The upwind position is generally defined based on a reference object. The direction in which the wind blows is based on the location at that time. As in the past, polluting factories were generally required to be built downwind (such as emitting waste gas) in order to avoid pollution caused by the wind.
It is based on a certain place as a reference. For example, if you stand next to a campfire in the wild (also called downwind), the wind will blow the fire directly towards you.
Upwind is a relative concept and needs to be defined by reference objects as standards.
When the wind target is blowing in the direction of the reference object, it is upwind.
As in the past, polluting factories were generally required to be built downwind (such as emitting waste gas) in order to avoid pollution caused by the wind.