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era.gd2gce.md

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eraGd2gce

[rv, xyz] = ERFA.gd2gce( a, f, elong, phi, height)

Transform geodetic coordinates to geocentric for a reference ellipsoid of specified form.

Given:

   a       double     equatorial radius (Notes 1,4)
   f       double     flattening (Notes 2,4)
   elong   double     longitude (radians, east +ve)
   phi     double     latitude (geodetic, radians, Note 4)
   height  double     height above ellipsoid (geodetic, Notes 3,4)

Returned:

   xyz     double[3]  geocentric vector (Note 3)

Returned (function value):

           int        status:  0 = OK
                              -1 = illegal case (Note 4)

Notes:

  1. The equatorial radius, a, can be in any units, but meters is the conventional choice.

  2. The flattening, f, is (for the Earth) a value around 0.00335, i.e. around 1/298.

  3. The equatorial radius, a, and the height, height, must be given in the same units, and determine the units of the returned geocentric vector, xyz.

  4. No validation is performed on individual arguments. The error status -1 protects against (unrealistic) cases that would lead to arithmetic exceptions. If an error occurs, xyz is unchanged.

  5. The inverse transformation is performed in the function eraGc2gde.

  6. The transformation for a standard ellipsoid (such as ERFA_WGS84) can more conveniently be performed by calling eraGd2gc, which uses a numerical code to identify the required a and f values.

References:

Green, R.M., Spherical Astronomy, Cambridge University Press, (1985) Section 4.5, p96.

Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 4.22, p202.

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.