I'm sure everyone here has seen many pictures of vanishing points defined by rails. What you may not know is that all parallel lines converge to the same vanishing point. In other words, if two lines share the same vanishing point in an image then they are parallel. If they do not, then they are not parallel. That is the key purpose of me overlapping the photographs in the way I have. By corresponding the vanishing points, we "make" the rails parallel with each other in the image plane to more clearly see the difference in width (gauge).
It turns out that in the way you matched the Spur to the lumber rails, you basically did align the vanishing point of the rails without realizing it:
This is not incidental or coincidental, it's the image property that I am trying to exploit to identify if these rails are standard gauge or not. So by "matching" these rails you aligned the vanishing points. This provides evidence that the gauge of the rails is very similar.
On the other hand, in your attempt to match the broad gauge to the spur in question, you put the vanishing point in a completely different location:
If you were to move and stretch the overlay so that the vanishing points match, you would find that the blue lines are much wider than the red lines. Visually, you can see that the first overlap provides a continuity that the second photograph does not.
So both examples you have given, in my view, are just more evidence that the rails in question are not standard (1435mm) gauge.
Edited 2 time(s). Last edit at 11/23/2021 10:06AM by Loco-Motive.