Line of Site Profile - Coverage Interpretation

The diagram shows four conditions of shading: green, yellow, red and clear. This is shown in the diagram below. There is broad correlation between coverage in mobile and broadcast services and the degree of Fresnel zone clearance showing that some degree of obstruction can be tolerated (though this depends on the path budget). Conversely, there is also correlation between performance of fixed links and the lack of obstruction; such systems generally require full or near-full Fresnel zone clearance. This coverage view is therefore useful in a number of radiocommunications services. It does however need to be interpreted with care.

The areas not shaded or clear are the most constrained with the full first Fresnel zone completely obstructed by terrain. This condition is shown in profile 1 with the breach illustrated by the dashed line of terrain. In mobile and broadcast services this will yield high excess diffraction loss and is unlikely to provide adequately coverage unless very close to the transmitter site.

Areas shaded red have the radio line of sight obstructed but do not have the obstruction so severe as to breach the upper boundary of the first Fresnel zone. This condition is again shown in the first profile considering the solid line of terrain.

Areas shaded yellow have the lower half of the Fresnel zone obstructed but do not have the radio line of sight breached. This is shown in 2 above.

Areas shaded green have the lower half of the Fresnel zone free of obstruction as shown in 3 above. This view is possibly the most useful of all views since it shows all areas on the ground where there is full Fresnel zone (FFZ) clearance from a given site. If areas having FFZ clearance from two sites coincide this indicates that a repeater might be viable at these points to link the two in the event that a clear path does not exist between them directly.