If you know the major and minor radi of the ellipse you can determine the center of the ellipse (mathematically). Then go in to sketch mode in the 2D drawing environment and place a center point at the mathematical center of the ellipse. Exit sketch mode. Now place your needed dimensions.
Thanks for your answer. I am trying to get it to work, but no success so far. I have a sheet metal part with oval (ellipse) holes on it. I've created the flat pattern for the part and separate drawings for the folded part and flat pattern. In the drawing for folded part, the Inventor recognises ellipse centers and allows me dimension them. In the drawing for flat pattern, it does not recognise those centers.
Then I would take the dimensions found in the formed drawing and apply them to the drawing with
the flat pattern in it. For example, say your formed drawing showed the center of the ellipse to be
1.5 inches and 2 inches from some point (where ever you are measuring from/to on the ellipse). Write
those values down and open you flat pattern drawing. With your cursor, select the view you wish to
add dimensions to (make sure the view highlites) then select the "Sketch" button at the top in the
toolbars. This activates sketch mode only for the view you selected. Now place a center point mark
somewhere close to the center of the ellipse. Constrain it with dimensions whose values are from
your form drawing (1.5 and 2 inches). Exit sketch mode. If your sketch dimensions "bleed thourgh"
just right click on them and turn their visiblities off. Now you can dimension to the center point of
you ellipse. Hope this helps.