EPSG Dataset :: v12.042test

Geographic3D to 2D conversion

Coordinate Operation Method Details [VALID]

Name:

Geographic3D to 2D conversion

Code:

9659

Operation is Reversible:

Yes

Formula:

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.

The forward case is trivial. A 3-dimensional geographic coordinate reference system comprising of geodetic latitude, geodetic longitude and ellipsoidal height is converted to its 2-dimensional subset by the simple expedient of dropping the height. The axis order change operates on coordinates of a point whose order change is described by the following matrix operation:

[Derived CRS 1st coordinate] [1 0 0] [Base CRS 1st coordinate]
[Derived CRS 2nd coordinate] = [0 1 0] * [Base CRS 2nd coordinate]
[Derived CRS 3rd coordinate] [0 0 0] [Base CRS 3rd coordinate]

The reverse conversion, from 2D to 3D, is indeterminate. It is however a requirement when a geographic 2D coordinate reference system is to be transformed using a geocentric method which is 3-dimensional. In practice an artificial ellipsoidal height is created and appended to the geographic 2D coordinate reference system to create a geographic 3D coordinate reference system referenced to the same geodetic datum. The assumed ellipsoidal height is usually either set to the gravity-related height of a position in a compound coordinate reference system, or set to zero. As long as the height chosen is within a few kilometres of sea level, no error will be induced into the horizontal position resulting from the later geocentric transformation; the vertical coordinate will however be meaningless.

Example:

(none)

Method
Parameters:

Parameter Name	Parameter Code	Sign reversal	Parameter Description

Meta Data

Remarks:

This is a parameter-less conversion.

Information Source:

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

Data Source:

EPSG

Revision Date:

May 22, 2015

Change ID:

[2015.018]

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.