Describes the ground distance interval of cells in a uniform elevation grid. For example, in the definition above of a USGS digital elevation model (DEM), it can be said that one of the standard products in the National Elevation Dataset (NED) has 30-meter post spacing; the term is synonymous with grid spacing. It is not exactly the same as GSD in reference to elevation models. GSD refers to the spacing of the actual measurements, whereas post spacing refers to the interval of the interpolated product generated from those measurements. The term post spacing is often used to mean GSD. This report follows the more formal definitions, but the reader should be aware of the ways these terms are commonly used (or misused) in industry literature.