When measuring size it's done from the horizon, you can see in the image I posted the angle in red never changes no matter how close or far away the pole is. This angle correlates with the poles physical height and can be measured directly with a sextant.
Are you saying that the human eye has limits when reading the trigonometry calculations on the sextant? We don't hold the sextant far enough away from us so that it disappears into the vanishing point.
Or is it only the trig limits when the 32 degrees is the only thing that shows up on the sextant? We still need another calculation to find distance and/or size.
Or is it the human eye limits reading only the degrees on trig tables? We don't hold trig tables far enough away from us so that they disappear into the vanishing point.
The vanishing point you are talking about is the vanishing point that makes the degrees the only thing necessary for finding distance and size. Standard science doesn't use this kind of vanishing point for calculating distance and size. You need at least one more calculation to find distance and size besides the degree calc. What is the other calculation you are using, and where are you getting it?
Of course making measurements is done from the horizon. As long as you are standing on the surface of the earth, you are standing on a horizon. Why? Because there are an infinite number of horizons. The things that determine a particular horizon location are, the distance away from the horizon, the height the horizon is measured at, and the direction that the measurement is taken in.
Consider two people looking at each other from different horizon points. How far apart are they? If they are only 6 inches tall, can they see each other on a horizon that two 6 foot tall people would see each other on? The sextant only measures degrees. You need to compare two sextant readings of two different sets of objects to begin to tell distance and size. This is the start into using parallaxes.