Garmin G1000 Pilot's Manual page 260

HAZARD AVOIDANCE
All weather product legends can be viewed on the Weather Data Link Page. For the NEXRAD legend
(Figure 6-5), press the LEGEND Softkey when NEXRAD is selected for display.
The display of radar coverage is always active when either NEXRAD or ECHO TOPS is selected. The
display indicates the currently available NEXRAD radar coverage and Echo Tops areas in a grayish-purple
color where information is unavailable or is not being collected. This means that the radar capability exists
in the grayish-purple areas, but that it is not active or is off-line.
R
EFLECTIVITY
Reflectivity is the amount of transmitted power returned to the radar receiver. Colors on the NEXRAD
display are directly correlative 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 NEXRAD echo intensities are measured in decibels (dB) relative to reflectivity (Z). NEXRAD
measures the radar reflectivity ratio, or the energy reflected
letter Z). The value of Z increases as the returned signal strength increases.
6-8
Figure 6-5 NEXRAD Data with Legend
Garmin G1000 Pilot's Guide for Cessna Nav III
back to
the radar receiver (designated by the
190-00498-01 Rev. A