Element: projection.datum[ ]
Element: projection.datum[ ]numeric
A datum shift to be applied when converting between longlat and the projection. The system always assumes that longlat coordinates are based on positions on the WGS84 ellipsoid. The datum shift adjusts for differences in ellipsoid for local regions. If the projection’s ellipsoid is WGS84, the value of this attribute is never used.
A datum shift may comprise 0, 3 or 7 numeric values, depending on whether or not a datum shift is required, and the datum shift transformation being used (see projection.datum_transform).
The first 3 values are always distance shifts, and are assumed to be in the current modeling units, but will be adjusted automatically on a subsequent change of modeling units.
When the datum has a shift in geodetic height (datum[3]), the shift is used in transforming longitudes and latitudes but does not result in a change of spot height.
Changing this value may change the projection depending on other projection attributes.