By obtaining high-precision terrain models, you can plan racking layouts on slopes without forcing the design and prevent rework or additional construction after installation.

Cross-section comparisons on-site that determine field speed

How quickly the differences between plan and actual conditions can be identified on site directly affects construction speed. LRTK’s "on-site cross-section comparison" is a highly effective tool in this respect. For example, consider checking whether the slope and elevations from earthworks match the design. Traditionally, after heavy equipment completed earthworks the surveying team would be called back to measure, and only after data processing would discrepancies with design cross-sections be evaluated. With LRTK, the site team can measure immediately after earthworks finish and compare the design cross-section and the actual terrain cross-section on the spot. If a discrepancy such as "we need to cut another 10 cm" or "a portion of the fill is higher than planned" is discovered, feedback can be given to the equipment operator immediately and corrective work can be completed the same day. As a result, rework and schedule delay risks are minimized, shortening the overall construction schedule.

Also, when comparing multiple construction options on site, LRTK’s cross-section measurements are highly effective. For example, when deciding a material delivery route, measuring the longitudinal gradient of each candidate path with LRTK allows immediate judgment of which route has the gentlest slope and is easiest to construct. Fine undulations that were not evident on paper drawings are revealed by actual measurement, increasing decision accuracy. The strength of "on-site cross-section comparison" supports rapid on-site decision-making and thereby greatly improves the overall work speed and efficiency.

Ease of use for anyone and LRTK advantages useful for inspection and acceptance

Another attraction of LRTK is its simple operability that anyone can handle. Even site managers or design staff without surveying expertise can obtain the necessary data by following prompts in a smartphone app and pressing a measurement button. With an intuitive UI and automatic recording functions, measured points are plotted on a map and elevation information is saved automatically. This helps prevent human errors such as "measuring incorrectly" or "transcription errors in notes." On-site personnel shortages and staff turnover are common, and simple-to-use equipment helps avoid reliance on specific individuals, enabling organizational implementation and sharing of site surveying.

Furthermore, LRTK can be used in the post-construction inspection and acceptance phases. During completion inspections of solar power plants, there are occasions to check whether slopes and drainage gradients match the design, or whether racking installation heights are correct. Where such checks were conventionally done by visual inspection or spot checks with a spirit level, LRTK enables rapid measurement of important locations and numeric recording. For example, by measuring slope angles at multiple points on a slope, you can attach the measured data as evidence in inspection reports. LRTK is also useful for routine inspections after operation begins, for monitoring ground subsidence or sediment accumulation due to aging. By comparing with baseline data collected once, you can quantitatively evaluate elevation changes and detect abnormalities early.

As described above, LRTK offers:

• Ease of use (operable without specialized skills)

• Immediacy (real-time results)

• Data accumulation and sharing (coordinate data managed and utilized via the cloud)

These advantages make LRTK useful across a wide range of stages from design to construction, acceptance, and maintenance. For those involved in solar projects on slopes, LRTK is a reliable tool that resolves concerns about on-site elevations and enhances operational efficiency.

Voices from the field: experiences that changed design decisions on slopes

Finally, here are firsthand accounts from sites that introduced LRTK and felt its effects. A construction manager involved in a mountain-area solar power project said that LRTK significantly changed design decision-making.

As this manager’s experience shows, the introduction of LRTK is transforming the decision-making process for design and construction. On slopes, where decisions used to rely on experience and intuition, being backed by data enables rational plan changes that eliminate waste. Reduced uncertainty about elevation differences eases psychological burdens on both designers and builders, allowing projects to proceed with greater confidence. Some on-site personnel even say, "We can’t imagine slope projects without LRTK anymore," suggesting that LRTK is becoming a new standard tool that fundamentally supports solar development on slopes.

Why not try simple elevation surveying with LRTK now?

Acquiring elevation information is a major challenge in planning and constructing solar power plants on slopes. As a solution, LRTK offers unprecedented ease and reliability. By greatly reducing the effort required for elevation surveying while securing the necessary data, LRTK makes safe design on slopes a practical reality. Those working in the field should consider trying this new surveying experience.

If you are interested in simple elevation surveying with LRTK, please feel free to [contact us](https://www.lefixea.com/contact). Our specialist staff will guide you carefully on how to use it in the field and on implementation plans. Make the latest LRTK technology your ally and ensure the speedy, reliable success of your solar projects on slopes!