fd60a641_Co_ordinate_Systems___CADTutor__Method_of_UCS_determination
[Object] Text, Block, Attribute [Method of UCS determination] 
The new UCS origin is the insertion point of the entity. The new X axis is defined in such a way that the entity will have a rotation angle of 0 in the new UCS.
AutoCAD Tutorial | User Co-ordinate Systems | CADTutor
Method of UCS determination