EPSG Dataset :: v12.003

Geographic3D to GravityRelatedHeight (ITAL2005)

Coordinate Operation Method Details [VALID]

Name:

Geographic3D to GravityRelatedHeight (ITAL2005)

Code:

1106

Operation is Reversible:

Formula:

This transformation involves the application of a height difference interpolated from a height correction model. The model provides height difference 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 height difference is achieved through a bi-linear interpolation of the grid, using the latitude and longitude of the point. This step provides the height correction (C) of the target datum above the ellipsoid of the source Geographic 3D CRS. C differs from the geoid-ellipsoid separation N because a vertical datum is a realisation of the geoid surface, not the geoid itself.

Then:
H = h - C

where h = the height above the ellipsoid in the source geographic 3D CRS
and H = the gravity-related height in the target vertical CRS.

The method is not reversible because the gravity-related height is 1-dimensional and not associated with a horizontal CRS.

Example:

For coordinate transformation: NZGD2000 to NZVD2016 height(2), code 9326:

For a point at 36°54'01"S, 174°46'46"E (36.9003°S, 174.7794°E), with NZGD2009 ellipsoidal height of 50.000 metres, to find its NZVD2009 height:

First using source CRS NZGD2000, code 4167, for interpolation, obtain the offsets at each of the surrounding grid nodes:
NW corner 36.9000°S, 174.7667°E, geoid height = 34.267m
NE corner 36.9000°S, 174.7833°E, geoid height = 34.293m
SE corner 36.9167°S, 174.7833°E, geoid height = 34.205m
SW corner 36.9167°S, 174.7667°E, geoid height = 34.185m

Then using bi-linear interpolation for 36.9003°S, 174.7794°E, geoid height = 34.285m

Then NZVD2016 height = 50.000 - (34.285) = 15.715m.

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

Information Source:

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

Data Source:

EPSG

Revision Date:

September 8, 2021

Change ID:

[2021.025] [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.