Complete on a Smartphone! The RTK Surveying Revolution Transforming Solar Construction

In solar construction sites, surveying is a critical process that supports safe and reliable work. Accurate survey data is indispensable at each stage—determining solar panel and pile positions, understanding terrain before site development, and verifying as-built conditions after construction. However, for large-scale solar power plants (mega-solar) with vast sites, conventional surveying methods have required substantial time and manpower, creating challenges for schedules and costs.

Recently, a new surveying approach combining smartphones with RTK (Real-Time Kinematic) positioning has attracted attention. “Smartphone RTK,” which equips a phone with a compact high-precision GNSS receiver to enable centimeter-level positioning, is ushering in an era when precise surveying tasks can be performed by a single person. This article explains in detail the importance of surveying in solar construction and the issues with traditional methods, how RTK surveying works and tips for improving accuracy, and the site transformations enabled by smartphone × RTK. It also describes the concrete workflow for solo pile-driving, existing-condition surveys, and as-built verification, the benefits of cloud-linked management of point clouds, photos, and coordinates, and concludes with an introduction to the smartphone construction support tool LRTK.

The importance of surveying in solar construction

In solar power facility construction, surveying plays a key role from the planning stage through construction and management. High-precision surveying is required in situations such as the following:

• Existing-condition survey: Before starting work, measure the site’s terrain, slopes, and solar irradiation conditions. Accurate terrain data provides the basis for earthwork planning and layout design.

• Pile-driving / stake-out: This is the marking of positions for piles that serve as the foundations for panel racking. In large mega-solar sites, hundreds to thousands of piles must be installed at precise positions and elevations. Insufficient surveying accuracy can cause misalignments during racking assembly, so millimeter- to centimeter-level precision control is required.

• As-built verification: After construction, inspect whether the actual installations (piles, racking, panel layouts, etc.) match the designed positions and elevations. As-built survey results are used for inspection records and handover documents; if deficiencies are found, corrective work or additional costs may be necessary, so high-precision verification is important.

• Earthwork volume calculation: For large-scale grading, survey data is used for cut-and-fill volume calculations. Accurate earthwork measurements directly affect proper earthwork planning and cost control.

Thus, surveying is an indispensable element that affects quality and efficiency in solar construction. The higher the accuracy of survey data, the more it contributes to optimized construction planning and the prevention of post-construction problems. On the other hand, conventional surveying methods have various issues that have caused inefficiencies and rework on sites. Let us examine those problems in detail next.

Problems with conventional surveying: two-person work, errors, rework

Conventional surveying has typically used total stations (optical surveying instruments) and general-purpose GNSS survey units, and has generally been performed by teams of two or more people. Surveying an entire large solar power site can take days, resulting in significant labor and scheduling burdens. The following issues have also been noted:

• High manpower and time burdens: Surveying that requires holding a pole-mounted prism by one staff member while another operates the instrument means multiple people must be assigned to a single site. Efficiency further declines in mountainous or obstructed terrain, and surveying alone can extend project schedules.

• Risk of rework due to errors: Manual surveying leaves room for human errors such as reading mistakes or recording errors. If pile positions are measured incorrectly, misalignment of racking or panel arrays may become apparent after installation, resulting in pile re-drives or rework. Such mistakes can cause schedule delays and additional costs.

• Dependence on skilled technicians: Setting up total stations, planning surveys, and adjusting data require advanced expertise. Projects often must rely on experienced surveyors, and with worsening labor shortages it is becoming difficult to secure such personnel. If work is concentrated in particular veterans, the absence of that person poses a risk of site stoppage.

• Inefficient data processing and sharing: Traditionally, survey data collected on-site was first handwritten in field notebooks and then entered into a PC back at the office for drafting and calculations. For large-area surveys the amount of data becomes huge, and manual input and organization take time. Furthermore, site information could not be immediately shared with designers or other departments, causing a time lag before survey results were reflected in updated drawings or plans.

As described above, surveying for solar construction has faced the dual challenges of the burden created by expansive sites and inefficiencies inherent to traditional methods. So what is RTK surveying, the technology gaining attention to solve these problems?

What is RTK surveying? Differences in accuracy from conventional technologies and how it works

RTK surveying is a method that dramatically improves positioning accuracy by applying real-time error corrections to satellite positioning such as GPS. Regular smartphones or handheld GPS units can have positioning errors of several meters, but RTK (Real Time Kinematic) technology can reduce errors to the order of a few centimeters. This is achieved by having the rover receiver (the surveyor’s device) receive correction information broadcast from known reference stations—such as permanent reference stations operated by the Geospatial Information Authority of Japan—and correct the minute phase deviations in satellite signals. Specifically, by comparing carrier-phase information received from multiple GNSS satellites (GPS, GLONASS, Michibiki/QZSS, etc.) between the reference station and the rover in real time and subtracting the error components, centimeter-level accurate positioning becomes possible.

Traditionally, achieving this level of high-precision positioning required expensive fixed GNSS survey systems and base station setups. However, in recent years network RTK services reachable via the internet and sub-meter-level augmentation services such as CLAS provided by Japan’s Quasi-Zenith Satellite System (Michibiki) have been developed, making RTK positioning accessible as long as a small receiver and a communication environment are available. As a result, centimeter-level positioning is becoming achievable using a smartphone combined with an inexpensive compact GNSS receiver, lowering the barrier to surveying—a truly revolutionary technological innovation.

What changes with smartphone × RTK?

So what changes on solar construction sites when smartphones are combined with RTK technology as “smartphone RTK”? The keywords are “high accuracy,” “labor reduction,” and “real time.” Here are the main benefits expected from introducing smartphone RTK:

• Surveys can be completed by one person: Survey tasks that previously required two to three people can be performed by a single person equipped with a smartphone and a compact GNSS receiver. Reducing personnel cuts labor costs and enables surveying to proceed even at sites with labor shortages.

• Dramatic improvements in work efficiency: There is no need to carry heavy tripods and surveying instruments or to repeatedly set up equipment at each survey point. Simply walking the site with a smartphone allows measurement and recording of necessary points, dramatically reducing surveying time. In practice, there are reports where a task that took three people 20 minutes was reduced to one person in 10 minutes after introducing single-person surveying.

• High-precision stake-out prevents rework: Smartphone RTK continuously displays an accurate current position in a global coordinate system. Because you can mark piles or points directly using coordinates from the design drawings, construction errors due to position offsets are minimized. For example, keeping pile position error within ±2 cm can prevent corrective rework in downstream processes.

• Operable without specialist knowledge: Intuitive smartphone app interfaces allow users without extensive surveying experience to perform surveying and stake-out tasks easily. Coordinate navigation that shows guide arrows and distance to a target point on-screen, and AR (augmented reality) features that overlay design positions on the camera view, enable reliable surveying without relying on “feel and experience.”

• Real-time data sharing: Measured coordinate data and photos can be uploaded to the cloud on the spot and shared immediately with managers or designers in the office. There is no need to return to the office to digitize data after work; survey results can be reflected in construction planning and quality checks immediately, accelerating the overall process.

By leveraging smartphone × RTK, surveying in solar construction is dramatically streamlined and reborn as a high-precision, low-dependency process. Next, let’s look at how, using smartphone RTK, a single person can carry out surveys, pile-driving, and as-built verification in practice.

Workflow for single-person pile-driving, existing-condition survey, and as-built verification

With smartphone RTK, each surveying process in solar construction can be performed seamlessly by one person. The following explains that workflow step by step.

• Existing-condition survey (pre-construction terrain capture): Before construction, conduct a detailed survey of the site. Walking the site while positioning with the RTK receiver attached to a smartphone allows efficient acquisition of terrain data even for large areas. If you combine LiDAR scanners or 360° cameras built into modern phones like the iPhone, you can simultaneously record surface point clouds and omnidirectional photos. The acquired existing-condition data is useful for earthwork planning and shadow simulation.

• Pile-driving / stake-out (foundation installation): Based on the pile coordinates specified in the design drawings, mark pile-driving positions on site. Smartphone RTK can display in real time the deviation between the preloaded design coordinates and the current position. The worker simply follows navigation arrows on the phone screen to reach the target point and drives piles or inserts marking pins at the specified locations. Without the need to allocate personnel for tape measures or traditional stake-out procedures, one person can accurately mark successive pile locations, allowing pile-driving for large solar power plants to be completed in a short time.

• As-built verification (post-construction inspection): After all pile-driving and installation work is complete, perform as-built surveying to verify construction results. Measuring coordinates and elevations of pile tops or panel corners with smartphone RTK allows immediate comparison with design values. Because measurements are simultaneously shared to the cloud, the office can grasp as-built conditions in real time. If deviations beyond tolerance are found, corrective actions can be taken early. This rapid feedback system contributes to quality assurance and prevents rework.

As described above, smartphone RTK enables one person to consistently carry out surveying, pile-driving, and verification. Next, we will examine the effects of cloud-linked data management that further supports this workflow.

Cloud linkage of point clouds, photos, and coordinates reduces management workload

Survey data obtained with smartphone RTK contributes significantly to streamlining management tasks when integrated with a cloud platform. Traditionally, organizing survey results and drafting drawings required a lot of effort, but the following cloud-enabled mechanisms make information sharing and data management between the field and the office much smoother.

• Immediate sharing and visualization of survey data: Coordinate values and photos of surveyed points obtained via the smartphone app can be uploaded to the cloud with one tap and shared instantly with the office over the internet. Uploaded data is automatically plotted on maps and in 3D views, enabling real-time visualization of site progress from the office.

• Centralized management of point cloud data: Point cloud (3D scan) data collected during existing-condition surveys and construction can be stored and managed in the cloud. Since point data is linked to precise position information, extracting cross-sections or calculating volumes later is straightforward. Large sets of point cloud files and photos are organized in the cloud, eliminating concerns about file loss or mix-ups.

• Simplified document creation: Cloud-stored survey data can be used directly to create reports and drawings. For example, automatic calculation functions for distances between survey points or areas allow immediate compilation of site reports and rapid creation of as-built drawings. With data centralized digitally, transcription errors and double entry are avoided, reducing management workload and improving operational quality.

With such cloud linkage, the survey data management cycle in solar construction becomes dramatically more efficient. Because all field-collected information is shared and accumulated immediately, communication losses among stakeholders are reduced, decision-making speeds up, and overall construction optimization can be expected.

Introduction and implementation proposal for the smartphone construction support tool LRTK

Finally, as a concrete solution to realize the smartphone RTK surveying revolution described above on-site, we introduce LRTK. LRTK is a smartphone-mounted RTK positioning device and cloud service developed by Refixia Inc., a startup originating from Tokyo Institute of Technology, and is a smartphone construction support tool that turns a smartphone into a high-precision surveying instrument. It consists of a small GNSS receiver called the “LRTK Phone,” which attaches magnetically to the back of an iPhone or iPad, an easy-to-use dedicated app, and a cloud service for storing and sharing data—together enabling the single-person surveying and data management workflows discussed in this article.

By introducing LRTK, you can take advantage of centimeter-level positioning via smartphone RTK, a coordinate navigation function that guides you to the points you want to measure, cloud management of point clouds, photos, and survey point information, AR-based guidance that overlays virtual models and guides on the camera image, and other features tailored to field needs. For example, simply pointing the device at the point you want to measure can automatically record the coordinates and upload them to the LRTK cloud for team sharing on the spot. The dedicated app emphasizes intuitive operation so that users without surveying expertise can operate it without difficulty.

LRTK is already being used in civil engineering and infrastructure inspection, and examples of single-person surveying for mega-solar construction are increasing. By combining centimeter-accurate positioning and AR-based visualization, anyone can become an effective field operator for surveying and pile-driving tasks. As a smartphone construction support tool that achieves both improved surveying accuracy and labor reduction, LRTK can greatly contribute to solving surveying challenges in solar construction. If you are struggling with survey efficiency or labor shortages in solar power plant construction management, consider evaluating LRTK, a smartphone RTK solution. The surveying revolution that can be completed on a smartphone may already be within reach for your site.