Nadir is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing a spacewalk. The term nadir can also be used to represent the lowest point reached by a celestial body during its apparent orbit around a given point of observation. This can be used to describe the location of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The sun is said to be at the nadir at a location when it is at the zenith at the location's antipode
Overhead join by crossing the upwind threshold and then turning downwind. With other traffic present in the circuit, the aircraft might be positioned downwind in the circuit behind or between other traffic in order to land in turn. Alternatives to the overhead join are to directly join the circuit by entering at a suitable corner, or a straight-in approach. If available, ATC will negotiate with the pilot which is the most appropriate method according to the current traffic situation. Standard Overhead Join 3-D diagram Standard Overhead Join poster reference Overhead join An overhead join is a conventional method for an aircraft to