Garmin G900X Pilot's Manual page 398

HAZARD AVOIDANCE
Displaying Precipitation weather information:
1) Select the MAP Softkey (for the PFD Inset Map, select the INSET Softkey). This step is not necessary on the
Weather Data Link (GFDS) Page.
2) Press the PRECIP Softkey.
Precipitation information shown represents highest level, composite reflectivity, of radar returns. The
display of the information is color-coded to indicate the weather severity level. All weather product legends
can be viewed on the Weather Data Link (GFDS) Page. For the Precipitation legend (Figure 6-68), press the
LEGEND Softkey when Precipitation is selected for display.
The display of no radar coverage is enabled when Precipitation is selected for display. Areas where radar
coverage is not currently available or is not being collected are indicated in gray shade of purple. A white tick-
marked boundary line depicts the selected coverage area of the GFDS weather data request. This boundary
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
letter Z). The value of Z increases as the returned signal strength increases.
382
Figure 6-68 Precipitation Weather
Product Legend
Garmin G900X Pilot's Guide
No Radar Coverage
Boundary of GFDS
weather data request
back to
the radar receiver (designated by the
190-00726-00 Rev. J