Mega-solar Surveying Dramatically More Efficient! Easy Solo Measurement with Smartphone RTK

In the construction and operation of mega-solar (large-scale solar power plants), site surveying is an indispensable and important process. However, for mega-solar sites that span from several hectares to several tens of hectares, conventional methods have tended to require a great deal of time and manpower. There are cases where multiple-person survey teams use total stations or GNSS surveying equipment and spend several days surveying, placing a heavy burden in terms of labor costs and scheduling. High-precision surveying also often relies on the skills of experienced technicians, creating a tendency for surveying work to become person-dependent. Against this backdrop, a new surveying method that leverages smartphones and RTK (Real Time Kinematic) positioning technology has been attracting attention. “Smartphone RTK,” which equips a smartphone with a compact RTK-GNSS receiver to enable centimeter-level positioning, is dramatically improving the efficiency of mega-solar surveying and making it possible for even a single person to perform precise measurements easily. Improving surveying workflows also shortens construction schedules, which is important for securing revenues through earlier operation of mega-solar projects. This article explains in detail the innovations smartphone RTK brings to mega-solar surveying, focusing on simplification of surveying, elimination of person-dependence, reduction of labor costs, and shortening of processes.

Challenges of Conventional Methods in Mega-solar Surveying

There are various purposes for surveying mega-solar sites. For example, there is as-built surveying for understanding terrain and planning earthworks during site selection, stake-out for positioning of solar panel arrays (driving stakes; depending on project scale, thousands of stakes may need to be placed accurately), and post-construction inspection of as-built (construction results) and earthwork volume calculations. While it is necessary to measure extensive areas accurately, conventional surveying methods have faced the following issues.

• Large sites require time and manpower: For mega-solar-scale areas, the survey range is very large, so pole-and-staff surveys with total stations or conventional GNSS surveying can take several days to several weeks to cover the whole area. Surveying typically requires teams of two or more people, and measurement efficiency further decreases in terrains with poor line-of-sight, such as mountainous areas.

• Advanced expertise required: Setting up total stations and adjusting and drafting measurement data require specialized knowledge, making work dependent on experienced surveyors. With a worsening labor shortage, securing experienced personnel is difficult, risking the work becoming person-dependent. Outsourcing is expensive, making frequent surveying updates difficult.

• Inefficient data processing and sharing: Traditionally, survey results were recorded in field notebooks and then entered into a PC and drafted back at the office. For surveying large sites, the volume of data is large, and manual organization takes time. Field measurement point information cannot be shared immediately with stakeholders, causing a time lag in feedback from surveying to design and construction, which can delay the overall process.

As described above, mega-solar surveying has faced the dual challenges of the “surveying burden due to scale” and the “inefficiency of conventional methods.”

The Era of Solo Surveying Opened by Smartphone RTK

As a solution to these challenges, surveying methods using smartphone RTK have emerged. Smartphone RTK refers to technology that enables centimeter-level real-time positioning by attaching a pocket-sized high-precision GNSS receiver to a smartphone. RTK positioning uses error-correction information distributed from known points such as control stations to correct positioning errors that would be several meters with standalone receivers to a few centimeters using signals from multiple satellites including GPS and Michibiki. Whereas RTK surveying once required expensive fixed equipment, it can now be easily realized with a smartphone and a small receiver.

Introducing smartphone RTK can be expected to bring the following revolutionary changes to mega-solar surveying sites.

• Easy and fast surveying by a single person: With smartphone RTK, surveying tasks that previously required two to three people can be completed by one person. Carry a smartphone with a receiver to the point you want to measure and simply tap a button on the screen to record high-precision position coordinates. There is no need to carry heavy tripods or prisms, and you can measure many points in a short time. Compared to conventional methods, work time can be drastically reduced, directly speeding up overall construction. As long as the sky is visible, you can position anywhere on a large solar plant site, greatly reducing the complicated equipment setup and transit time required for surveying.

• Intuitive operation without relying on specialist skills: Surveying via smartphone apps has user-friendly interfaces, and the app handles specialized calculations and complex instrument operations. Processes such as conversion to plane rectangular coordinate systems and geoid height corrections are automated, so even non-experts can perform accurate surveying. Because onsite staff, including younger personnel, can master the tools with short training, the burden of skills transfer and education is reduced. Eliminating person-dependence means that measurements can continue with stable quality even when the person in charge changes.

• Real-time cloud sharing and immediate use: Survey point data and observation information obtained with smartphone RTK can be uploaded to the cloud and shared on the spot. Immediately after field surveying, office PCs can access the data to reflect it in design drawings or revise construction plans, enabling process shortening. Digital centralized management of data also prevents errors from handwritten field notes or later transcription. Smooth information linkage between surveying and design/construction improves overall project efficiency.

There are also cost benefits. Portable GNSS receivers used for smartphone RTK are priced lower than conventional total stations or dedicated surveying GNSS units, and because you can use an existing smartphone, initial investment can be greatly reduced. There is no need to prepare multiple expensive instruments; for example, it is realistic for each field staff member to have their own smartphone RTK device. This leads not only to reduced labor costs, but also to savings on equipment rental and outsourcing. Costs previously paid to external surveying companies may become unnecessary, and the introduction cost can be recouped in a short period, offering significant managerial advantages.

Main Functions and Benefits Achievable with Smartphone RTK

Smartphone RTK solutions enable a variety of functions that were previously unthinkable to be realized on a single smartphone. The main functions and benefits particularly useful on mega-solar sites are summarized below.

• Centimeter-level high-precision positioning: By using RTK corrections, GPS errors that were 5–10 m (16.4–32.8 ft) in standalone positioning can be reduced to about ±1–2 cm (±0.4–0.8 in). Stable accuracy can be obtained even in mountainous areas far from control points, and vertical positioning is possible to about ±3 cm (±1.2 in). This allows accurate measurement and management of each panel’s installation position on large solar power plants, contributing to improved construction accuracy.

• Guidance to stake-out coordinates (layout): If you import coordinate data from design drawings into the smartphone, the device can navigate you to the point on site and indicate stake-out positions. As you approach the target coordinates, it will guide you with audio cues and on-screen displays to the exact point where a stake should be driven. This enables rapid and unambiguous stake location even on large development sites, greatly improving layout efficiency.

• 3D point cloud scanning and earthwork volume calculation: The latest smartphones have LiDAR scanners and high-performance cameras, and dedicated apps can capture surrounding structures and terrain as three-dimensional point cloud data. Combined with smartphone RTK, each point is assigned accurate coordinates, allowing the generation of high-accuracy 3D models without point cloud distortion during scanning. For example, by scanning terrain before and after earthworks and comparing, the app can automatically calculate volumetric differences for cut-and-fill, aiding daily earthwork management. Acquired point cloud data can be exported to CAD software or CIM systems, further promoting data linkage from surveying to design and construction.

• On-site display of design information with AR: AR (augmented reality) display functions that overlay design data onto the on-site view via the smartphone screen are also gaining attention. Uploaded plans or 3D models can be projected onto the scene to intuitively check whether construction is proceeding as designed. For example, you can visually verify through the smartphone whether racking or panel placement matches the drawings, helping prevent rework and supporting quality checks. Being able to overlay the completed image on site also aids explanations to stakeholders and consensus building.

• Geotagged photos with time-series management: Smartphone RTK automatically records high-precision coordinates and orientation with photos taken, and these are organized and viewable in the cloud. If fixed-point photos are taken periodically and displayed in time series, it becomes easy to review construction progress and equipment changes later. Photo management linked to survey data is powerful for report creation and stakeholder sharing, making visualization and information sharing of site conditions smart and efficient.

• Positioning even outside communication coverage: Mega-solar sites are often built in mountainous areas where there may be no cellular coverage. However, the latest smartphone RTK receivers support the CLAS satellite augmentation signal provided by Japan’s quasi-zenith satellite Michibiki, enabling centimeter-level positioning even where mobile networks are unavailable. This allows surveying work to proceed reliably without dependence on communications infrastructure.

• Cloud sharing and web browsing: Survey data, point clouds, and photos captured with a smartphone are immediately saved to the cloud and can be viewed and shared via a web browser. Even without dedicated software, as long as there is internet access, office PCs can display field data in 3D and measure distances, areas, and volumes between survey points. This enables project stakeholders in remote locations to always share the latest surveying information and make decisions quickly.

As described above, smartphone RTK offers numerous functions that directly support surveying simplification (anyone can measure easily), elimination of person-dependence (not relying on specific experts), reduction of labor costs (efficient work with fewer people), and process shortening (rapid data utilization). It is a powerful tool that can balance the precision and speed required for mega-solar surveying and support safe and reliable construction management.

:contentReference[oaicite:0]{index=0} An example of a smartphone RTK app’s coordinate navigation guiding a stake-out point. By following the on-screen guidance, even less experienced workers can reach the target location without hesitation. Moreover, by combining a wide-area terrain model created from drone aerial photogrammetry with detailed survey point data and point clouds obtained by smartphone RTK, it is possible to build an integrated digital surveying workflow from the air to the ground. Because data can be linked from ground stake-out to as-built management, smartphone RTK is expected to further accelerate DX (digital transformation) at mega-solar sites. It also aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction (improving construction productivity through ICT), and smartphone RTK can be seen as a new technology symbolizing on-site DX.

Dramatic Efficiency Gains in Smartphone Surveying with LRTK

A concrete tool for putting smartphone RTK into practice is a solution called LRTK. :contentReference[oaicite:1]{index=1} A pocket-sized LRTK receiver attached to an iPhone. By attaching it with a dedicated case in one touch, the smartphone quickly becomes a high-precision surveying device. LRTK is a smartphone-mountable RTK positioning device developed by a startup originating from Tokyo Institute of Technology; attaching it to an iPhone or iPad turns the device into a high-precision surveying instrument. Weighing only about 125 g and with a thickness of about 1 cm (0.4 in), it contains an internal battery that enables continuous measurement for about 6 hours. It can be attached in one touch via a dedicated case, and with an optional monopod (pole) it is comfortable to measure vertical positions and perform stake driving. Its pocket-sized convenience means it can be carried at all times and used whenever needed, which is a major on-site advantage. The high-sensitivity antenna supporting multiple frequencies stabilizes accuracy, and because it supports Michibiki CLAS, it can maintain precision even outside communication coverage. There have been reports confirming high accuracy even in environments where GNSS reception is unstable, such as inside forests, demonstrating LRTK’s positioning performance and stability.

By using LRTK, you can have an all-in-one solution for the functions introduced in this article: centimeter-level positioning, stake-out guidance, point cloud scanning, AR display, photo recording, and cloud sharing. In civil construction sites, a quiet boom has already started around the idea of “one smartphone surveying device per person,” and cases have been reported where productivity significantly improved because site personnel themselves handled surveying. For example, at sites where construction used to be halted while waiting for surveying, after introducing LRTK, site staff could immediately perform necessary surveys, eliminating waiting time and smoothing construction. For mega-solar surveying tasks as well, introducing smartphone surveying with LRTK can realize easy surveying that anyone can use, shortening schedules, reducing costs, and improving quality. In the near future, it may become commonplace to see workers surveying with a smartphone in hand at mega-solar sites. If you are facing challenges in surveying work, consider adopting these latest smartphone RTK solutions.