EPSG Dataset :: v12.049

Geographic3D to GravityRelatedHeight (EGM)

Coordinate Operation Method Details [VALID]

Name:

Geographic3D to GravityRelatedHeight (EGM)

Code:

9661

Operation is Reversible:

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 horizontal component of the source CRS) and interpolation must be made in the latitude and longitude of 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.

Example:

(none)

Method
Parameters:

Parameter Name	Parameter Code	Sign reversal	Parameter Description
Geoid (height correction) model file	8666		The name of the [path and] file containing height offsets. "Geoid model" is used loosely in the parameter name. If the offset is between the ellipsoid and the geoid then the offset will be the geoid separation N. When the offset is between the ellipsoid and a realisation of the geoid through a vertical datum then the offsets C will form a height correction surface. A height correction surface differs from a geoid model by small amounts due to the difference between the geoid and the actual datum surface as well as some other assumptions regarding the gravity field.

Meta Data

Remarks:

Applies to EGM84 and EGM96 models. For later model see Geographic3D to GravityRelatedHeight (EGM2008), method code 1025.

Information Source:

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

Data Source:

EPSG

Revision Date:

September 8, 2021

Change ID:

[2008.01] [2008.097] [2016.05] [2021.081]

Wildcard	Example
% or *	Any wildcard characters
? or _	One wildcard character
[ - ]	[ - ] Range e.g. N[a-c] will return all geodetic objects that contains a string starting with the letter 'N' or 'n' followed by any of the letters contained within the range specified within the square bracket, e.g. letters a, b and c.
\|	Or e.g. E[a\|e]M will return all geodetic objects that contains a string starting with the letter E(e), ends with the letter M(m) and also contain either the letter a or letter e.