getting to grips with surveillance(110)

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Figure 7-10 illustrates discontinuities when translating a spherical world map into a plane world map. The interrupted Goode’s projection shows areas near the Poles with minimal distortion.
. Black Bands: Incomplete Terrain Coverage For low latitudes, the terrain information extracted from the terrain database (spherical coordinates) is adapted to the current latitude for display (plane coordinates) with small distortions. Near 84° of latitude, the convergence of meridians implies some significant distortions when latitudes/longitudes are translated into distances. In other words, the terrain information cannot be adapted to the current latitude without visible discontinuities. These discontinuities appear as black bands on ND (the
amber TERR INOP indication is displayed on VD). When the aircraft gets closer to the North or South Pole, the discontinuities (i.e. black bands) get larger.

.  Magenta Areas: Unavailable
Terrain Information

The latitude range is - 90° to + 90°. When the aircraft flies to the North Pole, the latitude increases to 90°. When the aircraft passes the North Pole, the latitude decreases from 90° (vice versa across the South Pole). From a mathematical point of view, the latitude should increase when the aircraft flies to and passes the North Pole (i.e. …88°, 89°, 90°, 91°, 92°…). Due to the limits of the latitude range, the TAWS function considers there is no terrain information beyond 90° of latitude. The TAWS function displays the corresponding areas in magenta on ND (the amber TERR INOP indication is displayed on VD).
Note: EGPWS is also affected by these limitations. Refer to 4.1.5.5 – Terrain Display in Polar Areas.
7.1.4. WEATHER RADAR FUNCTION
The AESS Weather Radar function provides the same functions as conventional weather radars: weather detection with PWS and turbulence detection. The range goes up to 320 NM. The antenna scans an envelope of +/-80° in azimuth and +/- 15° in tilt. Refer to Figure 7-24.
The AESS Weather Radar function introduces a new concept: the weather radar does not directly display the weather information to the flight crew, but stores it in a 3D buffer. The 3D buffer significantly improves the weather analysis (i.e. on/off path weather, elevation mode, vertical view, Earth curvature correction, automatic ground mapping, weather displayed behind the aircraft) and the weather awareness.
Note: The weather radar basic principles remain identical to the ones described in 6 – Weather Surveillance –. Refer to this chapter for a refresher about weather radar physics.
7.1.4.1. WEATHER DETECTION
With weather returns stored in a 3D buffer, the AESS Weather Radar function provides different operating modes (automatic and manual). The following paragraphs describe the 3D buffer principles, and the automatic and manual operating modes.

 

7.1.4.1.1. 3D Buffer
　
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