The aspect ratio of an object is expressed as a value between zero and one (unit-less) and represents the ratio of the minor axis length over the major axis length of an ellipse that has the same second-moments as the particle. The figure shows a graphical representation of an ellipse with the same second-moments as the particle being analyzed. This method of calculating aspect ratio is more stable and less susceptible to noise variations than methods based on the absolute minimum and maximum dimensions of a particle.
