5 Things to Check to Avoid Failure When Outsourcing Surveying for Solar Power Plants

In the construction, operation and maintenance, and retrofit planning of solar power plants, it is important to accurately understand the on-site topography and equipment layout. Especially for sites involving large areas, slopes, drainage facilities, embankments, racking, and access roads, changes that are difficult to judge by visual inspection alone can occur. One readily usable method is external surveying, including drone surveying. However, outsourcing surveying does not always guarantee the expected results. If pre-order checks are insufficient, problems can arise such as failing to achieve the required accuracy, deliverables being difficult to use internally, site conditions not being reflected, or the need for re-surveying in later stages. This article organizes the items that operational staff should confirm in advance to avoid failures when outsourcing surveying for solar power plants.

Table of Contents

• Clearly define the purpose and intended use cases of the survey before outsourcing.

• Confirm the accuracy and deliverables required for drone surveying

• Share on-site conditions unique to solar power plants.

• Align the scope of work and responsibilities with the subcontractor.

• Confirm post-delivery utilization methods and any additional follow-up support.

• Summary

Clarify the purpose of the survey and its use cases before outsourcing

The first thing to confirm when outsourcing surveying for a solar power plant is to clarify what the survey is for.

Even when you use the word “survey,” the information required varies depending on the purpose, such as understanding topography before design, checking current conditions before construction, monitoring progress during construction, verifying as‑built conditions after completion, detecting changes during operation and maintenance, and assessing conditions after a disaster. If you outsource while the purpose is vague, even if photos and measurements are taken on site, the final deliverables may not align with what the person in charge ultimately needs to evaluate.

For example, when planning a new solar power plant, it is important to understand the site's overall topography, slopes, existing roads, drainage directions, and the relationship to surrounding boundaries. On the other hand, for operation and maintenance of an active plant, detecting changes that affect equipment operation—such as settlement around mounting racks, slope failures, clogged drainage channels, ruts in access roads, and stormwater flow paths—is emphasized. Even with the same drone surveying, design-oriented and maintenance-oriented projects differ in capture area, flight altitude, how point clouds and terrain data are generated, and how photos are organized, so the intended use should be specified at the time of ordering.

Prior to outsourcing, it's important to clarify who will use the deliverables, in what situations, and how. The way the deliverables need to be presented differs depending on whether they will be used by design staff, construction management staff, maintenance and inspection staff, or for explanatory materials for the client. For design staff, data that make coordinates and elevations easy to work with are necessary; for site management staff, materials that clearly show the correspondence with site photos and plan drawings are helpful. For reports to management or to the project owner, not only specialized point-cloud data but also organized materials that make locations of changes intuitively understandable may be required.

Especially at solar power plants, sites can be large and the terrain not simple. On reclaimed land, former forest land, around ponds, land converted from agricultural use, and sloped areas, ground conditions and drainage conditions can vary by location within the same site. Therefore, it is important not simply to photograph the whole site, but to specify in advance the locations you want to inspect closely. For example, places where puddles have formed in the past, areas where soil runoff has been observed, locations where the tilt of the mounting racks is a concern, the downstream ends of drainage channels, and spots where damage to maintenance roads is conspicuous are all information you should share with the contractor.

Also, it is necessary to confirm to what extent the surveying results will be used for decision-making. Depending on whether the material is for understanding the overall situation, for examining design or construction quantities, for determining repair scope, or for use as supporting documentation when explaining to stakeholders, the required level of accuracy and the strictness of record-keeping will vary. If it is for understanding the overall situation, prioritizing organization of a wide area in an easy-to-understand way may be appropriate, but if it relates to construction quantities or elevation management, measurement accuracy and the handling of control points need to be checked more carefully.

A common pitfall is when the client says, "Just measure it with a drone for now." With such a request, the contractor can perform general surveying and imaging, but may not be able to infer what the client actually wants to verify. In drone surveying of solar power plants, power generation equipment, terrain, drainage, boundaries, and operational/maintenance access routes are interrelated in complex ways, so insufficiently shared objectives reduce the value of the deliverables. Before commissioning work, it is important to concisely summarize the survey purpose, target scope, key points to be checked, the users of the deliverables, and the situations in which they will be used, and to align these with the contractor.

Confirm the Accuracy and Deliverables Required for Drone Surveying

Next, it is important to confirm the required level of accuracy and the format of the deliverables. When outsourcing surveying for a solar power plant, you need to decide in advance whether taking photos is sufficient, whether point cloud data is required, whether a terrain model is needed, or whether plans and cross-sections are necessary. If the ordering party makes a request without clearly specifying the deliverables, problems often arise after delivery, such as "you can see how it looks but cannot verify heights," "there are point clouds but we cannot handle them in-house," or "there are many photos but they cannot be matched to locations."

In drone surveying, images captured from the air are used to produce orthophotos, point clouds, elevation data, and three-dimensional models. Orthophotos make it easy to grasp the overall condition of a site in plan view and are useful for checking panel layout, access roads, drainage channels, slope faces, and vegetation distribution. Point cloud data allow three-dimensional verification of heights and shapes, making them effective for understanding ground undulations, the condition of fills and cuts, slope deformations, and settlement trends around support structures. Elevation data and cross-sections are practical deliverables for checking drainage gradients and graded surfaces and for considering repair plans.

However, which deliverables are required depends on the purpose. If used as inspection materials for maintenance management, an overall orthophoto, enlarged photos of areas of concern, and height information as needed can make it practical for fieldwork. On the other hand, if used to study ground deformation or drainage planning, data that allow confirmation of elevation differences and cross-sections are required. If used for construction management or as-built verification, you must also confirm the coordinate system, control points, measurement conditions, and methods of accuracy management. Before outsourcing, verify that the deliverables are appropriately specified—neither more nor less—relative to the purpose.

Regarding accuracy, the client and the contractor need to align their understanding. At solar power plant sites, the level of control required differs between surveying to observe overall trends and surveying to determine precise heights and positions. While drone surveying can efficiently capture wide areas, the quality of the deliverables varies depending on site conditions, imaging conditions, the placement of control points, and processing methods. It is important for the client to communicate how much accuracy is required, over what area heights and positions should be checked, and for what decisions the deliverables will be used, and to receive from the contractor a proposal for the appropriate surveying method.

Also, at solar power plants the panels cover the ground surface, so there are locations where the ground cannot be adequately captured by aerial surveying alone. The ground beneath panels, areas shaded by mounting racks, heavily vegetated areas, parts of slopes, and the inside of drainage channels can be difficult for drones to see. If you want to capture these kinds of locations, you need to consider supplementary ground surveys, close-range photography, or combining other methods as required. Rather than assuming that drone surveying can capture everything, it is important to determine in advance whether the targets you need to inspect are visible from above or are obstructed.

The format of deliverables is also an important item to confirm. Point cloud data and drawing data become difficult to use if they do not match the in-house viewing or design environments. Even if an external contractor delivers files in a common format, problems can arise such as the purchaser’s staff being unable to open them, files being too large to handle, coordinates not aligning, or necessary layers not being separated. Confirming the required data formats, coordinate systems, file-splitting methods, photo numbering/organization, and the scope to be reflected in the drawings before delivery can reduce rework after delivery.

Deliverables are more useful in practice if you consider both data that only specialists can handle and materials that site personnel can quickly check. Point clouds and terrain data are helpful for detailed analysis, but for routine inspection meetings and repair decisions, drawings that show areas of change, easily comparable photos, and materials that clarify the extent are often required. When outsourcing, be sure to tell the contractor whether you need not only specialist data but also organized materials that can be used for internal explanations. In outsourcing surveying for solar power plants, the key to success is less what you measure than how you make the measured results usable.

Sharing Site Conditions Specific to Solar Power Plants

Sharing site conditions is essential to avoid failures when outsourcing surveying for solar power plants. Unlike typical developed lots or construction sites, solar power plants have many facilities spread across the entire site, including panels, racking, collection equipment, access roads, fences, drainage channels, slopes, and cable routes. Furthermore, at operating plants there are constraints on safety management and work flow that require careful attention in how surveying is carried out. If the subcontractor does not sufficiently understand the site conditions, discrepancies will arise in flight planning, imaging coverage, access areas, and methods for supplementary surveys.

First, what I want to share is the extent of the site and the areas that can be accessed. At solar power plants, the fenced power generation area and the surrounding maintenance roads, slopes, drainage channels, and land near the boundaries can be intricately related. The area the client wants surveyed may not match the area that can actually be accessed. It is advisable to share in advance with the contractor materials that show the survey target area, no-entry zones, locations where vehicles can enter, areas accessible only on foot, and the boundaries with neighboring landowners. If verification near a boundary is required, it is also necessary to clarify whether the purpose of the survey is to determine the boundary or simply to confirm positions for management.

Next, sharing the equipment layout is also important. At solar power plants, even if panel rows appear neatly aligned, slopes, steps, racking heights, aisle widths, and the locations of drainage facilities vary from place to place. Equipment that is easy to see from above can still be difficult to access for ground-level work or supplemental measurements. In particular, areas under racking, between panel rows, around collection equipment, on steep embankments, and on easily waterlogged paths affect both work safety and surveying quality. Share any existing drawings or simple layout maps with contractors, and let them know which equipment and pathways require attention on site.

Drainage conditions are also an important inspection point at solar power plants. Because rainwater collects over large sites, the conditions of drainage channels, side ditches, catch basins, outlets, and slope drainage relate to ground deformation and sediment outflow. When using drone surveying for operation and maintenance, it is important not only to photograph the panels and the entire site, but also to check the terrain with an awareness of water flow. Share with your external vendor the locations that have previously flooded, places where water remains after rain, areas prone to sediment accumulation, and points where inflow occurs from slopes as priority inspection points. This makes it less likely that information related to drainage will be overlooked during shooting and data processing.

Vegetation and seasonal conditions also affect results. At solar power plants, the appearance of the ground surface changes significantly before and after mowing. If drone surveys are conducted when grass is tall, the ground surface can be difficult to see, which can affect understanding of the terrain. After mowing, it becomes easier to check the condition of the ground surface and drainage channels. Snow cover, mud after rain, strong winds, and shadows caused by intense sunlight also affect imaging quality and work safety. Rather than only telling contractors the desired survey date, it is effective to share site operational schedules as well, such as planned mowing, inspection dates, and locations you want checked after rain.

At an operating power plant, it is necessary to confirm both safety and operational aspects. When workers approach equipment, rules for entering areas around electrical equipment, whether an administrator will accompany them, permitted working hours, vehicle parking locations, and emergency contact information must be organized. When flying drones, consideration of the surrounding environment, the presence of third parties, wind conditions, takeoff and landing locations, flight routes, and notification of relevant parties is also important. Depending on the flight area and method, confirmations and procedures based on applicable laws and the administrator’s rules may be required. These matters are not only the responsibility of subcontractors but also information the client should provide as the site manager. Insufficient prior sharing can lead to situations on the day when flights cannot be carried out, planned areas cannot be entered, or necessary supplementary surveys cannot be performed.

Also, it is important to share past troubles and concerns without hiding them. Locations where subsidence is suspected, places that have experienced sediment runoff in the past, sites with repair histories, locations where drainage improvements have been carried out, and areas where racking tilt has been reported should all be prioritized for surveying. When subcontractors know this background, it can change how they assess the site in the field. Drone surveying of solar power plants is not simply a photography task; it is a means to visualize on-site issues. The more specifically site conditions are shared, the closer the deliverables will be to supporting practical decision-making.

Align the subcontractor's scope of work and responsibilities

One common problem with outsourced surveying is a misunderstanding about the scope of work and the scope of responsibility. The client may assume, "Because we commissioned the survey, they will prepare all the necessary documents," while the subcontractor may believe, "Our work is limited to the measurements requested and delivering the data." When this gap exists, additional documents may be required after delivery, the creation of explanatory drawings may become a separate job, or a site revisit may be necessary. When outsourcing surveys for solar power plants, it is important to decide specifically in advance what will be requested.

The first thing to confirm is the scope of on-site work. Clarify whether the subcontractor will only conduct drone flights, or whether the work also includes supplementary ground surveying, installation of control points and reference marks, and checks against existing drawings. In solar power plants, areas visible from above and areas that must be inspected on the ground are mixed. For example, scour beneath the mounting racks, the inside of drainage channels, small slope failures on embankments, and localized steps or unevenness on service roads can be difficult to assess from drone imagery alone. If you want to check such locations, decide in advance whether to include ground inspections and close-up photography in the scope of work.

Next, confirm the scope of data processing. The tasks vary greatly depending on whether you will create orthophotos from the captured data, generate point cloud data, produce elevation data, or go as far as creating cross-sections and difference comparisons. If comparison with previous survey data is required, you must also check whether it can be compared using the same coordinate system and equivalent conditions. In solar power plant operation and maintenance, there are many situations where you want to check not only the current condition but also where changes have occurred since the previous inspection. If you require difference comparisons, coordinate with your subcontractor or vendor to ensure that the quality and conditions of the comparison data are sufficient.

The scope of reports and explanatory materials is also important. It is often the case that what the client requires is not just the delivery of specialist data, but materials that can be used to explain matters to stakeholders. For example, materials that show locations of deterioration on drawings, materials that link photos to locations, materials that organize drainage concern points, and materials that indicate candidate areas for repairs. It is necessary to decide how much analysis to request of the subcontractor—whether only the organization of surveying results or also the extraction of on-site issues. For aspects that require specialized judgment, another approach is to assume that designers or managers will make the decisions and to ask the subcontractor to compile the information needed for those decisions.

Regarding the scope of responsibility, you should also confirm the scope of guarantees for the survey results and any precautions for their use. The applicability of surveying results varies depending on acquisition conditions and processing conditions. The ground surface beneath panels, areas covered by grass, locations affected by shadows or reflections, and areas that could not be accessed may result in limitations to the deliverables. Ask subcontractors to indicate within the deliverables which areas were adequately captured and which areas require caution, as this will reduce misunderstandings in subsequent processes. The client should also take care not to use the survey results beyond their original intended purpose.

Conditions for rework and additional responses are items you should confirm in advance. It is reassuring to clarify how each situation will be handled—such as if unexpected obstacles are found on site, if flights are impossible due to weather, if tall grass obscures the ground surface, or if the client makes additional requests. At solar power plants there are conditions that only become apparent once you visit the site. Because it is difficult to finalize everything beforehand, deciding in advance on the consultation procedure when changes occur, the handling of additional work, and the impact on delivery deadlines will help prevent operational problems.

When selecting a subcontractor, it is important to judge not only whether they can operate a drone, but also whether they understand the site characteristics of a solar power plant and can propose a scope of work that matches the client's objectives. The ability to photograph a large site is not the same as the ability to organize the results into deliverables usable for plant operations, maintenance, and design review. If, during meetings, a subcontractor can specifically explain which surveying methods are appropriate for the objectives, how they will compensate for hard-to-see areas, and how they will organize the deliverables, the delivered work will be more useful.

Confirm post-delivery usage methods and any additional follow-up actions

The success or failure of outsourcing surveying work is determined not at the time of delivery but by how usable the deliverables are in actual operations after delivery. In drone surveying for solar power plants, multiple deliverables may be provided, such as orthophotos, point clouds, drawings, photographs, and reports. However, if you cannot open them within your company, do not know where to look, find them difficult to share with site personnel, or cannot compare them with past data, the benefits of outsourcing will not be fully realized. It is important to anticipate how the deliverables will be used after delivery before placing the order.

First, it is important to decide who will be responsible for checking the deliverables. Surveying data is specialized, so sometimes after delivery it ends up being stored without anyone reviewing its contents. When multiple stakeholders are involved—design engineers, construction managers, maintenance personnel, and the client's management representatives—decide who will check which deliverables and how those checks will inform decision-making. In operation and maintenance of solar power plants, having a person familiar with the site review the deliverables can fill in contextual information that photos and point clouds alone make difficult to grasp. By combining survey results with on-site experience, you can reduce the likelihood of overlooking signs of deterioration.

Next, confirm how the deliverables will be viewed. Point cloud and three-dimensional (3D) data are useful, but they require more familiarity to handle than ordinary documents or images. It is helpful to distinguish whether you need materials that internal staff can review without a special environment, or whether specialist personnel will handle data for detailed examination. Not everyone needs to handle point cloud data directly. In practice, having overview materials based on the detailed data, maps showing the locations of changes, organized photos of areas to be checked, and explanatory materials on cross-sections and heights makes them easier to use in meetings and inspection planning.

This is also a point to confirm regarding methods for comparing with past data. At solar power plants, there are many items that change over time, such as ground subsidence, slope deformation, poor drainage, and damage to maintenance roads. The initial survey is important for understanding the current situation, but from the second survey onward, checking the differences from the previous survey improves the accuracy of maintenance and management. Therefore, it is important to store the current deliverables in a form that can be used for future comparisons. Recording the coordinate system, survey extent, control points, imaging conditions, processing conditions, and the structure of the delivered data will make it easier to compare during the next survey.

Discuss whether there will be a post-delivery briefing or review meeting before outsourcing. Survey results can be difficult to interpret if you only receive the delivered files. If the contractor explains the survey area, acquisition conditions, points to note, locations where abnormalities are suspected, and how to read the deliverables, the client will find it easier to understand the results. In particular, when outsourcing drone surveys at a solar power plant for the first time, it is important to know whether there will be a post-delivery explanation. Being able to confirm any questions during the briefing makes it easier to proceed with additional investigations or consider repairs.

Also confirm the process for additional requests. After delivery, there may be requests to check another area, obtain cross-sections of specific locations, compare with previous data, or add materials for stakeholder briefings. Confirm whether such additional work is possible, which data can be used as the basis, and whether a return visit to the site is necessary so you won’t be caught off guard later. In particular, if there are locations that could not be captured due to on-site conditions, additional shooting or ground checks may be required. Assuming post-delivery use, it is practically effective to maintain a communication channel with subcontractors.

Don't forget the rules for storing and sharing deliverables. Survey data for solar power plants can be large in volume and involve multiple stakeholders. You need to clarify who keeps the original, which documents are shared for on-site use, and which data are used by design and maintenance personnel. If file names and folder structures are hard to understand, you won't be able to find the materials you need at the next inspection. Organize and store the data so that the survey date, coverage area, type of deliverable, coordinate system, and creator are clear, and keep them in a state that can be used for future operation and maintenance.

Rather than treating outsourced surveying as a one-off task, it is also important to incorporate it into the power plant’s management cycle. There are multiple situations where drone surveying is useful: gaining an overall assessment before routine inspections, checking for changes or damage after heavy rain, verifying the ground after grass cutting, comparing conditions before and after repairs, and confirming the current state prior to expansions or renovations. If you consider from the first outsourcing how often, over what area, and with which deliverables you will perform checks going forward, surveying data will accumulate and become easier to use as material for decision-making in power plant management.

Summary

To avoid failures when outsourcing surveying for solar power plants, it is important that the client, rather than leaving everything to the contractor, organizes the purpose, accuracy requirements, site conditions, scope of work, and how the deliverables will be used after delivery. Drone surveying is an effective means to efficiently capture large sites and visualize terrain, equipment layout, slopes, drainage, and the condition of access and maintenance roads. However, if you commission the work with an unclear purpose, you may lack necessary information or find the deliverables difficult to use in practice.

First, clarifying the purpose of the survey and the contexts in which it will be used is fundamental. The surveying requirements differ between design studies, construction management, maintenance management, post-disaster inspections, and repair planning. After deciding who will use the deliverables and what decisions will be made, you need to communicate the survey extent and the key points to be checked to the contractor. In particular, for solar power plants, panel layout, racking, drainage channels, slopes, access roads, and boundaries are interrelated in complex ways, so sharing specific on-site concerns will determine the quality of the results.

Next, it is important to confirm the required accuracy and deliverables. The deliverables needed—orthophotos, point clouds, elevation data, cross-sections, photo organization, report materials, etc.—vary depending on the purpose. Drone surveying is well suited to capturing wide areas, but there are locations that are hard to see from above, such as beneath panels or ground surfaces covered by vegetation. By considering in advance whether the targets you need to inspect can be captured by drone alone or require supplementary ground verification, you can prevent misunderstandings after delivery.

Furthermore, it is essential to align the scope of work and responsibilities with the subcontractor. You need to clarify how far their tasks will extend among on-site work, data processing, drafting, preparation of comparison materials, report writing, and post-delivery explanations. Confirm the permitted uses and cautions for the survey results, and have them make clear any locations that could not be acquired and any areas where accuracy requires attention, as this will help prevent misuse in downstream processes.

Finally, it is important to plan for how the deliverables will be used after delivery. Survey data for solar power plants is not something to check once and then discard; it can be used for subsequent inspections, maintenance planning, comparison with previous data, and explanations to stakeholders. Confirming whether the deliverables can be opened internally, are easy to share with on-site personnel, and can be stored in a format that allows future comparisons makes it easier to achieve practical benefits that justify the outsourcing cost.

When outsourcing drone surveys for solar power plants, it is important not only to consider the technology itself but also how onsite issues are organized and converted into outcomes that support decision-making. If you carefully complete checks before placing an order, the survey results can serve as effective decision-making material in design, construction, and maintenance. If you want to efficiently grasp conditions across a large power plant and continuously manage changes in terrain and equipment, it is essential to focus on creating a system that produces survey deliverables that are easy to use onsite and to select an outsourcing partner and surveying method that match your objectives.