Bridge and Civil Structure Inspection by Drone

France has nearly 200,000 public road bridges, of which a significant proportion show signs of ageing requiring regular monitoring. Traditional inspection relies on under-bridge inspection platforms, scaffolding, rope access or lane closures — expensive and disruptive approaches that limit inspection frequency. Drone inspection provides a rapid, non-invasive alternative that reaches zones inaccessible from the road surface.

What bridge inspection by drone covers

Deck underside and soffits

The underside of a bridge deck is among the most critical zones to monitor: it is exposed to water runoff, freeze-thaw cycles and, for structures over watercourses, to spray and flooding. The drone flies beneath the deck, photographing in detail the soffit, cross-beams, haunches and girder flanges, identifying cracks, spalling and reinforcement exposure.

Piers and abutments

Bridge piers in watercourses are subject to scour, impact damage and biological colonisation (algae, roots). The drone inspects them from the waterline up, including the pier caps that support the deck. Abutment wingwalls are similarly documented for crack patterns and drainage issues.

Expansion joints and bearings

Expansion joints accumulate debris, can suffer from differential movement damage and are a common source of waterproofing failures. Bearing pads are inspected for condition, displacement and seating. These elements are critical for structural behaviour but difficult to examine closely from the road surface.

Parapets and railings

Parapet condition has direct safety implications. The drone documents corrosion of steel parapets, spalling of concrete barriers and damaged fixing points.

Photogrammetric survey option

In addition to close-up visual inspection, we can produce a photogrammetric 3D model of the entire structure — a precise mesh that enables:

• Measurement of crack widths and lengths from the office
• Comparison between inspection campaigns to quantify deformation or spalling progression
• Generation of a dimensioned record drawing for structures without as-built documentation

Our field approach

The DJI Matrice 4TD and its high-resolution sensors enable close-up flights in the confined spaces under bridge decks, with the 168 mm optical zoom providing detailed imagery from a safe distance when close approach is not possible (traffic, geometry constraints).

Deliverables include a structured inspection report with anomalies classified by severity and location, a complete georeferenced image archive and, where required, a photogrammetric 3D model.

Missions are planned to minimise traffic disruption: in many cases, inspection of non-trafficked faces (soffits, piers, abutments) requires no road closure whatsoever.