Geodetic datums define the:

• A. Size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth.
• B. Time zones of the Earth.
• C. Color schemes for maps.
• D. Elevation reference only.

Answer: (A)

Datums establish the size and shape of the Earth and define the origin and orientation of the coordinate systems used to map the Earth. A geodetic datum provides a reference surface—typically an ellipsoid, sometimes tied to a geoid—and a defined origin and orientation so that coordinates correspond to real locations on Earth for a given area. Because of this, the horizontal coordinates you collect or read depend on the datum in use; switching datums can shift positions and affect alignment with maps and surveys. Time zones are about longitudinal divisions and do not define a coordinate framework for mapping; color schemes are cartographic choices; elevation reference falls under vertical datums, not the horizontal framework provided by the geodetic datum.