Garmin GXM 30A - Manual (Page 37)

GXM 30A XM Radio Smart Antenna Owner’s Manual 30
NEXRAD Overview
NEXRAD Description
NEXRAD Radar is a Doppler radar system that has greatly
improved the detection of meteorological events such as
thunderstorms, tornadoes, and hurricanes. An extensive
network of NEXRAD stations provides almost complete radar
coverage of the continental United States, Alaska, and Hawaii.
The range of each NEXRAD is 124 nautical miles.
NEXRAD Abnormalities
There are possible abnormalities regarding displayed NEXRAD
images. Some, but not all, of those include:
• Ground clutter
• Strobes and spurious radar data
• Sun strobes, when the radar antenna points directly at
the sun
• Military aircraft deploy metallic dust (chaff) which can
cause alterations in radar scans
• Interference from buildings or mountains, which may
cause shadows
NEXRAD Limitations
Certain limitations exist regarding the NEXRAD radar
displays. Some, but not all, are listed for the user’s awareness:
• NEXRAD base reflectivity does not provide sufficient
information to determine cloud layers or precipitation
characteristics (hail vs. rain).
• NEXRAD base reflectivity is sampled at the minimum
antenna elevation angle. An individual NEXRAD site
cannot depict high altitude storms at close ranges, and
has no information about storms directly over the site.
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