Garmin GDL 69A GPS Receiver User Manual


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15
Part Two: Section 2
XM Weather
To display the NEXRAD Intensity Legend:
1. While viewing the XM Weather page, press the
MENU key to display the Page Menu.
2. Turn the large or small knob to select “Display
legend?”
3. Press ENT to display the NEXRAD Intensity
Legend.
4. Turn the large or small knob to scroll through
the full table. Press CLR to return to the normal
view.
NEXRAD Abnormalities
There are possible abnormalities regarding dis-
played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
NEXRAD Limitations
CertainlimitationsexistregardingtheNEXRAD
radar displays. Some, but not all, are listed for the
user’s awareness:
•NEXRADbasereectivity does not provide suf-
ficient information to determine cloud layers or
precipitation characteristics (hail vs. rain, etc).
• NEXRADbasereectivityissampledatthe
minimum antenna elevation angle. An indi-
vidualNEXRADsitecannotdepicthighaltitude
storms at close ranges, and has no information
about storms directly over the site.
• NeitherNEXRADweatherdatanortheageof
theNEXRADweatherdataaredisplayedata
zoomrangeoflessthan10NM.Theresolu-
tionofdisplayedNEXRADdatais2kilometers.
Therefore,whenzoomedinonthedisplay,
eachsquareblockis2kilometers.Theintensity
level reflected by the square will be the high-
estlevelsampledwithinthe2kilometersquare
area.
XM Weather METARs
XMWeatherMETARs(MeteorologicalAerodrome
Reports)areavailableontheXMWeatherpage.When
enabled(thatis,when“METAR”isshownintheupper
leftcornerofthepage),airportswithMETARinfor-
mationaboveacertainseveritylevelaremarkedwith
coloredagsonthedisplay.RefertotheXMWeather
legend for a description of the color code. The update
rate is every 12 minutes.
190-00356-30 Rev C
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