Original: The official Fujita scale category is determined by meteorologists (and engineers) after a ground and/or aerial damage survey; and depending on the circumstances, ground-swirl patterns (cycloidal marks), radar tracking, eyewitness testimonies, media reports and damage imagery, as well as photogrammetry/videogrammetry if motion picture recording is available.
Simplified: The official Fujita scale category is determined by meteorologists (and engineers) after a ground and/or aerial damage inspection; also including analysis of available sources such as eyewitness accounts and damage images and/or videos.