Inertial (non rotating) 3D cartesian coordinate reference system with its origin at the earth's center of mass and based on the GCRF reference frame
http://www.opengis.net/def/crs/OGC/0/ECI_GCRF
http://www.opengis.net/def/crs/OGC/0/ECI_GCRF
Earth-Centered Intertial, GCRF
All 3D space inside, on the surface, or around the earth, usually within the limits of the solar system
Earth centered, inertial, righthanded 3D cartesian coordinate system
http://www.opengis.net/def/cs/OGC/0/ECI
http://www.opengis.net/def/cs/OGC/0/ECI
Earth-Centered Intertial
http://www.opengis.net/def/axis/OGC/0/ECI-X
X
Aligned with the the vernal equinox (intersection of the ecliptic and the earth's equatorial plane), and directed so that it points to the sun around March 21st
http://www.opengis.net/def/axis/OGC/0/ECI-Y
Y
On the plane of the celestial equator, orthogonal to both X and Z, so that the frame is right handed
http://www.opengis.net/def/axis/OGC/0/ECI-Z
Z
Aligned with the earth spin axis, in the direction of the celestial north pole
GCRF datum for ECI frames
http://www.opengis.net/def/crs/OGC/0/DATUM_GCRF
Universe
GCRF frame anchored at the earth's center of mass with axes based on the ICRF frame (almost equivalent to J2000 with additional nutation corrections)
1950-01-01