# EPSG:9662

## Geographic3D to GravityRelatedHeight (Ausgeoid98)

### Attributes

Data source: OGP

Information source: EPSG guidance note #7-2, http://www.epsg.org

Revision date: 2016-12-15

#### Export

Definition: OGP XML

```<?xml version="1.0" encoding="UTF-8"?>
<epsg:informationSource>EPSG guidance note #7-2, http://www.epsg.org</epsg:informationSource>
<epsg:revisionDate>2016-12-15</epsg:revisionDate>
<epsg:changes>
</epsg:changes>
<epsg:show>true</epsg:show>
<epsg:isDeprecated>false</epsg:isDeprecated>
<epsg:isOperationReversible>false</epsg:isOperationReversible>
<epsg:example>(none)</epsg:example>
<gml:identifier codeSpace="IOGP">urn:ogc:def:method:EPSG::9662</gml:identifier>
<gml:name>Geographic3D to GravityRelatedHeight (Ausgeoid98)</gml:name>
<gml:formula>This transformation involves the application of a geoid-ellipsoid separation value interpolated from a geoid model. The model provides separation values at the nodes on a regular grid of latitude and longitude intersection points. The geodetic latitude and longitude used to interpolate within the grid are not affected by this transformation.

The grid is referenced to a specific geographic CRS (the source CRS) and interpolation must be made in this system.

Calculation of the separation is achieved through a bi-linear interpolation of the grid, using the latitude and longitude of the point. This step provides the geoid-ellipsoid separation (N) above the ellipsoid of the source Geographic 3D CRS.

Then:
H = h - N

where h = the height above the ellipsoid in the source geographic 3D CRS
and   H = the gravity-related height in the target vertical CRS.</gml:formula>