Achieving Zero Construction Errors with Centimeter-Class GNSS! Accuracy Management at Mega-Solar Sites Is Changing

The Importance of Accuracy Management in Mega-Solar Construction

A "mega-solar" typically refers to a large-scale photovoltaic power plant with an output of 1 MW (megawatt) or more. In such construction projects, the number of panels often ranges from several thousand to tens of thousands, and the number of foundation piles can also reach several thousand. Because the work covers a large area, even a slight angular error from a reference point can result in a large positional deviation at a distance, so high-precision positioning is required from the initial stages. Small positional deviations on a mega-solar construction site can lead to major problems. When installing thousands of solar panels across a vast site, a misalignment of just a few centimeters in the positions of racking posts or foundations can cause distortion across entire rows or interference with adjacent structures. For example, a deviation in post spacing can lead to misaligned holes in panel mounting brackets or insufficient cable length, requiring on-site adjustments or rework. Moreover, layout errors can affect sunlight exposure, reducing panel power generation efficiency and causing problems securing maintenance access routes. In projects that assemble many components like mega-solar, thorough accuracy management and getting the job right the first time are the keys to shortening construction schedules and ensuring quality. Eliminating construction errors also reduces wasteful rework, material disposal, and unnecessary machine operation, delivering environmental benefits such as reduced CO2 emissions. Because these are renewable energy facilities, the construction process should be pursued efficiently and sustainably.

Traditional Methods and Their Limitations (Manual Surveying, Rework, and Dependence on Individuals)

In conventional solar power plant construction, surveyors used total stations and levels to measure dimensions from reference points and indicated pile positions and heights with ground strings and batter boards. This manual-surveying-centric approach requires measuring hundreds or thousands of points one by one across large sites, demanding enormous labor and time. The work typically requires at least two people, and as long as humans read angles and distances and perform calculations, the risk of human error cannot be avoided. Even experienced veteran surveyors can struggle to set out points in areas with poor visibility, dense weeds, or uneven terrain, producing small errors. Additionally, surveying on steep slopes carries risks such as falls or rockfall, posing safety challenges.

Hand-based positioning also involves a high degree of dependence on individual skill, so survey accuracy tends to vary with the operator’s ability. If foundation pile positions are even a few centimeters off, the entire rack may no longer match the design, causing rework (reconstruction). Rework tasks—such as removing and re-driving piles or adjusting racks to fit reinstalled posts—represent catastrophic losses that delay schedules and increase costs. If positional corrections become necessary, inspections by supervisory agencies or clients can be postponed, damaging trust and delaying handover. The conventional approach always presented a dilemma of choosing accuracy or efficiency, which was a major challenge for site supervisors.

Positioning Accuracy of Centimeter-Class GNSS (RTK) and Its Evolving Field Use

Recent advances in satellite positioning technologies like GPS have been transforming site surveying. In particular, centimeter-class GNSS positioning using RTK (real-time kinematic) can reduce positioning errors that were previously on the order of meters to within a few centimeters (cm level accuracy (half-inch accuracy)). RTK achieves high accuracy by having the rover receive correction information from a base station in real time; in Japan, services such as CLAS (Centimeter-Level Augmentation Service) from the Quasi-Zenith Satellite System Michibiki and private networked base station services are available. By leveraging these systems, highly accurate coordinates can be obtained instantly anywhere on a large mega-solar site. Moreover, the shift to multi-GNSS and improved receiver performance means that cm level accuracy (half-inch accuracy) can now be obtained stably even in forests and mountainous areas. Centimeter-class positioning that was previously difficult in error-prone environments is now possible, enabling reliable operation at mega-solar sites located in suburban or mountainous regions.

The construction industry has accelerated digitization of surveying and as-built management, which formerly relied on specialized equipment and skilled personnel. Initiatives under the Ministry of Land, Infrastructure, Transport and Tourism promoting ICT construction (so-called i-Construction) have driven automation using GNSS in earthworks and site formation, such as GPS robotic total stations and machine-guidance-equipped heavy machinery. Recently, handheld RTK positioning devices that combine a smartphone with a small GNSS receiver have also appeared. The convenience of attaching a receiver weighing just a few hundred grams to a smartphone and starting centimeter-level positioning at the push of a button has dramatically lowered the barrier to on-site use. These devices require no complex setup or cable connections and are easy to carry thanks to built-in batteries. If the site coordinate system is preconfigured in the smartphone app, the obtained positioning data is automatically converted to Japan Plane Rectangular Coordinates and elevations. Thanks to the evolution of such smartphone RTK technologies, centimeter-level positioning has been incorporated into everyday site operations in a way that anyone can use.

Examples of Pile Driving, Earthworks, and Point-Cloud Scanning Leveraging Accuracy

How does using high-precision GNSS change accuracy management on mega-solar sites in practice? Below are representative use cases.

• Application to pile driving: Using centimeter-class GNSS for positioning the foundation piles that support solar panels enables piles to be installed exactly where shown on the drawings. Where pile centers used to be measured repeatedly with tape measures and transits, positioning can now be completed simply by following the guidance of a GNSS-equipped device. One person can indicate many pile positions in a short time, enabling labor savings and consistent accuracy compared with manual point setting. If all piles are in their designated positions, subsequent rack assembly proceeds smoothly, bringing the site significantly closer to zero construction errors.

• Use in earthworks and grading: High-precision positioning is also effective in earthworks for mega-solar sites. By equipping bulldozers and excavators with GNSS guidance, operators can view the design elevation and slope on a cab display and perform cutting and filling accordingly. This removes the need for workers to set batter boards or repeatedly measure heights on slopes, improving efficiency and safety. Even when heavy machinery is not used, technicians carrying portable RTK receivers can check grading accuracy on the spot, enabling construction that minimizes final deviations. Accurate site formation is directly linked to later stormwater drainage and foundation quality, so in mega-solar sites that require control down to the millimeter level, accurate earthworks from the beginning are a major advantage.

• Recording via 3D point-cloud scanning: GNSS accuracy enhances point-cloud scanning using drone aerial photography or smartphone LiDAR. Combining high-precision positional data allows millions of points of 3D point-cloud data to be assigned absolute coordinates, enabling accurate as-built (post-construction shape) records. For example, after completing site formation, a drone can capture the entire site to generate a terrain model, which can be overlaid with design data and color-coded to show deviations. This makes it possible to grasp details across large sites that were previously impractical to measure manually, and to detect localized settlement or tilting from the point cloud. Also, if the coordinates of pile heads are measured with smartphone RTK after pile installation and converted to a point cloud, all piles can be verified at once to confirm they are at the design positions and heights. Keeping such precise 3D records becomes a valuable data asset for later maintenance inspections and future expansion work.

Practical Examples of AR Guidance, Photo Records, and Cloud Sharing

Digital technologies are creating new styles of accuracy management and information sharing on site. The following features particularly support achieving "zero errors" in mega-solar construction.

• AR guidance: AR (augmented reality) technology that projects design target points and lines onto the smartphone or tablet screen is now practical. Because positions can be determined with high precision using GNSS, virtual pile markers and height reference lines displayed over the camera image align exactly with real positions. Workers can therefore perform pile driving or marking by following on-screen instructions without comparing drawings or using tape measures. On a vast mega-solar site, target positions can be confirmed from a remote safe location, and setting out on slopes or poor footing becomes easy. This intuitive guidance also enables less experienced technicians to set out points with accuracy comparable to that of veterans, reducing variability in accuracy due to skill differences.

• Photo records and as-built management: Taking photos of work areas with a smartphone at each stage while automatically recording their positions allows the creation of construction histories tied to precise locations. For example, photographing the top of each pile after pile driving makes it possible to list on the cloud which piles were driven, where, and when. Because photos are tagged with high-precision coordinates, they can be placed on as-built drawings and shared with stakeholders easily. Site reports that once relied on handwritten notes or verbal communication can now be made objective and comprehensive through photos plus positional data, helping prevent mistakes and oversights.

• Cloud sharing and real-time collaboration: Point-cloud data, set-out points, and photos collected by surveying apps linked to GNSS receivers can be uploaded to the cloud and shared instantly, allowing supervisors and design staff in the office to check the latest site conditions in real time. Problems can be identified and addressed early, and design data or construction drawings can be sent directly to field devices so work is always performed using the latest plans. Cloud platforms that automatically analyze uploaded data and generate reports are also appearing, greatly reducing time spent creating daily reports and as-built documentation. Real-time sharing and automated processing eliminate information gaps between the field and the office, enabling the entire team to work toward eliminating errors.

Tools and Operational Methods Required to Create a Zero-Error Site

To minimize construction errors, it is not enough to simply introduce devices; it is necessary to review overall site operations. First, it is important to establish an accurate reference coordinate system and ensure everyone shares and uses it. If the coordinates used by surveying equipment and design data are not unified, discrepancies may occur even with high-precision equipment. In addition, operational accuracy verification—such as performing daily check surveys at known points to confirm errors— is essential to ensure high-precision devices are working correctly. Next is digitalization and standardization of workflows. Manage processes of surveying → staking → inspection → recording consistently with digital tools to build systems that do not rely on the intuition or experience of veterans. For example, establishing rules such as always performing GNSS positioning and AR-based position confirmation before pile driving, and immediately performing point-cloud measurement after installation to check as-built conditions, allows immediate detection and recovery from errors.

Furthermore, education and training of field staff are indispensable. Although the latest surveying apps and devices are intuitive, realizing their full value requires personnel who can use them on site. Conducting thorough internal operation training and pilot implementations on small sites before rolling out gradually to all sites allows smooth transition while checking safety. Appointing staff familiar with digital technology as champions to provide immediate on-site consultation and problem resolution is also effective. Finally, creating a culture in which management and site supervisors lead the adoption of digital tools is important. A workplace culture that encourages trying new approaches without fear of failure is the foundation for achieving true zero errors.

Proposal for Introducing LRTK, a Smartphone-Integrated RTK Surveying Solution

As a solution that easily delivers the benefits of centimeter-class GNSS, AR, and cloud integration described above, there is a smartphone-integrated RTK surveying system called LRTK. LRTK is a product in which a small, high-precision GNSS receiver is attached to a smartphone, and it enables a single person to perform cm-level positioning and coordinate guidance (navigation), 3D point-cloud scanning, and AR projection without specialized surveying equipment. The receiver itself is lightweight and compact at only a few hundred grams, eliminating the need to carry bulky tripods or poles. A dedicated app and cloud service are linked, so positioning data, photos, and point clouds can be uploaded and shared on the spot, allowing real-time information exchange between the site and the office. Point clouds and survey deliverables obtained with LRTK can be output in formats compliant with the Ministry of Land, Infrastructure, Transport and Tourism’s 3D as-built management guidelines, facilitating inspections and electronic deliverables. LRTK makes surveying and setting out—tasks that previously depended on the intuition and skill of experienced staff—reproducible by anyone with a high degree of consistency. In other words, site supervisors and construction managers can perform necessary measurements and inspections on site without relying on specialized survey staff, helping to eliminate workflow bottlenecks.

For example, using LRTK on a large mega-solar site allows sequential surveying of pile positions according to drawing coordinates, confirming them on the smartphone AR display and then driving the piles in a seamless workflow. The obtained point-cloud data can be used to verify as-built conditions immediately, and any defects can be corrected on the spot. Introducing LRTK, which enables surveying to be completed with a single smartphone, dramatically improves the efficiency and accuracy of the entire process from positioning to construction management. For construction managers and survey technicians struggling with labor shortages and quality control, LRTK can be a powerful ally that elevates site productivity and reliability to the next level. If you are facing challenges in accuracy management, consider trying this latest technology on your site. By utilizing centimeter-class GNSS and smartphone RTK, you can move step by step toward the ideal of zero construction errors. (For details on LRTK features and case studies, please also see the [official site](https://www.lrtk.lefixea.com).)