Garmin GDL 88 User Guide - Page 31

NEXRAD Abnormalities, NEXRAD Limitations

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NOTE: FIS-B NEXRAD does not differentiate between frozen and liquid precipitation. The FIS-B NEXRAD intensity colors (as shown below) may differ from the intensity colors from other providers. 5.1.1 NEXRAD Abnormalities There are possible abnormalities regarding displayed NEXRAD images. Some, but not all, causes of abnormal displayed information include: • Ground Clutter • Strobes and spurious radar data • Sun strobes, when the radar antenna points directly at the sun • Military aircraft deploy metallic dust which can cause alterations in radar scans • Interference from buildings or mountains, which may cause shadows • Scheduled maintenance may put a radar off-line 5.1.2 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, etc). • 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. • The resolution of displayed Regional NEXRAD data is approximately two kilometers and the resolution of displayed CONUS NEXRAD data is approximately 10 kilometers. Therefore, when zoomed in on the display, each square block is two kilometers (1.08 NM) or 10 kilometers (5.4 NM) on a side. The intensity level reflected by the square will be the highest level sampled within the area covered by each block. 190-01122-03 Rev. A GDL 88 ADS-B Transceiver Pilot's Guide 5-3

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5-3
190-01122-03
Rev. A
GDL 88 ADS-B Transceiver Pilot’s Guide
NOTE
:
FIS-B NEXRAD does not differentiate between frozen and liquid
precipitation. The FIS-B NEXRAD intensity colors (as shown below) may
differ from the intensity colors from other providers.
5.1.1
NEXRAD Abnormalities
There are possible abnormalities regarding displayed NEXRAD images. Some,
but not all, causes of abnormal displayed information include:
• Ground Clutter
• Strobes and spurious radar data
• Sun strobes, when the radar antenna
points directly at the sun
• Military aircraft deploy metallic dust which can cause alterations in radar
scans
• Interference from buildings or mountains
, which may cause shadows
• Scheduled maintenance may put a radar off-line
5.1.2
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, etc).
• 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.
• The resolution of displayed Regional NEXRAD data is approximately
two kilometers and the resolution of displayed CONUS NEXRAD data is
approximately 10 kilometers. Therefore, when zoomed in on the display,
each square block is two kilometers (1.08 NM) or 10 kilometers (5.4 NM)
on a side. The intensity level reflected by the square will be the highest level
sampled within the area covered by each block.