Garmin gtn 625 GPS Receiver User Manual


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11-10
Garmin GTN 625/635/650 Pilot’s Guide
190-01004-03 Rev. B
Foreword
Getting
Started
Xpdr Ctrl
Com/Nav
FPL
Direct-To
Proc
Wpt Info
Map
Traffic
Terrain
Weather
Nearest
Music
Utilities
System
Messages
Symbols
Appendix
Index
11.1.5.2 NEXRAD Limitations
NEXRAD radar images may have certain limitations:
•NEXRAD base reectivity does not provide sufficient information to
determine cloud layers or precipitation characteristics. For example, it is
not possible to distinguish between wet snow, wet hail, and rain.
•NEXRADbasereectivity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 the site.
•Each square block on the display represents an area of four square
kilometers (2.15 NM). The intensity level reflected by each square
represents the highest level of NEXRAD data sampled within the area.
Block Area Is 4 km
2
(2.15 NM
2
)
Block Area Is 4 km
2
(2.15 NM
2
)
Figure 11-9 NEXRAD Data Blocks
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
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