I am trying to to build some terrains using DEMs.  I have read the documentation on gzbuilder on the website.  Unfortunately there isn't much of it.  I've also searched in vain for some examples elsewhere on the web and in the mailing list archives.  Can some one kindly point me to some some examples of using gzbuilder to build terrains using Digital Elevation Maps.  Also, an explanation of the UTM offsets, why they are needed and how to properly specify them would be helpful.  I apologize if this issue has already been addressed and I overlooked a good explanation somewhere else.