Garmin GPSMAP 695/696 Owner’s Manual 190-00919-00 Rev. G128Hazard AvoidanceOverviewGPS NavigationFlight PlanningHazard AvoidanceAdditional FeaturesAppendicesIndexNEXRAD AbnormalitiesThere are possible abnormalities regarding displayed NEXRAD images. Some, butnot 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 radarscans• Interference from buildings or mountains, which may cause shadows• Poor reception from Ground Based Transceivers (GBTs) can cause portions of thereceived radar imagery to not be displayedNEXRAD LimitationsCertain limitations exist regarding the NEXRAD radar displays. Some, but not all, arelisted for the user’s awareness:• NEXRAD base reflectivity does not provide sufficient information to determinecloud layers or precipitation characteristics (hail vs. rain). For example, it is notpossible to distinguish between wet snow, wet hail, and rain.• NEXRAD base reflectivity is sampled at the minimum antenna elevation angle. Anindividual NEXRAD site cannot depict high altitude storms at close ranges, andhas no information about storms directly over the site.neXrAd intensityColors are used to identify the different NEXRAD echo intensities (reflectivity)measured in dBZ (decibels of Z). “Reflectivity” (designated by the letter Z) is theamount of transmitted power returned to the radar receiver. The dBZ values increaseas returned signal strength increases. Precipitation intensity is displayed using colorscorresponding to the dBZ values.
