3D Topographic Surveying for Solar Power Plants｜LRTK Surveying Completed with Just a Smartphone

Introduction: Surveying for Solar Power Is Changing

On solar power sites, land surveying for plant construction is indispensable. However, in recent years, a new surveying approach that leverages smartphones and high-precision GNSS is dramatically changing how surveys are done. With initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and the broader acceleration of ICT use and DX across the construction industry, surveying is no exception. Terrain surveys that once required specialist surveyors and expensive equipment can now be performed by anyone with just a smartphone. This article explains the importance of 3D topographic surveying for solar power plant development and details the advantages of using the latest smartphone surveying solution, LRTK.

The Importance of 3D Topographic Surveying in Solar Power

For large-scale solar power projects in particular, precise knowledge of the terrain is essential because the scale of earthworks and panel layout directly affect power generation efficiency and project costs. When designing and constructing a solar power plant, accurately understanding the site’s topography is critically important. While surveying flat land is relatively straightforward, many suitable solar sites in Japan are on slopes or complex terrain. If elevation differences and slope angles are not properly understood, panel layout plans may become impractical or unexpected civil works may be required. 3D topographic surveying acquires the entire site’s undulations and terrain features as three-dimensional data, enabling accurate planning from the design stage. In solar power projects, optimizing panel tilt and layout to maximize solar irradiation requires three-dimensional terrain understanding. Furthermore, 3D data are powerful for estimating future rainwater flow (drainage planning) and calculating the extent and volume of earthworks needed for site leveling. In this way, understanding terrain in 3D directly improves design accuracy, reduces construction risk, and aids cost control for solar power plants.

Traditional Surveying Methods and Their Challenges

Traditionally, land surveys for solar power sites were carried out by surveyors using total stations or high-precision GNSS survey instruments to measure many points on site and create contour maps. Recently, drone photogrammetry has also been increasingly used to obtain wide-area 3D terrain data. While these methods can provide a certain level of accuracy, they have challenges.

For example, total station surveys require setting up equipment and multiple workers, and on large sites collecting points can take several days. Terrain maps interpolated from measured points can miss fine undulations. Drone photogrammetry can automatically map wide areas from the air, but it requires specialist operators, compliance with aviation regulations, time-consuming image processing, and high-performance PCs. These add cost and scheduling burdens that can impact development timelines. If re-surveying becomes necessary, outsourcing again is time-consuming. Although traditional methods are highly accurate, they often fail to meet field needs for speed and ease, creating demand for new solutions that can quickly and simply acquire terrain data.

What Is LRTK? How Smartphone-Only Surveying Works

LRTK is a solution that makes Real-Time Kinematic (RTK) high-precision positioning technology easy to use on a smartphone. Specifically, it consists of a small high-precision GNSS receiver attached to a smartphone and a dedicated app, turning the smartphone into a surveying instrument. By applying correction information from a reference station in real time to GNSS signals, RTK technology can improve position information that normally has errors of several meters to centimeter-level accuracy. The LRTK series makes this RTK positioning more user-friendly so it can be used on site immediately without complex setup or large equipment. With just a smartphone, surveying that used to require specialized instruments can be completed by attaching an LRTK device and using the app.

The LRTK application also automates coordinate transformations and data storage, allowing users without specialist knowledge to obtain accurate positioning data. For example, simply point the device at the location you want to measure and tap a button to record that point’s latitude/longitude and elevation (optionally including plane rectangular coordinates or geoid height). This ease of use enables site personnel themselves to perform surveying, allowing rapid on-site assessments without relying on external survey teams. LRTK is bringing a new “one device per person” style to the field, and it is quietly gaining popularity among construction managers and designers.

Workflow and Output of 3D Point Cloud Scanning

Using a smartphone camera or LiDAR sensor, LRTK can also record site topography as 3D point cloud data. The workflow is simple. Walk through the area you want to survey while pointing the smartphone; the surrounding terrain and structures are captured as many points (a point cloud) in real time. Standalone smartphone 3D scans typically suffer from position drift that distorts the terrain, but because LRTK constantly knows its own high-precision position, it can acquire accurate, undistorted point cloud data. After scanning, a 3D model reflecting ground undulations and partially completed earthworks is displayed on the smartphone for on-the-spot verification.

From the acquired point cloud data, you can measure distances between arbitrary two points or calculate area and volume for specific areas. The LRTK app enables basic measurements, and if you upload data to the cloud, you can review and measure in detail via a web browser on a PC without specialized software. Because the point cloud includes absolute coordinates, it is easy to overlay with design drawings or other survey data. For example, you can compare an existing terrain point cloud with a planned earthwork model to calculate cut-and-fill volume differences. With point cloud scanning, three-dimensional site surveying that used to take substantial time can now be performed by anyone in a short time.

On-Site Uses: From Earthwork Planning to Design and Volume Calculation

• Understanding existing terrain and earthwork planning: Create a ground model from LRTK-acquired point cloud data and overlay the proposed earthwork plan (where and how much to cut or fill) to accurately calculate the required earthwork volumes. This optimizes earthwork plans and improves cost estimation accuracy.

• Reflecting data in design and layout: Detailed 3D terrain data can be imported into CAD or surveying software and directly used for solar panel layout design. You can identify issues that are not obvious on flat maps, such as arrangements and racking height settings that respond to terrain slopes. Using LRTK’s AR features, you can also virtually display stakes or panels on the smartphone screen at their design positions to verify layout on site.

• Construction management and as-built verification: During construction, regularly scanning the site with LRTK allows you to check for deviations from design data and record daily changes in earthwork volumes according to progress. After completion, re-surveying the finished terrain helps verify that construction was carried out as planned (as-built verification).

• Volume calculation and reporting: For example, you can scan stockpiles of excavated soil or filled areas with LRTK and instantly calculate volumes. This enables quick management of material movements and rapid preparation of reports for construction stakeholders.

Specific Benefits of Introducing LRTK

• Significant reduction in survey time: Surveying and data creation that previously took several days can be completed with LRTK on the same day. Because point clouds are acquired in real time, you can begin planning and review immediately after measurement on site.

• Cost reduction: Reduce costs for expensive surveying equipment and outsourcing. Because you can survey in-house when needed, multiple inspections can be conducted at low cost.

• Data accuracy and coverage: In addition to centimeter-level accuracy from GNSS-RTK, point cloud data capture the terrain comprehensively, reducing oversights. Detailed terrain models improve design accuracy and suppress unexpected construction issues.

• Site-driven operation: Smartphone-based, intuitive operation means designers and site supervisors without surveying expertise can handle it. The “waiting for surveying” bottleneck disappears, enabling autonomous surveying whenever needed.

• Immediate sharing and collaboration: Measurement data can be shared with the office via the cloud immediately. Designers can review measured terrain on site and make swift decisions through real-time collaboration.

• Improved safety: Lightweight equipment improves mobility on rough or sloped ground. Surveys that previously required work at heights or on steep slopes can be performed from a distance or with point measurements from safer locations, reducing risk.

• Multi-purpose use: A single LRTK unit can be used not only for surveying but also for stake-out (marking stake positions), progress management, and equipment layout simulation (AR display). Its versatility as a field tool supports a one-device-per-person system that can raise overall operational efficiency.

Frequently Asked Questions (Accuracy, Data Use, Operability, etc.)

Q: Is smartphone surveying really accurate enough? A: The positional accuracy obtainable with LRTK is on the order of a few centimeters horizontally and a few centimeters vertically. This is comparable to traditional high-precision surveying instruments and is sufficient for the design and construction of solar power plants. Unlike the several-meter accuracy of built-in smartphone GPS, RTK corrections provide the high precision necessary to meet standards for public surveying.

Q: How can the acquired data be used? A: Point cloud data and coordinate lists obtained with the LRTK app can be stored and shared in the cloud and exported in common file formats (point cloud/coordinate data such as XYZ or CSV, or DXF/DWG). This allows import into the CAD software and design support tools you normally use. The LRTK cloud also offers browser-based functions for viewing data, distance measurement, cross-section creation, and volume calculation. You can immediately reflect 3D data acquired on site into design work and link it to deliverables.

Q: Can people who aren’t good with machines handle it? A: Yes. The dedicated app is very simple to operate and can be learned by site personnel with short training. The UI is intuitive—just press a button at the point you want to measure or walk the area you want to scan—and complex settings and calculations are handled automatically by the app. Because it uses a smartphone, the touch interface is familiar and easy to read. Replacing paper field notebooks with electronic notes and photos recorded on site is another convenient advantage.

Q: In what environmental conditions can it be used? A: GNSS positioning requires receiving signals from satellites, so clearer skies yield higher positioning accuracy. Accuracy deteriorates in forests or tunnels where satellite signals are weak, but many solar power sites are located on open land, so this is generally not an issue. RTK correction information uses a communications line, but if you are out of mobile coverage, you can set up a local base station to provide corrections. Regarding weather, light rain generally does not significantly affect surveying, but if your smartphone or device is not waterproof, use a waterproof case or other protection.

Q: What are the pros and cons compared to drone surveying? A: Drone photogrammetry can map vast areas in one flight, but it requires flight permissions, specialist skills, and data processing time. LRTK, which surveys from the ground by walking, can reliably capture areas difficult for drones such as under trees or around structures. Because results are available in real time and no special permissions are needed, LRTK is well suited for frequent on-site measurements and fine additional surveys. A good approach is to use LRTK for quick initial assessments in the early project stages and complement it with drone surveys when wide-area, high-detail mapping is required.

Future Outlook and the Evolution of LRTK

Smartphone surveying technology is expected to advance further. Improvements to both LRTK hardware and software, along with advancements in smartphone performance (for example, higher-performance LiDAR sensors and multi-band GNSS support), will further increase positioning accuracy and scanning efficiency. Enhanced cloud-based automated analysis is also noteworthy. In the future, AI might analyze scanned terrain data to propose optimal earthwork plans, or detect construction progress and terrain changes automatically from daily survey data. Further miniaturization and cost reductions could accelerate LRTK adoption across sites of all sizes. The LRTK series continues to evolve to meet these needs and holds the key to an era where “anyone can be a surveyor.” In the solar power industry, the spread of smartphone surveying is expected to dramatically increase project speed and accuracy.

Bringing Surveying Closer: Start Smartphone Surveying with LRTK

Surveying used to be a domain only for specialists. But with the advent of LRTK, surveying is becoming an everyday, accessible task. Those involved in solar power development can now measure site terrain themselves with a smartphone and immediately apply the data to design and construction planning. Under the concept of “bringing surveying closer,” the LRTK series aims to revolutionize on-site workflows. If you have only used traditional surveying methods so far, consider adopting smartphone surveying. By using high-precision, easy LRTK surveying, you can significantly improve the efficiency and quality of your solar power projects. The use of such digital technologies will likely be a key factor in the success of future solar power plant development. Now, bring the new standard of smartphone surveying to your site.