Easy elevation surveying for solar power plants｜Safe design for sloping land with LRTK

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

In solar power plant construction, handling elevation differences (undulations and slopes) on the site is a major challenge. Especially in Japan, where many mega-solar installations are built in mountainous or sloping areas, it is necessary to contend with non-flat terrain. If there are elevation differences on the order of several meters within the site, large-scale earthworks (embankment and cutting) will be required, directly affecting the construction schedule and costs. In places with steep slopes, there are also safety concerns such as landslide risks and the stability of mounting structures. The "elevation difference" is a practical factor that influences plant layout and construction planning, and it must be properly understood and addressed.

However, in practice projects sometimes proceed without sufficiently grasping terrain undulations during the planning stage, leading to unexpected situations during construction such as "there was a valley this deep" or "the volume of excavated soil increased more than planned." If rows of mounting racks for solar panels interfere with the ground or, conversely, sit too high above the surface, additional adjustments or rework will be necessary. To prevent such problems, it is important to accurately survey the site's elevation differences in advance and reflect them in the design. This article explains the challenges of acquiring elevation information on sloping land and describes an easy elevation surveying solution using a new technology called LRTK.

Required quality and quantity of surveying for designing solar power on sloping land

When designing a solar power plant on sloping land, more detailed topographic information is required than for flat land. Even on gentle slopes, there are often areas with sharp undulations such as depressions or ridge-like rises that are not obvious when looking across the entire site. Subtle elevation differences that cannot be read from plan views or existing topographic maps exist on-site, and overlooking them can cause discrepancies in the design. On sloping land, slight height differences can affect shading between adjacent panels and the design of rack leg lengths, so accuracy in the vertical direction is extremely important.

In addition, the density (quantity) of survey points must also be ensured. On large sloping sites, measuring only a few representative elevation points is not sufficient. For example, on a flat 50 m (164.0 ft) square plot, measuring the four corners might be enough to get a general sense, but on a sloping surface you cannot know how much elevation changes between those points. Capturing the overall shape of the slope requires placing many survey points in a fine mesh pattern or measuring heights continuously along cross-sections. Only with surveying that is robust in both quality and quantity can you confidently proceed with design on sloping land.

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

Several traditional methods have been used to understand terrain elevation differences. However, from the standpoint of quick and detailed surveying on sloping land, each has its limitations. Let’s look at representative methods and their issues.

• Surveying with a total station: An optical surveying instrument that measures the elevation of points on the terrain in conjunction with a prism-equipped staff. While accuracy is high, each observation takes time and there is a limit to the number of points that can be measured. On sites with large undulations you need to increase survey points to secure lines of sight, and as the survey area expands the workload—including manpower—increases. Also, setting up a tripod on a site where heavy machinery is doing earthworks is cumbersome, so this method is not suited for real-time monitoring of current conditions.

• Reading existing topographic maps / contour lines: Estimating elevation differences by reading contour lines from Geospatial Information Authority maps or existing earthwork plans. This approach can capture broad trends, but contour intervals (the resolution of elevation data) are coarse and cannot capture fine undulations. Reading from paper drawings also leaves room for interpretation, which can create discrepancies with the actual terrain. In many cases, drawings for previously developed land are outdated and differ from current conditions, so relying solely on them is risky when high design accuracy is required.

• Aerial surveying using drones: A method that has become widespread in recent years, using cameras or LiDAR mounted on drones to measure terrain from the air and generate point clouds and orthophotos. The major advantage is the ability to measure wide areas densely in a short time, but there are challenges in terms of immediacy and operational constraints. Drone flights are subject to weather conditions and aviation law approvals, and in wooded mountain areas the ground surface may be obscured by trees, making it difficult to obtain sufficient data. Additionally, post-processing the captured data requires specialized software and time, so it is difficult to meet on-site needs such as "I need to know the elevation difference of this section right now."

As described above, conventional methods involve a trade-off: those that provide precise elevation information are time-consuming and labor-intensive, while the more convenient methods lack accuracy or detail. Solar power projects on sloping land required a new surveying approach to fill this gap.

Immediate elevation understanding with LRTK (cross-section display / elevation-equipped point cloud / one-handed surveying)

Enter a new positioning technology called LRTK. With LRTK, it is possible to grasp site elevation differences in a short time while on-site. Specifically, it offers the following features:

• Instant on-site cross-section display: When surveying with an LRTK device linked to a smartphone, elevation differences between points and continuous terrain cross-sections can be drawn on the screen in real time. For example, measuring in a straight line from point A to point B on sloping land will immediately show the undulation profile (longitudinal section) between them. This visualizes steepness changes that are hard to perceive with the naked eye as numbers and graphs on the spot.

• Acquiring point cloud data with elevation information: LRTK leverages RTK-GNSS satellite positioning with centimeter-level accuracy (half-inch accuracy) to attach accurate latitude, longitude, and elevation to each measured point. By recording points at high density, you can obtain detailed point cloud data on-site and build topographic models that are comparable to those produced by laser scanners. The acquired point cloud can be transferred to a PC via the cloud or imported into CAD software for use in design, making it easy to reflect survey data in design work on the same day the measurements are taken.

• One-handed, easy surveying: LRTK equipment is compact and designed to be mounted to a smartphone and operated with one hand. Heavy tripods and complex initial setup are unnecessary, allowing you to start measuring whenever needed. Surveys that used to require two people can be done by one person walking the site and collecting data with LRTK. It performs well even in narrow forested areas or on poor footing where repositioning equipment for each point is a hassle. With intuitive operation, even those without specialist knowledge can use it, enabling anyone to obtain elevation information when needed.

By using LRTK in this way, you can grasp elevation differences on sloping land instantly and at high density. The next chapter discusses how this data can be applied concretely to earthworks planning and rack layout design.

Ease of volume calculation and slope measurement for earthworks planning on sloping land

Detailed elevation data obtained with LRTK is powerful for earthworks planning (cut-and-fill design) on sloping land. First, because cross-sectional data is immediately available, you can estimate earthwork volumes on site. For example, if you want to know how much of a slope must be cut to create a flat construction platform, measure the current ground cross-section with LRTK and compare it to the planned horizontal elevation to instantly determine the cross-sectional area to be excavated. Trying this for several cross-sections on-site gives you a sense of the overall balance of cut and fill, enabling you to estimate rough earthwork quantities the same day. Tasks that traditionally required bringing survey data back to the office for volume calculations can now be performed in a near real-time manner on site.

Slope (gradient) measurement is also simple with LRTK. For example, evaluating slope stability or checking the incline of service roads requires knowing the average gradient or elevation difference over a certain section. By measuring the elevations at the endpoints of a section with LRTK, you immediately obtain the elevation difference numerically, and combining that with distance information makes calculating the slope (in percent or degrees) easy. The smartphone app can display elevation differences between two points or read section gradients from the profile display, making it far more efficient and accurate than manual methods using a level or tape measure. These simple analyses allow you to repeatedly refine earthworks plans on-site and prepare balanced cut-and-fill designs.

High-precision terrain models useful for rack layout planning

High-precision terrain models generated by LRTK bring great benefits to the layout design of solar panel racks. On sloping land, ground elevation varies by rack row, so height adjustments for each rack and optimization of row spacing are important. Previously, designs were often made with only simple terrain models and adjusted during construction to match actual site undulations. Using detailed terrain data acquired by LRTK enables layout consideration that reflects actual site topography from the design stage.

Specifically, by importing point cloud or surveyed point data into CAD or layout design tools, you can accurately determine the elevation at each rack location. This allows you to estimate the required leg lengths for each rack and consider terraced arrangements in advance. For example, if only the center of a row is depressed, knowing the amount of that depression in the model enables you to prepare height-adjustment components beforehand or shift the layout to a flatter area.

Moreover, in areas with steep slopes you must carefully consider row spacing and panel angles to avoid mutual shading. Simulating these conditions on the terrain model lets you check whether rows will cast shadows on each other. Terrain models built with LRTK can also be used for power-generation impact assessment (shadow analysis) and foundation load evaluation, improving design reliability. Obtaining a high-precision terrain model enables reasonable rack layout planning on sloping land and helps prevent rework or additional construction after installation.

On-site speed driven by "instant cross-section comparison"

On construction sites, how quickly you can grasp differences between the plan and the current condition directly affects work speed. LRTK’s "instant cross-section comparison" is a highly effective tool in this regard. Consider confirming whether earthworks have achieved the designed slopes and elevations. Traditionally, after earthmoving by heavy equipment, a survey team would be called back and data processed before evaluating deviations from the design cross-section. With LRTK, the on-site manager can measure immediately after earthworks and compare the design cross-section with the actual terrain cross-section on the spot. If discrepancies such as "we need to cut another 10 cm (3.9 in)" or "some fill is higher than planned" are found, feedback can be given to the heavy equipment operator immediately and corrective work completed the same day. As a result, you can minimize rework and schedule delays, shortening the overall construction period.

When comparing multiple construction options on-site, LRTK’s cross-section measurement is also powerful. For example, when deciding a route for material access roads, you can measure longitudinal grades of candidate routes with LRTK and instantly judge which route has the gentlest slope and is easiest to construct. Fine undulations that were not apparent from drawings become evident through actual measurement, improving decision accuracy. This “instant cross-section comparison” supports rapid on-site decision-making and significantly enhances overall work speed and efficiency.

Ease of use for anyone, and LRTK advantages for inspections and acceptance

Another attraction of LRTK is its simple operation that "anyone can use." Even construction managers or designers without surveying expertise can obtain necessary data by simply following the smartphone app prompts and pressing the measurement button. With an intuitive UI and automatic recording, measured points are plotted on a map and elevation data is saved automatically, preventing human errors such as "measuring mistakes" or "transcription errors." On sites with labor shortages and frequent staff changes, easy-to-use equipment helps avoid dependence on specific individuals and enables organizational execution and sharing of on-site surveys.

LRTK can also be used in the post-construction inspection and acceptance phases. During final inspections of a solar power plant, there are occasions to confirm whether slope gradients of earthworks and drainage channels conform to design, or whether rack installation heights are correct. Where these checks used to be done by visual inspection or spot checks with a level, LRTK enables rapid measurement of key points and numeric recording. For example, if you measure slope angles of embankments at multiple locations, you can attach the data as evidence in inspection reports. LRTK is also useful for periodic inspections after operation begins to monitor ground subsidence or sediment buildup due to aging. By comparing with baseline data previously acquired, you can quantitatively evaluate height changes and detect abnormalities early.

As described above, LRTK offers:

• Ease of use (usable without specialist skills)

• Immediacy (results available in real time)

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

These advantages make it useful across a wide range of situations from design and construction to inspection and maintenance. For those involved in sloping-land solar power projects, LRTK is a reliable tool that relieves concerns about on-site "heights" and improves work efficiency.

Voices from the field: experiences that changed design decisions on sloping land

Finally, here is a field account from someone who introduced LRTK and experienced its benefits. A construction manager involved in a mountain-area solar power plant project says LRTK significantly changed their design decisions.

As this manager's account shows, LRTK’s introduction is transforming the design and construction decision-making process itself. On sloping sites, parts of the workflow that previously relied on experience and intuition are now supported by data, enabling rational plan adjustments with less waste. Reducing uncertainty about elevation decreases the psychological burden on designers and constructors, allowing them to proceed with greater confidence. Some in the field say they "cannot imagine sloping-site projects without LRTK," and it seems LRTK is becoming a new standard tool that fundamentally supports solar power construction on sloping land.

Why not try simple elevation surveying with LRTK now?

Acquiring elevation information is a key challenge in planning and constructing solar power plants on sloping land. As a way to solve this problem, LRTK offers unprecedented ease and reliability. By significantly reducing the effort of elevation surveying while securing the necessary data, LRTK makes feasible the reliable design that was once difficult on sloping land. If you are involved in practical work, please try this new surveying experience on site.

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 carefully guide you on on-site utilization and implementation plans. Equip yourself with the latest technology LRTK and make your sloping-land solar power projects speedy and reliably successful!