5 Steps to Use Drone Surveying for Solar Power Plant Site Development Planning

In planning the development of a solar power plant site, it is necessary to organize many conditions at an early stage, such as site elevation differences, drainage flow, the extent of earthworks, access routes, racking layout, and slope stability. Relying solely on walking the site makes it difficult to grasp the overall undulations of a large site, valley landforms, existing drainage channels, and the extent of embankments and excavations, and can leave oversights in the planning stage.

A particularly useful approach is using drone surveying to grasp current conditions. By photographing the entire site from the air and organizing topographic data and photographic information, you can increase the information available for pre-development decisions. However, drone surveying does not automatically produce a finished site development plan just by flying the drone. By deciding on the objectives, defining the survey area, and using the data while cross-checking it with on-site conditions, you can more effectively improve the accuracy of your planning.

This article explains, in five steps for practitioners using drone surveying in solar power plant development planning, how to proceed from assessing current conditions, through confirming design requirements and examining development approaches, to sharing with stakeholders.

Table of Contents

• Step 1: First, organize the conditions you want to confirm in the site development plan

• Step 2 Decide the drone survey area and the data to be acquired

• Step 3 Read the current topography and on-site risks

• Step 4 Verify the site development policy and panel layout

• Step 5 Compile into materials usable for construction, consultation, and maintenance management

• Summary: For solar power plant site development planning, grasp the overall picture early through drone surveying

Step 1: First organize the conditions you want to confirm in the site development plan

When using drone surveying for a solar power plant site development plan, the first thing to do is to make clear what you are surveying in order to confirm. In a development plan you look at multiple conditions simultaneously, not only the site area and perimeter but also ground slope, existing watercourses, connections to surrounding roads, boundaries with adjacent land, drainage destinations, construction machinery movement routes, and post-development maintainability. If you proceed with flights and analysis while the objectives are vague, you may later find that the surveyed coverage is insufficient or that the resolution at locations you want to check is inadequate.

Especially for solar power plants, land development plans and power generation equipment layout plans are closely related. Even land that appears flat can have subtle undulations that affect mounting rack heights, drainage between rows, maintenance access paths, and fence locations. In forested areas, slopes, mixed-use land, or fallow fields, it can be difficult to grasp overall gradient changes from site surveys alone, which can lead to discrepancies in estimated earthwork volumes and drainage planning. Therefore, it is important to organize the information you want to obtain from drone surveying according to the perspectives of land development, drainage, layout, construction, and operation and maintenance.

First, what we want to confirm is the current topography of the planned site. We identify elevation differences within the site, the orientation of ridges and valleys, existing depressions, locations likely to require cutting, and locations that can be adjusted by filling. Next, we check the drainage conditions. We clarify where rainwater flows in from and where it flows out to, whether there are existing channels or side ditches, and whether there will be any impact on adjacent land. Because a solar power plant receives rain over a wide area, misjudging drainage directions or the catchment area during the site development planning stage can lead to post‑construction scouring, muddy conditions, slope damage, and deterioration of maintenance roads.

Ease of construction is also important. Check whether material delivery vehicles can access the site, whether the slope allows construction machinery to operate, whether a temporary staging area can be secured, and whether there are trees or existing structures that would interfere with work during construction. Because drone surveys can observe a wide area from above, they make it easier to grasp conditions that are easy to overlook on site—around access routes, the back of the site, the rear sides of slopes, and near boundaries.

At this stage, it is also necessary to take an approach that does not rely solely on drone surveying. The positions of boundary stakes, legal regulations, ground strength, underground buried objects, and detailed rights relationships may require separate document reviews or specialized investigations. Drone surveying is a means to increase the information available for decisions on development plans, and it does not replace everything. For that reason, it is important to organize the items you want to check before surveying and to separate the information to be obtained by drone from the information to be confirmed by on-site investigations and design documents.

In practice, it is effective to share the assumptions of the land development plan among the client, designer, construction personnel, and surveyors before starting surveys. For example, whether you want to know the overall topography of the site, focus on drainage planning, use the data to consider panel layout, or use it to estimate earthwork quantities will change the survey area, the required data accuracy, and the points to verify on the ground. The more thorough the initial preparation, the more usable the drone survey data will be in later stages.

Step 2: Define the drone survey area and the data to be collected

Once you've organized the conditions you want to check, next decide the drone survey area and the data to be acquired. In construction planning for a solar power plant, it is not always sufficient to measure only the area where the generation equipment will be installed. Sources and outlets of drainage, delivery routes, elevation differences with adjacent land, and surrounding areas that may be affected by the development should also be checked. If you plan only within the site boundary, you may overlook rainwater flows and construction logistics, so it is important to consider including a slightly larger perimeter around the planned site when determining the survey area.

When determining the survey area, first consider the extent that will be affected by the site development. Locations where cut-and-fill will be carried out, places where slopes may be formed, areas being considered for detention ponds or drainage facilities, and locations where maintenance roads will be placed all require topographic information. Also, even areas not planned for development should be included in the survey if water could flow in from them or if they would serve as temporary access routes during construction, as including them makes decision-making easier.

Data acquired include aerial photographs, orthoimages, terrain models, point cloud data, and contour lines. Aerial photographs help verify the overall condition of the site and visual differences such as vegetation, existing roads, structures, wasteland, bare ground, and wetlands. Orthoimages, as planimetric images with positional distortions corrected, are easy to handle and serve as useful materials for overlaying with design drawings and explaining to stakeholders. Terrain models and point cloud data are used to examine elevation differences, slopes, and earthwork volumes. Contour lines are suited to intuitively grasping the flow of the terrain.

However, the data used for site development planning is not important solely because the images are clean. It is necessary to consider the required positional accuracy, vertical accuracy, how control points are established, the timing of image capture, the state of vegetation, and how the ground surface appears. During periods when vegetation is dense, the ground surface may not appear clearly in photographs, which can affect terrain interpretation. In forested or weedy areas before development, the surface visible from above may be the canopy or the tops of grass rather than the ground itself. Therefore, as needed, consider surveying after mowing, conducting on-site supplementary surveys, or combining with other surveying methods.

In a flight plan, it is important to avoid gaps or omissions in the imaging coverage. Solar power plant sites are often large and the terrain is not simple. Areas such as site edges, slope bottoms, valleys, locations near access points, and connections to existing roads tend to be important in the site development plan. If critical points end up at the edge of the imaging area, it can affect analysis accuracy and the ease of verification. Set the survey area with a margin and aim to have required locations nearer the center of the images, which makes later documentation easier.

Also, the placement of ground control points and check points is important. When using data obtained from drone surveying for site development planning, you need to ensure that it is possible to verify consistency with the site’s coordinates and elevations. If control points are insufficient or unevenly distributed, it can become difficult to assess elevation relationships across the entire site. Coordinate the placement of control points with the surveying personnel according to site conditions and required accuracy, and make sure they can later be overlaid on design and construction drawings.

Furthermore, pre-flight consideration of safety and the surrounding environment is indispensable. If there are residences, roads, power lines, transmission towers, trees, construction vehicles, or people coming and going nearby, determine the flight route and takeoff and landing sites carefully. Candidate sites for solar power plants are often in suburban or mountainous areas, so consider wind effects, communication conditions, terrain-related line of sight, and the presence of birds and other wildlife. Only with a safe flight plan can you obtain stable data usable for site development planning.

Step 3 Read the current topography and on-site risks

Once data has been acquired by drone surveying, read the existing terrain from the perspectives required for the site development plan. The important point here is not simply to look at elevation differences, but to identify early on the locations that are likely to become problematic after development. In the construction of a solar power plant, attention tends to focus on securing the surface to lay out the panels, but in reality it is necessary to consider drainage, slopes, access routes, maintenance circulation, sediment runoff, and impacts on surrounding land.

First, what you want to check are the high and low points across the entire site. On land with large elevation differences, trying to level everything can increase the amount of earthworks and may result in larger slopes. On the other hand, if you make use of the terrain and develop it in terraced steps, you need to consider the drainage direction of each terrace, the mounting structure height, the gradient of access paths, and how construction machinery will be moved. Using topographic data from drone surveys makes it easier to compare which areas should be heavily regraded and which areas should retain the existing terrain.

Next to check is the flow of water. Pre-development terrain may contain naturally formed water channels, low-lying areas, or places prone to dampness. These can appear in aerial photographs as differences in color or vegetation and can be identified in terrain models as valleys or depressions. If these features are ignored during site development, rain events can concentrate water, leading to muddy maintenance paths, slope scouring, erosion under panels, and accumulation of sediment. It is important to identify water flow at the planning stage of site development and consider drainage facilities and how to set grading.

Do not overlook elevation differences near the boundary. If the planned site is higher than adjacent land, care must be taken to prevent rainwater and sediment from flowing out after grading. Conversely, if the planned site is lower than the surroundings, water from outside can easily flow in, and on-site drainage alone may not be sufficient. Using drone survey data allows you to check elevation differences inside and outside the site and the condition of connection points from a broader perspective. However, since establishing the boundary itself requires separate documentation and on-site verification, it is also important not to judge solely by the appearance on the survey data.

In earthwork planning, the treatment of slope faces and slopes is also an important point to check. Placing equipment close to steep slopes can create burdens for ensuring safety during construction and for maintenance. When providing access routes at the top or bottom of a slope, it is necessary to consider rainwater flow, susceptibility to collapse, and ease of inspection. Drone surveying allows an overview of the extent of slopes and changes in gradient, making it easier to identify potential hazardous locations. As needed, conduct field surveys to confirm geology, springs or seepage, collapse scars, and the degree of soil compaction, and reconcile desk-based data with on-site conditions.

Existing obstacles and remaining items also affect site development plans. Trees, existing structures, old waterways, utility poles, farm roads, retaining walls, fences, scrap materials, and stonework are among the things that can often be spotted in aerial photos. Even when walking the site makes it difficult to inspect the entire area uniformly, reviewing drone survey images makes it easier to reduce oversights. Identifying items that need to be removed or protected prior to development will help minimize rework during the construction phase.

What matters in this procedure is to regard survey data not as the design answer but as material for identifying risks. By extracting areas of concern from the data, rechecking them on site, and reflecting them in the design conditions as necessary, you can improve the accuracy of the site development plan. Because a solar power plant requires long-term operation and maintenance after completion, it is important to consider not only the development phase but also, during operation, whether the site is unlikely to accumulate water, whether inspections will be easy, and whether mowing and repairs will be easy.

Step 4 Cross-check the land development policy with the panel layout

Once you have organized the existing terrain and risks, next reconcile the development policy with the panel layout. In a solar power plant it is important to balance arranging generation equipment efficiently with carrying out earthworks without undue strain. If you try to install too many panels and expand the development area excessively, cut-and-fill volumes will increase and managing drainage and slopes can become difficult. Conversely, if earthworks are constrained too much, the area available for installation can become limited and issues can arise with mounting heights and access planning.

Terrain data obtained from drone surveys helps evaluate that balance. For example, relatively gentle areas are easier to use as the primary locations for equipment placement, while steep slopes and areas prone to water accumulation can have earthworks minimized, be prioritized for access routes and drainage facilities, or be excluded from equipment placement. Considering layout while observing the terrain makes it easier to account for constructability and maintainability than deciding placement based only on plan area.

When considering the site development strategy, decide whether to level the entire area, create stepped terraces following the terrain, or grade only parts of it. Completely leveling the site makes layout planning easier, but can increase the volume of earthwork, the requirements for drainage treatment, and the scale of slopes. Creating stepped terraces along the terrain can reduce the amount of earthworks, but it requires careful attention to the connections between terraces, pathway gradients, drainage directions, and the fitting/details of support structures. With partial grading, verify that water will not pond at the boundary between installation and non-installation areas and that maintenance operations will not be interrupted.

When matching panel layouts, it is necessary to consider terrain conditions as well as solar irradiation conditions. Depending on slope orientation and surrounding elevation differences, inter-row spacing and access paths after grading can be affected. Also, when equipment rows are long, subtle changes in ground elevation can impact racking height and construction accuracy. Using terrain data from drone surveys to verify elevation differences and slopes for each layout area can reduce the risk of having to make adjustments on site later.

Consistency with the drainage plan is also essential. Prioritizing the placement of panel rows can obstruct the natural flow of water or leave insufficient space for drainage facilities. In land development planning, equipment and pathway layouts are adjusted while considering which direction to route rainwater, where to collect it, and where to discharge it. Referring to the valleys and low-lying areas identified by drone surveys makes it easier to avoid plans that force water to flow in the opposite direction.

The location of maintenance access paths is also an important element that links earthworks plans and equipment layout. At solar power plants, access paths are needed not only during construction but also for inspections, mowing, repairs, and equipment replacement after completion. If paths are too steep, allow water to flow in, or are prone to becoming muddy, the burden of operation and maintenance increases. By using drone survey data to check the slope of planned path locations and the surrounding drainage, you can consider earthworks plans that will be easier to use over the long term.

At this stage, it can be useful to compare multiple site development options. Examining options on the same terrain data—such as those that reduce earthwork volume, prioritize layout area, stabilize drainage planning, or emphasize construction logistics—makes it easier for stakeholders to make decisions. The important thing is not simply to create a surface for arranging power generation equipment, but to develop a plan that minimizes difficulties during both construction and operation.

Step 5: Summarize into documents usable for construction, consultation, and maintenance management

When the site development policy and layout direction become clear, compile the drone survey results into materials that can be used for construction, consultations, and operation and maintenance. In solar power plant planning, not only designers but also the client, contractors, landowners, parties involved in administrative consultations, and maintenance personnel—people from multiple perspectives—will review the materials. Therefore, rather than simply handing over technical data as-is, it is important to organize the materials so it is clear what decisions they are intended to inform.

First, in materials used for site development planning, clearly overlay the existing topography, the planned development area, drainage directions, delivery access routes, maintenance access routes, equipment layout areas, and areas requiring attention. Aerial photographs and orthophotos are materials that make it easy to convey conditions to stakeholders unfamiliar with the site. By overlaying topographic information and plan lines on them, it becomes easier to explain which areas will be developed, which will be left untouched, and where drainage will be directed.

Next, for construction personnel, clarify the locations that require attention during construction. Steep slopes, areas prone to becoming muddy, spots where drainage tends to concentrate, narrow sections of access routes, locations with existing structures, and areas near boundaries can all affect construction planning. If these locations are shared in advance using the results of drone surveys, it becomes easier to plan temporary works, position heavy equipment, arrange material deliveries, and prepare responses for rainy weather.

When preparing materials for consultations, avoid overly technical wording and organize them so that the relationship between the existing conditions and the planned measures is clear. In particular, explanations about drainage and sediment runoff should show not only how water flows within the site but also how the plan will limit impacts on the surrounding area. Current-condition images from drone surveys serve to visually supplement terrain features that are difficult to convey in words alone. However, because the required drawings, calculation reports, and survey deliverables for formal consultations or applications vary by case, you should prepare materials while confirming the required formats.

From a maintenance perspective, pre-construction drone survey data is also useful. When checking the terrain and drainage conditions after completion, understanding the pre-construction state makes it easier to compare where changes have occurred, where water is likely to collect, and which areas are more likely to require vegetation management. By keeping records with maintenance in mind from the planning stage, you also facilitate inspections and repair decisions after operations begin.

What you should pay attention to when preparing documentation is to clearly state the intended uses and limitations of the data. Drone survey results are useful for planning reviews, but when the ground surface is covered by vegetation or imaging conditions are poor, care is needed in interpreting the terrain. Also, boundaries, regulatory restrictions, ground strength, drainage capacity, and structural design each require their own verification. When using the data in materials, clarifying which parts were determined by the drone survey and which parts require separate confirmation will help prevent misunderstandings.

Ideally, the final document should allow decisions related to the site development plan to be viewed as a single, coherent flow. When understanding of current conditions, topographic risks, development policy, drainage policy, equipment layout, construction precautions, and maintenance check points are connected, stakeholders can discuss matters based on the same assumptions. Drone surveying is an effective resource for creating that shared understanding.

Summary: Grasp the overall picture of solar power plant site development planning early with drone surveying

In planning site development for a solar power plant, it is important to understand the terrain of the entire site as early as possible. Simply walking the site can make it difficult to confirm, all at once, elevation changes across a wide area, water flow, connections between slopes, and the conditions near access routes and boundaries. By utilizing drone surveying, you can grasp the whole site from above and more easily consider site development strategies based on photographs and terrain data.

The important thing is not to treat drone surveying as mere record photography. Organize the conditions you want to verify in the site development plan, determine the survey extent and the data to be acquired, interpret the existing topography and risks, reconcile the development approach with the panel layout, and compile the results into materials usable for construction and consultations so that decision-making during the planning stage becomes easier. In particular, drainage, slopes, maintenance access routes, haul/access roads, and impacts on surrounding land are items you should carefully check early on, because if problems are found after development the corrections tend to be substantial.

On the other hand, you should avoid deciding all aspects of a site development plan based solely on drone surveying. Boundary verification, geotechnical investigations, legal requirements, drainage design, structural assessments, and detailed construction methods require project-specific checks. Positioning drone surveying as a means of understanding current site conditions to efficiently advance these assessments makes it easier to use in practice.

In development planning for a solar power plant, visualizing the entire site early and creating a situation in which stakeholders can make decisions based on the same information helps reduce rework. By grasping the existing topography and water flow and comprehensively considering earthmoving volumes, equipment layout, construction access flow, and maintainability, it becomes easier to improve the accuracy of the plan.

When incorporating drone surveying for solar power plants into practice—from assessing existing conditions before site development to verification after construction—it is important to focus on acquiring and sharing survey data that are easy to handle on site. By organizing the required accuracy, the types of data to be collected, on-site supplementary surveys, and the workflow for documentation without depending on specific equipment or service names, you can make it easier to use the data consistently from site development planning through construction and maintenance.