Flown close to the structure with a high-resolution camera, giving imagery detailed enough to map fine surface defects. Where a defect is smaller than the imagery can genuinely measure, we label it as such rather than reporting a number the data cannot support.
Capture is from the side as well as from above. A structure photographed only from overhead has no geometry on its vertical faces, and a bridge pier is almost entirely vertical face.
Defect mapping
Cracking, spalling and surface deterioration are mapped onto the model with a position and an extent, so the same defect can be found and re-measured at the next inspection instead of re-discovered.
Access and airspace
Most structures sit under controlled airspace, over water or beside live traffic. Airspace coordination, a recovery plan and traffic management liaison are part of the job, not an extra line on the invoice.