Welcome to the L3 Harris Geospatial documentation center. Here you will find reference guides and help documents.
﻿
>  Docs Center  >  Libraries  >  ASTROLIB  >  ECI2GEO

ECI2GEO

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

## Calling Sequence

gcoord=eci2geo(ECI_XYZ,JDtime)

## Input

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.

None

## Output

a 3-element array of geographic [latitude,longitude,altitude], or an
array [3,n] of n such coordinates, double precision

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)

## Modification 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

© 2020 Harris Geospatial Solutions, Inc. |  Legal