What a wonderful idea, a DME vrs. Altitude graph, right on the approach plate! When I first saw that, on one of the first constant descent NPA approach charts, I thought it was brilliant (and it was!) back in the 80's. However, in Canada especially, there is the issue of low temperature; to be accurate, you'd have to calculate an additive to each DME point, based on surface temperature, and altitude above the field for each fix. I surmise that TC, having been faced with that problem, just decided it wasn't worth the hassle of adjusting each fix for temperature (at, say, -42, or whatever) for each fix, and shuffled it under the rug. If you just check the altitude vrs. DME, without temperature compensation, as a procedure, you could be really low; to check each fix could take 10-15 minutes in a holding pattern. TC probably said, "Why bother? Don't want that can of worms! Just let's not reference DME vrs. Altitude." Sam