Are you being oblique?
A piece of Mars: Barchan, or crescent dunes, are generally thought to form from winds blowing from a single direction. Reality isn’t usually that nice. Here are two barchans with crescent-shaped slip faces on their eastern (right) sides, indicating that the main dune-building winds blow from the west (left). However, ripples, an elongated dune arm, and steeper northern slopes hint at a secondary wind from the SE (lower right). (ESP_033272_1400, NASA/JPL/Univ. of Arizona)