pvtob¶

erfa.pvtob(elong, phi, hm, xp, yp, sp, theta)[source]¶

Position and velocity of a terrestrial observing station.

Parameters:

elongdouble array
phidouble array
hmdouble array
xpdouble array
ypdouble array
spdouble array
thetadouble array

Returns:

pvdouble array

Notes

Wraps ERFA function eraPvtob. The ERFA documentation is:

- - - - - - - - -
 e r a P v t o b
- - - - - - - - -

Position and velocity of a terrestrial observing station.

Given:
   elong   double       longitude (radians, east +ve, Note 1)
   phi     double       latitude (geodetic, radians, Note 1)
   hm      double       height above ref. ellipsoid (geodetic, m)
   xp,yp   double       coordinates of the pole (radians, Note 2)
   sp      double       the TIO locator s' (radians, Note 2)
   theta   double       Earth rotation angle (radians, Note 3)

Returned:
   pv      double[2][3] position/velocity vector (m, m/s, CIRS)

Notes:

1) The terrestrial coordinates are with respect to the ERFA_WGS84
   reference ellipsoid.

2) xp and yp are the coordinates (in radians) of the Celestial
   Intermediate Pole with respect to the International Terrestrial
   Reference System (see IERS Conventions), measured along the
   meridians 0 and 90 deg west respectively.  sp is the TIO locator
   s', in radians, which positions the Terrestrial Intermediate
   Origin on the equator.  For many applications, xp, yp and
   (especially) sp can be set to zero.

3) If theta is Greenwich apparent sidereal time instead of Earth
   rotation angle, the result is with respect to the true equator
   and equinox of date, i.e. with the x-axis at the equinox rather
   than the celestial intermediate origin.

4) The velocity units are meters per UT1 second, not per SI second.
   This is unlikely to have any practical consequences in the modern
   era.

5) No validation is performed on the arguments.  Error cases that
   could lead to arithmetic exceptions are trapped by the eraGd2gc
   function, and the result set to zeros.

References:

   McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
   IERS Technical Note No. 32, BKG (2004)

   Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to
   the Astronomical Almanac, 3rd ed., University Science Books
   (2013), Section 7.4.3.3.

Called:
   eraGd2gc     geodetic to geocentric transformation
   eraPom00     polar motion matrix
   eraTrxp      product of transpose of r-matrix and p-vector

This revision:   2021 February 24

Copyright (C) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

Navigation

pvtob¶