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4-67190-01102-02 Rev. B
Garmin G500 Pilot’s Guide
Foreword
Sec 1
System
Sec 2
PFD
Sec 3
MFD
Sec 4
Hazard
Avoidance
Sec 5
Additional
Features
Sec 6
Annun.
& Alerts
Sec 7
Symbols
Sec 8
Glossary Appendix A
Appendix B
Index
4.8.2.2 Ground Returns
The intensity of ground target returns depends upon the angle at which the
radar beam strikes the ground target (Angle of Incidence) and the reflective
properties of that target. The gain can be adjusted so shorelines, rivers, lakes,
and cities are well defined. Increasing gain too much causes the display to fill
in between targets, thus obscuring some landmarks.
Cities normally provide a strong return signal. While large buildings and
structures provide good returns, small buildings can be shadowed from the
radar beam by the taller buildings. As the aircraft approaches, and shorter
ranges are selected, details become more noticeable as the highly reflective
regular lines and edges of the city become more defined.
Bodies of water such as lakes, rivers, and oceans are not good reflectors,
and normally do not provide good returns. The energy is reflected in a forward
scatter angle with inadequate energy being returned. They can appear as dark
areas on the display. However, rough or choppy water is a better reflector and
will provide stronger returns from the downwind sides of the waves.
Mountains also provide strong return signals to the antenna, but also block
the areas behind. However, over mountainous terrain, the radar beam can be
reflected back and forth in the mountain passes or off canyon walls using up
all or most of the radar energy. In this case, no return signal is received
from this area causing the display to show a dark spot which could
indicate a pass where no pass exists.
4.8.2.3 Angle of Incidence
The angle at which the radar beam strikes the target is called the Angle of
Incidence. Incident angle (“A”) is illustrated below. This directly affects the
detectable range, the area of illumination, and the intensity of the displayed
target returns. A large incident angle gives the radar system a smaller detect-
able range and lower display intensity due to minimized reflection of the radar
energy.