Earth Bulge

This value is calculated based on the distances involved.

Significance of This Value:

The term "earth bulge" and "earth height" are often used interchangeable. It's generally considered that the term "earth bulge" refers not to the actual height of the ground (relative to the center of the earth) but, rather, to the apparent height that creates an obstruction for an electromagnetic wave. This apparent height is calculated based on the refractive index of the atmosphere. It's only when K=1 that the apparent height of the earth bulge is equal to the actual height of the earth at a particular distance.

Background and Technical Perspective:

Refer to the Refractive Index discussion to understand how the curvature of the earth appears greater than the physical, geometric spherical representation that might be used to calculate line-of-sight to the horizon based on a tangent line from a point at some height above the surface.