EPSG:9616

Note: These formulas have been transcribed from EPSG Guidance Note #7-2. Users are encouraged to use that document rather than the text which follows as reference because limitations in the transcription will be avoided.

A vertical offset allows calculation of coordinates in the target vertical coordinate reference system by adding a correction parameter A to the coordinate values of the point in the source system:
X2 = X1 + A1>2
where
X2 = value in the forward target vertical coordinate reference system.
X1 = value in the forward source vertical coordinate reference system.
A1>2 is the offset to be applied for the transformation from CRS 1 to CRS 2. Its value for the forward calculation is the value of the origin of the source CRS 1 in the target CRS 2.

For the reverse transformation from CRS 2 to CRS 1 the same formula is used but with the sign of the offset A1>2 reversed:
	X1 = X2 + (–A1>2)

The above formulas apply only when the positive direction of the axis of the source and target CRS is the same and where the two vertical CRSs share the same unit of measure. If either of these are to be changed then a concatenated operation including one or more conversions through intermediate vertical CRSs is required. See Height-depth reversal (code 1068) and Change of vertical axis unit (code 1069) for the required conversion methods.