What type of distance is described by the term 'angular distance' in relation to celestial navigation?

Angular distance in celestial navigation refers to a measure of the separation between two points on the celestial sphere, typically expressed in degrees, minutes, or seconds. This concept is crucial for navigators as it helps in determining the positions of celestial objects relative to each other and to the observer's location on Earth.

In the context of celestial navigation, angular distance is used to calculate and interpret the celestial coordinates of stars, planets, and other celestial bodies. It differs from the more common linear distance that is measured on a flat plane since the celestial sphere is a three-dimensional representation. Therefore, angular distance provides a way to convey the relationship between different celestial objects in a sky map layout, allowing navigators to accurately find their bearings during travel.

The other types of distances mentioned, such as linear, horizontal, and vertical distances, do not apply to the context of celestial navigation and instead pertain to measurements on Earth or within a plane. Linear distance measures straightforward separation in a straight line, horizontal distance pertains to distance measured along a flat surface, and vertical distance typically relates to elevation or depth measurements. None of these capture the concept of position in relation to the celestial sphere as effectively as angular distance does.