Which statement best describes the Terrestrial Coordinate System?

• A. Time-based coordinates using mean solar time
• B. Coordinates based on Earth's latitude and longitude, containing parallels and meridians
• C. Coordinates based on the celestial sphere, using declination and Greenwich Hour Angle
• D. Coordinates based on the observer's horizon, using altitude and azimuth

Answer: (B)

Terrestrial coordinates are a global grid fixed to the Earth's surface, defined by latitude and longitude. Latitude lines (parallels) run east-west and measure how far north or south you are from the equator. Longitude lines (meridians) run pole-to-pole and measure how far east or west you are from the prime meridian at Greenwich. This framework provides a single, worldwide position reference for any point on Earth, independent of the observer’s momentary viewpoint.

The other options describe different systems: time-based coordinates don’t locate a position on the planet, celestial coordinates use the sky (declination and Greenwich Hour Angle) to locate objects in space, and horizon coordinates (altitude and azimuth) are local, observer-centered directions relative to the current horizon.