6 Key Points for Using Drone Surveying in Routine Inspection Records of Solar Power Plants

In routine inspections of solar power plants, it is important to continuously record changes over a wide area—not only the condition of the power generation equipment itself but also the site, slopes, drainage, access roads, fences, and around mounting structures. Photographs and inspection forms taken during patrols alone can make it difficult to later explain where, to what extent, and since when changes have occurred. One useful method for this is drone surveying, which can capture the current condition from above as a planar record. By incorporating drone surveying into routine inspection records, you can objectively preserve the site’s condition and more easily organize materials for sharing among stakeholders, repair decision-making, and future comparisons.

Table of Contents

• Why drone surveying is useful for periodic inspection records of solar power plants

• Key point 1: Decide the inspection purpose and the scope of records first

• Key point 2 Standardize imaging and surveying conditions so they can be compared each time

• Key point 3: Record changes across the entire site, not just around the panels

• Key Point 4: Retain inspection photos linked to location information

• Key Point 5: Organize anomalous locations in a format that enables chronological comparison.

• Key point 6 Combine on-site inspections and drone surveying to make judgments

• Approach to Utilizing Periodic Inspection Records as Management Documents

• Summary

Why Drone Surveying Is Useful for Periodic Inspection Records of Solar Power Plants

Regular inspections of solar power plants are conducted to keep equipment operating stably and to identify factors that could lead to drops in power generation or accidents at an early stage. Inspection targets span a wide range, including solar panels, mounting structures, electrical equipment, cables, junction boxes, fences, gates, drainage facilities, slopes, access roads, and surrounding trees. As the size of a plant increases, it becomes more difficult to check the entire site uniformly by patrols from the ground alone. A method that only photographs locations noticed by visual inspection tends to leave insufficient information when you want to review the overall picture later.

The advantage of using drone surveying for routine inspection records is that it can capture a power plant’s condition as an area rather than as discrete points. Patrol photos are well suited to detailed checks of individual locations, but if the camera position and orientation are not consistent, comparisons with previous inspections become difficult. By contrast, images taken from above by drones and the orthophotos, point clouds, and 3D models derived from them become records that make it easy to get an overview of the entire site layout and its changes. This makes it easier to understand, together with their positional relationships, issues such as misaligned panel rows, slope deformations, clogged drainage paths, the extent of weed proliferation, and deterioration of access roads.

During regular inspections, it is important not only to identify whether there are abnormalities but also to be able to explain whether those abnormalities are progressing or have remained unchanged. For example, small slope failures or traces of poor drainage can be difficult to judge for urgency from a single inspection. However, if the same area is surveyed regularly with a drone, it becomes easier to compare whether the affected area has expanded since the previous inspection, whether water flow has changed after rainfall, or to what extent weed coverage has increased. This provides useful clues for prioritizing maintenance.

Also, in managing solar power plants, there are situations where the status must be explained to multiple stakeholders such as power producers, maintenance and inspection companies, construction companies, landowners, and insurance stakeholders. Records that only people who visited the site can understand tend to lead to subjective judgments. An overall record from drone surveying makes it easier to convey the situation to stakeholders who did not visit the site. By attaching overview images and geotagged anomaly locations to periodic inspection reports, you can clarify where the problem is and which area was inspected.

However, conducting drone surveying does not automatically produce good inspection records. If you shoot without a clear purpose, you may end up with many images that are hard to use when needed. To utilize them as regular inspection records, it is important to decide in advance what you will verify by flying, what area you will record each time, and in what format you will store the data. Also, before flying you must confirm the relevant laws and regulations, the facility manager’s rules, the surrounding environment, and safety conditions. Below, we explain in order six key points for using drone surveying for regular inspection records of solar power plants.

Key Point 1 Decide the inspection purpose and the scope of records first

When using drone surveying for routine inspection records, it is important to clarify the inspection purpose from the outset. Simply photographing a power plant from above can make it hard later to determine what the footage is meant to verify. Depending on whether the purpose is to capture the current condition of the entire site, to check changes in slopes or drainage, to determine mowing boundaries, or to document post-construction maintenance, the area to be photographed, the required resolution, and the items to be recorded will differ. By deciding the purpose first, you can reduce unnecessary shooting and produce results that are easy to use in inspection reports.

In a solar power plant, it is not sufficient to look only at the panel surfaces. Around the generation equipment there are locations that should be kept as inspection records, such as maintenance roads, drainage channels, retention ponds, slopes, neighboring property boundaries, fences, gates, vegetation, and cable routes. Especially at plants installed in mountainous or sloped areas, small slope failures, soil runoff, clogged drains, concentrated rainwater, and encroaching weeds or fallen trees can lead to operational risks. When conducting drone surveys, it is important to record not only the panel area but the full area managed as part of the power plant.

When deciding the areas to record, it becomes easier to operate if you separate the areas that must be photographed every time from the areas to be photographed additionally as needed. The areas that must be photographed every time are locations necessary for long-term comparisons, such as the entire site, main panel rows, maintenance roads, drainage routes, fence lines, and slopes. The areas to be photographed additionally include locations that were flagged in the previous inspection, places where damage or deformation is suspected after typhoons or heavy rain, and locations where mowing or repair work has been carried out. By dividing the areas in this way, you can maintain the efficiency of regular inspections while making it easier to prevent omissions in recording important locations.

Inspection objectives and the scope of records should be shared not only with on-site personnel but also with the managers and power generation operators who will receive the report. Even if on-site staff believe they have checked details thoroughly, if the information differs from what management wants to know, rechecks or additional explanations will be necessary. For example, what managers may want to know could include not only visual changes to the power generation equipment but also the condition of the land, impacts on neighboring properties, the post-disaster situation, and changes before and after repairs. If the purpose of the records is agreed upon before inspection, the results of drone surveys will be easier to use as reporting materials.

Also, when determining the coverage area, confirm flight safety at the same time. By identifying in advance power lines, trees, nearby buildings, roads, potential public access, wind conditions, takeoff and landing locations, and so on, you can develop a realistic inspection plan. Solar power plants cover large sites and may have elevation changes and obstacles depending on the location, so a flight plan adapted to the on-site conditions is necessary. To improve the quality of inspection records, it is essential to determine the area where imaging can be performed safely and stably.

Key Point 2 Ensure imaging and surveying conditions are consistent for repeatable comparisons

The value of periodic inspection records lies in being able to compare them with the previous and past records. Therefore, in drone surveying it is important to record under as similar conditions as possible each time. If flight altitude, coverage area, image overlap, flight path, imaging direction, handling of reference/control points, and output formats vary each time, it becomes difficult to determine whether visual differences are actual changes or simply differences in imaging conditions. When used for periodic inspections, a survey plan that ensures reproducibility is required.

What is particularly important is to record the same area with the same level of granularity. If, for example, you photographed the entire site roughly from a high vantage point last time but this time photographed only part of it in detail from a low position, it becomes difficult to make overall comparisons. Conversely, if you record the whole area under the same basic conditions each time and only add detailed shots of the necessary parts, you can check both overall changes and the details of individual locations. Establishing a standard inspection route and standard deliverables for periodic inspections makes it easier to maintain recording quality even when personnel change.

The time of year and time of day when photos are taken also affect how easy they are to compare. At solar power plants, the way shadows fall can change the appearance of panel rows and the areas around the racking. Grass growth and drainage conditions are influenced by the season and weather. When recording in line with inspection cycles—monthly, quarterly, semiannually, etc.—it is desirable to photograph under as similar conditions as possible. Of course, during emergency inspections after disasters or heavy rain, it may not be possible to match conditions exactly. Even in those cases, recording the date and time of the photos, the weather, the recent rainfall situation, and the shooting conditions will make later assessment easier.

When using survey results, positional consistency is also important. When creating orthophotos or point clouds, if the reference position shifts significantly each time, overlaying with past data becomes difficult. For periodic inspections, ensure positional accuracy using methods suited to the site, and establish control points or verification points as needed. Not every inspection requires highly accurate survey results, but if you want to compare the location or extent of deformations, measures to minimize positional shifts in the deliverables are necessary.

As inspection records, it is important to retain not only the images taken but also the flight date, responsible personnel, target area, reference standards used, conditions under which the deliverables were created, and any precautions taken during the inspection. Because the results of drone surveys are visually easy to understand, one may be tempted to be satisfied with saving only the images. However, when those records are reviewed months or years later, if it is unclear under what conditions they were created, their reliability as comparative material is diminished. For periodic inspection records, it is important to standardize procedures so that basic information is retained together with the deliverables.

Key point 3: Record changes across the entire site, not just around the panels

When it comes to inspecting a solar power plant, attention naturally tends to focus on equipment such as panels and mounting racks. Of course, panel damage, tilted racks, sagging cables, and abnormalities around connection points are important items to check. However, environmental changes across the entire site also have a major impact on the stable operation of the plant. If you use drone surveying for periodic inspection records, it's indispensable to adopt the perspective of recording the entire power plant as a single management target, not just the areas around the panels.

What you especially want to check in site-wide records is the flow of water. At solar power plants, panels are often arranged on developed or sloping land, and where rainwater flows, collects, or pools can lead to soil runoff, ground weakening, scouring of maintenance roads, or clogging of drainage facilities. With aerial records it becomes easier to grasp drainage routes, muddy areas, sediment accumulation, and changes in watercourses. Water flows that can only be partially seen from the ground can be confirmed as overall connections in overhead images.

The next important point is changes to slopes and developed surfaces. Small cracks, collapses, settlements, steps, and traces of soil runoff can be overlooked even when walking the site. Especially at large power plants, it takes time to visually inspect every slope up close each time. If slopes are recorded regularly by drone surveying, it becomes easier to check whether the shape has changed since the last time, whether the extent of collapse has widened, or whether there is any relation to drainage. If signs can be detected at an early stage, it becomes easier to decide on repairs or detailed investigations.

Drone surveying is also useful for managing weeds and trees. At solar power plants, overgrown grass can not only impede inspection work but also cause shading on panels, reduced visibility around fences, clogged drainage channels, and make it harder to identify wildlife access routes. By recording regularly from above, it becomes easier to see which areas are prone to growth, how much improvement occurred after mowing, and how to define the scope for the next maintenance. The extent of spread that is difficult to convey with on-site photos alone is easier to share with aerial records.

Checking fences and the areas around neighboring property boundaries is also important as part of routine inspection records. Leaning or damaged fences, the condition around gates, encroaching trees from adjacent properties, and the relationship with nearby roads and waterways are matters that cannot be overlooked in power plant management. Recording the entire site with drone surveying makes it easier to grasp the situation near boundaries and changes in the surrounding environment. However, legal determinations or confirmations of the boundaries themselves require expert verification based on survey results and related documents. Drone survey records should be regarded as tools for understanding current conditions and as materials for consultation.

Key point 4: Link inspection photos with location information

A common issue with regular inspection records is that, although photos are retained, it can be hard later to tell where they were taken. Even images that site personnel can recognize may lose their sense of position over time. If the person in charge changes, making that judgment becomes even more difficult. Because solar power plants have many similar rows of panels, close-up photos alone often make it hard to identify the exact location. When using drone surveying, it is important to link inspection photos with location information.

Marking abnormal locations on aerial overall images and orthoimages greatly improves the clarity of inspection records. For example, slope collapses, clogged drainage channels, damaged fences, weed overgrowth, and subsidence of access roads should be made verifiable both on the site overview and in on-site photographs. This allows readers of the report to immediately grasp not only the details of the abnormalities but also where within the power plant they are occurring. It also makes it easier to provide instructions to repair contractors and to recheck during the next inspection.

When linking records to location information, it is also important to align the granularity of the records. If you assign overly detailed numbers to every small observation, record creation takes longer and it becomes harder to sustain the process. Conversely, if you consolidate important abnormal locations too much, you will not be able to identify the specific places later. In periodic inspections, it is realistic to record at the units necessary for repair decisions and ongoing monitoring. For example, if there are multiple blockages within the same drain, you can group them as a drainage system while supplementing the details with photographs.

Inspection records have value not only for locations where anomalies were found but also for areas where no anomalies were observed. This is because, if a problem arises later, you can explain what the condition was at the time of the past inspection. If there is an overall record obtained by drone surveying, it can serve as supporting material to show that no major deformation was confirmed at the time of inspection. This also helps with continuity of management and accountability. In particular, when comparing before and after a disaster, whether past data from normal conditions exists is important.

Also, when saving inspection photos and location information, you should organize file names and folder structures. Including the date taken, power plant name, inspection type, coverage, and anomaly location number will make them easier to find later. As data grows, the absence of storage rules makes it time-consuming to locate necessary records. Because drone surveys generate many images and deliverables from a single inspection, it is important to design operations that address not only record creation but also ease of storage and retrieval.

Key Point 5 Organize anomalies in a form that allows comparison over time

The main purpose of regular inspections is not just to detect an anomaly once. It is also important to understand the progression of anomalies and to prioritize responses. When using drone surveying, it is important not to let captured results end up as one-off records, but to organize them so they can be compared over time. If you arrange the previous, current, and next data so they can be viewed side by side, it becomes easier to determine whether changes have occurred.

Time-series comparisons are particularly effective for slopes, drainage, weeds, maintenance roads, sediment accumulation, and around fences. These issues may appear minor during a single inspection but can progress over time. For example, you can check whether a small slope failure is spreading with each rain, whether sediment in drainage channels is increasing, or whether the area requiring mowing is expanding. Such comparisons can be easier to explain with overview records of the same area than with on-site photos alone.

When organizing chronologically, it is effective to record the condition of each anomaly. Leaving the initial inspection date, location, description, expected impact, response status, and whether a follow-up inspection is necessary makes monitoring over time easier. Combining overview images from drone surveys with close-up photos allows you to grasp both the extent and the details of an anomaly. For repaired areas, keeping records of the condition before, during, and after repair creates documentation that is easy to use as a response history.

However, caution is needed when judging changes based solely on how images look. The appearance of the same location can vary depending on flight altitude, lighting, the condition of vegetation, and ground moisture. To perform time-series comparisons properly, keep conditions as consistent as possible and carry out on-site verification when necessary. Drone surveying is an effective means of detecting signs of change, but not all anomalies can be conclusively identified from images alone. It is important to check suspicious areas from the ground and, when necessary, escalate to a professional investigation.

Chronological management also requires a system that makes it easy to review past data. Organizing records by fiscal year, by inspection cycle, and by anomalous location so that stakeholders can quickly access the records they need makes inspection reporting and repair decisions smoother. Simply storing data is not enough to put it to practical use. Clearly managing which records are the most recent, which locations are under observation, and which responses have been completed improves the quality of periodic inspection records.

Key Point 6 Combine on-site inspections and drone surveys to make assessments

Drone surveying is effective for periodic inspection records of solar power plants, but it cannot be relied upon as a complete substitute for on-site checks. Aerial records make it easy to grasp overall changes and spatial relationships, but they may not reveal loosening of small components, the condition of connection points, cable damage, internal abnormalities of equipment, or fine surface conditions of panels. Therefore, in periodic inspections it is important to combine drone surveying with ground-based visual checks and necessary measurement work.

In practice, it is convenient to first use drone surveying to grasp the overall condition of the site, extract locations suspected of abnormalities, and then confirm the details during on-site inspections. Rather than walking the entire site and then searching for areas of concern, identifying attention points from an aerial overview improves the efficiency of on-site checks. At large power plants or plants with significant elevation differences, this approach can be expected to reduce inspectors’ travel burden while making it less likely that important areas will be overlooked.

On-site verification confirms what the changes detected by drone surveys actually represent. Areas that appear to be soil washout in images may in fact be traces of temporary puddles. Conversely, deformations that look small in images may, upon closer inspection, involve deep scour or subsidence. By cross-referencing aerial information with ground information, you can improve the accuracy of your assessments. For inspection records, it is good to record the location identified by the drone survey together with the details discovered during on-site verification.

Inspections of electrical equipment must be carried out with consideration for safety and technical expertise. Distinguish between the areas where a drone can record the external appearance and the areas that inspectors should check in person while following safety procedures. Determining abnormalities in power generation equipment involves not only visual inspection but also changes in generated power, measurement results taken during inspections, maintenance history, and other factors. Records from drone surveys should be used for understanding current conditions and as explanatory materials; the actual equipment diagnosis should be performed following the necessary procedures.

In ad hoc inspections after disasters or strong winds, combining drone surveying with on-site verification is effective. First, assess from above the extent of damage and the conditions of areas that are difficult to access, and after identifying hazardous locations, conduct on-site investigations; this makes it easier to improve the safety and efficiency of the work. However, depending on conditions such as strong winds, rainfall, the surrounding environment, and people entering the area, flight may not be possible. Rather than forcing a flight, confirm conditions that allow safe recording, and when necessary make the decision to prioritize ground inspections.

Approach to Utilizing Periodic Inspection Records as Management Documents

Periodic inspection records created from drone surveys should not be used merely as images attached to inspection reports; it is important to accumulate them as maintenance and management documentation for the power plant. If each inspection result is recorded in the same format, weaknesses and management trends specific to each plant will become apparent. Identifying locations where water tends to pool, where vegetation grows easily, where slope changes are likely to occur, and where access roads are prone to deterioration can be reflected in future inspections and repair plans.

To use inspection records as management materials, it is important to standardize their level of detail. If overall images, close-up images of key locations, location maps of abnormal areas, on-site photos, response history, and items to check next time are organized in a consistent format, it becomes easier to compare them even when managing multiple power plants. If each plant uses a different recording method, the workload increases when personnel change or when checks are performed across multiple sites. Periodic inspection records should be treated not as free-form notes for each site, but as management data that can be used continuously.

The results of drone surveys can also be used as instructional materials for repairs and mowing. Simply describing locations verbally can make it difficult to convey the scope of work and priorities. By indicating the target area on aerial images and supplementing them with on-site photos for details, it becomes easier to align understanding with workers. Recording again after repairs allows you to retain materials for before-and-after comparisons. This makes it easier to connect the maintenance management flow of inspection, decision-making, action, and verification in the records.

Drone survey records are also useful for explaining matters to stakeholders. When reporting to power generation companies, consulting with landowners, handling inquiries related to neighboring properties, or sharing conditions after a disaster, materials that are understandable to people who have not seen the site are required. Even content that is hard to convey with text alone becomes easier to understand if there are overall images and location-tagged records. The effect of aerial overview records is especially significant when explaining the extent of an area or the spatial relationships involved.

On the other hand, the more records you keep, the more data accumulates. Simply saving large numbers of images from each periodic inspection makes it difficult to find the information you need. It is important to decide in advance the types of deliverables to save, naming rules, storage locations, viewing permissions, and sharing methods. Organize records by inspection round so that the latest and past records do not become mixed and confusing, and make important anomaly locations trackable in a list to improve practical usability.

Periodic inspection records also serve as basic reference material for future renovation or equipment upgrade work. The longer a power plant is in operation, the more situations arise where you need to check past conditions. Areas that had no problems immediately after construction can show changes in drainage or vegetation several years later. With regular drone survey records, it becomes easier to trace when those changes first appeared. This also helps with repair planning, budget considerations, and defining the scope of construction work.

Summary

Using drone surveying for periodic inspection records of solar power plants makes it easy to keep a clear record of the plant’s overall condition and facilitates comparison with past records and sharing with stakeholders. When a large site is inspected only by ground patrols, records tend to be biased toward individual photos, which can make it difficult to later explain positional relationships and the overall picture. By combining drone surveying, you can capture area-wide information on panel rows, around mounting racks, slopes, drainage, maintenance roads, fences, and the extent of weeds, making the data easier to use as periodic inspection records.

The important thing is not to make taking photos the objective itself. Decide the inspection purpose and the scope of records in advance, keep conditions consistent so each session can be compared, record changes across the entire site, and link inspection photos with location information. Furthermore, organize anomalous areas so they can be compared in time series and combine that with on-site verification to make judgments; this makes drone survey results into inspection records that are useful in practice. It is important to accumulate images not just as pictures but as management materials that can be used for repair decisions, mowing plans, post-disaster checks, and explanations to stakeholders.

In the maintenance and operation of solar power plants, it is essential to grasp on-site conditions, share them clearly, and link that information to subsequent actions. Drone surveying is one effective recording method that supports this workflow. If you want to improve the quality of periodic inspections and make plant management more transparent, it is important to organize in advance the objectives, the recording scope, safety conditions, and data management methods, with an eye toward acquiring and sharing survey data that are easy to handle in the field.