Table 3. Flight method and photographing rules for each bridge member.

Part	Model example	Start position	End position	The mode of flight	Shooting interval
Pier		Ground	The top of a bridge	Circular	2 to 3 seconds apart at flight speed 3 m/s (shooting rules: 80% overlap between each picture)
Copping		Front left	Right side of the back	Double grid (up-down, left-right)
Guardrail		Left guardrail	Right guardrail	Grid (left-right)
Floorboard		Upper left	Lower right	Grid (up-down)