1. On-screen graphics aren't accurate most of the time - thus they are usually not included in the "canon" definition
2. Said graphic in 'Enterprise Incident' WAS that original Jeffries-sketch - wrong window-size and bridge-dome included!
In this case, the drawings wound up in
The Making of Star Trek, which also provided dimensions and other specifications of the
Enterprise. This is really the foundation for assigning a length of 947 feet in the public consciousness. Given the history of the show, including the explosion of interest in it that occurred in the 1970s between TOS and TMP, it makes little difference whether those particular dimensions have what fans today would consider canonical status, because they nevertheless became part of the lore.
As is the case for any work of fiction,
Star Trek ultimately does not mesh with reality, and therefore to pursue nth-degree realism is a wasted effort. As another example, historical events have been stated to have occurred in
Star Trek's fictional history that we know didn't and/or won't happen for real. The characters also view events that did really happen somewhat differently than we do. That's simply a by-product of its fictional status.
The dimensions of the
Enterprise are no different. In order to "get it right," we'd actually have to build the damn thing, working FTL and working transporters included. How else could we know how big it would really have to be?
At some point you have to accept that your stage is good enough for theater, stop working on it, and just freaking move on and present a play. Okudograms and other displays are really quite similar to technobabble; as a part of the scenery they're part of what defines the setting.
And yes, as something that appears on-screen, they are all fully canonical. But like all canon, they do not necessarily contribute to narrative continuity.
