Table 2-1. Correction for the Earth's Curvature and Refraction
c. The general problem for intervisibility is determining how much a line of sight between two
stations will clear or fail to clear an intervening obstruction. Use the following formula to make this
determination:
h
=
The elevation of the line at obstruction (in meters)
h1
=
The elevation of the lower station (in meters)
h2
=
The elevation of the higher station (in meters)
d1
=
The distance from the lower station to the obstruction (in kilometers)
d2
=
The distance from the higher station to the obstruction (in kilometers)
The first two terms of the above formula are a solution of similar triangles. The last term is the
curvature and refraction correction. If the two stations are at the same elevation, the obstruction can be
cleared using signals of equal height, and the above formula becomes the following simple formula:
h = hl - 0.0676 d1d2
The height of the signal at each end becomes the following formula:
h1 = h + 0.0676 d1d2
d. For a given length (K) between stations, the elevation required at one station to see the other
station across a level surface (such as water) is K2 X 0.0676. If both stations are raised to the same
elevation, the height (h2,1) required at each
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EN0593
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