Relative to the perimeter. Perimeter: what separates an object from its environment, outline of the object.
It is all related to the perimeter. Perimeter is synonymous with edges, limits, border, outline, periphery, shore. In mathematics or better yet in geometry is the sum of the sides of a polygon.
The relevance to the perimeter. What measures a surface whatever its shape, square, Rhombus, rhomboid, trapezius, triangle, etc. Regardless, it would be anything contour measurement metrics.