Why/when would I need to define a Z coordinate system in arccatalog for my dataset?

Discussion created by mr.t on Apr 27, 2012
Latest reply on Apr 28, 2012 by vangelo-esristaff
While defining the projection for a new feature dataset, it occurred to me that I have not defined a z coordinate in a while. Well, I have some field data now with elevation (z values). Out of curiosity, why or when would I need to define a Z coordinate system?

Here's whats bothering me. If the projection is the same when the data was collected (x,y,z), do I still have to create a z coordinate in arccatalog? I mean the xy coordinate defined should cover this as well...correct? considering mean sea level does not change.

I would appreciate some simple scenarios why a z coordinate would be required in addition to an existing x,y coordinate already defined.

Thanks for taming my GIS curiosity.