Is Night Flight Possible in Drone Surveying? 5 Conditions to Check in Advance

Table of Contents

• Is nighttime flight possible in drone surveying?

• Condition 1: Organize the legal classification and required procedures

• Condition 2: Do not misunderstand the handling of flight location and time of day

• Condition 3: Ensure the aircraft and takeoff/landing environment allow safety checks even at night

• Condition 4: Determine whether nighttime is suitable for the purpose of the survey

• Condition 5: Finalize the operator, assistants, and record-keeping arrangements first

• Worksites suitable for night flights and worksites to be avoided

• Summary

Is night flight possible in drone surveying?

In short, it is possible to conduct nighttime flights for drone surveying. However, you cannot simply substitute a daytime flight with a nighttime one. As a rule, unmanned aircraft operations are to be conducted during daytime, and nighttime flights are a regulated type of operation. Moreover, "daytime" here does not mean the subjective sense of "while it's still light"; it refers to the period from sunrise to sunset as published by the National Astronomical Observatory. In other words, even if the site still appears to be in twilight, it may already be legally considered nighttime. If you are considering nighttime flights, you must first correctly understand this premise.

What matters in practice is not just whether you can fly at night. It is important to judge whether you can consistently produce survey results that are meaningful, whether you can ensure sufficient safety on site, and whether you can complete the necessary procedures in time for the scheduled date. In particular, night flights that are beyond visual line of sight and night flights over areas densely populated with people or houses are treated as requiring location-specific applications. Furthermore, when conducting beyond-visual-line-of-sight night flights over areas densely populated with people or houses, an application specifying not only the location but also the date and time is required. Night flights are not something where “if you obtain a permit you can do anything”; in practice, it is better to regard that the conditions can become much stricter at once depending on the flight type.

Therefore, when those responsible for drone surveying consider night flights, they need to check five things simultaneously—laws and regulations, the site, the aircraft, the deliverables, and the operational system—rather than simply pushing the work schedule later. If even one of these is left unclear, you may be able to conduct the flight itself but the project can easily stall because the results are unusable, applications are not submitted in time, the site manager does not grant permission, or arrangements for dealing with third parties cannot be put in place. Keep in mind that the feasibility of night flights is determined largely by operational design rather than aircraft performance, and doing so reduces the likelihood of failure.

Condition 1: Organize the legal classification and required procedures

The first thing to check is which legal category the flight falls under. Currently, aircraft weighing 100 g (3.5 oz) or more are regulated as unmanned aircraft under the Civil Aeronautics Act and are subject to registration and various rules. In that context, night flights are one type of specified flight. Furthermore, flight operations are categorized according to risk, and whether a flight is conducted with access-control measures to avoid flying over third parties or includes flights over third parties affects the required procedures and standards. Night flights are not subject to a single uniform application; they must be assessed by combining the flight location, the presence or absence of third-party management, the aircraft’s certification status, and whether the pilot holds a competency certificate.

A common misunderstanding here is the idea that "if you have the qualification, you can fly freely at night." In reality, for some Category II flights that meet certain conditions, a person holding a competency certificate can use an unmanned aircraft that has received aircraft certification, and by implementing the required safety measures and preparing a flight manual, permission or approval for night flight may not be necessary. However, that applies only when conditions are met — for example, after implementing access control measures, the total weight being under 25 kg, and having received any necessary limitation amendments. To conduct night flights without permission or approval, a limitation amendment for night flight is also required on the competency certificate. In surveying operations, where flight methods differ by site, there are many cases in which these conditions cannot be met, and as a result individual confirmation or application is often required.

Also, among night flights, nighttime flights over areas densely populated with people and houses and beyond-visual-line-of-sight (BVLOS) flights at night are areas that are difficult to proceed with using the approach of obtaining a broad, catch-all permission. Even the national standard manual states that such flights need to be treated as "location-specific applications." In other words, construction sites in urban areas, work sections with nearby residences, and automatic night flight routes must have their location conditions identified early, and site diagrams and flight paths must be organized together.

In practice, it is appropriate to begin preparing the application as soon as you consider conducting a night flight, and it is safest to submit at least 10 business days before the planned flight start date; preferably allow a margin of about 3–4 weeks. Because permission/approval applications require inclusion of third-party liability insurance details, you must also check the insurance validity period and coverage in advance.

Condition 2 Do not misunderstand how flight locations and time periods are handled

When planning nighttime flights, two points that are surprisingly often overlooked are when exactly it becomes nighttime and where you are allowed to fly. For the time period, the standard is not how it feels on site but the sunrise and sunset times announced by the National Astronomical Observatory. Because those times vary by season and region, using the same intuition for an urban area in winter and a rural area in summer can lead to incorrect judgments. Even if you only want to fly for a short period in the evening, if the operation crosses sunset it will be treated as a nighttime flight, so it is dangerous to judge based solely on expressions written on the site schedule such as "after 17:00" or "start at 18:00." Rather than relying on the surveying crew’s sense, it is necessary to plan the work schedule based on the astronomical times for that day.

When it comes to location, looking only at the Aviation Law is not sufficient. In addition to national flight permissions and approvals, restrictions overlap—areas around facilities covered by the Act on Prohibiting Flights of Small Unmanned Aircraft, prefectural and municipal ordinances, and rules set by facility managers. Around critical facilities there are zones where flights are prohibited even in peacetime, and temporary no-fly zones may be designated during disasters or for VIP responses. Furthermore, if emergency-use airspace is designated, flights are, in principle, not allowed in that airspace. Even when flying appears permissible under national rules, there are many sites where the facility manager’s permission is required or where nighttime use itself is restricted. Therefore, before deciding on night flights, it is necessary to consolidate and verify legal permissibility, consultations with managers, and restriction information for the site and its surroundings.

At survey sites, it is often thought that flying is easier at night than during the day because there are fewer pedestrians and vehicles. This notion is not wrong in itself, but nighttime does not automatically make operations safer. What matters is whether you can reliably restrict third-party entry. At night the aircraft is harder to see from the surroundings and passersby may not notice the flight area, so simply having fewer people is not enough. Only after you have thoroughly worked through whether the operation is contained within the construction yard, whether there is any possibility of people entering from adjacent roads, sidewalks, parking lots, or river maintenance paths, and how you will handle complaints from neighbors and manage guidance, will the feasibility of night flights become clear.

Condition 3: Ensure the aircraft and takeoff/landing environment allow safety checks even at night

In night operations, the core issue is not so much the aircraft's performance as whether you can create an environment in which safety checks can be conducted at night. The national standard manual states that when conducting night flights, beyond-visual-line-of-sight operations should not be performed, aircraft must be equipped with lights that allow the aircraft's orientation to be visually identified, and flights should be limited to ranges where those lights can be easily recognized. In addition, the intended flight route and surrounding obstacles must be pre-inspected during the daytime, and an appropriate flight path selected. In other words, entering a site for the first time at night and deciding and measuring the route on the spot is not compatible with the basic concept of night flight. If you are going to fly at night, a two-step approach—reconnaissance during the day and flight at night—is the prerequisite.

Furthermore, securing lighting at takeoff and landing sites is essential. Standard manuals require that, at nighttime takeoff and landing locations, sufficient illumination be provided by vehicle headlights, lighting equipment, etc. This is not only to make takeoff and landing easier to see, but also to ensure awareness of surrounding obstacles, ground conditions, personnel positions, and to enable reliable responses in the event of an emergency stop. On surveying sites there are often temporary materials, cables, level differences, puddles, and uneven ground, and footing conditions that are not problematic during daytime can become major causes of accidents at night. If flying at night, preparations should cover not only safety in the air but also creating a safe ground operations area.

Weather conditions must be checked more carefully at night than during the day. The standard manual states that flight must be terminated immediately if an unforeseen situation arises that makes safe flight impossible, such as gusts of 5 m/s or more, and that flights must not be conducted in clouds or fog where sufficient visibility cannot be ensured. At night it is harder to notice changes in wind or the onset of fog, and reflections from lights and reduced depth perception can make conditions appear more stable than they actually are. The more a site involves night flights, the more necessary it is to decide in advance to check the anemometer, set the criteria for evacuation decisions, establish withdrawal routes, and designate emergency landing locations. Safety checks should not be left to experience alone; it is important to put decision criteria for night operations into writing.

Condition 4: Determine whether nighttime is suitable for the purpose of surveying

This is the single most important condition for surveyors. Even if nighttime flights are legally permitted and site safety appears manageable, whether those flights will actually lead to useful survey results is a different question. Night flights are most suitable for recording conditions over a narrow area, inspecting facilities where perimeter access control is easy, and sites where daytime vehicle and worker traffic makes it hard to establish a flight zone. In short, it makes sense to consider night flights when doing so makes third-party control easier, clarifies the flight route, and allows the necessary information to be obtained in a short time. Conversely, simply shifting operations to night as a vague substitute for daytime work tends only to increase preparation costs and make results unstable.

Of particular concern is surveying that uses photographs as the primary material. At night, the difficulty of determining the unmanned aerial vehicle’s position and attitude and of detecting surrounding obstacles is one reason why nighttime flight is regulated in the first place. From that premise, it is natural to assume that the work of acquiring many visible images to stably produce orthoimages, photo-based point clouds, and shape reconstruction outputs is likely to be at a disadvantage compared with daytime. Even if the site is well lit, it is not easy to reproduce daytime conditions in terms of how subjects appear, shadows, blur, the identifiability of control points and reference points, and ensuring ground surface texture. Decisions should be based not on whether flying at night is possible but on whether the required-accuracy results can be produced at night; otherwise rework will occur in later processes.

On the other hand, measurements that focus on distance acquisition, a rough grasp of shape, or confirmation of changes within a limited area may still be feasible at night. However, even in those cases, nighttime-specific safety requirements—such as pre-checking the flight route, lighting for takeoff and landing sites, assistants, and access control measures—do not disappear. In other words, changing the sensor type does not eliminate the need for nighttime preparations; it merely changes how the deliverables are produced. Compatibility with nighttime operations varies greatly depending on whether the survey was commissioned for earthwork volume calculation, as-built verification, inspection records, or 3D modeling. Before deciding on nighttime flights, the most effective precheck is to once restate the required deliverables in words.

Condition 5: Secure the operator, assistants, and recording system first

For night flights, personnel readiness is more important than the aircraft. The standard manual specifies that pilots must be limited to those who have completed night flight training, and it requires that assistants also fully understand the characteristics of the unmanned aircraft to be flown. When conducting night flights within a permission/approval-exempt framework by utilizing a competency certificate, an amendment to the night flight limitation is necessary. Conversely, simply having extensive daytime piloting experience does not mean that the arrangements for night flight are sufficient. What is required on site are records of night piloting practice, clear division of roles with assistants, shared criteria for stop/abort decisions, reporting procedures, and verification of guidance routes. It is important to understand that night flight is not an operation that can be accomplished by one skilled pilot alone, but a task in which safety is achieved by the team.

Also, when conducting specified flights, advance notification of the flight plan and entry in the flight log are required. If you carry out a specified flight without reporting the flight plan, or if you do not keep a flight log or fail to record the required items, you may be subject to penalties. Because operations include management of records after the flight, you cannot give night operations special treatment and omit them based on on-site judgment. Furthermore, for flights conducted with permission or approval, notification of the flight plan, confirmation of other scheduled flights, reporting of accidents, and provision of medical assistance as necessary are required. Since it is harder to ascertain the situation in the event of a problem at night, sites with weak record-keeping systems suffer more during post-incident handling. Companies where the person who prepares application documents is different from the person who operates the flight on site should ensure that information is reliably handed over before night flights.

In practice, it is too late to discuss “can we go tonight?” immediately before a night flight. Ideally, cancellation criteria should be decided in advance. For example, cancel if lighting is inadequate; cancel if auxiliary personnel cannot be secured; cancel if fog or reduced visibility is observed; cancel if unexpected traffic occurs on surrounding roads — by doing this, decisions are separated from individual judgment. The standard manual also requires establishing a contact system with the police, fire department, and relevant agencies for emergencies. Because night flights increase the accident rate if run on a “those who can will do their best” basis, it is important to create operational criteria in advance that result in the same judgment no matter who makes them.

Sites Suitable for Night Flights and Sites to Avoid

Night flights are suitable for sites where the flight area can be clearly delineated. For example, on premises that are off-limits to unauthorized personnel and where daytime operations and vehicles have a major impact but access control is easier at night, night flights can be rational. If you need to quickly confirm the current situation, want to take aerial records while a facility is shut down, or the burden of dealing with third parties during the day is too high, night flights are well worth considering. In other words, night flights are effective not because it is dark, but because flight conditions are easier to control at night.

Conversely, it is better to forgo night flights at sites where you want to carry out large-area photogrammetry all at once, sites with many houses and roads nearby, sites where it is difficult to control third parties beneath the flight path, and sites where an initial survey has not sufficiently identified terrain and obstacles. In particular, when orthoimages or photo-based point clouds are the primary deliverables, there are often cases where prioritizing the reproducibility of deliverable quality over whether the flight is possible is preferable. If the only reason for choosing night flights is “there’s no time during the day,” alternative solutions—such as short daytime flights, redesigning for early morning or late afternoon, or combining with ground surveys—will often produce more stable results.

Summary

Night flights for drone surveying are possible, but deciding based only on whether they are possible leads to failure. What matters are five conditions: that the legal classifications and required procedures have been整理できている (have been sorted out); that there is no misunderstanding about the flight location and time of day; that the aircraft and the takeoff/landing environment allow safety checks even at night; that nighttime is truly appropriate for the surveying objective; and that the pilot, assistants, and recording system are fully in place. Night flights should be chosen only when these conditions are met, not as a substitute for daytime operations.

In practice, there are many situations where strengthening ground-based position management and pre-checks improves overall accuracy and safety more than trying to force operations into nighttime. If you want to reliably carry out pre-flight reference point checks, control point management, as-built verification, and current-condition assessment, an operational design that does not rely solely on aerial surveying is effective. For building such a field foundation, combining mechanisms that can quickly and precisely capture required points—such as LRTK (iPhone-mounted GNSS high-precision positioning device)—makes it easier to assemble a more realistic surveying plan that includes night flights.