Calculation of random errors

We consider a source of random error generating fluctuations on the interferograms; these fluctuations are random, uncorrelated, and of variance σ²E. By still referring to the GUM, the variance on the phase measurement corresponding to such a source of error can be expressed by:

This means that we simply have to sum the variances on each interferogram. We assumed that the fluctuations were random and (more importantly) uncorrelated between each image. Indeed, this simple relation does not take into account the correlations between variations. In practice, this assumption is often true.

The quantities are called the sensitivities of the algorithm.