Division Accounting for topography
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In cases where topography has to be taken into account (see Section 2.7.6), the aircraft height coordinate z has to be replaced by z′= z – zo (where zo is the z-coordinate of the observer location O) when estimating the propagation distance d. The geometry between aircraft and observer is shown in Figure 2.7.d. For the definitions of d and ℓ see Sections 2.7.14 to 2.7.19f1.
Figure 2.7.d
Ground elevation along (left) and lateral (right) to ground track
(The nominal ground plane z = 0 passes through the aerodrome reference point. O is the observer location.)
Annotations
Footnotes
- f1
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For non-level ground it is possible for the observer to be above the aircraft in which case, for calculating sound propagation z′ (and the corresponding elevation angle β — see Chapter 4) is put equal to zero.