Garmin Cirrus Perspective SR20 Pilot's Manual page 330

Integrated avionics system

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HAZARD AVOIDANCE

NEXRAD radar images may have certain limitations:

• NEXRAD base reflectivity does not provide sufficient information to determine cloud layers or precipitation

characteristics (wet hail vs. rain). For example, it is not possible to distinguish between wet snow, wet

hail, and rain. Undetermined precipitation types may be displayed as mixed.

• NEXRAD base reflectivity is sampled at the minimum antenna elevation angle. An individual NEXRAD

site cannot depict high altitude storms at close ranges. It has no information about storms directly over

• When zoomed in to a range of 30 nm, each square block on the display represents an area of four square

kilometers. The intensity level reflected by each square represents the

sampled within the area (Figure 6-12).

• Unknown precipitation below 52ºN is displayed as rain regardless of actual precipitation type.

Block Area is 4 km

The following may cause abnormalities in displayed NEXRAD radar images:

• Ground clutter

• Strobes and spurious radar data

• Sun strobes (when the radar antenna points directly at the sun)

• Interference from buildings or mountains, which may cause shadows

• Metallic dust from military aircraft, which can cause alterations in radar scans

Cirrus Perspective

Figure 6-12 NEXRAD Data - Zoomed

by Garmin – Pilot's Guide for the SR20/SR22SR22T

level of NEXRAD data

190-00820-08 Rev. A

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