When I link an architects file, the X and Y coords are fine, but the Z axis doesn't match. The 0 level in my file is not the same as the 0 axis in the architects file when look in elevation.

When opened separately they both say 0,0.

In fact in the elevations they both say 0,0 when linked, but they are at different heights.

Please help, it's now nearly midnight and I've been at this for hours

I've tried requiring coords and all sorts.

I just cant find out how to reset a Z value so both 0's are in the same place