Garmin GTX 330 GPS Receiver User Manual


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15
Part Two: Section 2
XM Weather
NEXRAD Intensity
ColorsareusedtoidentifythedifferentNEXRAD
echo intensities (reflectivity)measuredindBZ(deci-
belsofZ).“Reectivity”istheamountoftransmitted
power returned to the radarreceiver.Reectivity
(designatedbytheletterZ)coversawiderangeof
signals(fromveryweaktoverystrong).So,amore
convenient number for calculations and comparison, a
decibel(orlogarithmic)scale(dBZ),isused.ThedBZ
values increase as the strength of the signal returned
to the radar increases. There are seven gradations for
rain,twogradationsformixedrainandsnow,andtwo
gradations for snow.
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
190-00356-30 Rev F
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