Left: The result of Levenberg-Marquardt fitting algorithm (LMA) with least absolute residuals (LAR), on different number of tracked bright point structures. Right: Comparison of the curves based on Eq. (8) from different works. The black line represents this work, and it should be noticed that the similarity between the obtained results from this method with different numbers of tracked structures ((a) 650 CBP measurements and (b) 1577 CBP measurements) indicates the stability of this method.