You can set the units in Creo Elements/Direct 3D Access that you want to use for absolute measurements of your solid models. For example, if you have a block that has a length of 10mm, and load the part into Creo Elements/Direct 3D Access with the units set to inches, the length stays the same (10mm) but the value is displayed in inches (0.39 inch).
To change the active units:
• Click File > Settings > System. Click Units .
To view the active units, move the pointer to the global control buttons which display the active workplane, active part, and catch mode, then slide the scroll bar to move down the list of buttons.
The worksphere is the 3D space in which you can work and create parts. It can be considered as being like a globe around the origin of the Global Coordinate System. The worksphere radius is 100 meters (100,000mm). No portion of a part is allowed outside this worksphere. The minimum value you can work with is 1 micron or 0.000001mm.
When you first start Creo Elements/Direct 3D Access, the units are set to millimeters, degrees, and grams (mm | deg | g) by default.