Solo field surveying for solar power: Easily design in PVsyst with iPhone × LRTK

Challenges in field surveying for solar power plants

Accurate on-site survey data is indispensable for the development and design of solar power plants. In particular, power generation simulation software widely used in the industry, such as PVsyst, relies heavily on inputting information like terrain undulation and shading from surrounding obstacles, and the accuracy of power generation forecasts is greatly affected by these inputs. However, traditionally, such field surveying required team-based work and presented several challenges.

First, typical surveying uses specialized equipment such as total stations or RTK-GNSS receivers, requiring multiple personnel to visit the site. One person must set up and operate the equipment while another holds a prism at a distant point, so the work has typically required significant manpower and time. Drone-based surveying methods have also emerged, but they require specialized knowledge for piloting and data processing and are affected by weather conditions. As a result, performing detailed surveys at the planning stage has been difficult, and some developers have proceeded with design using only topographic maps or satellite imagery. This can lead to the later discovery of unexpected obstacles or elevation differences on site, creating a risk of design rework and inaccuracies in predicted power generation.

Furthermore, team surveying involves cost issues. Outsourcing to an external surveying company incurs expenses that can be burdensome for small projects. Schedule coordination is also necessary, and if it takes time to obtain data, design work can stall in the meantime. Even if one wants to perform precise simulations in PVsyst, results lack reliability when the underlying survey data is coarse. In this way, the inability to easily perform high-accuracy on-site surveys has long been a challenge in solar power plant design.

A revolutionary solution: iPhone × LRTK

As a response to the challenges above, the recent combination of smartphones and high-precision GNSS has become a viable solution. A representative example is solo field surveying using iPhone × LRTK. By attaching a compact RTK-GNSS receiver called “LRTK” to an iPhone equipped with high-performance sensors, this innovative method enables surveying work that used to require a team to be completed by a single person.

The latest iPhones are equipped with a LiDAR scanner (an infrared time-of-flight sensor) that can rapidly measure distances to surrounding three-dimensional objects and record them as point cloud data (a collection of many range points). While a smartphone alone can scan spaces using AR technology, ordinary GPS accuracy typically has errors on the order of several meters, so the captured point cloud will be offset from real-world coordinates. This is where LRTK comes in. LRTK is an ultra-compact RTK-GNSS module that can be attached to an iPhone or iPad and, by using correction information from network RTK or quasi-zenith satellite systems, enables centimeter-level positioning (half-inch accuracy) even with a smartphone. This device, called the LRTK Phone, is pocket-sized, weighing approximately 125 g and only 1.3 cm (0.5 in) thick, and can be attached to a smartphone with a one-touch dedicated case. The battery and antenna are integrated, so it is easy to carry without concern for external power or cable connections.

With the iPhone × LRTK combination, the following surveying tasks can be performed on site. First, the surveyor attaches the LRTK device to the iPhone and launches a dedicated app. By simply walking around while watching the smartphone screen, the surrounding terrain and structures are recorded sequentially as 3D point cloud data. For example, walking around a site with undulating terrain will capture the terrain’s elevation differences and the shapes of surrounding trees and buildings as point clouds. Because LRTK measures high-precision latitude, longitude, and elevation in real time and links them to the LiDAR point cloud, the resulting data becomes a 3D model that aligns with measured coordinates. Whereas traditional methods required effort to align survey points and tie them to control points, this method yields point cloud data that is consistent in an absolute coordinate system from the start.

In addition, combining the iPhone’s camera functions makes it possible to create point clouds or 3D models with color photo textures. The resulting digital twin (virtual replica) of the site reproduces the location visually and intuitively. The LRTK system also allows immediate cloud sharing of acquired data, making it easy to review the on-site point cloud model from the office. In short, iPhone × LRTK surveying enables the creation of a detailed digital 3D map of the site with just a smartphone. This allows solar power plant designers to obtain necessary survey information quickly and reflect it in designs on the spot, enabling agile responses.

Main effects and benefits of implementing solo surveying

Introducing the innovative solo surveying method using iPhone × LRTK brings various benefits to the solar power plant development process. Below are the main effects from the perspectives of operational efficiency and design accuracy.

• Significant improvement in operational efficiency: Surveys that previously took several people half a day to several days can be completed quickly by one person. There is no need to transport and set up heavy equipment, and surveys can be started whenever desired, eliminating waiting time for schedule coordination. This enables detailed on-site data to be obtained even at early project planning stages, dramatically shortening the cycle from design initiation to revisions. Reductions in personnel costs and outsourcing fees are also notable.

• Improved reliability through high-precision positioning: With RTK-GNSS corrections provided by LRTK, the acquired data consistently achieves cm-level positioning accuracy (half-inch accuracy). Because surveying results can be obtained directly in map coordinate systems (such as plane rectangular coordinates), there is no need for cumbersome tasks like later converting data to match control points. Important boundaries and reference elevations can be captured accurately, reducing discrepancies between designs and the site and allowing design and construction to proceed with confidence.

• Acquisition of detailed point cloud data: Point cloud surveying provides rich information, from subtle surface irregularities to the heights and positions of individual trees. Unlike traditional surveying that records only limited points, this approach digitizes the site comprehensively. For example, on sloped sites, gradient distributions across the entire area can be analyzed later, and obstacles both inside and outside the site can be visualized on the model. This prevents situations such as discovering a previously overlooked depression or taller-than-expected neighboring trees and enables decisions based on complete data from the initial layout phase.

• Smooth integration with PVsyst design: Accurate 3D data obtained from solo surveying directly supports PVsyst simulations. For example, generating a digital terrain model of the site from point cloud data allows layout design that accounts for undulation within PVsyst. In addition, importing surrounding trees and buildings as proximity shadow objects in PVsyst enables shading analysis based on real environmental conditions. These capabilities dramatically improve the accuracy of PVsyst power generation forecasts, strengthening project financial estimates and equipment specification considerations.

• Improved shading analysis accuracy: Shading evaluation is critically important for solar power. From the point cloud obtained by solo surveying, you can precisely determine the horizon and the angular heights of surrounding obstacles. Using this information to analyze shading over the year allows accurate prediction of which panels will be shaded and when on representative days such as the equinox, summer solstice, and winter solstice. As a result, you can optimize the layout to avoid shaded areas, or, if necessary, plan tree removal or negotiate height restrictions with stakeholders in advance, enabling shading countermeasures to be incorporated into the design. Using on-site survey data makes detailed shading simulations possible that desk-based estimates could not achieve.

• Immediate reflection in design data: Digitized survey results are easily integrated into design documentation and various data. For example, drawing contour lines from acquired point clouds produces detailed topographic maps that serve as the basis for layout planning. Overlaying proposed solar panel layouts on the survey data allows quick checks for conflicts with the current conditions. LRTK enables sharing of coordinate data for survey points via the cloud, so design staff can receive the data at their desks on the same day, load it into CAD or GIS, and proceed with design work. This greatly reduces information loss between the field and the design office and supports rapid decision-making and design changes.

iPhone × LRTK use case: from solo surveying to design implementation

Let’s look at a case where iPhone and LRTK were used for solo on-site surveying and the data was applied to design. For example, consider a plan for a medium-scale (several MW) solar power plant on hilly terrain. In this project, the engineer in charge visited the site alone during early development, attached the LRTK to an iPhone, and conducted the survey.

First, the engineer walked along the site boundary while scanning point clouds with the smartphone screen. In just a few tens of minutes of work, point cloud data capturing the entire site’s terrain undulation and the surrounding forest heights was acquired. At the same time, several distinctive features (for example, the position of a large rock on the site or key trees) were recorded with precise coordinates using the point positioning function. The acquired data was uploaded to the cloud immediately, and the office design team was able to check the 3D model almost in real time.

Next, a current 3D terrain model was constructed from the point cloud data and overlaid with proposed layout plans for examination. In PVsyst simulations, the surrounding forest extracted from the point cloud was imported as shadow objects to analyze seasonal impacts on power generation in detail. The analysis revealed that the southeast forest would cast shadows on some panel rows on winter solstice mornings. However, because this information was obtained in advance, layout optimization to avoid shading was possible during the design stage. Specifically, the affected panel rows were moved several meters to positions less prone to shading. The data also provided a basis for discussions with stakeholders about tree removal when necessary.

Furthermore, the high-precision data contributed to civil engineering design. Using accurate elevation data calculated from the point cloud to estimate cut-and-fill volumes for earthworks, the team found areas where quantities could be reduced compared to initial estimates and revised the construction plan to lower costs. This entire process, which would traditionally have required waiting for a surveying team’s report and repeated back-and-forth between the site and drawings, proceeded extremely quickly and accurately because the solo survey data could be used immediately. The person in charge was able to work with the feeling of “bringing the site back to the office for design,” and sharing the 3D model smoothed explanations and consensus-building with project stakeholders. This case is a good example of the usefulness that iPhone × LRTK solo field surveying brings to the solar power business.

Future outlook: the future opened by smartphone-complete surveying

The solo surveying method that combines smartphones and high-precision GNSS has the potential to become the standard not only in the solar power industry but across the construction and civil engineering sectors. Especially smartphone-complete surveying solutions like iPhone × LRTK, being compact, lightweight, and easy for anyone to use, are likely to spread as a “one device per person” on-site tool. The lower introduction cost compared to traditional surveying equipment will also accelerate adoption. Small-scale projects and companies will find the technology more accessible, expanding the scope of on-site digital transformation (DX).

What is expected going forward is stronger integration between such field survey data and various design software. Although point cloud data can already be imported into CAD and simulation software, future workflows will likely become even more seamless. For example, it may become possible to export terrain and obstruction object data for PVsyst from a surveying app with a single button. Also, by leveraging the accurate positioning information obtained by surveying, applications such as projecting and verifying designed layouts on site using AR (augmented reality) will advance. LRTK already realizes high-precision AR displays where virtual objects do not drift no matter how much you walk, and using this for verifying solar panel layouts would make it easier to share a completed-image among stakeholders before construction begins.

Further improvements in accuracy are also expected. With enhancements in smartphone sensor performance and the expansion of satellite positioning services (for example, wide-area augmentation signals from Japan’s quasi-zenith satellite system), an era in which centimeter-level accuracy is even more easily attainable is near. This will enable stable positioning and surveying even in mountainous or out-of-coverage areas, further smoothing site suitability surveys for solar power.

Finally, the LRTK that emerged amid these technological advances is a key solution that brings smartphone-complete simple surveying to the field. By simply attaching it to an iPhone, LRTK achieves both high-precision positioning and point cloud scanning and has made “solo field surveying for solar power” a reality. Seamlessly connecting site surveys to PVsyst simulations will improve the efficiency and reliability of the entire design and construction process. Those involved in solar power plant development are encouraged to consider using this smartphone surveying technology. With the spread of innovative tools such as LRTK, the deployment of clean energy is expected to progress more rapidly and smartly.