4.2.3.  DATA_GROUP

The global attribute DATA_GROUP has a two-field entry, specifying the origin of the data (experimental, model, or a combination of both) and the spatial characteristics of the data. The spatial characteristics indicate the dimensionality of the spatial grid of the dataset for a single data element, in addition to whether the spatial grid moves in space with time. The dimensionality that is expressed in DATA_GROUP by SCALAR(0D), PROFILE  (1D), and FIELD(2D or more) refers to the spatial dimensionality of the target in the dataset only. This is best explained by considering the example of an airborne LIDAR system: At a given point in time, this LIDAR system provides measurements at a single latitude and longitude location but for multiple altitudes. With time, this 1-dimensional spatial grid (fixed latitude and longitude, vector of altitudes) is moving in latitude and longitude. The two-field entry for this example thus becomes  EXPERIMENTAL;PROFILE.MOVING. For a list of allowed variables please refer to Table 7.2.

Type: STRING

Entry: Two semicolon-separated fields

Format: Data origin;spatial characteristics

Example 1: DATA_GROUP = EXPERIMENTAL;SCALAR.STATIONARY for a time-seriesof groundbased column measurements

Example 2: DATA_GROUP = MODEL;FIELD.STATIONARY for a 3-D model output on a fixed spatial grid