Petrimetrics formulas
All stereological formulas
Total length
or 
- a/l = 2d/π: Grid constant (2d/π units or ratio of area to length of semi-circle probe)
- asf: Area fraction (ratio of area of counting frame to grid-step)
- I: Number of intersections counted
- d = 2*Merz-radius where the Merz-radius refers to the radius of the semi-circle used to probe.
References
Howard, C. V., & Reed, M. G. (2005). Unbiased stereology. New York: Garland Science (prev. BIOS Scientific Publishers).