3D Topographic Survey for Solar Power Plants｜LRTK Survey 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, new surveying technologies that utilize smartphones and high-precision GNSS are dramatically changing how surveys are done. As the construction industry accelerates ICT utilization and DX—such as the Ministry of Land, Infrastructure, Transport and Tourism’s promotion of i-Construction—the surveying field is no exception. Terrain surveys that once required professional surveyors and expensive equipment can now be performed by anyone with just a smartphone. In this article, we explain in detail the importance of 3D topographic surveying in solar power plant development and the advantages of a modern smartphone surveying solution called “LRTK.”

The importance of 3D topographic surveying in solar power generation

Especially for large-scale solar power projects, the scale of earthworks and panel layout directly affect generation efficiency and project costs, so precise topographic understanding is essential. When designing and constructing a solar power plant, it is crucial to accurately grasp the on-site terrain first. While it is relatively simple on flat land, many of Japan’s suitable sites for solar power are on sloped or complex terrain. If elevation differences and slope angles are not correctly understood, panel layout plans may become infeasible or unexpected civil engineering work may be required. 3D topographic surveying allows you to acquire the site’s undulations and terrain features as three-dimensional data, enabling accurate planning from the design stage. In solar power generation, it is particularly necessary to optimize panel angles and layouts to maximize solar irradiation, and for that purpose a three-dimensional understanding of the terrain is indispensable. Furthermore, 3D data is powerful for estimating future rainwater flow (drainage planning) and the scope and volume of earthworks (land leveling). In this way, capturing 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 plants typically involved surveyors measuring many points on site using total stations or high-precision GNSS surveying instruments and creating contour maps. Recently, there has also been an increase in obtaining wide-area 3D topographic data using drone photogrammetry. While all of these methods can achieve a certain level of accuracy, they also have challenges.

For example, surveying with a total station requires setting up the instrument and multiple personnel, and on large sites it may take days to pick up points. Terrain maps interpolated from measured points may miss fine undulations. In the case of drone photogrammetry, you can automatically measure wide areas from the air, but it requires specialist operators, compliance with aviation law, time for image processing, and high-performance PCs. These factors become burdens in terms of cost and scheduling and can affect development timelines. Moreover, if re-surveying becomes necessary, it is cumbersome to request it externally again. Although conventional methods are highly accurate, they have not adequately met on-site needs in terms of speed and ease. Therefore, a new solution that can obtain terrain data more easily and quickly was needed.

What is LRTK? How smartphone-based surveying works

LRTK is a solution that makes the Real-Time Kinematic (RTK) high-precision positioning technology easily usable on a smartphone. Specifically, it consists of a small high-precision GNSS receiver that attaches to a smartphone and a dedicated app, turning the smartphone into a surveying instrument. By applying correction information from a base station to GNSS (satellite positioning) signals in real time, RTK technology can improve positional 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 settings or large equipment. With just a smartphone, surveying that used to require specialized equipment can be completed by attaching an LRTK device and operating an app.

The LRTK application automates coordinate transformations and data storage so that even users without specialist knowledge can obtain accurate positioning data. For example, you can hold the device over the point you want to measure and tap a button to record the point’s latitude and longitude and elevation (including plane rectangular coordinates or geoid height if needed). This ease of use enables site personnel themselves to conduct surveying, allowing rapid situational awareness without relying on external survey teams. In practice, LRTK is bringing about a new “one device per person” style where each person can survey with a smartphone, and it is quietly becoming popular among construction managers and design personnel.

Workflow and results of 3D point cloud scanning

By using a smartphone camera or LiDAR sensor, LRTK can also record site terrain as 3D point cloud data. The workflow is simple. As you walk through the area you want to survey while holding up the smartphone, the surrounding terrain and structures are captured in real time as numerous points (a point cloud). While standalone smartphone 3D scans normally suffer from gradual positional drift that distorts the terrain, LRTK continuously knows its precise position, enabling acquisition of accurate point cloud data without distortion. When scanning is complete, a 3D model reflecting ground undulations and even partially completed earthworks is displayed on the smartphone for immediate on-site verification.

From the acquired point cloud data, you can measure the distance between any two points or calculate the area or volume of a specific area. Not only can basic measurements be performed within the LRTK app, but if you upload the data to the cloud, you can view and inspect it in a web browser on a PC without specialized software. Because point clouds are tagged with absolute coordinates, it is easy to overlay them 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 volumes. With this kind of point cloud scanning, three-dimensional surveying that used to take considerable time can now be performed by anyone in a short time.

On-site applications: from earthwork planning and design to volume calculations

• Grasping current terrain and earthwork planning: Based on point cloud data obtained with LRTK, you can create a ground model and overlay it with the designed earthwork plan (where and how much to cut and fill) to accurately calculate required earthwork volumes. This enables optimization of earthwork plans and improves the accuracy of cost estimates.

• Reflecting data in design and layout: Detailed 3D terrain data can be imported into CAD and surveying software and directly used for designing solar panel layouts. You can identify issues that were not visible on a 2D map, such as arrangements matched to slope and the required heights for mounting frames. Additionally, using LRTK’s AR feature, you can virtually display stakes or panels in their designed positions on the smartphone screen to verify layout on site.

• Construction management and as-built verification: Even after construction begins, periodic site scanning with LRTK allows you to check discrepancies against design data and record changes in earthwork volumes as progress is made. After completion, re-surveying the finished terrain helps verify whether construction was carried out as planned (as-built management).

• Volume calculations and reporting: For example, you can immediately calculate the volume of spoil piles or backfill from earthworks by scanning with LRTK. This enables rapid management of soil movement and preparation of reports for construction stakeholders.

Concrete benefits of introducing LRTK

• Greatly reduced surveying time: Surveying and data creation work that used to take days can be completed with LRTK on the same day. Because point clouds are acquired in real time, planning and review can start immediately after measurement on site.

• Cost reduction: You can reduce the cost of expensive surveying equipment and external contracting. Since you can survey in-house as needed, multiple surveys can be conducted at low cost.

• Data accuracy and comprehensiveness: In addition to centimeter-level accuracy provided by GNSS-RTK, capturing terrain as point clouds reduces the chance of overlooking features. Detailed terrain models improve design accuracy and suppress unexpected construction issues.

• On-site-driven operation: Because it is smartphone-based and intuitive to operate, designers and site supervisors without surveying expertise can handle it. The time spent “waiting for surveying” is eliminated, enabling autonomous operation where you can measure whenever you need to.

• Instant sharing and collaboration: Measurement data can be shared with the office via the cloud instantly. Designers can check measured terrain on the spot and make decisions quickly, enabling real-time collaboration.

• Improved safety: Lightweight equipment improves mobility on rough terrain and slopes. Surveys that previously involved risk—such as on high or steep slopes—can reduce risk by scanning from a distance or taking point measurements from safe locations.

• Multipurpose use: A single LRTK unit can be used not only for surveying but also for staking out (marking stake positions), progress management, and equipment layout simulation (AR display). Its versatility as a site tool is high, and a one-device-per-person setup can be expected to raise overall operational efficiency.

Frequently asked questions (accuracy, data utilization, usability, etc.)

Q: Is smartphone surveying really accurate enough? A: Position accuracy achievable with LRTK is on the order of several centimeters in the horizontal plane and several centimeters in height. This is comparable to conventional high-precision surveying instruments and is sufficiently accurate for the design and construction of solar power plants. Unlike the several-meter-level accuracy of a smartphone’s built-in GPS, RTK corrections ensure the high precision required to meet public surveying standards.

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

Q: Can people who are not 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 through the area you want to scan—and the app automatically handles complex settings and calculations. Because it uses a smartphone, the screen is easy to read and touch operation is familiar. Instead of paper field notebooks, you can electronically record notes and photos on site, which is another convenience for the field.

Q: In what environmental conditions can it be used? A: GNSS positioning requires receiving signals from satellites, so you obtain higher positioning accuracy in open areas with clear skies. In forests or tunnels where satellite signals are weak, accuracy degrades, but many solar power sites are located on open land so this is generally not a problem. RTK correction information is received via a communication line, but if you are outside cellular coverage you can set up a base station and apply corrections locally. Regarding weather, light rain usually does not significantly affect surveying, but if the smartphone or device is not waterproof, please use a waterproof case or other protective measures.

Q: What are the advantages and disadvantages compared to drone surveying? A: Drone photogrammetry has the advantage of mapping vast areas at once, but requires flight permissions, specialist knowledge, and data processing time. LRTK, on the other hand, involves ground-based walking surveys, enabling reliable data capture under trees or around structures where drones may struggle. Because results can be verified in real time and no special permissions are required, LRTK is well suited to frequent on-site measurements and small additional surveys. A practical approach is to use LRTK for quick initial site assessment and supplement with drone surveys when detailed wide-area terrain mapping is needed.

Future prospects and evolution of LRTK

Smartphone surveying technology is expected to evolve further. Improvements to LRTK hardware and software, as well as enhancements in smartphone capabilities (for example, higher-performance LiDAR sensors and multi-band GNSS support), will further increase positioning accuracy and scanning efficiency. Strengthening automatic analysis functions on the cloud is also notable. In the future, AI might analyze scanned terrain data to propose optimal earthwork plans, or automatically detect construction progress and terrain changes from daily survey data. Further miniaturization and cost reduction could accelerate LRTK adoption on sites of all scales. The LRTK series continues to evolve to meet these needs and holds the key to an era in which “anyone can become a surveyor.” In the solar power industry as well, the spread of smartphone surveying is expected to dramatically improve project speed and accuracy.

Making surveying more accessible: start smartphone surveying with LRTK

Traditionally, surveying was an area left to specialists. But with the advent of LRTK, surveying is becoming a more familiar and routine task. Those involved in solar power plant development can now take measurements of the terrain themselves with a smartphone and immediately reflect that data in design and construction plans. Under the concept of “making surveying more accessible,” the LRTK series aims to revolutionize on-site workstyles. If you have only used conventional surveying methods until now, consider incorporating smartphone surveying. By utilizing high-precision, easy-to-use LRTK surveying, you can markedly improve the efficiency and quality of your solar power projects. In future solar power plant development, the use of such digital technologies will likely be the key to project success. Now, bring this new standard of smartphone surveying to your site.