By Andy Davis
I have recently received an AutoCAD support query from a client who was having a problem locating geometry within an XREF drawing. When he referenced this dwg into another container drawing at 0,0,0, the geometry in the XREF was shown offset from its true position.
The AutoCAD system variable INSBASE contains the insertion base point of a drawing. The base point is expressed as coordinates in the current UCS. When you insert or externally reference the current drawing into other drawings, this base point is used as the insertion base point. This may be used to enable the use of relatively small local coordinates within a drawing, but still have the drawing insert or xref in the correct location relative to a much larger coordinate system.
In my clients dwg, the value of INSBASE had been changed from 0,0,0. Using the BASE command, he reset the insertion base point back to 0,0,0. This time when he referenced his dwg into the container drawing at 0,0,0, the geometry in the XREF was shown at its true position.