Garmin G3X Touch Pilot's Manual page 150

Hazard Avoidance
NEXRAD Intensity
Colors are used to identify the different NEXRAD echo intensities (reflectivity)
measured in dBZ (decibels of Z). "Reflectivity" (designated by the letter Z) is the
amount of transmitted power returned to the radar receiver. The dBZ values increase
as returned signal strength increases. Precipitation intensity is displayed using colors
corresponding to the dBZ values.
FIS-B Radar Products
FIS-B weather provides two different Radar products, CONUS and Regional. The
system can display each individually or a composite (COMBINED). When Regional
Radar is displayed, only precipitation for your current region is displayed. The subdued
(grayish-purple colored) area represents the area not covered by the regional radar
product. When Combined radar data is viewed, Regional Radar data is displayed on
top of CONUS data and the time shown in the lower left corner is associated with
Regional Radar data only.
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NEXRAD Data
Garmin G3X Touch Pilot's Guide 190-01754-00 Rev. A