Five perspectives for documenting post-snow conditions at solar power plants using drone surveying

In solar power plants, it is important to check not only the snow itself but also meltwater channels left after snowmelt, movement of soil and sediment, muddy access routes, and signs of subsidence or scour around the racking. Especially at large plants, it can be difficult to grasp the overall situation from ground patrols alone, making it hard to explain where snow remains, where water is flowing from, and which sections need attention. One useful means in such cases is area-wide documentation through drone surveying.

This article outlines five perspectives that practitioners should keep in mind when documenting post-snowfall conditions at solar power plants using drone surveys. By treating the entire process—not just capturing aerial photos but also surveying power equipment, terrain, drainage, management/access routes, and producing documentation to inform recovery decisions—as a single workflow, it becomes easier to share inspection findings with stakeholders.

Table of Contents

• Purpose of recording with drone surveys after snowfall

• Viewpoint 1 Grasp the areal distribution of snow around power generation facilities

• Viewpoint 2: Record changes around the panel rows and mounting structures in chronological order

• Perspective 3 Confirm the drainage routes and the flow of meltwater

• Viewpoint 4 Confirm the safety of passageways and management circulation routes

• Perspective 5: Organize surveying results that can be used for recovery decision-making

• How to incorporate post-snowfall records into operations

• Summary

Purpose of recording with drone surveying after snowfall

After snowfall at a solar power plant, inspections are not just about whether snow remains. The items to check cover a wide range: snow remaining on panel surfaces that can lead to reduced power generation, the accessibility of maintenance walkways, clogged drainage routes, changes to slopes and prepared surfaces caused by meltwater, snowdrifts around fences, and signs of scour around equipment foundations. Walking the site to check is important, but after snowfall footing is poor and visibility is limited, so having a means to get an overview of the entire site makes it easier to assess the situation.

The advantage of drone surveying is that it can continuously record a large site from above. During routine patrols, inspectors may only be able to check areas near where they walked. On the other hand, if you create outputs such as plan views and terrain data from images captured by a drone, you can compare the condition of the entire site from the same viewpoint. This makes it easier to identify zones with heavy snowfall, zones where snow melted early, and zones where meltwater has accumulated, helping to assess risks across the entire power plant.

Also, records made after snowfall can be used not only for that day's inspection but also for future management. Trends such as snow remaining in the same locations each year, puddles forming near the same drainage channels, or certain slopes being prone to soil and debris flow can be overlooked by a single round of inspections. By continuously recording the same area with drone surveys, you can more easily prioritize facility management and maintenance and repairs by comparing current conditions with past states.

After snowfall at solar power plants, there are situations where one may feel pressured to hasten decisions about resuming power generation or restarting site inspections. However, even if things look fine at a glance, meltwater may have loosened the ground or only parts of access routes may be muddy. By adding aerial records, you can organize the situation into explainable documentation without relying solely on the experience of individual staff. This also helps multiple stakeholders—power plant operators, maintenance personnel, contractors, land managers, and others—to share the same information.

Viewpoint 1: Grasp the areal distribution of snow around power generation facilities

The first thing you want to identify at a solar power plant after snowfall is the distribution of where snow remains across the site. From ground level you can see the rows of panels and the condition of walkways directly in front of you, but it can be difficult to grasp which areas of the entire site have more or less snow. In particular, plants installed on slopes, sites with surrounding trees or structures, and sites where wind flow varies are prone to uneven snow accumulation.

In drone surveying, the entire power plant is photographed at a consistent altitude and overlap, and the images can be organized as continuous aerial views. This makes it easier to identify places where snow remains on rows of panels, where snow remains on the ground or walkways, and where drifts have formed along fences. Compared with taking only a few photos, it is characterized by being easier to explain the spatial relationships.

When assessing snow distribution, it is not enough to simply check where things look white. What matters is recording observations while considering how residual snow will affect power generation and maintenance. For example, if snow remains only along the lower edge of panels, part of the power-generating surface may be covered for an extended period. If snow remains on walkways, it affects the safety of patrols and recovery operations. If snow accumulates along fences, it can hinder perimeter inspections and drainage.

Around power generation facilities, it is useful to record the remaining snow conditions for each panel row. Even within the same power plant, the way snow remains varies with row orientation, terrain, wind effects, and the surrounding environment. If recorded from above, you can later check which areas are slow to melt and which sections should be paid attention to during patrols. Furthermore, when comparing changes in power generation, this serves as supporting information to explain the snow conditions at that time.

When shooting, the brightness of the snow surface can make images difficult to see. Because white snow reflects light easily, surface irregularities and boundaries can become hard to distinguish under certain shooting conditions. Therefore, when recording after snowfall, it is important to pay attention to the weather, time of day, the position of the sun, and how shadows fall. If possible, avoid extremely glaring times and shoot under conditions in which the boundaries of equipment and terrain are easy to discern, as this will make later checks easier.

It's important to record not only when snow remains but also when it begins to melt. Immediately after a snowfall everything may look uniformly white, but as melting progresses, places where water collects and the condition of the ground become visible. If you can record in stages—immediately after snowfall, during melting, and after melting—you can more easily identify where snow tends to remain and where water starts to flow out. Although photographing every stage each time may be difficult, being mindful of maintaining time-series records at important power plants makes it easier to improve management quality.

Viewpoint 2: Keep a chronological record of changes to panel rows and mounting structures

After snowfall inspections should record not only the snow remaining on panel surfaces but also the conditions around panel rows and mounting racks. At solar power plants, because panels are installed at an angle, snow can slide off the panels and accumulate at the lower edges or between rows. When this snow melts, water may concentrate around rack foundations and on the ground surface. Changes to the ground surface that appear after snowmelt can pose management challenges, sometimes more so than the snowfall itself.

When recording panel rows with drone surveying, it is important not only to photograph the whole area from above but also to ensure a resolution that allows the condition of each row to be distinguished. If you try to capture too wide an area at once, fine changes in individual rows and aisles become difficult to see. Conversely, if you get too close, the overall positional relationships become hard to understand. Depending on the purpose, using separate shots for overall situational awareness and for detailed inspection will create records that are practical and easy to use when reviewed later.

Items that should be recorded over time include the position of remaining snow immediately after a snowfall, puddles and wet areas during melting, and soil movement and surface roughness after melting. In particular, around the bases of mounting racks, water tends to accumulate during the melting process and the ground can become soft. Even if no major abnormalities are immediately visible, repeatedly recording the same locations will make it easier to notice changes at the next inspection.

Shadows on rows of panels and the way snow remains can look regular in aerial images. At the same time, you can also identify localized differences, such as certain rows having more remaining snow, only specific sections of the site having wet ground, or sediment accumulating in parts between rows. These differences are easily overlooked during ground patrols. By using aerial records to narrow down the sections that require attention and then performing detailed on-site inspections, you can make inspection work more efficient.

In records concerning the areas around mounting frames, it is important not to attempt to assess the load from snow solely from drone images. Drone surveying is an effective means of capturing changes in appearance and terrain, but judging structural safety requires design conditions and on-site verification. Therefore, rather than over-interpreting the information visible to drones, it is realistic to regard it as a primary source for identifying locations that may have potential anomalies.

Also, records of panel rows and around the mounting racks are useful when considering priorities for repairs and snow removal. For example, whether snow or water remains near the maintenance walkway or in a recessed section changes how work should be scheduled. If you can separate and organize sections that have a large impact on power generation, sections related to patrol safety, and sections likely to lead to drainage problems, it will be easier for stakeholders to align their decisions.

Perspective 3: Check drainage routes and meltwater flow

One thing that is easy to overlook at solar power plants after snowfall is the flow of meltwater. When snow melts, water collects in low-lying areas within the plant, drainage ditches, the toe of slopes, ruts in walkways, and depressions on graded surfaces. Unlike ordinary rain, snowmelt can continue to supply water over a period of time, causing the ground surface to remain wet for extended periods. As a result, it may lead to muddy conditions, soil and sediment runoff, clogged drainage channels, and small slope failures.

With drone surveying, you can identify from above where meltwater has collected and clarify its relationship with drainage paths. By inspecting the extent of puddles, ground that has changed color from wetness, channels where sediment has flowed, and snow or mud left around drains in the imagery, it becomes easier to infer the direction the water flowed. Even when conditions on the ground appear to be only isolated puddles, viewing from above can make it easier to read the overall water flow across the site.

When checking drainage routes, it is important to be aware of whether the drainage directions intended in the power plant's design match the actual flow of water. Even if drawings assume water will flow into drainage channels, on site water can flow in different directions due to ruts, ground subsidence, overgrown vegetation, sediment buildup, fallen leaves, or lingering snow. After snowfall is a time when such unexpected flows are especially likely to become apparent.

Particular attention should be paid to water flowing under the rows of panels and water crossing the maintenance paths. When water concentrates under the panel rows, the ground surface around the mounting foundations can change. Water crossing the maintenance paths causes erosion or muddiness of the paths, affecting the movement of patrol vehicles and workers. These effects may be noticeable from a single large event, but small changes repeated over time can gradually worsen. For that reason, it is meaningful to keep records after snowfall.

When inspecting drainage channels and gutters, it is necessary to separate information visible from above from information that should be checked up close on the ground. Even if drone imagery can confirm the location of drainage channels and how wet the surrounding area is, it may not be sufficient to fully verify details of blockages such as fallen leaves, mud, ice, or snow. In such cases, an effective workflow is to use drone surveys to extract suspicious locations and then focus on them during on-site patrols. Rather than walking the entire area at the same density, using aerial records to narrow down inspection points improves inspection efficiency.

When recording the flow of snowmelt water, it is helpful to note not only the date the photo was taken but also recent weather and temperature changes. Whether it snowed the day before, whether melting had been progressing for several days, and whether the day was clear or accompanied by rain will affect the amount of water and the condition of the ground. Attaching brief background information that cannot be read from the images alone makes it less likely that the situation will be misinterpreted later.

Viewpoint 4: Confirm the safety of aisles and management traffic routes

In post-snow inspections of solar power plants, the safety of access routes is as important as the condition of the equipment. Even if the power generation equipment shows no major abnormalities, safe patrols and restoration work can be difficult when walkways are frozen, snow remains, the ground is muddy, ruts have deepened, or walking along slopes has become hazardous. After snowfall the footing can be more unstable than it appears, so it is useful to assess the overall situation before entering the site.

Using drone surveying, you can inspect from above the access routes from the entrance to the main facilities, perimeter walkways, aisles between panel rows, paths along drainage channels, and so on. It becomes easier to organize which pathways still have snow, where water is accumulating, which areas are accessible to vehicles, and which areas require on-foot inspection. Especially at large-scale power plants, being able to grasp the condition of management routes in advance affects the safety of patrol planning.

When checking pathways, pay attention not only to white snow but also to dark, wet ground and shiny-looking areas. Places where moisture remains after snow melts can become slippery when temperatures drop. Also, on dirt pathways, meltwater can soften the surface, causing further deterioration from foot or vehicle traffic. If you record the extent of wet areas and the locations of ruts in aerial images, it will be easier to explain which areas to avoid and which may need repairs.

Recording access routes is important not only for ensuring worker safety but also for emergency response. If equipment malfunctions occur after snowfall, whether a route to the site can be secured is critical. Even if only the area near the entrance has been cleared of snow, if snow or water remains in the plant’s internal walkways, it may be impossible to reach the necessary locations. By surveying the whole site with a drone, you can plan movement routes before entering the site.

Also, the condition around fences and gates should be included among inspection items. Snow accumulation or snow removal can interfere with the opening and closing of gates, and snow may collect along fences, making perimeter inspections difficult. The perimeter tends to be checked after the central areas of the power generation equipment, but because it relates to intrusion prevention, drainage, and boundary management with neighboring properties, it is reassuring to include it in post-snowfall records.

When recording management routes with drone surveys, it's important not just to save images, but to do so in a way that makes it possible later to determine which routes are passable and which require caution. Techniques such as mapping area names and pathway names onto images, organizing capture locations, and marking hazardous spots on drawings make it easier to convey the situation to stakeholders who haven't been to the site. Safety checks tend to be described subjectively, but using aerial records allows the information to be shared more objectively.

Viewpoint 5 Organize as survey results usable for recovery decision-making

Post-snowfall drone surveying is not finished simply by taking photographs. What matters in practice is organizing the captured results into deliverables that can be used for restoration decisions and explanations to stakeholders. In power plant management, there are situations where multiple parties need to check conditions—not only on-site personnel but also the power producer, maintenance companies, contractors, landowners, and personnel involved in insurance and contracts. In such cases, having only a large number of photos makes it difficult to convey where the problem is, how extensive it is, and what should be prioritized.

When organizing survey results, first create an aerial image that can be used as an overall map to clarify the positional relationships within the power plant. Next, organize by section the locations where there may be remaining snow, puddles, soil movement, defective walkways, or poor drainage. This allows stakeholders to understand where the problem areas are within the entire power plant. Positional relationships that are hard to understand from site photos alone are also easier to explain when aerial records are available.

For use in recovery decisions, the capture conditions and the date and time of recording are also important. Conditions after snowfall change greatly over time. Places where snow remained in the morning may have melted by the afternoon. The flow of meltwater also changes with temperature, sunlight, and rainfall. Therefore, in the deliverables, recording the capture date, time of day, area covered, weather at the time of inspection, and the state of snow cover and melting to the extent known will make later judgments easier.

When making recovery decisions, it's necessary not only to determine whether anomalies are present but also to set priorities. By distinguishing locations with a large impact on power generation, areas affecting patrol safety, sites where leaving them unattended could lead to further terrain changes, and places likely to recur at the next snowfall, it becomes easier to establish a response policy. Using the results of drone surveys allows you to consider which locations should be checked first while showing the position and extent of each site.

However, there are limits to the information that can be obtained from drone surveying. Even if something can be confirmed in aerial images, the condition of the ground below or the internal state of structural members cannot be determined directly. Steps or small damage hidden under snow may also be invisible at the time of imaging. Therefore, survey results should be treated as one piece of information for recovery decision-making, and it is important to combine them with on-the-ground checks or specialized inspections as needed. Rather than making definitive conclusions based solely on drone surveying, it is more realistic to use it for broad situational awareness and focused verification.

When producing deliverables, it is also important not to make them overly complicated. In practice, materials that are clearly organized with an overall diagram, points of concern, on-site photos, and response policies can be easier to use than documents that are too detailed. You should decide the necessary level of granularity based on the scale of the power plant and the number of stakeholders. Keeping detailed survey data and compiling materials that are easy to use on site are separate tasks. By being mindful of both, post-snowfall records become not merely photo management but a basis for maintenance decision-making.

How to incorporate post-snowfall records into operations

To use drone surveying effectively after snowfall, it's important to set operational procedures in advance rather than scrambling to capture images once the snow falls. Decide in advance the snowfall threshold for imaging, which areas to prioritize, who will decide whether to carry out the survey, and who will receive the results after imaging; doing so makes it easier to act when snowfall actually occurs.

The first thing to consider is the standard imaging coverage. It may be ideal to photograph the entire power plant each time, but depending on site conditions you might also operate by focusing on the entrance, maintenance access paths, drainage channels, low-lying areas, slopes, and representative sections of the panel rows. If you know areas where snow tended to remain in the past or where water tends to accumulate, prioritizing the recording of those areas will increase the effectiveness of inspections.

Next, it is important to prepare baseline data from before the snowfall. Looking only at images taken after it snows can make it difficult to judge how much conditions have changed compared with normal times. Recording aerial images from the snow-free season and from routine patrols, the condition of site surfaces, the locations of drainage channels, and the condition of pathways will make it easier to compare changes after snowfall. Post-snowfall surveys are most valuable when there are records from normal conditions.

When planning a shoot, sufficient consideration must also be given to safety. After snowfall, conditions such as slippery takeoff and landing areas, unstable winds, poor visibility, and changes in appearance due to reflections off the snow surface can coincide. Rather than forcing a shoot, it is necessary to proceed only after confirming the aircraft’s flight conditions, the surrounding environment, the safety of workers, and considerations for third parties. Even within a power plant, attention should be paid to surrounding roads and neighboring properties, transmission and distribution equipment, trees, and other hazards, and safety management should be implemented according to on-site conditions.

When incorporating into operations, you also need to define the post-capture verification procedures. If it is unclear who will review the captured data, what criteria will be used to extract areas of concern, and in what format they will be shared, you will end up merely accumulating records that are not used. Because time is critical when responding after snowfall, it can be effective to share rough areas of concern on the day of capture and, if necessary, organize detailed results later as a phased operational approach.

Furthermore, records after snowfall can also be used for annual management. By comparing post-snowfall images from year to year, locations where snow tends to remain, where meltwater tends to concentrate, and where pathways tend to deteriorate become apparent. These trends can inform drainage improvements, pathway repairs, weed-control planning, reviews of inspection frequency, and preparations before snowfall. Accumulating them as maintenance and management data for the power plant, rather than treating them as one-off inspections, helps prevent future problems.

When sharing information with stakeholders, it is important not to rely too heavily on specialized surveying terminology. Indicating areas of concern on aerial images and drawings, and attaching site photos and brief explanations, makes the information easier to understand for people who have not visited the site. For example, it is effective to visually show which plots have a lot of residual snow, which pathways are difficult to use, and which drainage routes are collecting water. The results of drone surveys become more useful when treated not just as materials for engineers but as documents for everyone involved in power plant management to share situational awareness.

Summary

When recording post-snowfall conditions at solar power plants, it's important not only to check whether snow remains, but to consider the power generation equipment, the areas around mounting racks, drainage routes, maintenance access routes, and the compilation of documentation that can be used for recovery decision-making as an integrated whole. By utilizing drone surveying, you can record large power plants from the air as area-wide records, making it easier to organize snow distribution and meltwater flows that are difficult to grasp through ground inspections alone.

In particular, leftover snow on each panel row, changes around the racking foundations, muddy walkways, puddles around drainage channels, and snow drifts along fences are points you don’t want to overlook when managing a power plant after snowfall. Keeping these as aerial records makes it easier to prioritize on-site inspections and to explain the situation to stakeholders.

At the same time, rather than trying to make all judgments based solely on drone surveys, it is important to combine them with on-site inspections and specialized examinations. Information visible from above is well suited to gaining a broad overview and identifying areas of concern. For details and structural assessments that can only be confirmed on the ground, conducting additional checks as needed leads to more reliable management.

Records after snowfall are valuable not as one-off inspection documents but as historical data that can be used for operation and maintenance of the power plant. By comparing records from normal conditions with those taken after snowfall and identifying annual trends, you can apply the findings to pre-snow preparations, drainage improvements, pathway repairs, and revisions to inspection plans. To clearly preserve post-snowfall conditions at a large solar power plant, it is important to combine aerial records from drones with on-the-ground checks and organize them in a form that is easy to use as decision-making material.