another elevation question

[MikeHenson]

I have a data file, with "projectedz" field, which is supposed to be ground elevation. THis elevation is recorded in meters, but I need feet. If I convert this elevation to feet, but multiplying the z by 3.28084, I get an elevation that should be similar to what my usgs quad map shows.  I am consistently off 80-90 feet from my calculated elevation, to the quad elevation. IE....if I see a point on a quad marked 400', my calculated point is 320. Is my conversion correct? Shouldn't I simply do the multiplication like i mentioned to get feet?  Just looking for confirmation that what I am doing is correct. 

[MikeHenson]

Thanks Saul...you are most helpful as I try to navigate this software (and the forums!!)

[MikeHenson]

there was no conversion on the elevations when joining them to the gdb.  Whats odd, that I am figuring out is that the error is 80' all over the map. The discrepancy between the field mapped data and the usgs topo spot elevations from a 7.5 min quad map.  I am taking the elevations (dtm) and multiplying by 3.28 to come up with a us foot elevation.