Multirotor Configuration for Bridge Inspection

Overview

• Decide up front whether the output is visual record or photogrammetric product — they imply different overlap and different flight patterns.
• Underside and bearing areas are the reason most bridge work needs a multirotor rather than a fixed-wing.
• Coordinate with the road authority before flying over live traffic; access, not capability, is normally the critical path.
• Keep a consistent flight altitude along the deck so defect positions can be compared between surveys.

Access is the reason to fly, and the risk

Bridges are inspected from the air because the alternative is a truck, a lane closure, or a rope team. That is the value. It is also the constraint: the aircraft will be working close to a structure, often over water or traffic, usually in wind that behaves differently under the deck than beside it.

So the configuration question is not which camera, but whether the survey can be flown safely and repeatably at the required stand-off. Everything else follows from that.

What has to be captured

Bridge inspection looks for surface defects — cracking, spalling, corrosion staining, failed bearings, water ingress paths — and for change between inspections. The first requires resolution; the second requires the same framing each time. A survey that optimises for one will usually fail the other.

The practical resolution is to define a fixed set of viewpoints per structure and return to them. That turns a bridge into a repeatable route rather than a free-form flight, and it is what makes year-on-year comparison defensible.

Flying near and under the structure

Positioning degrades near large metal structures, and GNSS alone is not enough for the repeatability this work needs. Decide early whether the programme needs RTK, and whether the structure's geometry allows a safe stand-off on every face you intend to capture.

Under-deck work is a different risk category: signal environment, clearance and consequence of a position error all change. Where the underside cannot be captured safely by aircraft, say so at scope stage rather than discovering it during acceptance. A ground platform may cover the parts an aircraft cannot; see G-100.

Writing the deliverable

State the defects of interest, the resolution needed to see them, and the viewpoints that will be revisited. State how each finding is located on the structure — span, element, chainage or a fixed reference grid.

State what the survey does not cover. Bridge inspection by aircraft is a screening method; it does not replace the hands-on inspection that standards and engineers require. Saying that in the scope protects the programme from being over-sold internally, which is the usual reason these projects stop after year one.

Related pages

• M-30 heavy-payload long-endurance multirotorView
• M-15 with thermal imaging optionView
• M-10 compact inspection platformView
• Intelligent Payloads and AccessoriesView

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