A method of determining a hierarchy of estimated motion between a pair of image frames of a given scene, a first of said image frames designated as a reference frame and a second of said image frames designated as a target frame, the method comprising: a) calculating respective integral images for each of said image frames; b) selecting at least one corresponding region of interest within each frame; c) for each region of interest: i. calculating an integral image profile from each integral image, each profile comprising an array of elements, each element comprising a sum of pixel intensities from a swath of said region of interest for said frame, said calculating an integral image profile comprising sub-sampling said integral image at a first sub-sampling interval at a first selected level of said hierarchy and for each repetition of step c), sub-sampling said integral image at successively smaller sub-sampling intervals; ii. correlating said integral image profiles to determine a relative displacement of said region of interest between said pair of frames; iii. dividing each region of interest into a plurality of further regions of interest to go to the next level of the hierarchy; and iv. displacing said divided regions of said target frame at one level of said hierarchy according to a relative displacement determined for a region of interest corresponding to said divided regions of interest at a higher level of the hierarchy; and repeating step c) for said further regions of interest until a required hierarchy of estimated motion for successively divided regions of interest is provided. a) calculating respective integral images for each of said image frames; b) selecting at least one corresponding region of interest within each frame; c) for each region of interest: i. calculating an integral image profile from each integral image, each profile comprising an array of elements, each element comprising a sum of pixel intensities from a swath of said region of interest for said frame, said calculating an integral image profile comprising sub-sampling said integral image at a first sub-sampling interval at a first selected level of said hierarchy and for each repetition of step c), sub-sampling said integral image at successively smaller sub-sampling intervals; ii. correlating said integral image profiles to determine a relative displacement of said region of interest between said pair of frames; iii. dividing each region of interest into a plurality of further regions of interest to go to the next level of the hierarchy; and iv. displacing said divided regions of said target frame at one level of said hierarchy according to a relative displacement determined for a region of interest corresponding to said divided regions of interest at a higher level of the hierarchy; and repeating step c) for said further regions of interest until a required hierarchy of estimated motion for successively divided regions of interest is provided. i. calculating an integral image profile from each integral image, each profile comprising an array of elements, each element comprising a sum of pixel intensities from a swath of said region of interest for said frame, said calculating an integral image profile comprising sub-sampling said integral image at a first sub-sampling interval at a first selected level of said hierarchy and for each repetition of step c), sub-sampling said integral image at successively smaller sub-sampling intervals; ii. correlating said integral image profiles to determine a relative displacement of said region of interest between said pair of frames; iii. dividing each region of interest into a plurality of further regions of interest to go to the next level of the hierarchy; and iv. displacing said divided regions of said target frame at one level of said hierarchy according to a relative displacement determined for a region of interest corresponding to said divided regions of interest at a higher level of the hierarchy; and repeating step c) for said further regions of interest until a required hierarchy of estimated motion for successively divided regions of interest is provided.