Yes, that's right but you need some zero for your azimuth at different elevations and you still cannot see a leaning towards you or away from your position. Therefore you need to triangulate it.
No one needs to triangulate it because no one cares about quantitative measurements in a situation like that. The relevant information is whether there is displacement, the approximate magnitude, and whether (and at approximately what rate) it is increasing.
Here is a conversation you will never hear firefighters have:
"Chief, the lean is still increasing! We're at eight inches now."
"What direction?"
"We triangulated it, and the trend is toward the west-southwest."
"Okay, thanks. Move everybody over to the east-northeast side where they'll be safe."
Here's how to do it in real life: put one (1) transit close to the building, aimed 75 degrees or so upward with the cross hairs on a particular recognizable spot. (This is also convenient because it means the transit will be within the secured operations area, rather than sending personnel hundreds of yards away to place it and check it.) Periodically, check the view to see if the aim point has moved in any direction in the view, and by about how much.
Now, if the building is leaning directly toward the transit
and happens to also be slumping downward just the right amount at the same time you might miss it! Fortunately buildings will lean long before they slump down, unless they're already falling and it's too late to do anything about it.
The real comic irony here is that you're expecting firefighters, having placed multiple transits in precisely measured locations, to then track the movements of building features (either measuring the movement within the transits' fields of view or measuring the angular changes needed to re-aim the cross hairs), and then perform the calculations to determine the true building feature movement in three dimensions. All in real time in the midst of intense activity and danger at the fire scene.
And yet of the Truthers who have made all sorts of claims about measuring building movements at the start of the collapses, not one has been able to perform those same sorts of 3-D triangulation measurements and calculations, given safe armchairs to work from, hundreds of supposedly supportive engineers to consult with, and years of time!
I suppose that expecting firefighters to do things in minutes that no Truther can learn how to do in years at least shows that you hold them in high esteem. But it might help to remember that firefighters carry axes, not scalpels.
Respectfully,
Myriad