Density for Geodetic Catalog Files
Density refers to the density of the grid cells used in these data files. Each of these data files carries a grid density as part of the header information. In regions where data files overlap, the file with the densest grid (i.e., the smaller grid cells) is chosen to perform the conversion; under the presumption that the densest grid will produce the highest accuracy.
Users can use this argument to override the internal grid density of the grid file. That is, by overriding the internal density of a specific file to be lower than all others in a catalog, the user causes that specific file to have precedence over all of the other files.
Density is specified in minutes of arc. A zero or negative value must not be specified. Internal density values vary; in some cases the grid density in one direction is different than the other. Typical internal density values are: