5 Drone Survey Items Used in Pre-Installation Surveys for Solar Power Plants

In planning a solar power plant, the accuracy of pre-installation surveys greatly affects subsequent design, site preparation, construction, and maintenance. While walking the site to check on the ground is of course important, when the site is large, has varied terrain, dense vegetation, unclear drainage paths, or complex boundaries and existing structures, it can be difficult to grasp the overall picture by visual inspection alone. One useful method in such cases is drone surveying for solar power plants. Using aerial images and topographic data captured from above makes it easier to check the condition of a prospective site across its surface and to organize installation feasibility and design conditions.

This article explains, for practitioners, five items to check when using drone surveying for pre-installation surveys of solar power plants. Rather than simply ending with aerial photography, it organizes the perspectives from which data should be viewed to inform design, earthworks/site preparation, drainage, and construction planning.

Table of Contents

• Purpose of Using Drone Surveying in Pre-Installation Investigations

• Item 1 Check the topography and elevation differences of the entire site

• Item 2 Check for obstacles and shadows that affect panel placement

• Item 3 Check the drainage routes and areas where rainwater tends to accumulate

• Item 4 Confirm the delivery route and construction movement flow

• Item 5 Check boundaries, existing structures, and surrounding environment

• How to Leverage Drone Survey Data in Design and Construction

• Summary

Purpose of Using Drone Surveying in Pre-Installation Surveys

In pre-installation surveys for solar power plants, we verify whether a proposed site is suitable for installing generation equipment, whether there are major issues with earthworks or drainage, and whether heavy machinery and materials can be brought in safely during construction. While an on-site inspection alone can yield a lot of information, there are limits to assessing the entire site using the same criteria. In particular, for large sites, properties that include forests or slopes, land developed after conversion from agricultural use, or parcels adjacent to existing solar power plants, partial inspections can lead to incorrect conclusions.

The purpose of using drone surveying is to record site conditions from the air and present them in a form that allows later verification of the positional relationships of terrain and structures. By using planar images stitched from aerial photographs, elevation information that includes ground surface and vegetation, and three-dimensional models that can be created depending on conditions, it becomes easier to grasp subtle relief, drainage directions, vegetation distribution, and the ease of access that are easily overlooked on site.

However, drone surveying is not infallible. It may not always be possible to accurately capture the true elevation of ground surfaces covered by trees or grass, and imaging quality can degrade under conditions such as strong winds, rain, fog, or backlight. Also, when using acquired data for design drawings, it is necessary to properly organize survey accuracy, control points, coordinate systems, and processing methods. Before flight, you must also confirm applicable regulations such as aviation law and other relevant rules, consideration for the surrounding environment, access control, and safety management. Therefore, in pre-installation surveys it is important not to draw conclusions based solely on drone surveying, but to make judgments in combination with site inspections, existing drawings, land registry documents, drainage records, and information on ground conditions.

In planning a solar power plant, oversights in the early stages can lead to rework later on. For example, if greater-than-expected elevation differences are discovered after design, it may be necessary to review racking height, earthwork volumes, the drainage plan, and cable routing. If you later realize an access road is too narrow, you may have to change material delivery methods or the construction sequence. Using drone surveying during the pre-installation survey phase to visualize the overall site early is an effective way to improve planning accuracy.

Item 1 Confirm the overall topography and elevation differences of the site

In a pre-installation survey, the first things to confirm are the overall topography and elevation differences of the entire site. Because solar power plants deploy panels over a wide area, the land’s slopes, step changes, depressions, and traces of fill or cut significantly affect the plan. Even if the site plan alone appears to show no problems, in reality gentle slopes may continue across the site or there may be localized low-lying areas where water tends to collect.

In drone surveying, you can photograph the entire site from above and, through image processing, make it easier to grasp the terrain’s undulations. If you present the results as maps color-coded by elevation differences and as cross-sections, it becomes easier to consider which direction the terrain slopes, where earthwork is likely to be required, and where adjustments to the mounting structure’s height may be necessary. When walking the site, gentle slopes can be hard to perceive, but viewing data from above makes the overall tilt of the site and the flow of the terrain easier to understand.

What you should particularly check are not only the central area of the site but also the perimeter, the top and bottom of slopes, differences in elevation with adjacent land, and the connection to existing roads. At a photovoltaic power plant, you need to consider not only the area where panels will be installed but also locations for fences, drainage channels, maintenance access routes, substation/transformer equipment and related devices. If you only look at the layout of the main equipment, you may overlook issues with perimeter drainage and maintenance traffic flow.

When checking elevation differences, it is also important to consider the level of accuracy required for design. For pre-installation preliminary assessments, the data can be used to understand trends at candidate sites. On the other hand, if the data are to be directly reflected in earthwork design or construction drawings, it is necessary to establish ground control points, align coordinate systems, and cross-check with on-site surveys. If you do not clarify what purposes drone-derived data can serve, there is a risk of over-relying on data intended for preliminary checks in detailed design.

Also, in areas with abundant vegetation, height data created from imagery may include the height of the vegetation rather than the ground surface. During times when weeds are tall, in densely forested areas, or in woodland before logging, the visible surface may not match the actual ground surface. Therefore, when checking topography, it is important not to rely solely on the results of drone surveys, but to verify representative points on site and, if necessary, correct them with ground surveying.

By organizing the terrain and elevation differences in the pre-installation survey, you can evaluate early on the estimated earthwork volume, the orientation for panel placement, drainage planning, and the travel range of heavy equipment during construction. This is the basis for using drone surveys of solar power plants as material for planning decisions rather than merely as records.

Item 2 Check obstacles and shadows that affect panel layout

Next, we need to confirm the obstacles and sources of shading that affect panel placement. At a solar power plant, in order to secure power generation, it is necessary to consider layouts that minimize shading on the panels. If sources of shading are not identified during the pre-installation survey, layout changes may be required after design, or it may become difficult to achieve the expected power output.

In drone surveying, because you can check the entire site and its surroundings from above, it becomes easier to grasp the relative positions of obstacles that are difficult to see from the ground. Items to check include trees, utility poles, overhead lines, buildings, existing structures, vegetation at the top of slopes, and tall structures on adjacent land. Even if there are no conspicuous obstacles within the candidate site, trees or buildings outside the site may cast shadows depending on the time of day.

When verifying shadows, it is important not to make judgments based solely on images taken at the time of shooting. Because the sun’s elevation and azimuth change with the season and time of day, shadows that appear minimal in images from one day can have a large impact in winter or at morning and evening. Terrain and surrounding structure information obtained from drone surveys can be used as material for shadow assessment, but ultimately must be combined with design evaluations that take seasonal variations into account.

In a pre-installation survey, it is useful not only to identify shading factors but also to clarify what design responses will likely be required. For example, if trees run continuously along the south side of the site, consideration may need to be given to removal or creating separation distances. If there are tall buildings or slopes on adjacent land, responses to consider include setting the panel layout back, limiting the installation area, and confirming the impact of shading with power generation simulations.

Also, checking for obstacles affects not only power generation but also constructability. If there are leftover items, existing foundations, old drainage structures, or markers indicating possible buried objects on the site, they can impact piling and cable laying. Recording their positions with aerial imagery makes it easier to narrow down which areas to prioritize during on-site inspections.

In pre-installation surveys for solar power plants, it is important to consider not only the candidate site itself but also the surrounding environment. By using drone surveys to broadly understand the relationship with areas outside the site, shadowing and obstacle issues that often emerge later can be addressed at an early stage.

Item 3 Check drainage routes and areas where rainwater tends to accumulate

Drainage is an aspect that must not be overlooked when planning a solar power plant. If the flow of rainwater is not understood during the pre-installation survey, it can lead after construction to problems such as standing water, washout/erosion, slope failures, muddy access paths, and clogged drainage channels. Confirming drainage routes is especially important on reclaimed or filled land, sloping terrain, valley topography, and sites where rainwater flows in from the surrounding area.

Drone surveying helps identify drainage pathways. By assessing elevation differences across the surface, it becomes easier to estimate which direction rainwater is likely to flow and where it is likely to accumulate. Aerial images can sometimes reveal existing waterways, side drains, catch basins, culvert outlets, muddy areas, changes in vegetation, and traces of sediment accumulation. By combining this information, you can clarify which locations should be examined during field inspections.

When checking drainage, be aware that filming only in clear weather makes it difficult to see water movement. Even if you can estimate flow from topographic data, actual rainwater behavior varies with soil type, the condition of drainage structures, vegetation density, inflow from adjacent land, the gradient of existing roads, and so on. Therefore, based on terrain information obtained from drone surveys, conducting on-site inspections after rain and checking existing drainage facilities will allow for judgments that more closely reflect actual conditions.

In solar power plants, if standing water persists under panels or on access paths, ease of operation and maintenance declines. If paths become muddy, movement of inspection vehicles and personnel is hindered, and in areas where drainage concentrates there is a risk of soil erosion or scour around racking foundations. Identifying locations prone to rainwater accumulation before installation makes it easier to consider the positions of drainage ditches, the layout of maintenance paths, site grading, and sediment control measures.

Also, note that drainage does not necessarily terminate within the site. Rainwater may flow from upstream into the candidate site, or it may flow out from the site to adjacent downstream properties or roads. In the pre-installation survey, it is important to identify elevation differences near the site boundary, connections to existing water channels, downstream drainage capacity, and any locations that are likely to require coordination with neighboring residents or managers.

When confirming drainage routes using drone surveying, it becomes more practical for field work to separate and organize the information visible in images from the information readable from elevation data. Use images to check waterways and surface conditions, and use elevation data to identify flow directions and low-lying areas prone to collecting water. By overlaying these two, it becomes easier to share drainage issues among designers, construction personnel, and clients.

Item 4 Confirm the delivery route and construction workflow

In a pre-installation survey, it is necessary to check not only where to place the equipment but also how the construction will be carried out. In solar power plant construction, many materials—panels, mounting structures, piles, cables, electrical equipment, and fencing materials—are brought to the site. If there are problems with delivery routes or construction traffic flow, they can lead to delays to the construction schedule or additional work.

Using drone surveying, you can check from above the on-site and off-site roads, access routes, potential temporary yards, and heavy equipment movement paths. It provides an aerial overview of corners, changes in road width, slopes, difficulty of passing, and the positional relationship with material storage areas that are hard to discern from ground-level photos. Especially for candidate sites in mountainous areas or around farmland, issues tend to arise such as narrow roads leading to the site, unpaved roads, power lines or trees obstructing access, and roads that become easily muddy in rainy weather.

When checking construction access routes, movement within the site is as important as the route from the entrance to the installation area. Consider whether access aisles can be adequately secured after panel placement, whether heavy machinery can turn safely, whether steep slope areas can be avoided, and whether work can be carried out without crossing drainage ditches or embankments. Using images from drone surveys makes it possible to grasp the construction area as a large surface, making it easier to plan on-site movement routes in advance.

Also, at the pre-installation stage, drone surveying is useful for considering temporary construction plans. Material storage yards, worker parking areas, candidate locations for temporary site offices, and temporary stockpiles for excavated soil all affect efficiency during construction. By checking the terrain's undulations and drainage conditions to identify which locations are relatively easy to use, you can improve the accuracy of the construction plan.

However, aerial imagery alone cannot accurately determine road width or load-bearing capacity. Separate verification is required for points such as whether large vehicles can actually pass, whether there are issues with bridges or culvert covers, or whether consultation with road authorities is necessary. Drone surveys should be used as supplementary material to reduce omissions in on-site checks, and the final judgment should be made in combination with field inspections and confirmations with relevant parties.

Understanding construction access routes before installation has a positive impact on the design. For example, decisions about where to run maintenance paths, where to place fence entrances, and where to consolidate electrical equipment affect both construction and ongoing maintenance. By using drone surveying to obtain an aerial overview of the entire site, it becomes easier to plan layouts for solar power plants that are simpler to construct and manage.

Item 5: Verify boundaries, existing structures, and the surrounding environment

In the pre-installation survey, the final things to confirm are the boundaries, existing structures, and the surrounding environment. Because solar power plants use large areas of land, misunderstandings about boundaries or overlooking existing structures can lead to design changes and the need for coordination with neighbors. Drone surveying is useful for organizing and clarifying these positional relationships.

First, what you should check is the area around the site boundary. By overlaying boundary documents and survey results on drone survey imagery, it becomes easier to confirm where to place fences, the separation from adjacent properties, and how the site interfaces with roads and waterways. However, aerial images alone cannot establish the legal boundary. Determining the boundary requires registry documents, boundary markers, on-site inspections, ground surveys, and so on. Drone surveys are not intended to decide the boundary itself, but are appropriate to use as materials to clearly organize the conditions around the boundary.

Verification of existing structures is also important. Within the candidate site, there may be remnants of old waterways, retaining walls, agricultural facilities, utility poles, guy wires, drainage manholes, pavement traces, concrete foundations, wells, and reservoirs. These can affect panel layout, pile positions, cable routes, and site development plans. By identifying the locations of existing structures from aerial imagery, you can narrow down inspection points during field surveys and reduce omissions when reflecting them in design drawings.

When checking the surrounding environment, consider the relationships with adjacent houses, roads, farmland, forests, waterways, rivers, and other power generation facilities. At solar power plants, vehicle traffic during construction, rainwater runoff, reflection, vegetation management, and fence locations can become items that require coordination with the surrounding area. Taking an overview of the surrounding environment before installation makes it easier to identify and organize the points needed for explanations to neighbors and consultations with administrative authorities.

From a maintenance perspective, checking the surrounding environment is essential. If there are many trees nearby, you need to consider the effects of falling leaves and shade, future branch growth, and the risk of trees falling. When adjacent to farmland or forest, issues such as weed proliferation, animal intrusion, and sediment inflow also become management challenges. Recording the surrounding environment before installation provides a baseline for comparing changes after installation.

Data acquired by drone surveying also helps align understanding among stakeholders. When designers, construction personnel, clients, landowners, and maintenance managers talk while looking at the same images, they can share site conditions that are difficult to convey with words alone. In particular, locations near boundaries and the positions of existing structures can appear different depending on the viewing angle on site. Having aerial records makes it easier to reduce oversights and misunderstandings.

Approach to Utilizing Drone Survey Data for Design and Construction

When using drone surveying for pre-construction surveys of solar power plants, the important thing is not simply acquiring data itself but clearly defining what decisions the acquired data will be used to inform. If you capture imagery with unclear objectives, you may end up with attractive photos but lack the information necessary for design and construction.

First, it is important to decide on the items to check before the survey. Depending on whether you want to see the terrain, drainage, shading factors, or access routes for delivery, the shooting area, required resolution, flight altitude, and method of ground verification will change. Rather than photographing only the site, it can be more useful for pre-installation surveys to include surrounding roads, waterways, adjacent properties, and both upstream and downstream areas.

Next, it is necessary to organize coordinates and reference points. When overlaying design drawings and ground survey results, decide in advance which coordinate system to use, where to place reference points, and what level of accuracy is required. The required level of control differs depending on whether the materials are used for preliminary review or for reviews close to construction. By determining the necessary accuracy according to the purpose, it becomes easier to avoid excessive work or insufficient investigation.

When checking data, it is effective not to treat images, topography, elevation differences, on-site photos, and notes separately, but to link and organize them using the same location information. For example, if you find an area of concern in aerial imagery, linking it to photos and notes taken on site makes it easier for designers to verify later. Organizing the flow of drainage, obstacles, and challenges with access routes along with location information also makes the material easier to use for meetings.

Drone survey data can be used not only before installation but also for comparisons during and after construction. If you record the pre-installation condition, it becomes easier to confirm what has changed after earthworks, whether drainage routes are as planned, and whether impacts from material storage areas or temporary roads remain. For future maintenance, knowing the pre-installation topography and surrounding environment provides clues for considering the causes of any changes or deterioration.

At the same time, it is important not to place too much trust in drone survey data. Buried objects not visible in images, soil conditions, ground bearing capacity, legal boundaries, drainage-rights relationships, road-use conditions, and the like require separate surveys or confirmations. Drone surveying is a means of visualizing the entire site and increasing the information available for decision-making, and it does not resolve all risks on its own. In pre-installation investigations, centering on drone surveying while combining on-the-ground inspections and review of relevant documents will yield survey results that are usable in practice.

To use drone surveying for solar power plants effectively, it is important to be aware of the workflow of survey, design, construction, and management. By reflecting issues found during pre-installation surveys in the design conditions, sharing them as precautions during construction, and linking them to post-completion operation and maintenance, the value of drone surveying is enhanced.

Summary

In pre-installation surveys for solar power plants, it is important to identify early the overall site topography, shading factors, drainage routes, access routes for delivery, boundaries, and existing structures. By using drone surveying, you can inspect large candidate sites from above in an area-wide manner, making it easier to clarify terrain variations and spatial relationships that are difficult to discern from on-site inspections alone.

Particularly, checking topography and elevation differences relates to the site development plan and racking layout. Checking obstacles and shadows relates to power generation and layout considerations. Checking drainage routes is important to prevent puddling and washout after construction. Checking access routes and construction traffic flow directly affects the ease of carrying out the work. Checking boundaries, existing structures, and the surrounding environment is essential to reduce the risk of design changes and the need for coordination with neighbors.

However, drone surveying is not something that can be completed by simply looking at the acquired images. It only becomes a survey usable in practice when you develop a shooting plan suited to the purpose, organize control points and coordinates, cross-check with on-site inspections, and reflect the findings in design and construction. Before flight, you must also organize checks on the flight location, surrounding facilities, third-party access, safety management, applicable laws and regulations, and confirmation with the relevant authorities. If you use drone surveying during the pre-installation investigation stage, you can reduce oversights in the early planning phase and make it easier for stakeholders to share site conditions.

Potential sites for solar power plants may appear similar, but their topography, drainage, surrounding environment, and construction conditions vary. Therefore, it is important to record the site broadly and as accurately as possible, in a form that can be checked later before installation. By using drone surveying not merely as aerial photography but as material for design and construction decisions, it becomes easier to enhance the planning accuracy of solar power plants.

If you want to organize the entire process from pre-installation surveys through design, construction, and maintenance, it is important to proceed while confirming drone surveying operation methods that match the site conditions. By organizing the objectives, accuracy, flight conditions, and the scope of on-site verification in advance, it becomes easier to apply the acquired data to practical work.