NovasCel2Ter Method

This function rotates a vector from the celestial to the terrestrial system. Specifically, it transforms a vector in the GCRS (a local space-fixed system) to the ITRS (a rotating earth-fixed system) by applying rotations for the GCRS-to-dynamical frame tie, precession, nutation, Earth rotation, and polar motion.

Definition

Namespace: ASCOM.Tools.Novas31
Assembly: ASCOM.AstrometryTools (in ASCOM.AstrometryTools.dll) Version: 3.0.0-rc.1+86c25ce733aebb4d8b1b8a62e84770ea5e972bea

C#

public static short Cel2Ter(
	double JdHigh,
	double JdLow,
	double DeltaT,
	Method Method,
	Accuracy Accuracy,
	OutputVectorOption OutputOption,
	double xp,
	double yp,
	double[] VecT,
	ref double[] VecC
)

VB

Public Shared Function Cel2Ter ( 
	JdHigh As Double,
	JdLow As Double,
	DeltaT As Double,
	Method As Method,
	Accuracy As Accuracy,
	OutputOption As OutputVectorOption,
	xp As Double,
	yp As Double,
	VecT As Double(),
	ByRef VecC As Double()
) As Short

Parameters

JdHigh Double: High-order part of UT1 Julian date.
JdLow Double: Low-order part of UT1 Julian date.
DeltaT Double: Value of Delta T (= TT - UT1) at the input UT1 Julian date.
Method Method: Selection for method: 0 ... CIO-based method; 1 ... equinox-based method
Accuracy Accuracy: Selection for accuracy
OutputOption OutputVectorOption: 0 ... The output vector is referred to GCRS axes; 1 ... The output vector is produced with respect to the equator and equinox of date. (See note 2 below)
xp Double: Conventionally-defined X coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds.
yp Double: Conventionally-defined Y coordinate of celestial intermediate pole with respect to ITRS pole, in arcseconds.
VecT Double: Position vector, geocentric equatorial rectangular coordinates, referred to GCRS axes (celestial system) or with respect to the equator and equinox of date, depending on 'option'.
VecC Double: Position vector, geocentric equatorial rectangular coordinates, referred to ITRS axes (terrestrial system).

Return Value

Int16

               0 ... everything is OK
               1 ... invalid value of 'Accuracy'
               2 ... invalid value of 'Method'
            > 10 ... 10 + error from function 'CioLocation'
            > 20 ... 20 + error from function 'CioBasis'

Remarks

Note 1: 'x' = 'y' = 0 means no polar motion transformation.

Note2: 'option' = 1 only works for the equinox-based method.

Version Information

.NET Standard

Supported in: 2.0