Class societies will credit a close-up survey from drone footage instead of staging. What owners keep missing is the condition attached: the flying has to be done by a firm approved as a service supplier, and a surveyor has to be watching while it happens. Owning a drone is not the qualification. Being approved is.
The Cost Sitting Inside Every Tank Survey
A close-up survey of a ballast tank has always been an access problem before it is an inspection problem. To look at the upper structure the way the rules require, someone has to get there. That has traditionally meant staging built inside the tank, rafting on partially flooded ballast, or a cherry picker where the geometry allows one. The inspection itself might take an afternoon. Building the access to make it possible takes considerably longer and costs considerably more.
The expense is only part of it. Erecting staging inside a confined space puts people in the tank for days rather than hours, and every one of those hours carries the atmospheric, access and working-at-height risks that make enclosed space entry one of the most dangerous routine jobs at sea. The survey is not the hazard. Reaching the survey is.
Remote inspection changes the arithmetic, and class rules have accommodated it for years now. What has not changed is that the acceptance comes with conditions, and the conditions are where most of the confusion sits.
What “Close-Up” Actually Means
The phrase has a precise definition, and it is worth quoting because everything else follows from it. A close-up survey is one where the details of structural components are within the close visual inspection range of the surveyor, normally within reach of hand.
That standard is what any alternative has to satisfy. The question a class society asks about drone footage is not whether the images look good. It is whether the surveyor was able to examine the structure to the same standard they would have achieved standing next to it with a hammer in their pocket. Resolution, lighting and coverage all matter because they are what determine whether that threshold has been met.
The test is not “did you photograph the structure”. It is “could the surveyor examine it to the standard of being within reach of hand”. Footage that fails that test does not credit the survey, however impressive the flying was.
What Class Will Accept Instead
Remote Inspection Techniques, usually shortened to RIT, are recognised in the IACS Unified Requirements as an alternative means of carrying out a close-up survey. IACS Recommendation 42, the guidance on their use, was revised in June 2016, and related Unified Requirements took effect in January 2019.
RIT is broader than drones. The accepted means include divers, remotely operated vehicles, unmanned robot arms, climbers, and other methods acceptable to the society. Drones are simply the option that has become practical fastest for tank and hold structure, because they reach the upper regions of a space without anything being built underneath them.
Where it is accepted, the benefit is exactly the one owners want: the surveyor obtains what they need to credit the close-up survey without the rafting, cherry pickers or staging that would otherwise be required to put them within arm’s length of the steel.
The Condition Everybody Misses
Here is the part that turns a good idea into a rejected survey. Where a RIT is used as an alternative to close-up survey and is not carried out by the society itself, two things must both be true.
First, the inspection must be conducted by a firm approved as a service supplier under IACS UR Z17. That is the same approval regime that governs firms carrying out thickness measurements, and it is not a formality. It involves verification and audit by the classification society before the firm is permitted to perform the service at all.
Second, the inspection must be witnessed by an attending surveyor of the society. In practice this generally means the surveyor observes the inspection through a live video feed while it happens, rather than reviewing a recording afterwards. The surveyor is conducting the survey; the drone is how they see.
Approval under UR Z17: The firm is verified and audited by the classification society before it may supply the service. An unapproved firm cannot credit a close-up survey regardless of the quality of its equipment.
Qualified operators: Relevant training and qualification of the personnel flying the aircraft, evidenced rather than asserted.
Adequate live-stream resolution: The feed has to be good enough for the attending surveyor to examine structural detail in real time, which is a higher bar than footage that looks acceptable on playback.
Proper illumination: Tank interiors have no ambient light. Lighting carried by the aircraft is part of the capability being approved, not an accessory.
A reporting trail: Data obtained during the inspection is compiled into a final report that forms part of the survey record.
Why the Distinction Is Commercially Sharp
Plenty of contractors own capable aircraft and can produce excellent imagery of a tank interior. That capability is genuinely useful for an owner’s own condition monitoring, for planning a repair scope, or for deciding whether a space needs attention before the surveyor arrives. None of it credits a close-up survey.
The gap between those two things is the whole commercial question. An owner buying drone inspection for survey credit is not buying flying hours or camera specifications. They are buying an approval held by the firm and a workflow the attending surveyor will accept. Those are the only two features that determine whether the staging can be left on the quay.
Ask a prospective provider for their UR Z17 approval and which societies hold it. If the answer is a description of their equipment, they are selling you photography, not survey credit.
Where Remote Inspection Does Not Help
RIT displaces access, not judgement, and it does not displace every kind of examination. Two limits are worth being clear about before building a survey plan around it.
The Malaysian Question Worth Asking Early
Commercial drone operation in Malaysian airspace sits under the Civil Aviation Authority of Malaysia, and the framework has been moving. CAAM announced in 2025 that it was replacing the 2016 regulations with a risk-based framework aligned to ICAO, with an Authorisation to Fly governed by Safety Information SI-01/2025 and applications submitted well in advance of the activity.
Whether any of that reaches inside a ballast tank is a question worth putting to CAAM directly rather than assuming. Aviation regulation governs airspace, and the interior of an enclosed compartment aboard a vessel is not obviously airspace in the sense the rules contemplate. We could not find a published CAAM position either way, and the honest answer for an operator planning work in Malaysian waters is to ask before the survey rather than after.
Two authorities, two different questions. Class decides whether the inspection credits the survey. CAAM decides whether the flight was lawful. An approval from one says nothing about the other, and a provider who conflates them has not thought about it hard enough.
Frequently Asked Questions
Can drone footage replace a close-up survey?
It can be accepted as an alternative means of carrying out one, which is not quite the same thing. Remote Inspection Techniques are recognised in the IACS Unified Requirements, but where the work is not performed by the society itself it must be conducted by a firm approved as a service supplier under UR Z17 and witnessed by an attending surveyor. Footage produced outside that arrangement does not credit the survey.
What counts as a close-up survey?
A survey where the details of structural components are within the close visual inspection range of the surveyor, normally within reach of hand. That definition is the benchmark any remote alternative has to meet, which is why resolution, lighting and coverage are treated as capability requirements rather than preferences.
Does the surveyor have to be present?
An attending surveyor must witness the inspection. In practice that usually means observing a live video feed while the flight is underway rather than reviewing recorded footage afterwards. The surveyor is performing the survey and the aircraft is the means of seeing, which is why a recording submitted after the fact does not serve the same purpose.
What is IACS UR Z17?
The IACS Unified Requirement setting procedural requirements for service suppliers, including firms carrying out survey by Remote Inspection Techniques as an alternative to close-up survey. It is the same approval framework that covers thickness measurement firms, and approval follows verification and audit by the classification society.
Does remote inspection cover thickness measurement?
No. Thickness measurement is a contact technique and a separate approved service. A remote visual pass may inform where gaugings are needed, but it does not gauge steel, and a survey requiring thickness measurement still requires a provider approved for that work.
What should an owner ask a drone inspection provider?
Whether they hold service supplier approval under UR Z17, which classification societies recognise that approval, how the live feed is delivered to the attending surveyor, and what lighting and resolution they can demonstrate inside an unlit tank. Answers about airframes and camera sensors describe equipment rather than eligibility.
Sources: IACS Unified Requirement Z17, procedural requirements for service suppliers including firms engaged in survey using Remote Inspection Techniques · ClassNK, IACS UR Z17 Rev.21 (January 2025) · IACS Recommendation 42, Guidelines for Use of Remote Inspection Techniques for Surveys, revised June 2016 · DNV, Survey by remote inspection techniques: use of approved service suppliers · Safety4Sea, Remote inspection techniques on the rise · Bureau Veritas, New advances in drone technology for class surveys · Civil Aviation Authority of Malaysia, Safety Information SI-01/2025 on Authorisation to Fly
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