Proof that nothing has grown into your approach
The protection surface over an approach is a plane, and the only question that matters is whether anything crosses it. We fly an arc that rides on that plane and hold the camera on a point that also lies on it, so any object breaking through visibly cuts the sightline on camera. Vegetation, a new roofline, a crane that was not there last year.
A geometric check, then a visual one
The same surface is tested twice, once against your survey data and once against what the camera sees.
The surface is constructed, not estimated
The protection surface is built for the runway direction from its own geometry: where the surface starts relative to the threshold, how wide its inner edge is, and how fast it diverges outward, using the ICAO Annex 14 values where you have not published your own. Its slope comes from your published figure, or is derived from the published glide path. Every surveyed obstacle on the airfield is then tested against that solid: does its footprint fall inside the surface, and does its top break through the plane above it. Anything that does both is named before the drone leaves the ground.
Then the sightline has to agree
Survey data goes stale, which is the whole reason for the flight. The arc is flown at the altitude the plane reaches at that radius, with the camera locked on a safe point out on the extended centre line that sits on the same plane. That makes the sightline a physical sample of the surface: anything penetrating it passes in front of the camera rather than being inferred from a spreadsheet. The sweep either side of the runway axis covers the sector the crew uses, and the whole pass is on video, so the finding is evidence rather than an assertion.
What the report answers
The obstacle rows of the visual aids protocol, plus the geometry the check was run against.
No object breaks through the obstacle protection surface for the runway direction, tested against the surveyed obstacle set and again on the flown sightline.
The runway lighting and markings stay in view all the way down the approach, with nothing screening them.
The plane the check is run on, taken from your published value or derived from the published glide path.
Origin offset from the threshold, inner edge width and outward divergence used to build the surface.
The arc sweeps the sector either side of the runway axis rather than sampling the centre line alone.
Each object that breaks the surface is reported with its surveyed position and top height, so the cut or the notification can be scoped.
The full approach pass is recorded, so the clearance finding can be reviewed rather than taken on trust.
Built for both sides of the runway
Airports get compliant inspections without closures. Certified drone operators get a new service line through the partner program.