Distinguish geodetic coordinates from grid coordinates.

• A. Geodetic coordinates are latitude, longitude, and ellipsoidal height; grid coordinates are planar x,y in a map projection.
• B. Geodetic coordinates are x,y; grid coordinates are latitude, longitude, and height.
• C. Geodetic coordinates are time stamps; grid coordinates are energy values.
• D. Geodetic coordinates are only two dimensions.

Answer: (A)

Geodetic coordinates describe a position on or above the reference ellipsoid using angular measures and height, while grid coordinates place a point on a flat map via a map projection. Specifically, geodetic coordinates use latitude, longitude, and ellipsoidal height, which locate you on the curved surface and slightly above it. Grid coordinates, by contrast, are planar x and y in a projected coordinate system, expressed in linear units (often meters), created by projecting the curved Earth onto a plane. This projection makes measurements on the map convenient but introduces distortions relative to the real surface. For example, GPS provides geodetic coordinates, whereas a UTM grid gives x and y in meters within a zone. The other options mix up the components or dimensions—for instance, suggesting geodetic coordinates are x,y or that grid coordinates involve latitude and height—and include irrelevant items like time stamps or energy values.