Refer to the following documentation for the list of available vertical coordinate systems,esrSRVerticalCSType Constanr<a href="http://edndoc.esri.com/arcobjects/9.2/ComponentHelp/esriGeometry/esriSRVerticalCSType.htm" target="_blank">http://edndoc.esri.com/arcobjects/9.2/ComponentHelp/esriGeometry/esriSRVerticalCSType.htm</a>