7 Advantages and Precautions of Drone Surveys for Solar Power Plants

In surveying solar power plants, it is important to quickly grasp a large site and organize information that can be used for design, construction, and maintenance. A plant has a wide range of items to check, such as developed/graded areas, slopes, drainage facilities, mounting racks, rows of panels, maintenance roads, perimeter fences, and surrounding trees. If you try to handle everything with only ground surveys and on-foot inspections, the time spent moving around the site increases, and there is a risk of approaching hazardous areas or overlooking checks.

One of the methods used there is drone surveying. By systematically photographing from the air and creating orthophotos, point clouds, digital surface models, and terrain models, it becomes easier to check conditions while getting an overview of the entire site. However, flying a drone does not automatically produce accurate survey results. Mistakes in flight planning, ground control points, check points, imaging conditions, coordinate management, or the way deliverables are used can result in data that is difficult to use for design or construction decisions.

This article summarizes the main benefits of using drone surveying at solar power plants and the points to check before implementation. When using the survey results, it is important to consider not only the visual clarity of aerial photographs but also accuracy management, safety management, and how to explain the findings to stakeholders.

Table of Contents

• Why drone surveying for solar power plants is gaining attention

• Benefit 1: Quickly grasp large sites

• Benefit 2: Reduce the burden of inspecting slopes and hazardous areas

• Benefit 3: Gain an aerial overview of panel layouts and areas around racking

• Benefit 4: Useful for estimating earthwork volumes and site grading

• Benefit 5: Easy to use for checking drainage planning and stormwater issues

• Benefit 6: Makes it easy to keep maintenance and inspection records

• Benefit 7: Easy to use as explanatory materials for stakeholders

• Accuracy and coordinate management to be aware of in drone surveying

• Imaging conditions that commonly cause failures at solar power plants and how to address them

• Approach to stabilize results by combining with ground surveying

• Practical points to check before introducing drone surveying

• Summary: Balancing overall site understanding and accuracy management is important in surveying solar power plants

Why Drone Surveying of Solar Power Plants Is Attracting Attention

In surveying a solar power plant, it is necessary not only to measure area and distances, but also to comprehensively check the site’s overall elevation differences, grading/earthwork shapes, drainage directions, slope conditions, locations of maintenance roads, layout of panel rows, and the impact of surrounding obstructions. As the scale of the plant increases, relying solely on walking the site becomes time-consuming, and omissions in records and differences in understanding among personnel are more likely to occur.

Drone surveying is attracting attention because it makes it easy to comprehensively capture an entire power plant from above. While ground surveying can readily obtain point and line information with high accuracy, consolidating that information is necessary to share a view of the whole site at once. With drone surveying, processing the captured images allows creation of orthophotos and three-dimensional data that provide an overview of the entire site. This makes it easier for site, design, construction, and management personnel to review the situation while looking at the same materials.

In a solar power plant, the items to be checked change at each stage: before site preparation, during construction, after completion, and during operation. Before site preparation, checks focus on the terrain and surrounding environment; during construction, on progress and as-built conditions; after completion, on maintenance roads, drainage facilities, and records of panel layout; and during operation, on vegetation growth, sediment runoff, and changes around equipment. Drone surveying also offers practical advantages because it makes it easy to retain records of information from each of these stages.

However, when using drones at solar power plants, the task of taking photographs and the task of producing surveying deliverables need to be considered separately. If it is simply aerial photography, visual clarity is prioritized, but when used for surveying, flight altitude, image overlap, control points, coordinate system, processing conditions, and verification of deliverable accuracy are important. It is essential to determine the required accuracy according to the objective and to operate while reconciling with ground surveys and existing drawings.

Advantage 1: Quickly grasp large sites

A clear benefit of drone surveying for solar power plants is that it makes it possible to efficiently grasp the condition of large sites. Solar power plants are installed on various types of land, such as former forest land, converted agricultural land, reclaimed land, former factory sites, and idle land. When a site is large, simply walking the entire area to check it takes a lot of time, and inspecting slopes, drainage channels, and along the perimeter fence in detail imposes an even greater burden.

By using drones, you can photograph the entire site from above along a predetermined route. By processing the captured images, you can view the entire solar power plant as a single map, making it easier to organize an overall picture of the site. This is especially useful at plants with many rows of panels, where the view from the ground can look repetitive and it can be difficult to determine your current position or which areas have already been checked. With aerial images, it becomes easier to explain which areas were inspected and where abnormalities or uninstalled sections remain.

It is also effective for pre-construction site surveys. Because it provides a bird’s-eye view of existing terrain, trees, structures, roads, areas near boundaries with adjacent properties, and low-lying areas where drainage tends to collect, you can identify locations that require attention during the planning stage earlier. Changes in elevation and the extent of embankments that are easy to miss at ground level also become easier to clarify spatially when viewed from above.

However, being able to capture images quickly is not the same as meeting the accuracy required for survey results. If the flight altitude is too high, it becomes difficult to discern fine details, and if image overlap is insufficient, processing results will be unstable. To efficiently survey a large site, rather than needlessly expanding the capture area, it is important to create a flight plan after determining the required resolution and the intended use of the deliverables.

Benefit 2: Can reduce the burden of inspecting slopes and hazardous locations

In solar power plants, there are many locations that require caution when inspecting from the ground, such as sloped terrain, engineered embankments, areas around drainage channels, unpaved maintenance roads, and perimeter zones overgrown with vegetation. Especially after rain or during construction, there can be mud, unstable slopes, drop-offs or uneven ground, temporary structures, and paths used by heavy machinery, and attempting to walk and inspect these areas can significantly increase the risk of slips, falls, or contact with equipment.

By using drone surveying, you can assess conditions from above before approaching hazardous locations. Being able to record slope failures, soil runoff, ditches where rainwater tends to concentrate, damage to maintenance roads, and changes to the perimeter while maintaining a certain distance is a major advantage. It also aids safety management by reducing the number of times site personnel must enter dangerous areas directly.

When inspecting slopes, it can be difficult to grasp the overall shape and extent of failures based only on impressions from the ground. Using aerial imagery and three-dimensional data makes it easier to clarify which areas have changed and how drainage directions relate to locations prone to collapse. This then serves as a basis for deciding repair priorities and the scope of additional investigations.

On the other hand, there are limits to the information that drones can capture. Ground surfaces covered by grass, areas beneath trees, fine details under panels, and the backs of structures can be difficult to assess from aerial images alone. There are also items that require close-up inspection, such as cracks and small steps. Therefore, drone surveying is effective for initial identification of hazardous locations and for broad-area checks, but for places that require a final decision it is important to combine ground inspections and detailed surveys.

Benefit 3: Allows an overview of panel layout and the surroundings of the mounting structures

In solar power plants, the layout of panels, rows of racks, access roads, fences, electrical equipment, and drainage channels are intricately related. From the ground you may be able to see the rows and pathways in front of you, but it can be difficult to grasp the overall layout balance of the plant and its connections with adjacent areas. Drone surveying allows you to verify the alignment of panel rows, open spaces, and maintenance access routes from above in an integrated way.

When construction is underway, it makes it easier to verify whether the placement has shifted significantly from the design drawings, whether there are any irregularities in the orientation of panel rows or the provision of access aisles, and where uninstalled areas and material storage yards are located. After completion, it can be kept as a record of the overall layout of the facility, which is useful for future inspections and renovations. Because power plants have long operational periods, clearly recording the as-built condition at completion forms the foundation for maintenance management.

Drone surveys are also effective for checking conditions around mounting structures. For example, there are changes that are easier to notice from above—such as whether there are spots where water tends to pool between panel rows, whether maintenance walkways have become narrowed, or whether vegetation is prone to overgrow in specific areas. The advantage is that you can grasp tendencies across an area that are difficult to detect by checking points one by one on the ground.

However, confirming the precise condition of the panels and mounting racks themselves requires methods suited to the purpose of the photography. In standard survey photography, you cannot check fine details such as the condition of individual bolts or the state of the rear surface. In addition, panel surfaces are prone to reflections, and their appearance changes depending on the time of shooting and the sun’s altitude. Deciding in advance what you are photographing for—layout verification, progress checks, maintenance records, etc.—will make the results more usable.

Benefit 4: Useful for understanding soil volumes and earthwork shapes

In the construction of solar power plants, it is important to understand the status of earthworks and site grading. Elevation differences within the site, the extent of cut and fill, slope geometry, drainage gradients, and the elevation of access roads all affect constructability, safety, and maintenance. By creating point clouds and terrain models through drone surveying, it becomes easier to verify the terrain’s undulations and the formed earthworks across the site.

In earthwork volume management, comparing terrain data from before and after construction provides data for understanding the distribution of cuts and fills. With traditional cross-section surveys alone, changes between survey lines must be interpolated, but drone surveying can capture the ground surface over wide areas as continuous surfaces, making it easier to visually confirm trends in change. It is also a convenient method for monitoring the progress of land development and for use as consultation materials.

Especially at solar power plants, not only the power generation equipment itself but also the site's drainage and slope stability affect long-term operation. If the developed site's shape differs significantly from the plan, rainwater may concentrate in unexpected locations and maintenance roads may become difficult to use. Recording the terrain with drone surveying allows you to identify problematic areas early during construction and makes it easier to follow up with additional inspections.

On the other hand, when using it to determine earthwork volumes and the shape of finished surfaces, accuracy control is particularly important. If the placement of ground control points is insufficient, the ground surface is covered by vegetation or materials, errors occur at the edges of the image capture area, or processing conditions differ each time, the reliability of comparative results decreases. For applications that require accuracy—such as contract quantities, construction quality/as‑built control, or deliverables conforming to public surveying standards—it is advisable to confirm the required specifications in advance and to verify reference points and key cross‑sections by ground surveying.

Benefit 5 Easy to use for checking drainage plans and rainwater issues

Drainage planning is crucial at solar power plants. When panels, mounting racks, and access roads are installed across a large site, the way rainwater flows can change from before construction. If drainage channels, catch basins, side ditches, slope toes, the cross slope of access roads, low-lying areas, and other features are not properly checked, puddling, scour, sediment runoff, and slope damage may occur during rainfall.

In drone surveying, because it makes it easy to get an overview of elevation differences across an entire site and how the terrain connects, it provides material for considering which way rainwater is likely to flow and where water is likely to accumulate. By overlaying the positions of drainage channels, slopes, and maintenance roads on orthophotos, it becomes easier to explain conditions on site. Photographing after rain can sometimes record patterns of puddles and wet areas.

It is also useful for checking drainage during operations and maintenance. At operating power plants, vegetation overgrowth, sediment accumulation, clogging of drainage channels, and minor slope failures can gradually progress. By regularly photographing the same area, it becomes easier to detect changes by comparing them with past conditions. If inspectors correlate abnormalities noticed on site with the geolocation information in aerial images, it can be used to inform repair planning.

However, you should avoid concluding drainage performance based solely on drone survey results. Actual rainwater flow is influenced by surface compaction, soil type, vegetation, the cross-section of drainage structures, rainfall amount, inflow from surrounding areas, and other factors. Drone surveys are one means of identifying drainage risks, but it is important to combine them, as needed, with on-site inspections, verification of drainage facility dimensions, and checks of conditions after rainfall.

Benefit 6 Easier to keep maintenance and inspection records

Solar power plants are not finished when construction is complete; they require ongoing maintenance over the long term. During operation, various inspections are necessary, such as mowing, cleaning drainage channels, checking slopes, inspecting fences, repairing access roads, checking surrounding trees, and inspecting for abnormalities around equipment. By conducting drone surveys regularly, it becomes easier to keep records of the overall condition of the power plant.

The value of records increases over time. For example, if you can compare the condition immediately after completion, the condition several months later, the condition after rainfall, and the condition before and after mowing, it becomes easier to grasp trends in change. Trends such as certain slopes being prone to soil runoff, certain drains tending to accumulate sediment, and peripheral vegetation tending to encroach on power generation equipment are difficult to see from one-off inspections. Continuous aerial records provide material for determining maintenance priorities.

Another advantage is the improved clarity of inspection records. In inspection reports made up of only text, explanations of locations and scope can be difficult to convey. By using aerial images, the positions of abnormal locations and the surrounding conditions can be shared visually. Even when multiple stakeholders—such as management companies, power generation operators, contractors, and landowners—are involved, being able to view the same images while discussing makes it easier to reduce gaps in understanding.

However, when using it as a maintenance management record, standardizing the imaging conditions is important. If the flight altitude, coverage, orientation, or timing vary greatly each time, it becomes difficult to compare with past data. If you plan to use it for regular inspections, it is convenient to decide on flight routes and deliverable formats so that imaging can be done according to the same criteria. In practice, it is important not only to keep records but also to store them in a state that makes later comparisons easy.

Benefit 7: Easy to use as explanatory materials among stakeholders

In the planning, construction, and maintenance of solar power plants, many stakeholders share information. Designers, surveyors, construction personnel, project owners, maintenance managers, electrical equipment personnel, landowners, and officials responsible for administrative consultations each view matters from different perspectives. A major advantage of the results of drone surveys is that they are easy to use as materials to explain site conditions to these stakeholders.

Ground-level photos are useful for explaining areas close to the subject, but they can make it difficult to understand where those areas are located within the entire power plant. Aerial imagery, on the other hand, makes it easier to show positional relationships across the whole site and to share problem areas and the scope of work. For example, aerial imagery is helpful when explaining the location of drainage channels, the extent of slopes, material storage areas, unfinished sections, and planned repair areas.

It can also be used for progress reporting during construction. At large power plants, it can be difficult to describe in words which areas have had mounting racks installed, how far panel installation has progressed, or what stage access roads and drainage systems are at. If you have aerial overview materials from drone surveys, it becomes easier to share progress and issues. When communicating the situation to stakeholders in remote locations, it also makes it easier to convey the scale of the site.

However, even when used as explanatory material, it is important not to rely solely on visual clarity. If it is to be treated as survey results, you need to clearly state when the photos were taken, what area was covered, and how reliable the coordinates and scale are. Organizing the materials so that viewers do not mistake them for photographic materials, survey results, or reference maps will help prevent problems.

Accuracy and Coordinate Management to Watch for in Drone Surveying

In drone surveys for solar power plants, what you need to pay particular attention to are accuracy and coordinate management. Even if you can produce clean images from above, they become difficult to use for design and construction management if positions are shifted or elevations are unstable. Coordinate consistency is especially important—more than appearance—when the data are used for site preparation, earthwork volume calculations, as-built measurements, drainage analysis, and verification against existing drawings.

The first thing to confirm is the purpose—what the deliverables will be used for. If they will only be used to grasp the overall site situation or as explanatory materials, the required level of accuracy may be relatively relaxed. On the other hand, if they will be used for overlaying with design drawings, earthwork quantity comparisons, as-built verification, or management of equipment locations, you need to appropriately place control points and verification points and produce results that are consistent with ground surveys. If you capture data while the purpose is still unclear, you may later discover that the required accuracy has not been met.

Unifying coordinate systems is also important. If a power plant’s design drawings, development plans, boundary documents, ground survey results, and drone survey results are each managed with different coordinate systems or datums, misalignments will occur when they are overlaid. It is important to organize in advance the coordinate system, origin, orientation, and height reference to be used on site, and to record which standard was used for the survey deliverables. At sites operating with local coordinates, the transformation parameters and the handling of control points must be clearly defined.

Attention must also be paid to the placement of control points. If control points are clustered on one side, lacking at site edges, or not sufficiently placed in areas with elevation differences, the processed results are more likely to show errors at the edges and in height. For large power plants or sites with undulating terrain, arranging them to surround the target area and, if necessary, placing points inside as well is an effective approach. The visibility and installation locations of control points are also important; choose places that can be clearly interpreted in aerial images and easily rechecked on site.

It is also important to establish validation points. Control points are used for processing, whereas validation points are used to check for deviations in the results. By using validation points, you can confirm how closely the processing results match the field coordinates. In surveying solar power plants, it is essential not only to assess the appearance of the deliverables but also to compare the actual coordinate values to verify accuracy.

Shooting Conditions Prone to Failure at Solar Power Plants and Countermeasures

In drone surveying, the quality of results can vary greatly depending on imaging conditions. At solar power plants there are many factors to watch for during image capture, such as panel reflections, repeated identical equipment shapes, a mix of grassy areas and bare ground, slopes and elevation differences, and trees and power lines around the perimeter. Even if the flight route is automated, if it is not suited to local conditions the processing results can become unstable.

First, what you should pay attention to is image overlap. If the overlap between photos is insufficient, image processing may have difficulty linking feature points, which can cause distortions in orthomosaic images and point clouds. In particular, in areas where similar patterns continue—such as rows of panels—image processing can more easily misidentify positional relationships. It is important to ensure the necessary overlap and, where appropriate, adjust the flight direction or the shooting course.

Next, there are effects from reflections and shadows. At solar power plants, panel surfaces easily reflect light, and depending on the time of capture, blown highlights or glare/reflections can occur. Strong reflections make it difficult to discern features in the image and can affect interpretation. Also, when the sun is low, shadows lengthen, making it harder to see the condition of slopes, underneath panels, and around equipment. Depending on the purpose of the capture, it is important to choose times when reflections and shadows are minimal.

The effects of wind should not be overlooked. In strong winds, the aircraft’s attitude can become unstable, which may lead to blurred images and deviations in the flight path. Solar power plants are often located in open areas, so winds that feel weak on the ground can have a greater impact at altitude. For both safety and to maintain the quality of survey results, flights should be avoided under such conditions.

Attention should also be paid to the condition of grass and other vegetation. When grass is tall the ground surface can be obscured, causing a terrain model to reflect the top of the grass rather than the actual ground. If the purpose is to check formed shapes or earth volumes, it is preferable to photograph after mowing or at times when the ground surface is easily visible. For maintenance purposes, when checking the extent of grass growth, it may be necessary to intentionally record the pre-mowing condition, so schedule the timing according to your objective.

Approach to Stabilizing Results by Combining with Ground Surveying

Drone surveying is convenient, but it does not replace all types of surveying. In the practical work of solar power plants, it is important to combine drone surveying and ground surveying to improve the reliability of results. Drones are well suited to capturing wide areas from a planar perspective, while ground surveying is suited to control points, critical structures, boundaries, detailed dimensions, and height verification. By using each method for its respective strengths, the outputs become more practical and usable in the field.

For example, for pre-construction site assessment, one method is to capture the overall terrain of the site with drone surveying and verify boundaries, existing structures, and control points with ground surveying. For progress checks during construction, record the overall progress with drones and confirm critical elevations and positions with ground surveys. For as-built documentation, retain the overall layout with aerial imagery and supplement on-the-ground information for facilities, access roads, and locations requiring drainage works, creating records that are easy to use later.

What's important when coordinating with ground surveying is aligning the reference systems. If the drone survey results and the ground survey results are produced using different references, their positions won't match when overlaid. You need to organize reference points, coordinate systems, vertical datums, file names, creation dates, and survey extents, and clarify which deliverables are the official management documents. Deciding naming rules and storage locations for each site in advance will also reduce the effort of searching for files later.

Also, it is important not to overtrust the results of drone surveys. Point clouds and terrain models generated by image processing contain errors from reflections, shadows, vegetation, camera angle, and processing conditions. In particular, areas under panels or trees, grassy areas, the edges of slopes, and locations near the water surface tend to be unstable. For locations used to make important decisions, it is safer to assume they will be verified on the ground.

Practical Points to Check Before Introducing Drone Surveying

Before introducing drone surveying at a solar power plant, it is important to organize the objectives, deliverables, required accuracy, flight conditions, legal compliance, and operational framework. Simply capturing images without a plan can leave you short of the information you need later. Conversely, by clearly defining the objectives you can determine the necessary capture area and deliverables, reducing unnecessary work.

The first thing to confirm is the purpose of the survey. Depending on whether it is an on-site survey, a design study, a construction progress check, earthwork volume estimation, a completion record, or a maintenance inspection, the required deliverables will differ. In some cases orthoimages alone may be sufficient, while in others point clouds, terrain models, cross-sections, or overlays with existing drawings are necessary. Do not leave the purpose vague; it is important to work backward from how the deliverables will be used.

Next, check the accuracy requirements. The required coordinate accuracy and height accuracy differ depending on whether the material will be used as explanatory documentation or for design and construction management. If accuracy is required, you should decide in advance where to place control points and validation points and how to coordinate with ground surveying. The recipient of the deliverables should also clearly state what level of accuracy they expect to help prevent misunderstandings.

Checking flight conditions and legal requirements is also essential. Aircraft above a certain weight flown outdoors must be registered, and depending on conditions—such as operating near airports, in densely populated areas, above a certain altitude, at night, beyond visual line of sight, or in close proximity to people or property—permission or approval under the Aviation Law or notification of a flight plan may be required. The presence of houses, roads, railways, power lines, communications facilities, forests, or wind corridors around a power plant also affects flight planning. At construction sites on the premises where workers and heavy machinery are present, it is important to arrange takeoff and landing locations, access control, and communication arrangements in advance.

The way deliverables are stored is also important in practice. In drone surveying, multiple types of data are generated, such as images, processing data, point clouds, orthophotos, and drafted materials. If file names and storage locations are not organized, it takes time to find the necessary data later. Managing files so the capture date, extent, purpose, coordinate system, and processing conditions are clear makes them easier to use for future comparisons and reports.

Also, it is advisable to decide in advance who within the company or on-site will verify the results and who will use them for decision-making. Because the outputs of drone surveys are visually easy to understand, they may seem to allow stakeholders to make immediate judgments, but using them without understanding survey accuracy and processing conditions can lead to misunderstandings. Sharing how to interpret the deliverables, the cautions, and the scope of use will help prevent problems after implementation.

Summary Surveying solar power plants requires balancing a comprehensive overview and precision management

The benefits of drone surveying for solar power plants are not limited to efficiently understanding large sites. It significantly reduces the burden of inspecting slopes and hazardous areas, provides an overview of panel layouts and the conditions around mounting racks, helps identify grading and drainage risks, preserves maintenance records, and can be used as explanatory material for stakeholders. Especially for facilities like power plants that cover wide areas and are operated long-term, aerial records become the foundation of site management.

On the other hand, drone surveying is not without limitations. If image acquisition conditions, control points, check points, coordinate management, consistency with ground surveys, or the way deliverables are used are handled incorrectly, the data may look neat but be difficult to use for practical decision-making. For surveying solar power plants, it is important to determine the required accuracy according to the purpose and to consider dividing roles: drones for broad-area assessment and ground surveys for verifying critical points.

When introducing drone surveying, clarify in advance what you want to measure, which deliverables are required, what level of accuracy is needed, and which reference system will be used to manage coordinates. Additionally, by designing operations to cover flight conditions, safety management, legal compliance checks, data storage, and methods for sharing information with stakeholders, you will make it easier to realize the benefits of drone surveying.

For efficient site assessment, construction management, and maintenance of solar power plants, it is worth considering the use of drones tailored to surveying applications. Rather than judging solely by the clarity of aerial photographs, it is important to choose a method suited to the site while ensuring the accuracy, reproducibility, and recordability necessary to use the results as survey deliverables.