The distance is needed only to calculate the Supergalactic Cartesian 
Coordinates or to convert between different Ecliptic Coordinates.<BR>
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In all the other coordinate systems you are defining only the location 
of an object on the sky. In cartesian coordinates you are defining the 
location in space (x, y, and z -coordinates) so you must include the 
distance to accomplish that. For objects within our solar system the 
distance must be included in Ecliptic conversions because these distances 
are in the same magnitude with the distance between the Sun and the Earth 
and in some cases even with the distance between the Earth centre and the 
topocentric location. Therefore the distance is needed to avoid even 
drastic errors (think about an object lying between the Sun and the Earth!!).
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