A method for characterising motion of one or more objects in a time ordered image dataset comprising a plurality of time ordered data frames, the method comprising: selecting a reference data frame from the plurality of time ordered data frames (210); extracting a plurality of image patches from at least a part of the reference data frame (220); identifying a location of each image patch of at least a subset of the plurality of image patches in each data frame (230); defining, based on the identified locations, a mesh for each data frame, wherein vertices of each mesh correspond to respective identified locations of image patches in the corresponding data frame (240); and deriving, from the meshes, a motion signature for the time ordered image dataset, the motion signature characteristic of the motion of the one or more objects in the plurality of time ordered data frames (250).