Horizon Definition | GIS Dictionary

horizon

[navigation] The apparent or visible junction of land and sky. Also known as the geographic horizon.
[geodesy] The horizontal plane tangent to the earth's surface and perpendicular to the line through an observer's position and the zenith of that position. The apparent or visible horizon approximates the true horizon only when the point of vision is very close to sea level.
[aerospace] The apparent curve separating the observer's location on a celestial body from the celestial sphere. The higher the observer, the lower and more distant the visible horizon.