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 . 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 .