Horizon Dip Measurements

The horizon dip measurement is the angle between the horizontal (the line perpendicular to the vertical at a specific point) and the apparent horizon.

On a globe, you would expect this angle to increase with increasing altitude, because the horizon would drop away with the curve. In fact, we can calculate the expected dip of the horizon for any altitude using this formula:

$\text{Dip}=\sqrt{\frac{2h}{R}}$

Where:
h = the height or altitude of the observation
R = the radius of the earth (6,378 km)

Here is a table of the expected dip of the horizon for various altitudes:

style="background:#d0e5f5;align:center"Altitude	Dip
10,000 km	drop1

On a flat earth, if the plane is infinite, you would expect no drop of the horizon with increasing altitude. You would just be able to better resolve distant points because of the greater angular resolution between them. If the plan is finite, there would be slight dip of the apparent horizon from the horizontal, but not nearly as much as on the globe. We can calculate this expected dip for any altitude as well.

Measurements will be forthcoming.