z-Axis

z-axis - [coordinate systems] In a spherical coordinate system, the vertical line that runs parallel to the earth's rotation, passing through 90 degrees north latitude, and perpendicular to the equatorial plane, where it crosses the x- and y-axes at the origin (0,0,0).

[Category=Geospatial ]

Source: esri, 16 October 2012 09:20:04, http://support.esri.com/en/knowledgebase/GISDictionary/term/abbreviation