Four drone surveying checks for solar power plants useful before inspection

Table of contents

• Why conduct drone surveys before inspecting a solar power plant

• Check 1 Organize the current status of the entire power plant and the inspection targets

• Check 2: Confirm flight conditions and prerequisites for ensuring safety

• Check 3 Align the approach to desired deliverables and surveying accuracy

• Check 4 Prepare data management with an eye toward use after inspection

• Linking drone surveying of solar power plants to improved inspection quality

The Importance of Conducting Drone Surveys Before Inspecting Solar Power Plants

When inspecting a solar power plant, it is important not only to search for anomalies after arriving on site but also to understand the overall condition of the entire site beforehand. A plant has a wide range of items to check—panels, racking, electrical equipment, maintenance roads, drainage facilities, slopes, fences, and surrounding vegetation. Trying to grasp the whole picture by visual inspection from the ground alone makes it easy to overlook things and tends to increase travel time on the day of inspection. This is where a drone survey of the solar power plant carried out before the inspection becomes useful.

Conducting a drone survey before an inspection allows a comprehensive overhead view of the entire power plant. From this vantage point, you can check issues such as misaligned rows of panels, the condition of access paths, drainage flow, sediment accumulation, overgrown weeds, and changes around fences that differ from ground-level observations. Because potential areas of concern can be organized before entering the site, inspectors can more easily decide where to focus their attention. Especially at large power plants, having prior information can greatly change the efficiency of inspections.

Inspections of solar power plants need to look not only at the generation equipment itself but also at the surrounding environment that can lead to reduced power output or increased maintenance burdens. For example, shadows from vegetation growth, muddy areas caused by poor drainage, small slope failures, deterioration of access roads, and the risk of intrusion from outside the fence are items that tend to require more extensive responses the longer they remain undiscovered. If you regularly record the overall site with drone surveying, it becomes easier to compare differences from the previous inspection and to set inspection priorities.

However, simply flying a drone does not immediately improve inspection quality. Before the inspection, if you do not decide what you want to check, what area to capture, what level of accuracy and resolution is required, and who will use the acquired data and how, you may not be able to make practical use of the images or point clouds even if you acquire them. If, despite having taken the photos, it becomes hard to identify locations when reviewing them later, difficult to use them for comparisons, or hard to organize into reports, the effectiveness of the survey will be limited.

In pre-inspection drone surveying of solar power plants, it is important to be aware of the flow of site condition assessment, safety confirmation, deliverable design, and data utilization. This article explains four checks that field personnel should confirm before inspection: overall site condition assessment, flight conditions and safety assurance, deliverables and surveying accuracy, and post-inspection data management. By adopting a preparation mindset that is easy to use on site, drone surveying can be transformed from a mere photography task into information gathering that supports the accuracy and efficiency of inspections.

Check 1: Organize the overall current status of the power plant and the inspection targets

The first things to confirm with a drone survey before an inspection are the overall condition of the power plant and the inspection targets. Even among solar power plants, conditions vary: some sites have panels neatly arranged on flat, developed land, while others are installed on slopes or in mountainous areas, near reservoirs or farmland, or close to houses and roads. By clarifying in advance the site shape, panel layout, access routes, relationship with adjacent land, and the presence of hazardous points, planning the drone survey becomes much easier.

First, clarify what will be inspected. The required imaging coverage varies depending on whether you want to check only the surface condition of the solar panels, also inspect the mounting racks and foundations, or understand drainage paths and changes to slopes. For example, if the primary focus is confirming the layout of the power generation equipment, it is important to plan to photograph the panel arrays broadly and uniformly. On the other hand, if you want to check for sediment runoff or poor drainage, you need to look not only under the panels but also around the site perimeter, drainage ditches, catch basins, the base of slopes, and beside maintenance roads.

When organizing inspection targets, it is useful to also check past faults and maintenance records. Locations that have tended to experience weed overgrowth, areas where water tends to collect after rain, spots prone to panel shading, and places where fences have been damaged are all candidates to focus on during drone surveying. If you have the previous inspection report or on-site photos, matching the camera positions and viewpoints makes it easier to compare changes. Linking past information with the current survey plan improves the quality of pre-inspection preparation.

At a solar power plant, attention is also required for areas that are difficult to see from the ground. The far side of panel rows, the upper parts of sloped terrain, vegetation outside fences, and downstream sections of drainage channels can take a long time to inspect by patrols alone. Aerial photography makes it easier to see the overall connectivity of the site, estimate directions where water is likely to collect, and identify locations prone to shading. In particular, even when ground-level photos only show individual spots, aerial images allow you to confirm each spot’s relationship with its surroundings at a glance, helping to assemble an inspection plan.

When organizing the current conditions, the boundary of the photography area is also important. At sites where the power plant’s site boundary is difficult to discern, review the site plans and confirm on-site landmarks before flight. Knowing landmarks visible from above—fences, gates, roads, drainage channels, slopes, adjacent buildings, utility poles, trees—makes post-flight data organization easier. Because care must be taken to avoid unnecessarily photographing areas outside the site, it is important to decide in advance how far the recording should extend.

Also, before inspecting a solar power plant, it is useful to put into words the issues you want to confirm on site. The aim of the imaging changes depending on whether you want to look for candidate causes of reduced power generation, check for terrain changes after heavy rain, confirm the area before mowing, or record the current condition before equipment replacement. If you shoot widely with the purpose unclear, you may end up with only increased data volume, and post-processing and review may take longer. Deciding the purpose beforehand makes it easier to determine the required area, altitude, angle, and resolution.

Pre-inspection drone surveying is a process that connects the desk-based review before going to the site with on-site safety checks. By understanding the overall layout of the power plant, organizing the inspection targets, and comparing them with past issues, the plan for the inspection day becomes more concrete. If it becomes clear which route to patrol, which areas to prioritize, and which equipment to inspect first, you can reduce wasted inspection effort and more easily carry out the necessary checks within the limited time.

Check 2: Confirm flight conditions and safety assumptions

When conducting drone surveys at solar power plants, confirming flight conditions and safety measures is essential. Although a plant covers a wide area, it contains many elements that require attention during flight, such as panels, mounting racks, power lines, utility poles, trees, fences, access roads, and nearby facilities. Even if the site appears open from above, obstacles may be close at takeoff and landing locations or during low-altitude flight. Pre-inspection surveying must be based not only on achieving imaging results but also on developing a plan that ensures safe flight.

The first thing to confirm is the takeoff and landing location. Although drones are aircraft that fly overhead, safety during takeoff and landing is extremely important in practical operations. Within a solar power plant you may be able to use service roads or open spaces, but you need to be careful of gravel, grass, slopes, mud, strong reflections, and nearby racking or fences. It is important to choose a site where takeoff and landing can be performed stably, the pilot can easily maintain visual line of sight with the aircraft, and access by third parties can be controlled. If you arrive on site without deciding on a takeoff and landing location and hesitate, the start of filming will be delayed and the overall inspection schedule will be affected.

Next, check the airspace and surrounding obstacles. Around the power plant there may be transmission lines, distribution lines, communication lines, utility poles, transmission towers, trees, signs, buildings, and mountain slopes. In particular, power lines are easy to overlook and can blend into the background, making them hard to see. Before deciding on the flight route, perform a visual inspection on site and plan with adequate margin so the aircraft does not come too close. On sloped terrain, ground elevation varies by location, so even if you think you are flying at a constant altitude, be aware that the distance to the ground and trees can change.

Weather conditions are directly linked to surveying quality and safety. On windy days the aircraft is more easily blown off course and captured images are more prone to blur. Rain or fog reduce visibility and require consideration of their effects on the aircraft and equipment. Solar panels reflect light strongly, so at certain times of day images may be washed out or the surface condition may be difficult to see. Depending on the inspection purpose, it is important to choose times of day with fewer shadows and less reflection. When selecting the day for shooting, consider not only the weather but also sunlight, wind, ground conditions, and the placement of personnel.

Checking the flight rules is also necessary. Drone flights require procedures and compliance measures appropriate to the location, the aircraft, the flight method, and the surrounding environment. Even if a solar power plant is on company-managed land or land managed under contract, the items to confirm may change depending on its relationship to nearby roads, residences, railways, public facilities, airport surroundings, densely populated areas, airspace reserved for emergency operations, and so on. In practice, it is important to check the latest laws and flight rules, internal company regulations, and the client’s safety standards, and to complete the necessary procedures and approvals before carrying out work. If you confirm these matters during the pre-inspection preparation stage, you can reduce cancellations or plan changes on the day.

Safety considerations for third parties and workers are also important in drone surveying at solar power plants. If mowing, electrical equipment inspections, weeding, repair work, patrols, and so on are carried out simultaneously on the inspection day, adjust operations so that the flight area and ground work area do not overlap. Decide on communication methods among the pilot, assistants, inspectors, and plant managers so it is easier to respond to sudden entries or vehicle movements. It is also safer to share in advance the criteria for interrupting flights if people or vehicles approach.

Caution is required when approaching equipment. Getting too close to panels or mounting racks not only increases the risk of contact but also makes you more susceptible to air disturbances and pilot error. Even when you want to capture detailed images, rather than flying lower than necessary, it is important to set shooting conditions that match the objective and ensure a resolution that can be verified in post-processing. When conducting close inspections of specific areas, plan them separately from wide-area shooting and carry them out only after thoroughly confirming the safety of the surroundings.

Emergency response measures should also be decided before inspections. Clarify the criteria for suspending operations in cases such as unstable communications, increasing wind, aircraft warnings, a third party approaching, or sudden rain. Because solar power plants are large, it is also important to have a system to avoid losing track of the aircraft's position. Assign assistants to conduct visual checks so the pilot does not focus too narrowly on the camera view. Operations that prioritize safety will, as a result, lead to more stable survey outcomes.

Check 3 Align the Desired Deliverables with the Approach to Survey Accuracy

When conducting drone surveying before inspections, it is important to decide in advance what deliverables you want to obtain. Whether you only need to take photographs, create an orthomosaic of the entire power plant, produce a 3D point cloud or terrain model, or retain geotagged images for inspection reports will affect the shooting method and the required accuracy. If you carry out the work without a clear purpose for the deliverables, you may find after shooting that necessary information is missing and that reshooting is required.

Common deliverables used before inspections of solar power plants include aerial photographs, stitched images of the entire plant, diagram-style images that show positional relationships, three-dimensional data, and detailed photographs of specific locations. Aerial photographs are well suited for understanding current conditions and allow the overall picture of the inspection target to be shared quickly. Diagram-style images make it easy to confirm the positions of panel rows, walkways, drainage channels, fences, and slopes, and are an easy-to-use format for inspection planning and reporting materials. Three-dimensional data is useful when you want to check inclinations and level differences, changes in embankments and slopes, and the accumulation of sediment.

When deciding on deliverables, consider who will use the data. Whether an on-site inspector will view it before their rounds, a maintenance manager will check it in a report, the client will be briefed, or repair personnel will determine the scope of work affects how the information needs to be presented. For inspectors, it is important that locations and points of concern are clearly identified so they won’t be confused on site. For managers, it is important that changes since the previous inspection and areas of risk are clear. When used as explanatory material, images and annotations that are easy for non-specialists to understand are required.

It is important to set a level of surveying accuracy that matches the intended purpose. High accuracy is not required for every pre-inspection survey. If the objective is to understand overall site conditions or to check patrol routes, it may be sufficient to have positional information that clarifies relative locations within the power plant. On the other hand, if you need to verify subsidence, slope deformations, drainage gradients, sediment volumes, or changes in equipment layout, higher positional accuracy and repeatability may be required. Balancing purpose and accuracy makes it easier to avoid excessive work or inadequate results.

Shooting conditions also greatly affect the quality of the deliverables. When stitching images together, adjacent photos need to have sufficient overlap. If the altitude is too high, you can efficiently capture a wide area, but it becomes harder to detect small anomalies. If the altitude is too low, details become easier to see, but the number of photos increases, and flight time and processing time become longer. At solar power plants where panels are arranged regularly, many images will look similar, so attention must be paid to the flight route, overlap, and securing landmarks.

If alignment is important, also consider how to handle reference points and targets. If you want to compare the same location each time, it is useful to record durable landmarks such as gates, corners of access roads, drainage inlets, fence posts, and equipment foundations. If more precise position management is required, you can establish reference or control points on site. However, if the pre-inspection purpose is a simple current-condition check, overly complicated preparations become a burden. It is practical to determine the necessary preparations based on the deliverables you require.

At solar power plants, reflections and shadows also affect the clarity of the resulting images. During times when reflections off panel surfaces are strong, areas that appear white in images increase, making it harder to discern surface conditions and row boundaries. Conversely, when shadows are long, it becomes easier to confirm the shadows of racks and surrounding trees, while fine details of the ground surface may become difficult to see. If the inspection purpose is to check the influence of vegetation, the way shadows fall becomes important; if the purpose is to grasp equipment layout, conditions that make the whole site appear uniform may be preferable. It is necessary to select shooting times according to the objective.

It's also important to standardize the granularity of deliverables. Decide in advance whether you want to see the current state of the entire power plant in a single image, view it divided by blocks, or enlarge only suspected anomalies — doing so will make post-capture organization smoother. In large power plants, an overall image alone can make details hard to see, while detailed images alone can make spatial relationships difficult to understand. Therefore, combining an image that shows the whole site, images for each section, and detailed images of areas of concern makes the materials easier to use as pre-inspection reference documents.

The results of drone surveying become material for decision-making on the day of inspection. For example, they can be used to first check plots where weeds are rampant, to focus inspections after rain on low-lying areas suspected of poor drainage, or to include potential fence-line damage sites in patrol routes. If you align your thinking on deliverables and accuracy in advance, the captured data will more readily lead to on-site actions. Considering purpose, deliverables, accuracy, and imaging conditions together is the basic way to enhance the effectiveness of pre-inspection drone surveying.

Check 4 Prepare data management with an eye toward post-inspection utilization

Drone surveys before inspections are not finished simply by taking photos. It is important to think in advance about how to use the acquired images and three-dimensional data on the day of inspection, in post-inspection reports, for the next inspection, and for repair planning. If data management is inadequate, it can take time to find the necessary photos later, and you may not know which location was photographed. In maintenance management of solar power plants, the same locations are often checked continuously, so it is essential to organize data in a format that makes it easy to accumulate.

First, decide on a method for organizing files. Arrange them so the shooting date, power plant name, section name, purpose of the shoot, and whether the images are before or after inspection are clear; this makes them easier to search later. At large-scale power plants, the number of images grows large, so simply saving everything together immediately after shooting makes management difficult. Save overall photos, section photos, detailed photos, processed data, and report materials separately, and ensure stakeholders can access the data they need.

Next, decide how to record anomaly candidates and areas of concern. For locations flagged during drone surveying, it is more practical for field work to keep not only images but also the position, description, priority, and the results of any on-site verification as a set. For example, record plots where weed impact is suspected, points where a drainage channel appears to be clogged, spots where slope failure is suspected, or areas where fence deformation is visible, and append the results of the on-site inspection on the day of the check. Connecting the prior aerial check with the on-the-ground visual confirmation increases the credibility of the inspection records.

When using reports after inspections, how images are presented is also important. Combining an overall map that shows where in the power plant a potential anomaly was found with detailed, zoomed-in images of the relevant area makes it easier for stakeholders to understand. Even when ground photos alone make it difficult to explain locations, indicating the position on aerial images helps the client and managers grasp the situation. In reporting materials, it is practical to avoid drawing firm conclusions and to separately organize the facts confirmed by drone surveys, items requiring on-site verification, and items that should be considered for action.

In ongoing management, comparison with previous data holds great significance. Changes in the condition of a solar power plant can be difficult to judge from a single inspection. The growth of weeds, accumulation of sediment, slope changes, occurrence of poor drainage, and changes around fences are all influenced by season and weather. Conducting drone surveys regularly under conditions as similar as possible so that the same locations can be compared makes it easier to grasp trends in those changes. Accumulating data from pre-inspection surveys forms the foundation for long-term maintenance management.

We also need to consider how data will be shared. Different stakeholders—inspection personnel, maintenance companies, power plant managers, design engineers, and repair personnel—need different information. Simply giving everyone a large amount of raw data will bury the information they need. By separating simple materials for on-site checks, report materials for managers, and raw data for detailed analysis, you can provide information that is easy to use for each stakeholder. It is also important to consider the scope of sharing and viewing permissions to avoid unnecessary dissemination of data.

Also, when saving data, keep future reuse in mind. If you review it months or years later, you may not be able to make accurate comparisons if you don’t know the conditions at the time of capture. Briefly record the capture date, weather, coverage area, flight altitude, purpose of imaging, inspection target, on-site verification results, and so on to make it easier to understand the context later. Past data becomes especially valuable for post-disaster inspections and for before-and-after comparisons of equipment updates. Keep in mind that data should be preserved not only for immediate use but also as reference material for future decision-making.

Drone survey data collected before inspections can also be used in maintenance planning. If you have data that captures current conditions—such as confirming mowing areas, planning cleaning of drainage facilities, prioritizing slope repairs, deciding on maintenance road repairs, and arranging fence repairs—it becomes easier to organize on-site work. Because it can be used not only to identify abnormalities but also to consider the work scope and material delivery routes, survey data serves as an information foundation for overall maintenance management, not just the inspection department.

One thing to be careful about in data management is not to over-rely on images and 3D data. Drone surveying can efficiently inspect wide areas, but images alone sometimes cannot provide a definitive judgment. The backs of panels, fine details of wiring, interiors of junction boxes, fastening points of mounting racks, and subsurface conditions require on-site confirmation. Being aware of the division of roles—using drone surveys to narrow down anomaly candidates and ground inspections to make final confirmation—makes it easier to achieve both inspection accuracy and efficiency.

Linking Drone Surveys of Solar Power Plants to Improved Inspection Quality

By performing drone surveys before inspecting a solar power plant, you can grasp the overall picture before entering the site and more easily organize the key points to check. Simply walking through a large site on the ground in sequence takes time and is prone to oversights. By combining information from above, you can view the relationships among panel rows, walkways, drainage facilities, slopes, fences, and surrounding vegetation as a whole, making it easier to develop a concrete inspection plan.

The important thing is not to treat drone surveying as mere preliminary photography. By organizing the overall current state of the power plant and the inspection targets, confirming flight conditions and safety prerequisites, aligning the desired deliverables with the required surveying accuracy, and preparing data management with an eye toward post-inspection use, survey results become information that can be used on site. Clarifying not only the coverage and image clarity but also who will use the data, when, and for what decisions increases its practical value.

The benefits of pre-inspection surveying are not limited to the day of the inspection. By comparing with past data, it becomes easier to track changes in weeds, drainage, terrain, fences, and access/maintenance roads. It can also be used for checks after disasters or heavy rainfall, for recording the current condition before equipment updates, and for before-and-after comparisons of repairs. Because solar power plants are facilities operated over the long term, recording conditions at each inspection and establishing a system to capture changes contributes to stable operation.

However, drone surveying cannot fully replace all inspection tasks. It is necessary to separate information that can be obtained from the air from information that can only be verified on the ground. In practice, drone surveying is best used as a means to narrow down inspection targets, streamline on-site verification, and strengthen the persuasiveness of reports. By combining survey data with on-site verification results, you can gain a more three-dimensional understanding of the power plant’s condition.

To connect drone surveying of solar power plants with improved inspection quality, it is important in the preparation stage to clarify the objectives and to create a flight plan and deliverable design suited to the site conditions. Simply organizing which area to capture, what level of accuracy is required, and how the data will be used for inspection can greatly change the ease of use after capture. A small amount of preparation before the inspection reduces uncertainty on the inspection day and results in data that are useful for reporting and future management.

If you want to make site condition assessment, pre-inspection checks, and the accumulation of maintenance data more practical, it is important to consider the process as a single continuous workflow from surveying through to data use. By establishing a drone surveying system that is easy to use on site, inspections of solar power plants become more efficient and easier to explain. As a next step, if you want to further improve on-site surveying accuracy and data utilization, select equipment and software that match your company’s inspection objectives, the scale of the power plant, the required deliverables, and your operational structure, and concretize an operational method that can be continued without strain.