The Hausdorff-Besicovitch dimension is the mathematical expression of the dimension of objects. The generalized approach of Hausdorff makes this definition useful for natual objects.
  • Self-Similarity Method

    Take a line, a square and a cube, each with a unary length.

    If you divide that length by two, keeping the same space, you finally end up with two segments of half-length, four squares with each one-fourth of the original surface and nine cubes with each one-ninth of the original volume.

    Again, dividing the unary length segment by three yields, respectively, 3 lines, 8 squares and 27 cubes.

    Summarizing this into a table, we have:


    Expressed mathematically, the property of the object, its length, area or volume, noted N, is related to its dimension, noted D, by:

      N = rD

    Taking the logarithm on both sides of the equation and solving for D, we finally obtain the expression of the Hausdorff-Besicovitch dimension:

      D = log (N) / log ( r)

    Intuitively, N can be considered as the number of self-similar objects created from the original object when it is divided by r.

    Taking the cube as an example, replace N by 27 and r by 3, and you got the dimension of the cube:

      D = log (27) / log ( 3) = 3

    Replacing the members N and r of the equation by the adequate values and one can compute the Hausdorff-Besicovitch or fractal dimension of any object.

  • Box-Counting Method

    The Box-Counting method is useful when the fractal curve fits the boxes of a simple grid.

    To use the Box-Counting method, draw a fractal curve into a square area. Divide that area in small boxes so that the self-similarity drawings fit the size of the small boxes.

    As an example, the Squares Curve is drawn on such a grid.

    Box-Method example from Squares Curve

    The number of boxes covered by the fractal curve is then determined and the Hausdorff-Besicovitch or fractal dimension is then calculated using the fundamental formula of the box-counting method:

    N = 1 / dD

       where N: number of boxes covered by the fractal curve
       where d: size of the grid box (see below)
       where D: fractal dimension of the curve.

    This formula relates the fractal dimension with the size of the small boxes that made the overall grid.

    Solving for D, we got:   dD = 1 / N

    Taking the logarithm on both sides gives:

    log d * D = - log N

    and then D = -log N / log d

    To simply the calculations, one can take the side length of the grid as a unit value and define r as the number of small boxes along one side of that grid.

    The formula becomes:   D = -log N / log (1/r)

    which, finally, gives:   D = log N / log r

    Woops, it's the self-similarity formula showed above !!!

    The number of boxes, noted N, is then recorded for different values of r. Plotting log(N) on the y-axis against log(r) on the x-axis should give a straigth line, whose slope is equal to the fractal dimension.