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Abteilung Astronomie

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ECI2GEO Source code in eci2geo.pro

ECI2GEO

Name
     ECI2GEO
Purpose
     Convert Earth-centered inertial coordinates to geographic spherical coords
Explanation
     Converts from ECI (Earth-Centered Inertial) (X,Y,Z) rectangular
     coordinates to geographic spherical coordinates (latitude, longitude,
     altitude).    JD time is also needed as input.
     ECI coordinates are in km from Earth center.
     Geographic coordinates are in degrees/degrees/km
     Geographic coordinates assume the Earth is a perfect sphere, with radius
     equal to its equatorial radius.
Calling Sequence
     gcoord=eci2geo(ECI_XYZ,JDtime)
Input Parameters
       ECI_XYZ : the ECI [X,Y,Z] coordinates (in km), can be an array [3,n]
                 of n such coordinates.
       JDtime: the Julian Day time, double precision. Can be a 1-D array of n
                 such times.
Keyword Parameters
       None
Output Parameters
       a 3-element array of geographic [latitude,longitude,altitude], or an
         array [3,n] of n such coordinates, double precision
Common Blocks
       None
Procedures Used
       CT2LST - Convert Local Civil Time to Local Mean Sidereal Time
Example
       IDL> gcoord=eci2geo([6378.137+600,0,0], 2452343.38982663D)
       IDL> print,gcoord
       0.0000000       232.27096       600.00000
       (The above is the geographic direction of the vernal point on
       2002/03/09 21:21:21.021, in geographic coordinates. The chosen
       altitude was 600 km.)
       gcoord can be further transformed into geodetic coordinates (using
       geo2geodetic.pro) or into geomagnetic coordinates (using geo2mag.pro)
Revision History
       Written by Pascal Saint-Hilaire (Saint-Hilaire@astro.phys.ethz.ch) on
              2001/05/13
       Modified on 2002/05/13, PSH : vectorization + use of JD times

Last modified by pro2html on 2002 May 18 at 03:22 UTC

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Jörn Wilms (wilms@astro.uni-tuebingen.de)
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