Angular Interference (Cosine Error Effect) - Decatur Electronics GHD User Manual

GHD & SCOUT
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7.3 Angular Interference (Cosine Error Effect)

The cosine effect causes the system to display a speed which is lower
than the actual vehicle speed. This condition occurs when the target
vehicle's path is not parallel to the antenna, including conditions such
as the vehicle traveling on a curve or hill.
As the angle between the beam of the antenna and the target vehicle
increases, the displayed speed decreases. Ideally, an angle of zero (0)
degrees is preferable, because the displayed speed is the actual target
vehicle speed. However, in all uses of police radar, the radar device is
always at a slight angle to the target vehicle to avoid collisions.
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Radar
An angle between the antenna and the
target vehicle causes the cosine effect.
Angle
Figure 7.3a
USER'S MANUAL
Velocity
Vector