Technical Details
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HHooww RRaaddaarr W
Woorrkkss
Traffic radar, which consists of microwaves,
travels in straight lines and is easily reflected
by objects such as cars, trucks, even
guardrails and overpasses. Radar works by
directing its microwave beam down the
road. As your vehicle travels into range, the
microwave beam bounces off your car, and
the radar antenna looks for the reflections.
Using the Doppler Principle, the radar
equipment then calculates your speed by
comparing the frequency of the reflection of
your car to the original frequency of the
beam sent out.
Traffic radar has limitations, the most
significant of these being that it typically can
monitor only one target at a time. If there is
more than one vehicle within range, it is up
to the radar operator to decide which target
is producing the strongest reflection. Since
the strength of the reflection is affected by
both the size of the vehicle and its proximity
to the antenna, it is difficult for the radar
operator to determine if the signal is from a
sports car nearby or a semi-truck several
hundred feet away.
Radar range also depends on the power
of the radar equipment itself. The strength of
the radar unit’s beam diminishes with
distance. The farther the radar has to travel,
the less energy it has for speed detection.
Because intrusion alarms and motion
sensors often operate on the same frequency
as radar, your XR70 will occasionally
receive non-police radar signals. Since these
transmitters are usually contained inside of a
building, or aimed toward the ground, they
will generally produce much weaker read-
ings than will a true radar encounter. As you
become familiar with the sources of these
pseudo alarms in your daily driving, they
will serve as confirmation that your XR70’s
radar detection abilities are fully operational.
21
HHooww LLaasseerr ((LLiiddaarr)) W
Woorrkkss
Laser speed detection is actually LIDAR
(Light Detection and Ranging). LIDAR
guns project a beam of invisible infrared
light. The signal is a series of very short
infrared light energy pulses, which move, in
a straight line, reflecting off your car and
returning to the gun. LIDAR uses these light
pulses to measure the distance to a vehicle.
Speed is then calculated by measuring how
quickly these pulses are reflected given the
known speed of light.
LIDAR (or laser) is a newer technology
and is not as widespread as conventional
radar, therefore, you may not encounter laser
on a daily basis. And unlike radar detection,
laser detection is not prone to false alarms.
Because LIDAR transmits a much narrower
beam than radar, it is much more accurate in
its ability to distinguish between targets and
is also more difficult to detect.
AS A
RESULT, EVEN THE BRIEFEST
LASER ALERT SHOULD BE TAKEN
SERIOUSLY.
There are limitations to LIDAR equipment.
LIDAR is much more sensitive to weather
conditions than RADAR, and a LIDAR
gun’s range will be decreased by anything
affecting visibility such as rain, fog, or
smoke. A LIDAR gun cannot operate
through glass and it must be stationary in
order to get an accurate reading. Because
LIDAR must have a clear line of sight and is
subject to cosine error (an inaccuracy, which
increases as the angle between the gun and
the vehicle, increases) police
typically use LIDAR equipment parallel to
the road or from an overpass. LIDAR can be
used day or night.
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