Baseline Dimension
The Baseline Dimension 
tool creates
a series of dimensions that are all measured from a common baseline — the first
point you pick. Each dimension is offset from the previous one so the values do
not overlap.
Creating a baseline dimension
-
Select the Baseline Dimension tool.
-
Pick the first dimension point. This point becomes the common baseline. Hold Ctrl to pick an aligned reference line, or Shift to pick a perpendicular reference line.
-
Pick the second dimension point. Hold Shift to set the dimension angle.
-
Move the mouse to position the dimension line, then click to place it.
Repeat the command to add further dimensions from the same baseline.
The Text, Tolerance, and Angle input boxes let you override the dimension text, add a tolerance, and set the angle of the dimension line. See the section overview for the options shared by all dimension tools.