What are grid coordinates in a map projection?

• A. Geodetic coordinates
• B. Planar x, y in a map projection.
• C. Longitude and latitude on the ellipsoid.
• D. Height and time.

Answer: (B)

Grid coordinates are the planar x and y positions on a map produced by applying a map projection. A projection transforms points from the Earth's curved surface, typically given as longitude and latitude on the ellipsoid, into coordinates on a flat plane so maps can be drawn and measured with a ruler. In practice these grid coordinates are often labeled as easting (x) and northing (y) and are usually expressed in meters within a specific grid system like UTM. This is why grid coordinates correspond to positions on the map’s grid after projection. Longitude and latitude on the ellipsoid are geodetic coordinates, not grid coordinates, and height and time are not used as grid coordinates either.