190-02177-02 Rev. A
Garmin G1000 NXi Pilot’s Guide for the Cessna NAV III
SY
STEM
O
VER
VIEW
FLIGHT
INSTRUMENTS
EIS
AUDIO P
ANEL
& CNS
FLIGHT
MANA
GEMENT
HAZARD
AV
OID
ANCE
AFCS
ADDITIONAL
FEA
TURES
APPENDICES
INDEX
279
HAZARD AVOIDANCE
The system displays either base or composite radar imagery, depending on the region.
Region
Radar Reflectivity Type
United States
Composite Reflectivity
Canada, Europe, Australia
Base Reflectivity
The base reflectivity precipitation weather product shows the radar returns from the perspective of a single
antenna tilt angle. The composite reflectivity precipitation weather product shows the
highest
radar energy
received from multiple antenna tilt angles. The display of the information is color-coded to indicate the
intensity of the echoes and the type of precipitation.
All weather product legends can be viewed on the ‘Map - Weather Data Link (CNXT)’ Page. For the
Precipitation legend, press the
Legend
Softkey when Precipitation is selected for display.
Boundary of radar
coverage area
No radar coverage
Figure 6-19 NEXRAD Weather Product Legend
The display of radar coverage is enabled active when Precipitation is selected for display. Areas where
precipitation radar coverage is not currently available or is not being collected are indicated in gray shade of
purple. A white boundary line depicting the selected coverage area of the Connext Data Request encloses the
precipitation data when this weather product is displayed.
r
eFlectivity
Reflectivity is the amount of transmitted power returned to the radar receiver. Colors on the Precipitation
display directly correlate to the level of detected reflectivity. Reflectivity as it relates to hazardous weather
can be very complex.
The role of radar is essentially to detect moisture in the atmosphere. Simply put, certain types of weather
reflect radar better than others. The intensity of a radar reflection is not necessarily an indication of the
weather hazard level. For instance, wet hail returns a strong radar reflection, while dry hail does not. Both
wet and dry hail can be extremely hazardous.
The different radar echo intensities are measured in decibels (dB) relative to reflectivity (Z). Weather
radars measure the reflectivity ratio, or the energy reflected
back to
the radar receiver (designated by the
letter Z). The value of Z increases as the returned signal strength increases.