5 Steps to Create a Flight Plan for a Solar Power Plant Using Drone Surveying

When conducting drone surveys at a solar power plant, the quality of the results is not determined solely by the operations on the day of the flight. It is important to organize in advance which area to cover, at what altitude, in what order, and under what conditions flights will be conducted. Solar power plants in particular involve complex interactions among panel rows, racking, fences, maintenance roads, slopes, drainage channels, and surrounding trees, so if the flight plan remains vague it can easily lead to missed coverage, re-flights, and reduced quality of point clouds and orthophotos.

This article explains five practical steps for creating a drone survey flight plan for solar power plants, assuming tasks such as site condition assessment, site development planning, as‑built verification, identification of stormwater flow routes, and operation and maintenance.

Table of Contents

• Step 1 Clarify the site objectives and the survey scope

• Step 2: Check constraints and safety conditions before flight

• Step 3 Design imaging conditions and flight route

• Step 4 Incorporate reference points and checkpoints into the plan

• Step 5 Decide the on-the-day operational procedures and the data verification steps

• Common Pitfalls to Watch Out for in Flight Planning for Solar Power Plants

• Summary

Step 1 Clarify the site objectives and the survey scope

The first thing to do in drone surveying of a solar power plant is not the flight itself, but to clarify what you are trying to verify with the survey. Even when flying over the same plant, whether the goal is creating a current-condition map, comparing before and after site development, checking panel layout, or understanding drainage routes will change the required capture area and accuracy, the flight altitude, and how the deliverables are produced.

For example, if the purpose is to understand the terrain before site development, it is necessary to broadly grasp the overall elevation differences of the site, slopes, valley areas, existing roads, drainage outlets, and so on.

On the other hand, for post-construction verification, it is important to organize the spatial relationships of panel rows and racking areas, maintenance paths, inside and outside of fences, and the positions of retention ponds and drainage ditches in a way that is easy to understand.

If the purpose is maintenance and management, planning should be oriented toward inspection targets such as vegetation overgrowth, sediment accumulation, locations where puddles form, and damage to access routes.

Before creating a flight plan, first confirm the deliverables required by the client and the site manager. Clarify whether orthophotos, point cloud data, contour lines or cross-section checks, or before-and-after construction comparison materials are needed. If you fly while this is still unclear, you may take many images but lack the necessary angles or coverage, resulting in the need for re-shooting.

At solar power plants, the site boundary and the area you actually want to inspect may not coincide. You need to decide in advance whether it is sufficient to cover only the area inside the fence, whether to include the drainage outfall, or whether to include adjacent roads and surrounding slopes. Especially when checking rainwater pathways or sediment runoff, photographing only inside the plant can make it difficult to determine causes and the extent of impacts. If areas outside the site are to be included, you will also need to confirm entry and flight permissions, so it is important to clearly define the target area during the planning stage.

In addition, solar power plants often cover large areas, and it is not uncommon for sites to have uneven terrain. Whether you fly the entire area at once or divide it into sections affects battery replacement, takeoff and landing locations, worker movements, and safety monitoring arrangements. If site maps, plan drawings, existing floor plans, aerial photographs, or past survey results are available, those should be checked while dividing the survey area.

When defining the coverage area, it is also important to leave some margin at the edges of the deliverables. If you capture right up to the minimum required area, distortions or gaps are likely to appear at the edges after image processing. If there are features whose positional relationships you want to verify later—such as fences, roads, road shoulders, drainage ditches, or retention ponds—include a little area beyond the target in the capture to make the material easier to use.

Furthermore, deciding priorities for each surveying objective makes on-site decision-making easier. If constraints such as weather, wind, remaining battery, or sunset prevent capturing the entire area as planned, deciding in advance which areas must be captured makes it easier to secure the minimum necessary deliverables. For drone surveys of solar power plants, specifying the objectives, coverage, deliverables, and priorities is indispensable as the first step in flight planning.

Step 2: Confirm constraints and safety conditions before flight

Once the survey area is decided, the next thing to check is the conditions for flight. In drone surveying, you cannot formulate a flight plan based solely on on-site circumstances. You need to check relevant laws and regulations, airspace, the surrounding environment, hazards within the site, weather, radio signal conditions, etc., and incorporate them into a plan that allows safe operation.

Solar power plants are often installed in suburban or mountainous areas and may at first glance seem like easy places to fly. However, if there are residential areas, roads, railways, power lines, communications facilities, schools, factories, rivers, forests, or farmland nearby, attention must be paid to flight routes, altitudes, and monitoring arrangements. If there is pedestrian or vehicular traffic in the vicinity, takeoff and landing sites and emergency landing locations must be selected carefully.

Before flight, confirm what type of airspace the area falls under. Under the Aviation Law, there are airspaces where permission or confirmation of whether flight is allowed is required, such as around airports, emergency-use airspace, altitudes of 150 m (492.1 ft) or more above the ground or water surface, and over densely populated areas. In addition, night flights, flights beyond visual line of sight, flights less than 30 m (98.4 ft) from people or property, flights over event venues, transport of hazardous materials, and dropping objects may require approval or additional safety measures as flight methods. In actual operations, it is important to check the latest regulations, the status of aircraft registration, and field conditions, and to complete the necessary procedures before making plans.

Specific hazards unique to solar power plants include transmission equipment, high-voltage equipment, overhead lines, surveillance cameras, meteorological observation equipment, fences, and structures surrounding power conditioners. These not only become obstacles to flight routes but can also cause accidents or equipment damage if approached too closely. In flight planning, identify the locations of obstacles in advance using drawings and on-site inspections, and set routes with sufficient clearance.

At power plants in mountainous or sloped terrain, attention must be paid to wind variations caused by the topography. On ridges, in valleys, on slope faces, at cut sections, and on embankments, the wind felt at ground level can differ from the wind aloft. In particular, above the panel surface the direction the wind passes through and the way it becomes turbulent can make the aircraft more prone to being blown off course. In the flight plan, establishing how to check wind direction and wind speed, the criteria for aborting a flight, and the placement of spotters will increase safety.

Selecting takeoff and landing sites is also important. Some solar power plants have limited flat, open areas. Even when using maintenance roads or vacant lots, you need to check for gravel, grass, slopes, mud, vehicle traffic, and worker movement paths. The takeoff and landing site should be chosen not only so the aircraft can be placed safely but also so the operator can easily check the aircraft’s condition and the surrounding area. If the flight area is extensive, consider dividing takeoff and landing sites by section.

Also confirm interference with on-site work on the day of the flight. If grass cutting, mounting structure work, electrical work, inspections, material deliveries, heavy machinery operations, etc. are being carried out simultaneously, drone flights may hinder those operations. Conversely, dust from on-site work, vehicle movement, and personnel entering the site can become flight risks. The flight plan must include notifying relevant parties, access control, and adjustment of work hours.

Safety conditions are not just about avoiding hazards. They are also important for achieving stable imaging and reducing the need for re-flights. Strong winds, rain, fog, backlighting, low clouds, and the low light just before sunset can affect image quality and aircraft operations. Rather than making a subjective on-site judgment about whether a flight is feasible, deciding cancellation and postponement criteria in advance reduces misunderstandings among stakeholders.

Step 3: Design imaging conditions and flight route

After confirming safety conditions, design the actual capture conditions and the flight route. The results of drone surveying are heavily influenced by image overlap, resolution, motion blur, brightness, camera angle, and how well the flight follows the terrain. At solar power plants, reflections from panels, shadows cast by racking, slope undulations, and narrow, elongated site shapes all have an impact, so settings need to be configured more carefully than for typical flat-ground photography.

The first consideration is flight altitude. The lower the flight altitude, the easier it is to see ground details, but the number of photos increases and flight time becomes longer. The higher the flight altitude, the more efficiently you can capture a wide area, but it may be unsuitable for confirming fine details. For surveying solar power plants, it is effective to adopt an approach that separates the altitude for overall overview from the altitude for inspecting important areas, depending on the required deliverables.

Next, ensure sufficient overlap between images. In drone surveying, if adjacent images do not overlap enough, it becomes difficult to correctly estimate spatial relationships during image processing. This is especially true at sites with rows of solar panels, where repeating patterns can make it hard for image processing to extract feature points. Rather than following a route that captures only panel surfaces, it is important to plan so that objects that provide positional cues—walkways, fences, slopes, ground surfaces, drainage channels, etc.—are captured to a reasonable extent.

Set the flight route to match the shape of the site. For power plants that are close to rectangular, a route running along the long axis can be more efficient. Conversely, for plants in mountainous areas or divided into multiple sections, assigning routes by section makes it easier to prevent missed shots and battery shortages. For complex sites, it’s safer not to rely solely on automated flight and to plan on supplementing with additional shots around the edges and near obstacles.

In solar power plants, attention must also be paid to panel reflections. Depending on the sun’s position, the panel surface can reflect strongly, causing parts of the image to become overexposed or making it difficult to detect feature points. Planning the shooting time affects quality as well — for example, avoid times with strong reflections, adjust the flight direction, and take cloud cover and solar elevation into account. However, because weather cannot be completely controlled, be prepared to fine‑tune shooting conditions based on the situation on the day.

For power plants on sloped terrain, addressing elevation differences is important. If you fly at a constant altitude, you may be farther from the ground on the valley side and closer on the ridge side. As a result, image resolution can vary and the risk of approaching obstacles increases. At sites with large undulation, it is necessary to adjust flight altitude to the terrain and to fly by subdividing the area. For places with significant topographic changes, such as slopes, valley bottoms, and around regulating ponds, planning to supplement them with separate routes makes the accuracy of deliverables easier to stabilize.

Also, there are subjects that are difficult to grasp from vertical-only photography. Consider supplementary oblique shots as needed for the sides of drainage channels, slope failures, conditions beneath mounting racks, deformations along fences, and overhanging nearby trees. However, images used as surveying deliverables and images used as inspection records serve different purposes. It is important to separate, during the planning stage, the primary capture used for creating orthophotos and point clouds from the supplementary capture for explanatory materials so they do not get confused.

When designing flight routes, consider battery management as well. At large power plants, you may need to replace batteries partway through a planned flight route. Returning mid-route interrupts the continuity of imaging, so it is easier to operate if you break the flight at section boundaries or near service roads. Including battery change locations, storage for spare batteries, whether charging is possible, and safety checks during the exchange in your plan will reduce confusion on the day.

Imaging conditions and flight routes are not just combinations of settings. They are determined by comprehensively considering the purpose of the deliverables, the shape of the site, safety conditions, working time, and the ease of image processing. In drone surveying of solar power plants, it is important not only to capture broad, uniform coverage but also to reliably capture the objects needed for decision-making.

Step 4 Incorporate reference points and verification points into the plan

To ensure positional accuracy in drone surveying, it is necessary to incorporate the handling of control points and check points into the flight plan. At solar power plant sites, even if orthoimages and point clouds can be created, they become difficult to use for construction verification or as comparative materials if their positions do not match the site coordinates or design drawings. To make survey deliverables usable in practice, it is important to clearly define the coordinate reference before flight.

The first thing to confirm is the coordinate system to be used. Clarify whether it will be managed in a public coordinate system or handled as a site-specific local coordinate system, and how it will be reconciled with the coordinates in the design and construction drawings. In solar power plants there may be multiple drawings, such as grading plans, panel layout plans, electrical equipment drawings, and drainage plans. If the reference datum differs between drawings, it can cause discrepancies when those drawings are overlaid with drone survey results.

When installing reference points, choose positions that are clearly visible in images. Avoid placing them on panels, in areas prone to shadows, spots hidden by grass, or locations that may be covered by vehicles or materials. Choose locations that are easily identifiable from above and easy to measure on site—such as access roads, open ground, or flat areas near fences—to make operations easier. Reference points should be distributed in a balanced manner around the perimeter and within the interior of the target area.

Check points are used to verify the quality of deliverables. If image processing is performed using only control points, the processed results may look tidy at first glance, but it becomes difficult to judge how much they are displaced in other locations. By setting check points, you can confirm how well the produced deliverables align with on-site measured values. The concept of check points is especially important when using them for pre- and post-construction comparisons or for as-built verification.

At solar power plants, there are constraints on where reference and check points can be placed. The spaces between panel rows are narrow, and mounting racks, wiring, and weeds can get in the way. Around equipment that is generating power, there may also be safety-related access restrictions. During the flight planning stage, you need to confirm whether surveyors can reach the locations without difficulty and whether workers can safely install and retrieve them.

Setting up control points in a rush on the day of the flight tends to lead to mistakes. Decide in advance how to name points, where to place them, how to measure them, how to record photographic records, and how to manage coordinate data. If point names do not match among site photos, the survey field book, and the names within the processing software, mix-ups can occur during post-processing. At sites such as solar power plants, where the scenery is repetitive, it is especially important to clearly record point names and positions.

Control points and check points also affect the flight route. Even if they are installed, they cannot be used effectively if they appear only at the edge of images, are hidden by shadows, or if there are an insufficient number of photos. When creating the flight plan, adjust the route and overlap so that each point appears clearly in multiple images. If necessary, include a plan to perform additional imaging focused only around the control points.

When conducting regular drone surveys for power plant maintenance, it is important to ensure that comparisons can be made against the same baseline each time. If the handling of control points, the coordinate system, the imaging coverage, or the flight altitude changes significantly between the previous and current surveys, it becomes difficult to compare changes. If you want to continuously monitor subsidence, scour, sediment deposition, vegetation growth, or changes in drainage paths, keeping a reproducible flight plan will make later analysis easier.

Control points and check points are elements that underpin the reliability of deliverables. In a flight plan, you need to decide not only where to fly but also which control standard will be used to produce the deliverables and which points will be used to verify quality. This makes it easier to use drone survey results for on‑site decision‑making and explanatory materials.

Step 5: Decide the day-of operational procedures and data verification

A flight plan is not complete simply by creating a route on paper or on a screen. Only when you decide who will check what on the day, the order in which tasks will be performed, and what will be checked after the imaging does the plan become usable in practice. In drone surveys of solar power plants, because sites are large and often involve multiple stakeholders, it is important to specify operational procedures in detail.

On the day of operations, we first check the weather, wind, on-site work conditions, access boundaries, and the movements of people and vehicles nearby. Even if a flight plan was prepared the day before, you may not be able to fly as planned if on-site conditions have changed. For example, a vehicle may be parked at the planned takeoff/landing point, mowing work may be underway, materials may be stored there, or the wind may be stronger than expected. During the pre-flight inspection, we confirm the differences between the plan and the site and adjust the route or sequence as necessary.

Clarify the work structure. By separating the pilot, assistant, observer (spotter), and on‑site liaison, it becomes easier to balance safety checks and filming operations. Even at small sites, it is a heavy burden for the pilot to monitor the screen, the aircraft, and surrounding safety all at the same time. Especially at solar power plants, there are many hazards to watch for over a wide area, such as roads outside the fence, workers on the site, overhead lines, and areas near slopes. Assigning the monitoring role in advance enables quicker response in case of an abnormal situation.

Before starting the flight, check the aircraft, transmitter, battery, recording media, positioning status, camera settings, flight route, and return settings. Basic oversights—such as camera settings left configured for the previous inspection, insufficient free space on the recording media, or insufficient battery level—can cause unexpectedly large rework on site. Incorporating checklist items into the flight plan reduces the chance of missed checks by the person in charge.

During capture, be aware not only of whether the flight is proceeding as planned but also whether the images are being captured in a usable condition. Strong reflections, motion blur, focus issues, exposure fluctuations, sudden changes in cloud shadows, obstacles appearing in the frame, or irregularities in the shooting interval can cause problems in post-processing. If you notice any abnormalities, rather than discovering them all after the flight, check some images on site and decide whether a reflight is necessary.

When flying by section, check the number of photos taken, the coverage, the capture of reference points, and the image brightness at the completion of each section. If you only notice missed shots after finishing all sections, you may need to move around the site again or face changed lighting conditions, which reduces efficiency. Because solar power plants cover large areas, it can take time just to return to the far edge of the site. Planning to perform a quick check after each flight unit will reduce the burden of re-shooting.

Post-flight data management should also be considered part of the flight plan. Organize and store which plot each image belongs to, the date and time of the flight, the purpose of the capture, and how it corresponds to the control point data. If folder and file naming rules are ambiguous, images can be mistaken during post-processing. Version control of the data is especially important when surveys span multiple days or when comparing before-and-after construction.

To the extent possible on-site, it is also important to check for missing images or extreme blur. Even if detailed point cloud processing and orthomosaic creation will be performed in the office, performing at least a basic check on-site allows you to determine the need for a reflight that same day. For power plants in mountainous or remote locations, revisiting them later can be a major burden, so including on-site verification procedures in the flight plan contributes to operational efficiency.

Finally, keep a flight log. Recording the flight date and time, weather, wind conditions, flight area, personnel in charge, control points used, purpose of the imaging, on-site changes, and whether a reflight was conducted will help explain deliverables and plan future surveys. Drone surveying of solar power plants can be used not only for a one-time capture but continuously during construction and maintenance phases. Keeping records makes it easier to improve flight plans for future operations.

Common Pitfalls in Flight Planning for Solar Power Plants

A common mistake in flight planning for solar power plants is assuming that photographing the entire site is sufficient. Shooting a wide area with an automated flight may seem adequate at first glance, but if the locations needed for the deliverables’ intended purpose are not captured, the results become difficult to use in practice. Problems such as wanting to see drainage paths but not capturing the downstream outlets, wanting to compare earthworks but missing the edges of slopes, or wanting to verify as-built conditions but having unclear reference points tend to arise from insufficient clarification of objectives before the flight.

Another common mistake is underestimating panel reflections and shadows. Because solar power plants have the same-shaped panels arranged over wide areas, image-processing features tend to become biased. Furthermore, reflections and shadows change with the sun’s angle, significantly altering how images appear. If shooting times are chosen carelessly, parts of the image can become overexposed or dark shadows can spread, making the ground or structures you want to inspect difficult to see. In flight planning, it is important to consider the season, time of day, weather, and the orientation of the subject.

A caution: don't prioritize flight-route efficiency too much. Capturing the entire site in a short time is important, but if you focus solely on efficiency, you can easily end up with insufficient coverage of edges and areas around obstacles. Areas along fences, slopes, detention ponds, drainage ditches, and the ends of maintenance roads are often important for power plant maintenance and construction verification. In addition to the overall route, planning supplemental photography of key locations will make the material easier to use later.

Leaving the placement of control points up to the field is another mistake to avoid. Control points are not something you can just set; they only become meaningful when they appear in the images, are measured correctly, and are reflected in the deliverables. If you place them where they are obscured by grass or shadows, are captured only at the edges of images, or where point names can easily be confused, they will be difficult to use in post-processing. It is important to align the flight plan and the control point plan on the same drawing rather than consider them separately.

Also, the work time is sometimes underestimated relative to the size of the site. In drone surveying, not only the actual flight time but also site inspection, control point placement, aircraft checks, battery changes, image verification, data organization, and communication with stakeholders take time. Solar power plants involve long travel distances, and movement can be slowed by slopes and mud. In plans with no margin, later verification tasks may be omitted, resulting in missed shots or missing records.

Furthermore, failing to keep a record of changes to the flight plan is also problematic. Although the route may be altered on the day due to wind or work conditions, if the changes are not recorded, the reasons will become unclear when reviewing the deliverables later. By recording which sections were flown as planned, which were supplemented with additional imaging, and which were cancelled, it becomes easier to ensure accountability for the deliverables.

In drone surveying of solar power plants, it is important at the flight planning stage to consider imaging quality, safety, surveying accuracy, and data management together. Rather than creating only the flight route, planning by working backward to a state where the deliverables can be used reduces re-flights and rework.

Summary

When planning a flight for drone surveying of a solar power plant, first clarify the survey objectives and scope, then confirm airspace, site conditions, and safety requirements. Based on that, design the flight altitude, image overlap, flight route, supplementary photography, and battery-replacement workflow, and incorporate control points and checkpoints into the plan. Finally, by determining the day’s work procedures, post-flight data verification, and record management in advance, it becomes easier to balance the quality of deliverables with on-site operational efficiency.

Solar power plants are large sites with many elements to check, such as panel rows, mounting racks, slopes, drainage facilities, access roads, and surrounding trees. Simply photographing the whole site from above may not yield survey deliverables that are practical for field work. For tasks such as creating as-built drawings, comparing earthworks, verifying as-built conditions, identifying drainage routes, and maintenance management, it is important to organize the information needed for each purpose and to create a flight plan that ensures complete photographic coverage.

In practice, insufficient pre-flight preparation often directly leads to re-flights and rework in post-processing. Rather than deciding things once you are on site, check drawings and existing documentation in advance and determine the flight area, takeoff and landing points, control points, locations for supplemental imaging, and data management procedures; doing so makes it easier to carry out stable surveying even within a limited time.

To carry out drone surveying of solar power plants more reliably, it is important to organize the entire workflow from flight planning to data utilization. When considering a survey system that is easy to use on site, be sure to confirm operational methods that match your objectives, including the aircraft to be used, positioning methods, the handling of control points, the analysis environment, and data management procedures.