Root element describing the grid or set of grids used for a particular transformation Root element describing the grid or set of grids used for a particular transformation This represents a flat list of grids. Hierarchies can be imposed on the grids in a separate structure within each Grid. Represents a single grid, of which a grid file might have several Combines several coordinates (usually 2) to one vector Coordinate (based on source coordinate reference system) Represents a single grid, of which a grid file might have several Grid position, size, and resolution/density The grid offset data One single node in the grid, describing the offset at on point Coordinate offset This represents the precision of the offset. The precision is represented as the maximum absolute error, given in the same unit of measure as the offset itself. If the local precision within the grid is unknown, the global maximum possible error shall be quoted. Data with unbounded (unknown) possible error would be worthless, thus some quote of precision is mandatory. If the original data source does not explicitly specify precision, but is reputed to be of high quality, an absolute error of 0 (perfect precision) shall be quoted. Grid position, size, and resolution/density Lower left corner of the grid (coordinates based on source coordinate reference system) Upper right corner of the grid (coordinates based on source coordinate reference system) Grid resolution/density (unit of measure based on source coordinate reference system) One single horizontal line within the grid One single node in the grid, describing the offset at one point Represents a single coordinate; the unit depends on the elsewhere specified source coordinate reference system Represents a coordinate reference system (identified by EPSG id) Represents a transformation (identified by EPSG id) Defines a single transformation, with source and target CRS, using this grid file The source coordinate reference system The transformation using this grid file The target coordinate reference system Defines the set of transformations using this grid file Specifies a hierarchy that the grid is member of, and its parent within that hierarchy Specifies the hierarchy URI Specifies the parent node IDREF Defines creation and update date and time One single (horizontal) row within the grid (all rows have the same number of nodes) The unit type (length or angle) The EPSG unit ID How many base units are equal to one of these units? The base unit of length is meter, the base unit of angle is radians.