4 Ways to Improve Inspection Routes for Solar Power Plants with Drone Surveying

Inspections of solar power plants are essential for the early detection of anomalies in power generation equipment, overgrowth of vegetation, drainage failures, deformations of slopes and pathways, trespassing, and fence damage. On the other hand, plant sites are often large and undulating, and panel rows, racks, access roads, drainage channels, slopes, and fences are frequently arranged in complex layouts. Relying solely on traditional on-foot inspections can make it time-consuming to cover the same locations each time, increasing the likelihood of oversights and variability in inspection quality.

A practical option is drone surveying for solar power plants. By using aerial photographs, orthomosaic images, elevation data, and geotagged records captured from above, you can reassess inspection routes in terms of safety, efficiency, and inspection accuracy while gaining an overview of the entire site. This article explains four ways operational personnel can improve solar power plant inspection routes using drone surveying.

Table of Contents

• Why drone surveying helps improve patrol routes

• Method 1: Organize inspection targets by taking an overview of the current situation

• Method 2: Reconfigure the safe route based on elevation differences and passage conditions

• Method 3: Divide key inspection areas and set patrol priorities

• Method 4: Continuously improve by overlaying patrol logs with survey data

• Considerations when improving inspection routes in drone surveying

• Summary

Why Drone Surveying Helps Improve Patrol Routes

A solar power plant’s patrol route is not simply something that allows you to walk around the site. It is important that generating equipment can be inspected safely, that locations prone to abnormalities are not overlooked, that travel time is not increased unnecessarily, and that patrols can be conducted without difficulty even when conditions change, such as after rain or during periods of heavy vegetation growth. Especially in large-scale plants or plants on slopes, places that look close on a drawing can in reality be difficult to reach because of embankments, waterways, level differences, mud, fences, or rows of mounting racks.

By using drone surveying, you can check the overall condition of a power plant from above. It makes it easier to organize, like a single current-condition map, aspects that are hard to grasp from ground level: the arrangement of panel rows, the continuity of maintenance walkways, the spread of vegetation, drainage routes, the condition of slopes, and the relationship with surrounding boundaries. This makes it easier for inspection personnel to design routes objectively based on current conditions, rather than walking each time relying only on experience.

On foot patrols, personnel tend to keep following routes they are familiar with. While familiar routes may seem efficient, they can create locations that are deprioritized for inspection, areas that are hard to see, or spots that are unconsciously avoided because they are difficult to access. Reviewing aerial imagery and terrain data obtained from drone surveying makes it easier to detect such patrol biases. For example, along perimeter fences, at drainage channel junctions, beneath slopes where vegetation grows easily, behind rows of panels, and among groups of racks set away from access roads are places where inspection frequency can drop during normal patrols.

Additionally, the condition of a solar power plant changes with the seasons. From spring to summer, vegetation can become more overgrown, narrowing the width of pathways. After heavy rain, sediment and puddles can remain in drainage channels and low-lying areas. In regions with snowfall or freezing conditions, the routes available for inspection may change depending on the season. Conducting regular drone surveys allows these changes to be recorded and used to update inspection routes.

Improving patrol routes is not an initiative solely to shorten working time. It is site management aimed at enhancing safety, standardizing inspection quality, and enabling early detection of abnormalities. Drone surveying helps by visualizing the entire site and providing more information to support patrol decision-making. However, capturing images with a drone does not eliminate the need for patrols. It is important to distinguish information that can be obtained from above from information that can only be determined through close-up, on-the-ground inspections.

Method 1: Get an overview of the current situation and organize inspection targets

The first way to improve patrol routes is to use drone surveying to obtain an aerial overview and organize the inspection targets. At a solar power plant, there are many items to check—not only panels and mounting racks, but also junction boxes, collection equipment, access roads, drainage channels, retention ponds, slopes, fences, gates, signage, cable routes, areas requiring grass cutting, and so on. Trying to grasp all of these solely through ground patrols tends to rely on the inspector’s memory and past paper drawings.

Using aerial images and georeferenced current-condition data created by drone surveying makes it easier to organize the positional relationships of inspection targets. First, check how the access road extends from the site entrance, which passages exist between panel rows, where along the perimeter fence walking is possible, and which direction the drainage facilities flow. Then, separate the locations to always check during inspections, the locations to check depending on conditions, and the locations to check additionally when abnormalities occur.

If this organization is not in place, inspection routes become haphazard. You end up only checking equipment near the entrance and may neglect drainage channels at the back of the site or inspections along fences. Conversely, trying to visit every location with the same intensity each time can take more time than necessary. By taking an overview of the current situation and classifying inspection targets, it becomes easier to separate routes by purpose—daily patrols, periodic inspections, post-rain inspections, inspections before and after weeding, and checks after construction.

For example, for daily patrols, routes that allow a brief check of the exterior of power generation equipment, main access routes, gates, parts of fences, obvious vegetation contact, and puddles are suitable. On the other hand, periodic inspections require routes that cover the site perimeter, drainage routes, slopes, the rear side of panel rows, and the ends of racking rows that are not usually accessed. After heavy rain, it is more reasonable to prioritize checking low-lying areas, junctions of drainage ditches, places prone to sediment inflow, and the lower parts of slopes.

The advantage of drone surveying is that such route design can be carried out based on current conditions rather than relying solely on intuition. By viewing aerial images, you can grasp where the inspection targets are distributed within the site and plan the order of movement. If you distinguish the orientation of the panel rows, aisle widths, passageways between mounting racks, areas accessible to vehicles, and areas that can only be inspected on foot, patrol personnel will be less likely to get lost.

Also, when organizing inspection targets, it is important not to rely solely on design drawings or construction drawings. At solar power plants, the way paths are used can change during post-construction operations; some routes may become easier to walk due to weeding, while others may become harder to pass because of vegetation or sediment. Paths shown on drawings are not necessarily safe to walk on in the field. By overlaying the latest site conditions obtained from drone surveys, inspection routes can be brought closer to actual conditions.

When organizing inspection targets, it is also necessary to standardize the notation of names and locations. On site, the same place may be called different things by different people, such as "north slope," "back of the upper terrace," or "rear of the 3rd row." This makes handing over records and sharing information about abnormal locations difficult. Based on drone survey data, organizing plot names, row numbers, aisle names, perimeter directions, and the positions of drainage facilities makes it easier to link inspection records with on-site verification.

What matters in this approach is not to let drone surveying end as mere photography. Rather than looking at the captured images and stopping at "we understand the whole," you need to concretely identify inspection targets and drill down to which locations should be checked and how frequently. Conducting a bird's-eye overview of current conditions, classifying inspection targets, and reflecting them in routes will lead to a reassessment of inspection operations.

Method 2: Reconstruct a safe route based on elevation differences and passage conditions

The second way to improve patrol routes is to use drone surveys to assess elevation differences and passage conditions and to redesign safer routes. Solar power plants are not always installed on flat ground. On sites such as former forest land, reclaimed land, sloping terrain, properties with level changes, and valley topography, movement during patrols can itself be burdensome. Especially after rain or during the summer growth season, slippery slopes, muddy paths, hard-to-see steps, and drainage ditches hidden by grass become hazards.

In drone surveying, it is sometimes possible to create data that captures not only aerial images but also elevation differences and terrain undulations. This makes it easier to determine which direction patrol personnel are ascending or descending, whether they are crossing steep slopes, or whether they are taking unsafe shortcuts. A route that appears short on a map may, in reality, have large elevation differences and be unsuitable for patrol. Conversely, a slightly longer route with gentler gradients and more stable footing can be safer and, as a result, lead to more consistent patrol quality.

When planning safe routes, it is important not to use the shortest distance as the only criterion. For inspections of solar power plants, being able to walk continuously without strain is more important than having a short travel time. Routes that descend a steep slope and then climb again, routes that cross grass-covered slopes, routes that repeatedly cross drainage ditches, and routes that pass through narrow gaps between panel rows increase fatigue and the risk of falls for inspection personnel. By using drone surveys to check the terrain and passage conditions and changing routes to avoid hazardous areas, accidents during inspections can be prevented.

At power plants with significant elevation differences, work efficiency can vary greatly depending on whether inspections are carried out one-way from the upper tier to the lower tier, whether sections are visited in order of proximity to the entrance, or whether patrols begin on foot after proceeding as far as vehicles can go. By reviewing drone survey data and considering the patrol start point, turnaround points, locations for breaks and record checks, and routes that allow an easy return in an emergency, it becomes easier to create a patrol plan suited to the site.

Moreover, passage conditions are not determined by terrain alone. The width of maintenance roads, the condition of road shoulders, vegetation growth, the flow of rainwater, the location of drainage facilities, the arrangement of mounting structures and cables, and the distance to fences also play a role. Even if aerial imagery makes a pathway appear continuous, in reality it may be overgrown with vegetation, have level differences, or be severed by drainage ditches. After identifying suspicious locations with drone surveying, it is important to carry out on-the-ground checks where necessary and reflect those findings in patrol routes.

When reorganizing safe routes, we also take into account the timing of inspections. In solar power plants, the locations of shadows and backlighting change depending on the time of day. In the morning and evening, slopes and the unevenness of pathways can be difficult to see, and in summer, fatigue from high temperatures cannot be ignored. By using drone surveys to understand the positional relationships of pathways and slopes, it becomes easier to plan inspection sequences that consider sunlight and visibility.

Furthermore, patrol routes vary depending on whether they are walked alone or divided among multiple people. On a solo patrol, you need to prioritize ease of return, ease of communication, and avoiding hazardous locations. When multiple people patrol, dividing the area into sections and deciding on rendezvous points and communication methods in advance improves efficiency. Visualizing the entire power plant with drone surveying also makes it easier to allocate areas of responsibility.

What matters with this method is to judge patrol routes not by whether they can be walked, but by whether they can be walked safely, repeatedly, and with the same quality. A slope that can be passed once may not be suitable for use in monthly patrols. Drone surveying objectively confirms the terrain and current conditions and provides the information needed to review patrol sequences so they can be carried out without undue strain.

Method 3: Divide priority inspection areas and determine patrol priorities

The third way to improve patrol routes is to use drone surveys to divide the site into priority inspection areas and set patrol priorities. Trying to inspect the entire solar power plant site at the same density every time can take too much time. However, if inspections are oversimplified, early detection of anomalies becomes difficult. What becomes necessary, therefore, is varying the intensity of patrols according to on-site risk.

Using drone surveying, you can identify, on an area-wide basis, locations within a power plant that require attention. You can confirm, from aerial imagery and topographic information, areas prone to vegetation growth, low-lying spots where drainage tends to collect, slopes where sediment is likely to flow, boundary sections that are easily approached from outside, places likely to be shaded by rows of panels, and locations with frequent vehicle or worker traffic. If you designate these locations as priority inspection areas, it becomes easier to prioritize patrol routes.

For example, in areas where vegetation proliferates quickly, issues such as shadows on the panels, insufficient walkway width, contact with fences, and intrusion routes for pests can arise. By using drone surveying to check the extent of vegetation, it becomes easier to decide which routes to prioritize walking before weeding and which routes to use to inspect the finished condition after weeding. In particular, vegetation behind rows of panels and below slopes that are hard to see from the ground can be checked from above to reduce oversights.

Areas to focus on regarding drainage are also important. At solar power plants, inspections should target clogged drains, sediment accumulation, puddles, runoff from slopes, and washout or scour of access roads. Rather than walking all the access routes in the same sequence after heavy rain, it is more practical to use drone surveys to identify locations where water tends to gather and low-lying terrain, and inspect those first. Because the routes of rainwater can be difficult to discern from the ground alone, there is value in viewing the whole site from above and reflecting that in the inspection sequence.

Fences and boundary areas are also places that should be prioritized. The perimeter is long, and it takes time to check everything on foot every time. However, locations that are easy to approach from the outside, areas close to roads or neighboring properties, places where visibility is obstructed by slopes or trees, and locations that have shown signs of damage or intrusion in the past should be inspected preferentially. Using drone surveys to get an overview of the perimeter and deciding in advance which sections to focus on during patrols makes it easier to maintain the accuracy of perimeter inspections.

When dividing priority inspection areas, consider not only the likelihood of anomalies but also the impact if they occur. Areas where shadows on panels are likely to affect power generation, areas where poor drainage is likely to lead to soil erosion, areas where damaged pathways could hinder patrols and maintenance work, and areas where fence damage could become a safety management issue should be given higher priority. Overlaying past patrol records on drone survey data makes it easier to determine which locations should be the focus of inspections.

Also, priority inspection areas are not fixed once decided. The locations that require attention change with the seasons, weather, construction, weed control, and changes in the surrounding environment. From spring to summer, vegetation; during the rainy season and typhoon periods, drainage; in winter, freezing and snow accumulation; and after construction, removal of temporary installations and the condition of walkways—the focus of inspections shifts. Regular drone surveys make it easier to update the priority areas.

Setting priorities for patrols reduces variability in judgment among personnel. Experienced staff naturally prioritize hazardous locations, but when personnel change or when working with external contractors, it can be difficult to convey which areas should be the focus. By clarifying priority inspection areas based on drone surveys, it becomes easier to standardize patrol quality.

What is important with this method is not to let locations of concern identified by drone surveys end as one-off observations. By incorporating them into patrol routes, setting the inspection frequency, and reflecting them in the items recorded, site management can actually improve. By designating priority inspection areas, you can create routes that do not miss important locations even within limited patrol time.

Method 4: Continuously improve by overlaying patrol records and survey data

The fourth way to improve inspection routes is to overlay inspection records with drone survey data and continuously review the routes. Inspection routes are not finished once created. Site conditions change, and the movements of personnel change as well. A route created initially is not necessarily optimal six months or a year later. Therefore, it is necessary to have a system to record inspection results and match them against current-condition data acquired by drone surveys.

Patrol records should note abnormal locations, the date and time of inspection, the inspector, photographs, position, response status, and the need for reinspection. When these records are linked to location information, it becomes easier to check the distribution of anomalies on drone survey data. For example, you can identify trends such as repeated sediment accumulation in the same drainage channel, rapid vegetation growth on particular slopes, recurring muddy spots on the same pathway, or persistent loosening of fences in parts of the perimeter.

When this trend becomes apparent, the points for improving patrol routes also become clear. If locations where anomalies recur are placed in the latter part of the route, consider changing the order so they can be checked in the earlier part of the patrol. If too much time is being spent on locations where anomalies are infrequent, review the inspection frequency and methods. If anomalies are concentrated in locations that are difficult to inspect on foot, it may be necessary to redesign the combination of aerial inspections using drones and ground inspections.

Overlaying patrol records with survey data can also help improve the time spent on tasks. Rather than simply shortening patrol time, you can examine which sections take longer, which movements are duplicated, and which checks can be incorporated into other routes. In a large power plant, just walking from the entrance to the far end and back can take a lot of time. By checking corridor connections and the relationships between sections using aerial data and reviewing the actual inspection points from patrol records, you can more easily reduce unnecessary back-and-forth.

As part of continuous improvement, not only past abnormalities but also changes after corrective actions are checked. By confirming whether the influence of vegetation decreased after weeding, whether puddles improved after cleaning drainage channels, whether soil runoff settled after slope repairs, and whether patrols became easier after pathway maintenance, the effectiveness of measures can be evaluated. If the same area is regularly recorded with drone surveys, comparison with the previous record becomes easier.

Be careful to keep the granularity of records consistent. If one person leaves detailed photos while another only provides text, it becomes difficult to compare them later. To make use of drone survey data, inspection records also need to be kept in a consistent format. Standardizing how locations are recorded, how photos are taken, how anomalies are classified, and how response status is written will turn the records into data that can be used for continuous improvement.

Also, reviewing patrol routes should not necessarily be completed solely by on-site personnel. This is because stakeholders such as facility managers, maintenance personnel, weed-control staff, civil works managers, and power plant operations managers prioritize different points. Using current-condition data created by drone surveying as a shared reference allows stakeholders to discuss while viewing the same site. Conditions in locations that are difficult to convey verbally also become easier to share when there are aerial images and location data.

Improving patrol routes is the accumulation of small revisions. Even changes such as altering the order from the entrance, adding priority inspection areas, avoiding hazardous slopes, using a different route only after rain, adjusting the frequency of perimeter checks, or separating vehicle movement and foot patrols—if continued—will make a difference in patrol quality. Drone surveying provides the foundation for making those revisions based on records rather than on intuition.

What's important with this method is not to simply store the survey data and stop there. You need an operational process that combines the survey data with patrol records, compares differences from the previous survey, and updates routes and inspection items. By using drone surveys before and after regular patrols, you can capture changes at the site and continuously improve patrol routes to match actual conditions.

Points to Note When Improving Inspection Routes with Drone Surveying

Drone surveying can help improve inspection routes, but simply introducing it does not automatically improve inspection quality. When utilizing it, you need to clarify the purpose of the survey, the data to be collected, the division of roles with on-site verification, and the operational rules. Especially at solar power plants, it is important to distinguish between information visible from above and information that can only be judged by approaching on the ground.

Aerial images make it easy to grasp the spread of vegetation, the condition of pathways, drainage routes, changes in slopes, and the overall situation of the perimeter, while they may not allow confirmation of fine equipment damage, the condition of wiring, abnormalities at connection points, loose bolts, or the internal condition of devices. Therefore, it is realistic to position drone surveying not as a replacement for on-foot inspections but as an aid to make on-foot inspections more efficient and better focused.

Flight planning also requires attention. Solar power plants contain panels, racking, electrical equipment, communications equipment, surrounding trees, power-transmission-related facilities, fences, and other items, so it is necessary to consider obstacles during flight and ensure safety. Before flying a drone, confirm the site's flight conditions, the surrounding environment, notification to relevant parties, any required procedures, and the safety management system. Because laws and regulations can change, it is also essential to check the latest information at the time of operation.

Also, the accuracy of data obtained from drone surveying varies depending on flight altitude, imaging conditions, how ground control points are handled, processing methods, and the site environment. If the objective is to improve patrol routes, highly accurate survey results are not necessarily required in every case. However, when using the data for position verification, area measurement, comparing terrain differences, or post-construction inspection, you should determine the required accuracy in advance. Using data with an accuracy that does not match the intended purpose can lead to incorrect judgments.

The frequency of data updates is also important. Using old aerial imagery to determine inspection routes can lead to discrepancies with current conditions. Vegetation growth, clogged drainage channels, pathway damage, removal of temporary structures, and repair work can change how walkable a site is within a few months. If you intend to use it to improve inspection routes, it is advisable to consider regular updates and ad-hoc updates after typhoons, heavy rain, or construction.

Consideration must also be given to data sharing among stakeholders. Even if there are images and drawings created by drone surveys, they will not be effectively used if site personnel cannot view them, if they are not shared with maintenance contractors, or if updated and older versions coexist. Data used to review inspection routes should be kept under version control so it is clear when they were captured, what area they cover, and which routes they have been applied to.

Furthermore, when improving patrol routes, it is important to incorporate the opinions of on-site workers. Even if a route looks good in aerial data, it may turn out to be slippery, overgrown with grass, have poor visibility of the ground, suffer from weak communication reception, be exposed to extreme heat, or make it difficult to park work vehicles. Creating candidate routes with drone surveying, verifying their practicality through ground checks, and reflecting the opinions of the responsible personnel is the safe approach.

After changing a patrol route, always integrate it into operations. Simply creating a new route map is not sufficient. Sharing with patrol personnel, updating checklist items, reviewing record formats, establishing reporting procedures for abnormal conditions, and organizing how to handle temporary routes after rain or disasters will ensure improvements take hold on site. Drone surveying is an effective means of visualizing the field, but the ultimate quality is determined by operational design.

Summary

To improve inspection routes at a solar power plant, it is important to take an overall view of the site, organize the items to be inspected, establish safe routes, define priority inspection areas, and continuously review them based on inspection records. Drone-based surveying is an effective means of grasping current conditions to support these tasks. By utilizing aerial imagery and terrain data, it becomes easier to identify imbalances in routes, missed inspections, hazardous spots, and redundant movements that are difficult to notice through on-foot inspections alone.

The first method is to take an overview of the current conditions and organize inspection targets. By checking the condition of panels, walkways, drainage facilities, slopes, fences, and vegetation from above, and separating routes by purpose—such as daily inspections, periodic inspections, and post-rain inspections—you can reduce wasted inspection effort and oversights. The second method is to reorganize safe routes based on elevation differences and passage conditions. Rather than choosing the shortest distance, selecting routes that can be walked safely and repeatedly lowers the burden on inspection personnel and reduces the risk of accidents.

The third method is to divide the areas for focused checks and determine patrol priorities. By identifying locations where abnormalities are likely to occur or where impacts would be large—such as vegetation, drainage, slopes, perimeters, and walkways—you can design patrol routes that ensure important spots are not missed even with limited time. The fourth method is to overlay patrol records with survey data and pursue continuous improvement. It is important to keep updating patrol routes while monitoring past abnormalities, changes after responses, work time, and tendencies for missed checks.

Drone surveying is not intended to replace inspections of solar power plants, but rather serves as a basis for decision-making to make inspections safer and more efficient. By separating information that can be obtained from the air from information that should be confirmed on the ground, and by organizing flight plans, accuracy, data updates, stakeholder sharing, and operational rules, you can increase the effectiveness of improving inspection routes.

If you want to review the patrol routes of a solar power plant, start by organizing the current patrol routes and the items to be checked, and begin by visualizing the current conditions with drone surveying. For large sites, sloped terrain, sites with abundant vegetation, or sites that require drainage inspections, using aerial data can help specify concrete areas for improvement. As an option to enhance patrol safety and inspection quality, consider employing drone surveying that matches the site conditions.