For the exterior elevation, the baseline/datum (finished floor) is 0,0, elevation marker has a field that reads the elevation from the y plane.  However, the interior elevation may have a higher finished floor level.  How can I get the elevation marker w/ a field that auto updates, to read off the 2nd finished floor elevation (or any baseline).  There may be several finish floor levels in one drawing.  Is there a way to define additional reference points?  I've included a sample to try to clarify what I'm seeking...

Eventually, see my DWG file : FEET-METERS.dwg that you can find in the CAD Blocks library right here in the site : Launch a search with : FEET-METERS.

It explains the use of alternative dimensions which is also your case but it includes the use of the command DIMORDINATE.

When you put a dimension with DIMORDINATE you will be abble to have dimensions in X direction and Y direction wich will be your choise.

This dimension have a grip at the 0,0 point and for you will have to set a zero on each floor to have 2 dimordinate correct dimentions.

Instead of setting a new UCS each time you want to dimension a ceiling you can copy a dimordinate allready made and GRIP A NEW THE GRIP OF THE 0,0.

To modify and have an automatic updating of the elevation DIMORDINATE you will have to use the command STRECH.

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