5 Perspectives for Assessing Candidate Sites for Solar Power Plant Development Using Drone Surveys

When evaluating potential sites for solar power plant development, relying only on desk-based research can lead to discovering issues once you're on-site—such as the amount of earthworks required, drainage, access roads, the surrounding environment, and maintainability. It's important to grasp not only the site's area and solar irradiation conditions, but also topographic variation, slope conditions, existing structures, the relationship with adjacent properties, rainwater flow, and future inspection routes. Drone surveying is useful for capturing a wide candidate site from above and organizing materials for development decisions based on photographs and point cloud data.

This article explains, for practitioners, five perspectives to check when investigating potential solar power plant sites using drone surveying.

Table of Contents

• Why drone surveying is useful for surveys of potential development sites

• Perspective 1 Understand terrain undulations and land development risks

• Perspective 2: Confirm the flow of water related to the drainage plan

• Perspective 3: Consider panel placement and maintenance access routes

• Perspective 4 Organize risks related to the surrounding environment and boundaries

• Perspective 5: Preserve as baseline data usable for future inspections

• How to Use Drone Surveying to Inform Candidate Site Selection

• Summary

Why drone surveying is useful for development site investigations

When evaluating potential sites for solar power plants, we typically consider a combination of cadastral maps, topographic maps, aerial photographs, existing documents, and on-site surveys. These are indispensable for understanding an overview of a candidate site, but they may not fully reveal actual surface undulations, vegetation conditions, drainage flows, locations where maintenance roads could be routed, or how the site interfaces with surrounding features. In particular, in forests, developed-but-unused land, sloping terrain, fallow land, or land being considered for conversion from agricultural use, areas that look flat on drawings can, on the ground, have small steps or depressions, muddy patches, insufficient drainage ditches, or easily erodible slopes.

Drone surveying is characterized by its ability to capture the entire candidate site from above and to organize the data not only as photographs but also as three-dimensional terrain information. In surveys conducted by people on foot, the areas inspected inevitably tend to be biased toward locations that are accessible. Places with dense vegetation, the lower parts of slopes, low-lying areas toward the back of a site, and areas near boundaries with adjacent properties are easily overlooked during a short on-site inspection. By using drones, you can obtain an aerial overview of the whole candidate site and later review, with images and point clouds, any spots that caught your attention during the site visit.

At solar power plants, not only power generation but also site development costs, drainage measures, racking installation, maintenance access routes, material delivery, disaster risk, impacts on neighboring communities, and the ease of future inspections affect project viability. If these factors can be roughly grasped at the early stage of site selection, it becomes easier to sort which sites should be developed, which require additional investigation, and which should be considered for early abandonment. Drone surveying does not by itself decide development feasibility, but it is an effective means of increasing the information available for decision-making and of sharing a common on-site understanding among stakeholders.

Also, in candidate site surveys for solar power plants, multiple stakeholders inspect the land from different perspectives. Project planning personnel look at area and layout efficiency. Design personnel check topography, earthworks, and drainage. Construction personnel assess access roads for deliveries and work spaces. Operations and maintenance personnel consider inspection routes after completion and the ease of mowing. When aerial images and three-dimensional data produced by drone surveys are available, each stakeholder can discuss while looking at the same materials, making it easier to reduce discrepancies in understanding.

When evaluating candidate sites, since this is still the stage before detailed design begins, it is not necessary to determine everything with high precision. However, terrain conditions overlooked at this early stage can lead to major rework later. For example, part of the site may be lower than expected and prone to collecting rainwater; slopes may be steep and expand the area of earthworks; a location where you thought panels could be placed may need to accommodate a maintenance road; or there may be existing drainage channels near the boundary. To discover such issues early, there is value in using drone surveying at the outset of candidate site investigations.

Perspective 1: Assess terrain undulation and land development risks

The first thing to confirm at a prospective solar power plant site is the terrain’s topography. Even if the site appears to have sufficient area, it may actually have steep slopes that make racking installation and earthworks more difficult. Plan views and existing aerial photographs alone can make it hard to discern fine undulations and steps, the boundaries between fill and cut, and traces of past grading. By using drone surveying to capture the terrain as a surface, it becomes easier to identify which areas are relatively flat and which areas have concentrated slopes or steps.

In solar power plants, a certain degree of flatness may be required to arrange panels efficiently. However, this does not mean the site must be perfectly flat; acceptable terrain conditions vary depending on the racking type, layout plan, and construction methods. Therefore, during the site survey stage it is important not to judge the terrain simply as good or bad, but to identify where and to what extent there are undulations and to clarify how they are likely to affect site development and racking design.

By checking the three-dimensional data created from drone surveying, it becomes easier to distinguish places within candidate sites that have large elevation differences, ridge-like highs, valley-like lows, areas where natural terrain remains, and places that may have been artificially developed. This allows you to separate the zones where panels can be easily installed from the zones where earthworks or reinforcement may need to be considered. Especially on sloped land, even if it appears gentle, when viewed as a continuous surface there can be risks of drainage problems or soil runoff.

When considering site development risks, it is necessary to pay attention not only to the average slope of the entire candidate site but also to localized changes in elevation. Conditions such as only the access from the road being steep, an old watercourse trace in the center of the site, signs of soil collapse along the perimeter, or slopes remaining from past earthworks can be missed by merely walking the site. By combining drone overhead imagery with topographic data, you can locate and verify these localized changes within the context of the whole candidate site.

Also, when developing a solar power plant site, it is necessary to consider not only where to place the panels but also maintenance roads, drainage facilities, material storage areas, and access routes for construction vehicles. If you evaluate candidate sites by prioritizing only panel layout, you may later find it difficult to secure effective movement routes for construction and maintenance. By using drone surveys to understand the terrain, you can more easily devise a plan from the early stages that minimizes difficulties by taking into account routes that are easy for vehicles to use, layouts that reduce earthwork quantities, and the directions in which rainwater will flow.

When checking terrain variations, it is important not only to look at point cloud data and elevation data as-is but also to cross-reference them with on-site photographs. At candidate sites with a lot of grass or trees, it can be difficult to fully capture the ground surface. Because the heights seen from above may include the height of vegetation, depending on the condition of a candidate site it may be necessary to perform supplementary on-the-ground checks or combine results with other surveying methods. Do not over-rely on drone survey results; it is important to separate the aspects that can be used for site selection from those that require additional verification.

At the stage of selecting development candidate sites, a practical point is to identify early the areas likely to require extensive earthworks before calculating earthwork costs precisely. This serves as the basis for judging whether the layout can avoid highly undulating areas, whether generation capacity can be secured while minimizing earthworks, or whether the site is feasible as a candidate at all. Drone surveying plays a role in visually and spatially supporting this initial judgment.

Viewpoint 2: Confirm the flow of water related to the drainage plan

At candidate sites for solar power plant development, confirming drainage is extremely important. While attention tends to focus on the installation of panels and mounting structures themselves, proceeding with planning without understanding where rainwater flows in from and where it flows out to can lead after completion to standing water, erosion, sediment runoff, damage to maintenance roads, and runoff to adjacent properties. Especially on sloped terrain, valley topography, or land that readily accumulates water from the surroundings, it is essential to confirm water flow at an early stage.

In drone surveying, because you can grasp elevation differences across the entire candidate site, it becomes easier to estimate low-lying areas where water tends to collect and the channels through which rainwater readily flows. Even from aerial photographs alone, you may be able to identify spots that remain wet, areas where vegetation differs from the surroundings, traces of sediment flow, existing drainage ditches, waterways, side ditches, ponds, and deposits near slope toes. These are important clues when considering drainage planning.

When checking drainage at a candidate site, looking only within the property is not sufficient. You need to confirm whether water might flow in from upstream, whether rainwater could enter from adjacent roads or forested areas, whether it can be discharged into downstream channels or gutters, and whether it would affect the surrounding land. Aerial images taken by a drone make it easy to capture the relationship between the candidate site and the surrounding topography in a single image, making it easier to explain the connectivity of water inside and outside the site.

In solar power plants, rain that falls on panel surfaces can concentrate on the ground. Depending on the post-installation ground conditions and slope, rainwater may gather along specific lines and erode the ground. If, at the candidate site stage, there are already rainwater flow paths, placing rows of panels or access roads over them may cause problems for maintenance after completion. By confirming the terrain and drainage directions with drone surveying, it becomes easier to avoid drainage-sensitive locations when considering panel layouts and access road plans.

For drainage checks, it is ideal to observe the site on location after rainfall, but during a candidate site survey you cannot always inspect it post-rain. Even in that case, combining terrain data obtained from drone surveying with on-site photographs allows you to estimate locations where rainwater is likely to accumulate. Traces of puddles, muddiness, sediment deposits, the way grass is flattened, and ground surfaces that are darker than their surroundings can be clues indicating poor drainage or water flow.

However, drone surveys cannot completely determine water flow. Groundwater, soil permeability, existing culverts or covered drains, flow rates during heavy rainfall, and the capacity of nearby drainage facilities all need to be verified separately. The role of drone surveys is to detect drainage risks early and to lead to more detailed investigations and design considerations. In candidate site surveys, organizing the information visible from drones and the information that should be confirmed on the ground helps reduce the risk of omissions in subsequent investigations.

A drainage plan affects not only the assessment of a potential development site but also the relationship with the surrounding area. If there is a risk of sediment or rainwater flowing onto adjacent properties or downstream areas, it can influence the project plan itself. Preparing materials that explain the terrain around the candidate site using drone surveys will be useful not only for internal review but also for discussions with designers, contractors, and other stakeholders. Being conscious of drainage from the early stages also contributes to the long-term stable operation of a solar power plant.

Perspective 3: Consider panel placement and maintenance access routes

When evaluating potential sites for a solar power plant, it is necessary to consider not only how many panels can be installed but also how inspections will be carried out and how mowing and repairs will be performed after completion. If you focus solely on maximizing the number of panels relative to the site's area, management access ways can become narrow, access to the lower parts of slopes can become difficult, and inspections may require detours. Considering operation and maintenance from the development stage is important for reducing long-term operational burdens.

By using drone surveying to get an overview of the entire candidate site, it becomes easier to identify contiguous flat areas suitable for placing panels, terrain that looks easy to use as pathways, locations that would be difficult for vehicles to enter, and existing site features that could obstruct material deliveries. Land that from the ground reveals only a limited area can, when viewed from above, make the shape of the site and awkward unused margins clear. This makes it easier in the initial layout planning stage to consider the balance between power generation equipment and maintenance access routes.

At solar power plants, after completion, regular patrols, visual inspections, weed control, cleaning of drainage channels, equipment checks, and responses to abnormalities are required. Therefore, it is important to secure routes that managers can walk safely and routes that allow vehicle access when necessary. By utilizing drone survey data, it becomes easier to consider how to connect the site entrance to each facility, whether steep slopes can be avoided, and whether to avoid routing paths through areas where water tends to accumulate.

If a candidate site has existing roads, farm roads, or access tracks, they cannot necessarily be used as-is. There may be conditions that cause problems during construction or maintenance, such as insufficient width, steep gradients, susceptibility to becoming muddy in wet weather, tight bends, or proximity to neighboring property boundaries. By confirming the relationship between existing routes and the entire candidate site using drone overhead imagery, and supplementing that with ground surveys to verify surface conditions and accessibility, you can develop a more realistic circulation/access plan.

In evaluating panel placement, sunlight exposure and the effects of shadows are also important. From images obtained by drone surveying, you can identify objects that may cast shadows—surrounding trees, buildings, slopes, utility poles, and adjacent structures. Because the impact of shadows changes with the season and time of day, you should not make a final decision based solely on drone surveying; a shadow analysis should be conducted as needed. Even so, if you can identify features likely to cause shading at the candidate site stage, the initial accuracy of layout planning is likely to improve.

Also, if the candidate site is elongated or if there are level changes or waterways within the site, it can be difficult to arrange panels efficiently. Even if the drawings show sufficient area, in reality there may be many small, hard-to-use sections that make it difficult to secure the assumed capacity. By overlaying terrain and site-shape data based on drone survey data, it becomes easier to separate the effective area available for layout from the areas that should be left for access routes, drainage, and maintenance space.

If you try to improve maintenance access routes after completion once problems arise, it may require relocating equipment or carrying out additional construction. At the site survey stage, it is important to anticipate where future inspectors will walk, from where they will approach equipment, and where they can work safely. Drone surveying can be used not only to improve layout efficiency but also as planning documentation to make the power plant easier to operate.

Perspective 4 Organize risks related to the surrounding environment and boundaries

When assessing candidate sites for solar power plants, it is necessary to check not only on-site conditions but also the surrounding environment and boundary areas. A site may look fine when viewed in isolation, but elevation differences with adjacent land, road connections, distances to nearby residences, relationships with farmland and forests, existing waterways, power lines, trees, cliffs, and reservoirs or ponds can all affect development plans. Drone surveying is effective for comprehensively understanding the candidate site together with its surroundings.

One point to be careful about regarding boundaries is that the on-site appearance and the boundaries shown in documents do not necessarily match. Images captured by drone surveys are useful as supplementary material for boundary confirmation, but they do not legally determine boundaries. It is important to check boundary stakes, existing fences, waterways, roads, field ridges, rows of trees, etc., in aerial images and, when necessary, verify boundary markers and related documents on the ground. At the site selection stage, you should consider risks and avoid placing equipment too close to the boundary.

When assessing the surrounding environment, it is also necessary to consider impacts on neighboring areas. In the development of solar power plants, vehicle traffic during construction, drainage, sediment runoff, landscape, glare/reflection, noise, and vegetation management can affect relationships with the local community. If drone aerial images are available, it becomes easier to explain how a candidate site is positioned relative to nearby roads, residences, farmland, and waterways. Identifying these points of contact with the surroundings early on helps prepare for subsequent consultations and explanations.

There may also be features around a development candidate site that could hinder construction or maintenance. For example, trees overhanging from outside the site, narrow bridges along roads, existing waterways, equipment related to power transmission and communications, steep slopes, and roads with traffic restrictions. These can be confirmed by on-site surveys, but adding an aerial perspective from drone surveying makes it easier to clarify the positional relationships of obstacles and their impact on the entire candidate site.

Particularly for candidate sites near forested areas or slopes, attention should be paid to the possibility of sediment inflow and fallen trees from the surrounding area. If there are steep slopes outside the site, improving only the site itself may still leave it vulnerable to influences from the surrounding terrain. It is important to take an overview of upstream slopes, stream channels, drainage paths, and existing landslide scars, and, where necessary, follow up with specialized geotechnical or disaster-prevention assessments. Drone surveying can help detect these surrounding risks at an early stage.

Risks near boundaries affect both construction and maintenance. During construction it is necessary to prevent materials and vehicles from crossing the boundary, and after completion fences, access routes, drainage facilities, and weed-control areas must be properly managed. If areas of concern are recorded on the overhead materials produced by drone surveys, it becomes easier for designers, construction personnel, and maintenance personnel to share the same understanding.

When evaluating potential sites, it is important not only to identify the area of land usable for development but also to clarify areas that are difficult to develop. If you sort out early on places that are too close to property boundaries, spots prone to being overshadowed by surrounding features, areas affected by drainage, and locations that require coordination with neighbors, you will be better able to avoid unrealistic plans. Drone surveying can be used not only to visualize a site's attractions but also as a means to reveal constraints that warrant attention.

Perspective 5 Leave as baseline data that can be used for future inspections

Drone surveying carried out at potential development sites provides not only information for determining whether development is feasible but also baseline data that can be used for future inspections and maintenance. A solar power plant is not finished when construction is complete; its equipment and site need to be managed over a long period. Therefore, recording the pre-development condition is useful for comparing before-and-after construction and for checking changes after completion.

Photos and point cloud data obtained from drone surveys at the candidate site stage serve as records of the pre-development topography, existing drainage routes, vegetation conditions, surrounding features, and the conditions near boundaries. Even if the topography changes after construction, if the pre-development condition remains, it becomes easier to confirm where earthworks were carried out, where drainage facilities were installed, and which areas were originally low. This also helps organize construction records and maintenance records.

At a completed solar power plant, it is necessary to regularly check for erosion caused by rainwater, ground subsidence, changes in slopes, clogging of drainage channels, proliferation of weeds, growth of surrounding trees, changes around fences, and so on. If pre-development data is available, comparing it with post-completion drone inspection data makes it easier to identify locations where changes have occurred. This is especially meaningful at large plants, where walking the site to check everything takes time, so continuously accumulating aerial records is worthwhile.

To use data as foundational material, it is important to establish rules for photography and data management. Even data captured solely for candidate site surveys should be recorded with potential future reuse in mind; recording the shoot date, area covered, weather, shooting conditions, data types, how coordinates are handled, responsible personnel, and any points of caution will make reuse easier. If the storage location or file names are unclear, the data may be unusable when needed several years later.

Also, when sharing drone survey data with stakeholders, you need to be aware of who will view the materials and for what purpose. Materials for project decision-making, materials for design review, materials for construction planning, and materials for operations and maintenance require different presentations. An aerial overview image of the entire candidate site is easy to use for internal briefings, terrain data is useful for design review, and materials that indicate points of concern are useful for handover to construction and maintenance. Even the same drone survey outputs become more valuable when organized according to their purpose.

To make baseline data usable for future inspections, simply keeping attractive photos is not enough. It is important that the data be organized in a way that makes locations clear, that the extent of candidate sites is clearly defined, that explanations of key points are attached, and that the data is stored at a granularity that allows later comparison. In solar power plant development, the personnel responsible for planning, design, construction, and operation & maintenance may change. Keeping the data in a state that allows the on-site conditions at the time to be understood makes handovers between responsible parties easier.

Drone surveys at the candidate site stage are often regarded as temporary investigations for initial assessment. However, materials that record pre-development conditions become valuable information that cannot be reacquired after completion. By organizing them as baseline data that can be reviewed later, they become information assets that support not only development decisions but also construction management, post-completion inspections, and long-term maintenance.

How to Use Drone Surveying to Inform Candidate Site Selection

To utilize drone surveying at candidate sites for solar power plant development, it is important not to make image capture the purpose in itself but to clarify what decisions the survey is intended to inform. Whether you want to examine the site’s topography, assess drainage risk, gather material for panel layout planning, clarify conditions around boundaries, or record baseline criteria for future inspections will change the required coverage and the way results are compiled.

First, review existing materials to grasp an overview of the candidate site. Check topographic maps, registration and boundary documents, information on roads and waterways, materials on the surrounding environment, past aerial photographs, and organize the areas you want to focus on during the drone survey. If you conduct shooting without forming hypotheses in advance, you may later find that the necessary coverage is insufficient. For example, if you only photograph the site itself and do not include the upstream slopes or the downstream drainage outlets, the data will be difficult to use for drainage assessment.

Next, carry out on-site safety checks and flight planning. If using a drone, you need to confirm applicable laws and local conditions, the safety of the surrounding area, consideration for third parties, permission from landowners and other stakeholders, and the planned flight area. If a candidate site is in forested areas, near residential neighborhoods, close to roads, near power lines, or in locations prone to wind, avoid risky flights and prioritize safety when planning. On-site safety management affects not only survey efficiency but also the reliability of the results.

When photographing, being mindful of both overview shots that capture the entire candidate site and detailed shots that show areas of concern will make the documentation more useful. Overview photos alone make it difficult to grasp minor issues, while detailed photos alone make it hard to understand spatial relationships within the site. By linking and organizing the overview and detailed images, stakeholders can more easily understand the situation without visiting the site.

At the data processing stage, photos, point clouds, terrain models, elevation information, and positional information are organized according to their intended purpose. At the candidate-site stage, the accuracy required for the final design is not necessarily demanded, but because the materials will be used for decision-making it is important to make clear what level of accuracy and what constraints apply. It is necessary to share with stakeholders that in areas with dense vegetation there are limits to capturing the ground surface, that appearance can change depending on imaging conditions, and that these materials are not documents for definitively establishing boundaries or rights.

When summarizing results, rather than simply handing over the data, organizing them according to the perspectives needed for site selection makes them more practical to use. If you document in text and images the terrain’s relief, drainage flow, areas suitable for layout, management access routes, points to note near boundaries, the surrounding environment, and locations requiring additional investigation, they will be easier to use in business decision-making and design review meetings. The results of drone surveys should be used not only as data for specialists but as materials for creating a shared understanding among stakeholders.

When evaluating candidate sites, it is important not to draw conclusions based solely on drone surveys. Many factors affect whether development is possible, including ground conditions, legal regulations, grid connection, land rights, site development permits, drainage negotiations, agreements with neighboring parties, and construction conditions. Among these, drone surveys are an effective means of understanding on-site topography and conditions. Combined with other investigations, they lead to more realistic development decisions.

In practice, there are cases where multiple candidate sites are compared. In such situations, organizing the results of drone surveys according to the same criteria makes it easier to compare differences between sites. For example, one candidate site may have a large area but high development risk, while another may have a smaller area but clearer drainage and maintenance access; being able to make such comparisons provides decision-making factors that are not visible from simple area or estimated power generation capacity alone.

Summary

When investigating potential sites for solar power plants, drone surveying helps capture on-site conditions across the area and create materials that are easy to share among stakeholders. In particular, organizing findings around five perspectives—topographic relief, drainage flow, panel layout and maintenance access routes, the surrounding environment and site boundaries, and baseline data usable for future inspections—makes it easier to reduce oversights of candidate sites.

When evaluating potential development sites, it is necessary to consider not only area and solar exposure conditions but also the ease of site preparation, stormwater management, material delivery logistics, post-completion maintenance, and impacts on the surrounding area. Aerial imagery and three-dimensional data obtained from drone surveys provide supporting material for these assessments at an early stage. Because they allow confirmation of areas that are difficult to grasp by walking the site alone, they make it easier to identify early on locations that require additional investigation or that need special attention in planning.

That said, drone surveying is not a panacea. Factors such as soil strength, groundwater, legal boundaries, permits and approvals, the capacity of drainage facilities, and local consultations must be verified separately. The key is not to over-rely on drone survey results, but to use them as an entry point for site selection and to proceed to the necessary detailed investigations and design reviews.

In surveys of candidate sites for solar power plants, recording the pre-development conditions is also highly important. If terrain, drainage, and the surrounding environment are retained as data before site development, they can be used for pre- and post-construction comparisons and for inspections after completion. By organizing data from the initial survey stage with future operation in mind, it becomes easier to improve the planning quality and maintainability of the power plant.

If you consider the entire process—from site selection, on-site surveys, and the use of point cloud data to post-completion inspections—it's important to position drone surveying not merely as photography but as an information infrastructure that links development decision-making and maintenance management. If you want to efficiently advance site assessment for a solar power plant, consider an approach tailored to the candidate site's conditions, including surveying methods suited to your objectives and consultation with specialist contractors.