# These are VRTs, constructed on top of the auxilliary datasets distributed by Qiu et al.
I'm trying to use the experimental implementation of Fmask4 algorithm, but these files gswo150.vrt and gtopo30.vrt you said you built it based on the AuxiData from Qiu et al, could you please share those files or tell me how you build it based on the original files from Qiu et al?