One of the most confounding things about navigating Arrakis is the shifting sands. Storms can change the whole topography, erase or cover entire landmarks. Even on a seemingly calm night, you can wake up to find everything changed, your bearings gone with your dreams.
The Fremen, however, seemed to have no trouble navigating the desert, despite its mutable and capricious nature. They likened it to the face of someone you are intimate with. “Even when your mother frowns, you still recognize your mother,” is something of a proverb.
The Fremen are intimate with the face of the dunes, despite its changing expressions.