1. A surveillance system comprising: a video capturing unit capable of capturing video of an area, the video comprises a first image and a second image; a detecting unit configured for subdividing each image into a plurality of subdivisions and calculating a contrast value for each subdivision to produce a contrast value matrix associated with the corresponding image; a comparing unit configured for comparing each element of the contrast value matrix associated with the second image with a corresponding element of the contrast value matrix associated with the first image and determining a compared value matrix associated with the second image; a calculating unit configured for weighting the compared value matrix using a preset weight value matrix to determine the location of movement in the second image; and a controlling unit configured for adjusting aim, focus or the aim and the focus of the video capturing unit.