I’m trying to reverse engineer the zoom level vs. FOV. I’ve taken some measurements, and my best guest currently is that 0% is 135deg and 100% is 15deg field of view. If others have some patience, please contribute numbers/measurements.
Find an airport with good reference/landmark points. Pick a spot on the airport where you have some references points like buildings (looking at them head on). Zoom until some reference points touch the edge of the screen. Measure these in Google Earth (e.g. distance between the references points) and measure distance to the middle of the line between them.
I’ve done this at KORS with the following results (at a given zoom leve, X feet of something is visible left to right from Y feet away) on 16:9 display:
0% 240 feet, 48 feet
30% 244 feet, 88 feet
50% 218 feet, 100 feet
60% 400 feet, 236 feet
75% 144 feet, 140 feet
94% 53 feet, 163 feet
They’re not perfectly linear (zoom vs FOV) so would need lot more samples. But as I said, these seem to point 0-100% being 135deg to 15deg, with 50% being 75deg FOV.