hor·i·zon·tal co·or·di·nate sys·tem
/ˌhɔːrɪˈzɒntəl koʊˈɔːrdənət ˈsɪstəm/
An astronomical coordinate system that locates celestial objects relative to the observer’s local horizon. It uses altitude (angular height above or below the horizon) and azimuth (angular distance measured along the horizon) as its two main coordinates.
The horizontal coordinate system is one of the simplest ways to describe the position of celestial objects as they appear from a specific place on Earth at a specific time. Unlike the equatorial coordinate system, which is fixed to the celestial sphere, the horizontal system is relative and changes continuously with the Earth’s rotation. A planet or star is identified by its altitude, which shows how high above or below the horizon it is, and its azimuth, which gives the direction along the horizon, measured from north. In astrology, while this system is more technical than interpretive, it underpins the concept of a planet’s visibility—for example, determining whether a planet is above or below the horizon at the time of birth, which can influence chart delineation and the strength or prominence of certain placements.
Source, Cindy McKean, Wiki
