  A new non-parametric method based on Gaussian Processes was proposed recently
to measure the Hubble constant $H_0$. The freedom in this approach comes in the
chosen covariance function, which determines how smooth the process is and how
nearby points are correlated. We perform coverage tests with a thousand mock
samples within the LCDM model in order to determine what covariance function
provides the least biased results. The function Matern(5/2) is the best with
sligthly higher errors than other covariance functions, although much more
stable when compared to standard parametric analyses.
