Note: Values marked with a * are not dependent on Refraction in reality. The marked values show the apparent values if refraction is not zero. So to display the real values, set Refraction = 0. This is true for all Horizon Data as well.

Visible, Hidden: how much of the object size is hidden behind the horizon and how much is visible.

Angular Size, Visible∠, Hidden∠: same as above but in angular size. The angular size is arctan( size / distance ) in degrees.

Refraction Angle: How much of the object is lifted due to refraction expressed as an angular size. See Refraction-Angle ρ how this angle is calculated.

Lift Absolute: absolute amount of apparent lift of the object with respect to eye level due to refraction.

Relative to Horizon: amount of apparent lift of the object with respect to the horizon due to refraction. The horizon appears lifted with respect to eye level by refraction too. If an object lies behind the horizon, its lift relative to the horizon is smaller than the absolute lift of the object with respect to eye level.

Target Top∠, Target Top∠ FE: Angle α between target top and eye level for globe and flat earth (FE) respectively. The angle is positive if the target top is above eye level. Some theodolites measure a so called zenith angle ζ. The zenith angle is the angle between the vertical up and the target top. The correlation between this angles is α = 90° − ζ.

Tilt θ: is the angle the target is tilted backwards. This is the same as the angle between the observer, the center of the earth and the target.

Drop: is the amount the surface at the target has dropped from the tangent plane at the surface of the observer. This is the exact value, not the approximation from "8 inches per miles squared".

Bulge Height: is the maximal amount the surface appears to bulge up from the direct line through the earth from the surface at the observer and the surface at the target.

Dist on Surf: is the distance of the horizon line from the base of the observer along the surface.

Drop Angle: is the angle between the horizon line and the eye level line as measured at the observer.

Dist from Eye: is the line of sight distance of the horizon line from the observer.

Dist on Eye-Lvl: is the distance of the horizon measured on the eye level plane.

Drop from Surf: is the drop of the horizon line as measured down from the tangential plane with origin at the surface of the obsever.

Drop from Eye-Lvl: is the drop of the horizon line as measured down from the tangential plane with origin at the observer height. Drop from Eye−Lvl = Drop from Surf + Observer Height.

Latitudes in the northern hemisphere are positive, in the southern hemisphere negative values.

Positive Acceleration, Force, Curvature Radius and Course Deviation act horizontally to the right as seen in the moving direction, negative values act to the left.

An unbalanced Coriolis Acceleration causes a circular flight path to the right or left with a certain Curvature Radius. At a certain Distance you reach a certain Course Deviation from the straight course.

Note: if the Curvature Radius gets too small, you can't reach the destination at Distance. You will turn back in a circle. In this case, as soon as the Course Deviation exceeds the Curvature Radius, the Course Deviation field will be dispayed with a red background color.

Note: as you progress along your (curved) track, the Coriolis Acceleration would change in reality according to the current latitude and so would the Curvature Radius. This calculation assumes a constant Coriolis Acceleration along the track, just to give a picture. If you fly east near the equator and would not correct for the Coriolis acceleration, you would fly in a slalom course along the equator.

Aircrafts and the Coriolis Effect

For a more detailed explanation see How Airplanes correct for the Coriolis Effect.

If the atmosphere would not be dragged along with the surface of the earth and the atmosphere would not drag embedded aircrafts with it, aircrafts would have to correct for the Coriolis force to maintain the desired ground track. The autopilot would correct the deviation by slightly bank the aircraft in the opposite direction of the coriolis force. This bank generates an equal but opposite horizontal force component that cancels the Coriolis Force. This bank angles are unperceivably small (much less than a degree). Pilots don't have to account for this correction, as the the atmosphere together with the auto pilot does this automatically while correcting for any course deviations e.g. due to side wind components.

Exmaple:

• Latitude = 52°
• Speed = 500 km/h
• Mass = 50,000 kg

Results in:

• Coriolis Acceleration to the right = 0.016 m/s²
• Coriolis Force to the right = 796 N

The Lift Force produced to balance the weight of the aircraft is:

• Lift Force = Mass * gravitational acceleration = 490,500 N

The bank angle to the left needed to balance the Coriolis Force would be:

• Bank Angle = atan( Coriolis Force / Lift Force ) = 0.093°