Nexrad Intensity - Garmin GTN 625 Pilot's Manual

11.4.2.3
Foreword
Colors are used to identify the different NEXRAD echo intensities (reflectivity)
Getting
measured in dBZ (decibels of Z). "Reflectivity" is the amount of transmitted power
Started
returned to the radar receiver. Reflectivity (designated by the letter Z) covers a
Audio &
wide range of signals (from very weak to very strong). So, a more convenient
Xpdr Ctrl
number for calculations and comparison, a decibel (or logarithmic) scale (dBZ),
Com/Nav
is used. The dBZ values increase as the strength of the signal returned to the
radar increases.
FPL
11.4.2.4
When enabled, NEXRAD weather information is shown. Composite data
Direct-To
from all of the NEXRAD radar sites in the United States is shown. This data is
Proc
composed of the maximum reflectivity from the individual radar sweeps. The
display of the information is color-coded to indicate the weather level severity.
Wpt Info
Refer to the legend for a description of the color code.
The NEXRAD option has selections of Regional, CONUS, or Combined
Map
NEXRAD. CONUS NEXRAD includes a composite of available NEXRAD radar
imagery across the 48 states. Regional NEXRAD is a composite of available
Traffic
NEXRAD radar imagery in a local area, showing a more detailed image
than CONUS NEXRAD. FIS-B weather data reception requires line-of-site
Terrain
communication between the receiver and the ADS-B ground station. Incomplete
Regional and/or CONUS NEXRAD imagery displayed on the MAP and FIS-B
Weather
Weather Pages of the affected products is an indicator of poor FIS-B reception.
Nearest
Affected Areas
Any area in the continental United States (CONUS) or Alaska where the
Services/
Music
distance from ADS-B ground stations, or the combined effect of distance and
low altitude, is sufficiently great may cause poor reception. A good source of
Utilities
information for ground station coverage can be found at:
http://www.faa.gov/nextgen/flashmap/
System
Reception will improve in some affected areas as the FAA completes the
Messages
NextGen ADS-B ground station infrastructure. However, due to line-of-sight
broadcast characteristics, operators with properly installed and functioning
Symbols
equipment may still receive incomplete FIS-B data when signal reception is
limited by the distance from ground stations combined with a low altitude.
Appendix
Index
11-54

NEXRAD Intensity

NEXRAD
Garmin GTN 625/635/650 Pilot's Guide 190-01004-03 Rev. K