Using cm-level GPS for Solar Power Plant Site Surveys | LRTK Enables Precise Positioning for Anyone

In recent years, the installation of solar power generation (mega-solar) has been progressing nationwide. Along with this, site surveying for solar power plants has become increasingly important. Accurately understanding the area, terrain, and elevation differences of a planned power plant site directly affects panel layout planning, construction efficiency, and safety. However, traditional surveying required specialist knowledge and time, placing a heavy burden on small and medium-sized operators. At the forefront of attention is the high-precision positioning technology using centimeter-level GPS. This article explains the benefits of cm-level GPS (RTK technology) for surveying solar power plant sites and introduces LRTK, a solution that makes this high-precision positioning easy for anyone to use.

Why site surveying for solar power plants is important

In solar power plant construction, it is essential to first obtain an accurate grasp of the site's current conditions. If you do not survey in advance the site area, boundary locations, elevation differences, and slope angles, problems can arise such as the planned panel layout not fitting the actual land. For example, a situation where "during the planning stage it seemed the panels would fit within the site, but after starting construction, inaccurate land surveying caused the panels to protrude" must be avoided. The larger the mega-solar project, the more a small surveying error can significantly impact the overall plan.

Elevation data for the site also affects the design of mounting structures and earthwork volume calculations for grading. If the terrain is measured correctly, you can adjust panel placement so that panels receive sunlight at optimal angles and accurately calculate the required amount of fill and cut. Conversely, insufficient surveying information can lead to rework during construction—such as "changing the mounting height because the ground is steeper than expected" or "misestimating the amount of soil to move"—resulting in increased costs and schedule delays. Thus, accurate on-site surveying before construction is the foundation for the success of solar power plants.

Traditional surveying methods and their challenges

However, performing accurate conventional surveying required specialized skills and expensive equipment. Typically, surveyors use a total station (an optical surveying instrument) or precision GNSS receivers to establish control points and measure land details. This approach involves the following challenges:

• Equipment cost and preparation burden: Assembling a full set of high-precision surveying equipment requires a large investment and can cost millions of yen. The equipment is heavy, and transporting and setting up tripods, batteries, and other gear at the site is laborious. Preparatory work is also required, such as installing control stakes at known points and setting their coordinates.

• Dependence on specialists: Accurate surveying requires experienced surveyors and technicians. If a company lacks such personnel, it must hire an external surveying firm. Outsourcing increases costs and requires schedule coordination, making it difficult to quickly measure data during the planning stage when time is tight.

• Limits of positioning accuracy: General handheld GPS units or smartphone GPS functions can have errors of about 5–10 meters, which is unusable for surveying large sites or precise stake-out. Traditionally, to compensate for these errors one had to painstakingly measure with a transit or perform multiple coordinate transformation calculations.

• Lack of real-time results: With conventional methods, you had to take the measured data back to the office to produce drawings before seeing the final result. If omissions or errors were discovered on-site, inefficient repeat visits for re-surveying were often required.

Because of these challenges, there has been a growing demand for "getting high-precision survey results more easily and quickly." Especially for solar projects that require surveying quickly at many sites nationwide, relying on specialized equipment and personnel made both cost and time barriers high.

High-precision positioning with centimeter-level GPS (RTK)

A technology that addresses these challenges is RTK (Real-Time Kinematic) positioning, a centimeter-level GPS technique. RTK reduces satellite positioning errors so that positional errors can be reduced to a few centimeters. Standalone positioning (a single receiver) typically has meter-level errors, but RTK, through an error correction mechanism, can reduce that by about 1/100, i.e., to the centimeter range.

RTK works by receiving satellite signals simultaneously at a reference station and a rover station, with the reference station sending its observed error information to the rover in real time for correction. Specifically, you either set up a reference station near the site with a known accurate coordinate or use public electronic reference stations or commercial correction services. The reference station computes error data and transmits it via radio or the Internet to the rover (the surveyor's receiver), which applies the corrections to its measurements to achieve high accuracy.

Because this processing is performed in real time for each measurement per second, a rover can obtain centimeter-level positions even while moving—one of RTK's major advantages. Accuracy also stabilizes when the distance to the reference station is short, since error factors are more common. Recently, network RTK (such as VRS) that allows online retrieval of correction data from nearby electronic reference points without setting up your own reference station has become widespread. In Japan, electronic reference points are established nationwide, and using them makes it easy to obtain centimeter-level positioning in a global coordinate system. Additionally, systems that receive correction signals directly from satellites—such as the centimeter-level augmentation service (CLAS) provided by the quasi-zenith satellite Michibiki (QZSS)—have appeared to further improve positioning accuracy. With these enhanced technical foundations, RTK positioning has become far more accessible than before.

Benefits of using cm-level GPS in surveying for solar power plants

The advantages that centimeter-level positioning brings to the field are immense. In solar power plant site surveys, there are many situations where the high-precision location data from RTK proves useful. Here are the main benefits:

• Improved layout accuracy: High-precision surveying allows you to realize panel layout plans at the designed positions and spacings. When you can determine positions at the centimeter level, you can accurately stake out locations for piles and mounting structures so that all panels are placed according to the intended layout. This maximizes power generation efficiency and prevents later problems like "array shifts causing some panels to be shaded."

• Survey efficiency: With RTK-GPS, one person can rapidly collect survey points over a large site. Compared to traditional methods where a survey team would spend days measuring with tapes or a total station, you can gather current condition data in a short time. Even on uneven land, walking the site while collecting data efficiently captures terrain and elevation data, greatly reducing labor.

• Real-time on-site verification: RTK survey data can be used immediately on-site. Acquired coordinates can be plotted on a tablet or smartphone map to visualize boundaries and planned installation positions. This eliminates the time lag of "measuring and only seeing results after returning to the office," allowing you to quickly check for measurement omissions or inconsistencies on-site. You can also perform quick earthwork volume estimates from the measured terrain data and make on-the-spot planning assessments for grading works.

• Cost reduction: Being able to perform precise surveys quickly in-house can reduce outsourcing and additional construction costs. With fewer work stoppages waiting for survey results and the ability to flexibly respond to plan changes on-site, overall project costs can be lowered. Accurate initial site survey data enables correct material procurement and method selection, cutting waste.

By incorporating centimeter-level GPS positioning into solar power plant site surveys, you gain benefits in accuracy, speed, and cost. So how can this high-precision positioning be made easily available to anyone? One answer is the new surveying device called LRTK, introduced next.

Precise positioning anyone can do: the arrival of LRTK

Although RTK surveying is highly useful, its operation traditionally required specialized equipment and advanced skills. Enter the revolutionary device "LRTK terminal," which enables cm-level positioning easily using a smartphone. LRTK is a small, high-precision GNSS receiver that attaches to a compatible smartphone or tablet. By connecting via Bluetooth (or similar) and launching a dedicated app, anyone can immediately start centimeter-level positioning that previously required surveying equipment worth hundreds of thousands of dollars.

The strengths of the LRTK terminal are its combination of high accuracy, low cost, and portability. Its accuracy rivals traditional bench-top RTK-GNSS units, delivering horizontal accuracy around 1–2 cm and vertical accuracy around 3–4 cm. It provides reliable positioning that conforms to domestic satellite positioning standards, making it possible to achieve public survey-level accuracy. Yet the device is compact enough to fit in a pocket, eliminating the need to carry heavy surveying rigs to the site. All you need is a smartphone, the LRTK terminal, and communications. You no longer need to haul heavy equipment into forests or remote sites—surveying becomes lightweight and mobile.

Ease of use is another major advantage. With LRTK, even those without specialist knowledge can perform surveys with intuitive smartphone operations. The app supports communication settings with reference stations and complex coordinate system settings, so users won’t get lost. For example, conversions to Japan’s coordinate system (the World Geodetic System) are processed automatically, allowing the data to be used directly in digital maps or CAD drawings. Real-time correction data retrieval is built in, and models that can receive Michibiki (QZSS) satellite augmentation signals maintain high accuracy even in mountainous areas without cellular coverage. Due to this convenience, LRTK is attracting attention as a new tool for on-site digital transformation (DX), bringing high-precision positioning closer to construction and surveying sites.

Examples of LRTK use on solar plant sites

So how does using LRTK in a solar power plant site survey actually work? Here is one example of the workflow:

• Measuring existing terrain: First, walk the planned power plant site with a smartphone equipped with LRTK and take position measurements at key points. Measure boundaries, corner points, and locations with significant elevation changes, plotting points in real time on the app’s map. This provides an immediate visual understanding of the land shape and gradients.

• Reflecting survey data in design: The high-precision measured points can be shared instantly with design staff. For example, data can be uploaded via the cloud to the office PC to create detailed terrain maps and contour lines in CAD software. Based on these, panel layouts can be optimized. You can adjust mounting heights and row spacings to match the terrain and analyze layouts to maximize solar exposure.

• Staking out pile and installation positions: Once the layout is finalized, import the coordinate data back into the LRTK app and mark stake positions on-site. By following the app’s guidance to move to specified coordinates, you can identify the mounting points for the panel racks. Where stakes used to be measured out with drawings and tapes, LRTK navigation enables position staking with centimeter-level accuracy. One person can identify positions using the smartphone while another marks them, enabling efficient and accurate stake-out across large sites.

• On-site verification and adjustments during construction: LRTK remains useful during construction. After installation, you can measure the actual positions of piles and immediately verify whether they match the planned coordinates. Early detection of minor deviations allows corrections before panel installation. Additionally, during grading work you can regularly measure ground elevations with LRTK to check whether excavation and fill meet the planned heights. Real-time earthwork recalculations help adjust heavy equipment deployment and improve construction management precision.

As shown above, using LRTK allows continuous use of high-precision location data from site surveying through construction management for solar power plants. LRTK helps streamline the traditionally segmented process of "survey → design → construction," speeding up information sharing between the field and the office.

Conclusion: Making solar power plant surveying accessible with LRTK

Accurate site survey data is a critical factor that determines the success of solar power projects in planning and construction. The adoption of RTK surveying with centimeter-level GPS is transforming precision positioning—once exclusively done by professional surveyors—into a more accessible and routine task. Driving this trend are user-friendly high-precision devices like LRTK.

By using LRTK, companies without specialized survey teams can quickly understand on-site conditions in-house. From site investigation to stake-out, consistent accuracy control becomes possible, enabling immediate response to design changes and issues. As a result, overall project quality and speed improve and unnecessary costs are reduced.

Now that precise surveying is within everyone’s reach, it’s time to take full advantage of these benefits at solar power sites. If you have an opportunity to survey a solar plant site, try the easy and high-precision positioning offered by LRTK. Its simplicity and accuracy, which overturn conventional wisdom, are sure to impress you. LRTK, at the forefront of the new era in high-precision positioning, can become a reliable ally for your solar project.