Dawn, side view. A pilot stands on higher ground by the launch pad. The drone takes off and flies out over low ground toward a mast with wires. A gauge shows temperature T falling toward the dew point Td until the spread is small. Fog forms in the low ground along the flight path, hiding the mast and wires and swallowing the drone, while the launch area still looks clear. The line of sight to the drone turns red. As the fog lifts the drone returns and lands. With a wide spread selected, no fog forms. Schematic: no temperatures or distances are shown.
