Square pixel

Pixels of the same x and y dimensions (pixel aperture ratio PAR = 1). In the case of rectangular (non-square) pixels (usual in TV) one must maintain the aspect ratio when measuring objects, because the dimensions of stored frames aren't equal to true dimensions; resolutions along x and y axes aren't the same. Use of square pixels solves such problems - picture elements are equally arrayed in both directions, and allow easy addressing.
Thus aspect ratio of the image does not require adjustment. This is needed in image processing tasks requiring accurate image measuring.