Our team was appointed to capture a full drone survey of a coastal cliff face at Aberdyfi on the Gwynedd coast. The cliff is steep, unstable in places and sits directly above a public area, so getting surveyors onto the face itself was never going to be safe or practical.

Traditional access would have meant rope teams, scaffold or long road closures, and even then the coverage would have been patchy. The client needed a complete, measurable record of the whole cliff face that could be used for design work, condition assessment and future comparison – all captured in a single visit, without putting anyone on the rock and without shutting the area down for days.

We planned the job around three separate drone flights, each doing a different job, so nothing was missed. The first was a coastal LiDAR mission. LiDAR fires pulses of light at the surface and measures how long they take to bounce back, which builds a dense cloud of measured points. It works well on a cliff because it picks up the shape of the rock even where vegetation, shadow or overhangs would confuse a camera on its own.

The second flight was a mapping mission, flown in a controlled grid pattern to give us the overlapping imagery needed for photogrammetry and to tie the whole survey together geometrically. The third was a dedicated photographic mission, capturing high-resolution stills of the face for visual reference and for draping onto the finished model.

Flights were flown at roughly 25 to 30 metres from the face, close enough for real detail but far enough to keep a safe distance from the rock. We deliberately flew wide on some passes to make sure the full extent of the cliff was covered, including the sections that fall away at either end.

Ground control was picked up alongside the aerial work using laser scanning, so everything could be brought onto a single coordinate system rather than floating on its own. Before any of it started, the working area was cordoned off to keep the public clear of the take-off and landing zone and to protect the survey team on the ground. The whole site was captured, packed down and the area handed back the same day.