5 Drone Surveying Points to Check Before Regulatory Confirmation for Solar Power Plants

When conducting drone surveys at solar power plants, it becomes easier to understand the terrain of the large site, the status of earthworks, drainage routes, slopes, access and maintenance roads, and the surrounding environment. However, whether flight is possible cannot be determined solely by the size of the site or the purpose of the work. If you proceed with planning without confirming airspace, flight operations, nearby facilities, land management authority, local ordinances, and management rules, even when the need for surveying is high you may find that flight conditions and safety management have not been adequately addressed at the implementation stage.

Solar power plants in particular are facilities with a wide range of site conditions, such as forests, former farmland, reclaimed land, riverbanks, around reservoirs/ponds, industrial parks, and locations adjacent to residential areas. At some sites, not only confirmation under the Aviation Act is required, but also considerations related to land use, forests, rivers, roads, natural parks, and nearby residents. Regulatory checks should, as a prerequisite, be confirmed with experts and relevant authorities based on the latest information, but organizing the purpose of the drone surveying and the site conditions in advance makes it easier to narrow down the points that need to be confirmed.

In this article, for practitioners searching for information on "solar power plant drone surveying," we explain five points you should review before checking regulations. Do not rely on this article alone to determine whether permits or approvals are required; instead, use it as a preparatory checklist to reduce the chance of overlooking items.

Table of Contents

• Organize the flight objectives and the survey deliverables first

• Verify the constraints on airspace and flight methods against on-site conditions.

• Expand the scope of verification for land managers and surrounding facilities

• Identify legal and regulatory issues related to terrain modification and drainage.

• Organize into a format that can be used for recording, sharing, and re-surveying.

• Summary

Organize the flight objectives and survey deliverables first

When considering drone surveying at a solar power plant, the first thing to clarify is "what are you flying for?". When it comes to regulatory checks, people tend to start with airspace and permit applications, but in practice if the flight purpose is vague the number of items to check becomes too large. Whether it is to grasp existing conditions before site development, to confirm as‑built conditions after completion, to assess topography for renovation planning, or to investigate the causes of poor drainage or scour, the required flight area, imaging conditions, flight altitude, imaging direction, and survey deliverables will differ.

For example, if you want to check level differences on a maintenance road or deformations of a slope face, simply photographing the entire site uniformly may not be sufficient. You need to focus on photographing the road shoulder, drainage ditches, catch basins, the toe of slopes, and locations suspected of settlement so the images can later be cross-referenced with on-site photos and inspection records. On the other hand, if you want to grasp overall ground surface changes across the whole site, it is important to standardize the flight route and the handling of reference points so the same area can be surveyed repeatedly under the same conditions.

Before regulatory checks, also clarify the intended uses of the survey deliverables. The imaging plan will vary depending on whether you want to update cadastral maps with orthophotos, confirm graded surfaces with 3D point clouds and elevation data, track ground-surface changes by differencing, or prepare overhead photos for reports. If you only confirm flight conditions while the deliverables remain vague, you may, after proceeding with procedures and adjustments, end up with data that are difficult to use for practical decision-making.

Also, drone surveying should be considered not only in terms of whether it can be flown, but also whether safe takeoff and landing are possible, whether assistants can be deployed, whether there is a possibility of third parties entering the area, and whether the flight would require unsafe maneuvers around power transmission equipment or mounting racks. In solar power plants, rows of panels, mounting racks, cables, fences, monitoring equipment, electrical equipment, and access roads are dispersed over a wide area. By narrowing the purpose of the flight, you can avoid unnecessary low-altitude flights and flights that are too close to equipment, and make it easier to organize both regulatory checks and safety measures.

In preliminary preparations, it is practical to divide the survey area into "areas that must be acquired," "areas to acquire if possible," and "areas not to be flown." Even when it is necessary to survey an entire power plant at once, distinguishing in advance the locations that require caution—neighboring residences, roads, rivers, forests, critical facilities, and areas near power lines—makes the items to confirm with relevant agencies and land managers more concrete. Conversely, planning to "capture the whole area" while the purpose is unclear can excessively expand the scope of required confirmations and lengthen the time needed for coordination.

Furthermore, it is important that the purpose of the flight be expressed in the same terms among all stakeholders. If the client says "inspection," the on-site personnel says "survey," and the management company says "report preparation," the actual required deliverables can become misaligned. Before confirming regulatory matters, summarizing the purpose, scope, deliverables, and use cases on a single memo will make it easier to explain when communicating with the parties you need to confirm with. The success of drone surveying depends not only on piloting on the day of the flight but also on this initial organization.

Cross-check airspace and flight method constraints with site conditions

In drone surveying of solar power plants, confirming the airspace and flight methods is particularly important. When flying an unmanned aircraft that falls under the Aviation Law outdoors in Japan, it is necessary to check no-fly zones and rules for flight methods. Aircraft weighing 100 g or more are treated as unmanned aircraft under the Aviation Law, and depending on the flight location and method, you may need to confirm permits or approvals, notification of flight plans, aircraft registration, and so on. Note that whether procedures are required varies depending on the aircraft, flight details, category, and site conditions, so checking the latest guidance is a prerequisite.

Solar power plants are often thought to be located in suburban or mountainous areas, but not all sites are equally easy to fly. Around airports and similar facilities, over densely populated areas, in airspace 150 m (492.1 ft) or higher above the ground or water surface, or in emergency-use airspace, there are site-specific conditions that must be checked. In particular, for disaster recovery, inspections of ground-surface changes after heavy rain, and emergency surveys following landslides, attention must be paid to manned aircraft activity and whether emergency-use airspace has been designated. If emergency-use airspace is designated, flights—even those for which permission has already been obtained—may be treated as not allowed, so it is essential to check immediately before flight.

When checking airspace, looking only at the power plant's site boundary is not sufficient. Even if a drone takes off and lands within the site, its flight path, turns, edges of the survey area, and emergency escape areas may approach locations outside the site. This is especially true for large-scale solar power plants, where the site may be long and narrow, extend along valleys or ridgelines, or be divided into multiple parcels separated by roads or waterways. It is important to plot not only the survey area but the entire flight plan on a map and overlay it with the surrounding airspace conditions.

Check flight-method constraints together with on-site conditions. Consider whether the flight can be conducted within visual line of sight, where assistants can be positioned, how to manage third-party access, whether you are attempting to fly at night or in conditions approaching adverse weather, and whether you can maintain appropriate distances from people and property. At solar power plants, people tend to assume no third parties will enter because the site is fenced, but in reality there may be management roads, farm roads, forest roads, inspection paths for transmission equipment, or access points to adjacent land nearby. Do not simply judge that it is safe because it is within the site; you need to check, including the movement routes of people and vehicles.

Be careful when lowering flight altitude to improve surveying accuracy. Flying lower makes it easier to inspect fine details, but it also reduces the distance to panels, mounting structures, power lines, trees, slopes, and terrain undulations. Because not only regulatory limits but also safety margins shrink, evaluate whether that altitude is truly necessary for the required deliverables. If you need detailed views of slopes or drainage channels, separating the overall survey from focused-area imaging and planning flights by purpose will reduce risk.

Also, if there are flight conditions that will likely require applications or confirmations, preparations should be made by working backward from the planned flight date. At solar power plant sites, the periods suitable for surveying can be limited by factors such as after grass cutting, inspection days, construction schedules, power outage work, maintenance operations, and checks after rain. If regulatory checks are delayed, you can end up in a situation where the site’s schedule is fine but organizing the flight conditions is not completed in time. If you organize in advance the airspace, flight method, aircraft, pilot, flight purpose, date and time, route, and safety measures, it will be easier to proceed with the necessary confirmations.

When confirming airspace and flight methods, it is important to make judgments on a site-by-site basis. Relying only on empirical rules such as "we were able to fly here last time," "we flew at the power plant next door," or "it's in the mountains so there shouldn't be a problem" is insufficient. Airspace information, nearby facilities, site usage, flight methods, the aircraft used, and the operational setup differ for each project. Before checking regulations, cross-check these items with site diagrams and make sure all stakeholders are discussing them under the same assumptions; this is the quickest way to reduce rework in later stages.

Expand the scope of verification for land managers and surrounding facilities

In regulatory checks for drone surveying, in addition to confirming compliance with aviation law, it is important to check with land managers and nearby facilities. Even when flying within the premises of a solar power plant, stakeholders may be divided among multiple parties such as the landowner, power generation company, management company, maintenance company, construction company, and neighboring landowners. You need to clarify in advance who has the authority to approve flights, whether takeoff and landing sites may be used, and how far into the site you are allowed to enter.

Solar power plants may combine areas such as sections for power generation equipment, areas for substation/transformer equipment, access and maintenance roads, balancing ponds, drainage channels, slopes, green spaces, and unused land. However, the registered land parcels, leased area, management area, and maintenance contract area do not necessarily match exactly. When establishing drone takeoff and landing points, you need to confirm that the land is actually available for use, that vehicles may be parked there, and that you will not obstruct third-party access.

Checking surrounding facilities is also essential. Under the Act on Prohibition of Flight of Small Unmanned Aircraft, etc., flights of small unmanned aircraft are restricted at designated facilities and in the surrounding area of approximately 300 m (984.3 ft). Even if an exception applies, notification to the prefectural public safety commission, etc., may be required, so if there is a possibility of being close to a designated facility, it is important to check the flight area and surrounding facilities on a map. If there are critical facilities, airport-related facilities, defense-related facilities, national government agencies, or nuclear-related facilities near a solar power plant, separate checks may be required in addition to the usual airspace confirmation.

Near a solar power plant there may be substations, public facilities, roads, railways, schools, hospitals, residential areas, tourist facilities, and so on. Even if the power plant site itself appears to be problem-free, there may be facilities within the surrounding flight area that need to be checked. Especially for large sites, part of the site may approach the zone requiring checks of surrounding facilities, so don’t judge only by the center point—assess the site perimeter and the entire flight route.

There may also be cases involving natural parks, national forests, rivers, dams, reservoirs, coastlines, ports, and airspace over roads. At these locations, in addition to the Aviation Law, it may be necessary to check the usage rules and access conditions set by facility managers, land managers, municipalities, and relevant agencies. Even if the location where a drone will be flown is within a power plant site, if the takeoff and landing locations, placement of assistants, vehicle waiting areas, or the scope of filming relate to surrounding controlled areas, they should be included in prior confirmations.

When confirming with the land manager, it is more practical to convey specific conditions rather than simply asking "May we fly a drone?" Summarize the flight date, backup date, flight time window, takeoff and landing locations, flight area, number of pilots, number of assistants, number of vehicles, purpose of use, types of data to be collected, scope of access, and whether neighbors will be informed, so the other party can more easily make a decision. Especially at solar power plants, the risk increases if inspection work, weed control, or maintenance of electrical equipment overlap, so coordination with the site schedule is also necessary.

Consideration for nearby residents and adjacent properties is something you should think about even before checking regulations. In drone surveying, even if you intend to photograph power plant equipment, adjacent houses, gardens, farmland, workshops, vehicles, and people may be captured. Even if the deliverables are intended for surveying or management, handling of image data requires caution. It is reassuring to establish operational rules in advance, such as limiting the shooting area to the minimum necessary, avoiding photographing adjacent properties unnecessarily, selecting images to be used in reports, and restricting recipients with whom data is shared.

Even if the power plant manager has approved the flight, there may be separate managers for nearby facilities or adjacent land. Forest roads, farm roads, waterways, river-management access paths, and maintenance land under power lines, etc., vary by site in terms of allowable uses and precautions. If you plan to use them as takeoff and landing locations or as places to position ground assistants, you need to confirm the land’s ownership and authority relationships. By widening your assessment of these areas before checking regulations, you can more easily avoid problems such as discovering that a location cannot be used just before a flight.

Identify legal and regulatory issues involved in terrain modification and drainage

Drone surveys of solar power plants make it easier to identify graded surfaces, slopes, drainage routes, subsidence, scouring, sediment runoff, and damage to maintenance roads by viewing the site from the air. However, this information is not merely a site-condition check; it can be linked to regulatory verifications related to land use and disaster prevention. In particular, solar power plants constructed by developing forested or sloped land may give rise to site-specific issues that need to be checked, such as the Forest Act, erosion control (sabo), river-related regulations, farmland laws, municipal ordinances, development permits, and disaster prevention agreements.

When developing forest land to install solar power generation facilities, a forest land development permit under the Forest Act may be involved. In privately owned forests covered by the regional forest plan, if development activities are undertaken for the purpose of installing solar power generation facilities, alterations to land conditions that exceed a certain scale may require permission from the prefectural governor. Whether a site is subject to these requirements depends on the area's designation status, the scale of development, timing, and individual conditions; therefore, you should not judge based solely on survey results but verify in conjunction with plans/drawings, land registration records, and administrative materials.

Whether a project falls under such a system cannot be determined by drone surveying alone. However, terrain data and images obtained by drone surveys are useful for organizing the current situation, checking slope conditions, confirming the locations of drainage facilities, and detecting signs of sediment movement. Before checking regulations, organizing which areas have undergone terrain changes, which zones are related to forests or slopes, and where drainage is flowing will provide explanatory material when consulting experts or administrative offices.

Checking drainage is also important. At a solar power plant, rainwater on the panel surfaces, surface water flowing over regraded surfaces, seepage from slopes, ditches along access roads, balancing ponds, sedimentation basins, and discharge points are complexly interrelated. By using drone surveys to understand terrain elevation differences and the directions in which water tends to flow, it becomes easier to identify inconsistencies in drainage gradients, water collection points, and locations prone to scour. These should be assessed in combination with on-site inspections and a review of the design documents.

However, there are limits to the information that drone surveying can reveal. Photographs and three-dimensional data can capture trends of the ground surface, but they may not directly confirm underground drainage, culverts, soil properties, the internal condition of structures, sliding within slopes, or the causes of blockages in drainage facilities. Therefore, rather than treating drone survey results as a "confirmation of anomalies," it is more practical to position them as "materials for extracting candidate locations that should be checked on site."

Before conducting a regulatory review, it is helpful to consider which regulatory issues the topographic data might relate to. For example, the extent of fills and cuts, slope gradients, outlets of drainage facilities, traces of sediment having flowed off-site, connections to rivers and waterways, impacts on adjacent properties, collapse of maintenance roads, and sediment accumulation in detention basins may, even if they appear to be mere maintenance issues, lead to questions about disaster prevention and land use. Organizing these on a map makes it easier for stakeholders to share the same understanding of current site conditions.

In particular, at existing solar power plants, the as-built drawings at completion may not match the current site conditions. Settlement after land development, scouring after heavy rain, clogged drainage channels, sediment accumulation, repairs to access roads, additional fill, and the presence of temporary passageways can all change the current situation. Conducting a drone survey to capture the current conditions before legal and regulatory checks makes it easier to find changes that cannot be seen from the drawings alone.

Also, if refurbishment or expansion is planned, drone survey results can be used not only for planning studies but also to check impacts on existing facilities. When creating new drainage channels, widening maintenance roads, repairing slopes, changing panel layouts, or relocating fences, surrounding land use and drainage routes may change. If you capture the current topography before regulatory checks, it becomes easier to determine the scope of what should be reviewed.

Drone surveying does not substitute for legal judgments themselves. However, it can be an effective means of organizing the on-site information needed for regulatory checks. By identifying issues related to terrain alteration and drainage early, it becomes easier to choose which authority to consult, prepare documentation, attend on-site inspections, and determine whether additional surveying is required.

Organize into a format suitable for recording, sharing, and re-surveying

For drone surveys conducted before regulatory confirmation, it’s important not to consider the job finished once the photos are taken. In managing solar power plants, there are many situations where you need to compare data from multiple points in time—not only the initial survey results but also data from several months later, after heavy rains, after repairs, and before and after renovations. For this reason, you should record the flight plan, shooting conditions, survey area, control points, deliverables, and items to be checked so that they can be verified under the same conditions next time.

The basics of record-keeping are to document when, where, for what purpose, and under what conditions the survey was conducted. Organize the flight date, weather, wind conditions, flight area, takeoff and landing locations, pilot, assistants, access control methods, subjects photographed, types of deliverables, coordinate system and reference points used, and any observations or cautions noticed on site. If these are not recorded, when reviewing only the deliverables later it will be difficult to tell whether they provide information usable for regulatory checks or field decision-making.

In solar power plants, because there are many stakeholders, it is also important to make materials easy to share. Power plant operators, management companies, maintenance companies, construction firms, designers, and experts who provide administrative consultation each want slightly different information. Site personnel may want to see paths of easy passage and hazardous spots, while designers may want to see terrain and drainage. Managers may want to grasp the overall picture as a report. Drone survey deliverables become more useful when they are organized in an easy-to-view manner by intended use.

As pre-regulatory materials, a map showing the overall location of the power plant, the planned flight area, takeoff and landing locations, adjacent facilities, roads, rivers, waterways, forests, residences, potentially important facilities, and access-controlled areas is useful. It is important not only to include detailed survey results but also to prepare materials that make at a glance the issues that need to be checked. When consulting experts and relevant authorities, progress is more likely if you show the specific area and purpose rather than simply saying, "We want to fly a drone at a solar power plant."

In data management, file names and storage locations should not be overlooked. In drone surveying of solar power plants, multiple types of data are generated, such as images, videos, orthophotos, point clouds, elevation data, reports, site photographs, flight plans, and inspection notes. Organizing them so that the project name, power plant name, survey date, survey purpose, scope, and version number are clear will reduce the effort of searching later. It is especially important to keep documents related to regulatory checks in a way that anyone can understand the background and sequence of events.

When planning for a re-survey, consider whether the same conditions can be reproduced. To track changes in the ground surface, subsidence, scouring, and poor drainage, it is essential that the previous and current data can be compared. If flight altitude, imaging coverage, timing of capture, vegetation growth, control points, or processing conditions change significantly, it becomes difficult to determine whether the differences are actual changes or due to differences in surveying conditions. It is important to record the conditions necessary for the next comparison at the time of the initial survey.

Records related to regulatory compliance also tie into on-site safety management records. Keeping documentation of pre-flight checks, notifications to relevant parties, access control, perimeter checks, decisions to abort flights, and contact information for incidents makes it easier to plan future operations. On large sites such as solar power plants, the person in charge may change. For continuous management, it is essential to ensure handover through records rather than relying on the predecessor’s experience.

The results of drone surveys can be used not only for regulatory compliance but also for routine inspections, maintenance planning, retrofit planning, and post-disaster recovery planning. To do this, captured data must be organized not as a mere collection of photos but as information that can be used for on-site decision-making. Linking acquired data with location information, the intent of the imaging, inspection results, and points to check on the next inspection makes the materials easy to use in the practical management of power plants.

Summary

When considering drone surveying before regulatory checks for a solar power plant, it is important not to decide based solely on whether flight is possible. First, organize the flight objectives and deliverables and clarify what the survey is intended to confirm. Next, review airspace and flight-method constraints against site conditions, and identify issues related to required procedures and safety measures. In addition, you need to look beyond aviation law to verify matters such as land managers, surrounding facilities, national parks, state-owned forests, rivers, roads, and adjacent properties.

Solar power plants occupy large sites, yet site conditions vary greatly from one location to another. For installations developed by clearing forested land, those close to residential areas, those near rivers or reservoirs, facilities within industrial parks, and projects that involve refurbishing existing installations, the points that need to be checked differ. Drone surveying is an effective means of grasping current conditions, but it does not automatically handle judgments about laws and management rules. That is precisely why clarifying objectives before surveying and organizing records after surveying are important.

In practice, before consulting experts or relevant authorities about regulatory matters, assembling the flight area, takeoff and landing locations, surrounding facilities, land managers, deliverables, terrain alterations, drainage routes, and shared documents makes the review process easier. Conversely, if these items are unclear when you consult, additional checks may be required, which can affect survey schedules and maintenance workflows. This difference in prior organization becomes especially apparent for inspections after heavy rainfall, pre-renovation surveys, completion verifications, and management map updates, where decisions must be made within a limited time.

Drone surveying of solar power plants is not merely the act of viewing a site from above; it is also the creation of foundational materials that support plant maintenance, disaster prevention, regulatory compliance checks, and stakeholder briefings. To fly safely and produce usable deliverables, it is essential to carefully connect site conditions with the items to be checked. By standardizing preparations before regulatory checks, the results become easier to use not only for initial surveys but also for re-surveys and retrofit planning.

To efficiently understand the current conditions of a large solar power plant and connect that understanding to regulatory checks and maintenance decisions, it is important to establish a drone surveying setup that is easy to operate on site. By treating the sequence from acquiring survey data through organizing, sharing, and comparing it with the next survey as a single workflow, on-site personnel can make more consistent decisions. Rather than relying solely on specific equipment or service names, choosing methods that fit site conditions, regulatory checks, safety management, and the intended use of the deliverables is a safe way to present information in a practical pre-publication article.