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teSentry
User Manual of Site Sentry ANPR/Speed Camera System
17
Chapter 4
Adjusting the Radar Sensor
continued
4.1
An overview and understanding of the COSINE effect
Microwave radars are susceptible to a phenomenon known as the COSINE effect.
This is a generation of a greater speed figure by a reflection from a target vehicle passing
within close proximity to the radar at an obtuse angle, ie. the closer a vehicle passing is to
90° adjacent to the radar sensor, then the more likely this same target is to generate a
‘rogue reflection’, especially if the vehicle has large flat sides like a box van or articulated
vehicle.
In normal circumstances where a Speed Indicating Device (SID) is placed at the side of a
road, this issue rarely presents itself as a problem because the SID barely has time to react
to the ‘spike’ in reported speed as the vehicle passes in close proximity and thus the speed
message is typically not displayed on the sign. This ‘spike’ can be as much as 180% of the
actual speed of the tracked target vehicle.
However, since we are recording all reported speeds and conjoining these speed readings
with real time video footage it is very important that we carry out measures which will
eliminate the COSINE effect from our recordings.
We have gone to great lengths to provide a set of radar adjustment tools to make this
mitigation possible, namely, ‘Speed Error Percent’, ‘Speed Negative Error Percent’ and
‘Speed Distance Disable’ which I will describe in detail with respect to vehicle proximity.
4.2
Parameters in which the COSINE effect will need mitigation
&
&
circa 4m
COSINE
zone
This vehicle is outside the COSINE ‘Spike’ zone
This vehicle is about to cross into the COSINE
‘Spike’ zone
valid speed readings
valid speed readings
Содержание SiteSentry
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