TCO Information Update
http://home.vicnet.net.au/~tco/html/camera.htm
accessed on 1 March 2003
The Speed Camera
The speed cameras used by the T.C.O. are supplied by Gatsometer BV in Holland.
The Gatsometer MRC System, referred to as the Gatso Type 24 MRC Slant Radar is
operated by trained members of the Victoria Police Traffic Operations Group.
Before operating the cameras, police members complete a 4 day training course
in which they are examined in both theory and practical aspects of the speed
camera. Cameras are operated in areas which have been identified as having speed
related problems, areas identified as high risk roads based on validated speed
complaints, or in traffic accident blackspots. They can be used anywhere
throughout Victoria at any time of the day or night.
Radar Speed Camera Set-up
The radar unit may be set up on a tripod or mounted in an unmarked police vehicle
positioned at the side of the road. The radar beam is transmitted at an angle of
20 degrees across the road. The Camera Control Unit is set up by programming certain
information such as the time, date, film magazine number, speed zone, film type, the
direction of the traffic to be covered, and the threshold speed, and connecting it
to the camera. The 35mm camera operates as an ordinary camera, but it is controlled
by the Camera Control Unit and Radar Control Unit, and can photograph 2 speeding
vehicles per second.
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How the Gatso Type 24 MRC Slant Radar Operates
The radar unit transmits a radar beam, at a frequency of 24.125 GHz, which is 5
degrees wide, 20 degrees high and slanted at an angle of 20 degrees across the road.
As a vehicle travels through the beam, the reflected radar frequency is changed
(Doppler effect) and the beam is reflected back to the radar antenna. The antenna
receives any signals which arrive from the same 5 degrees by 20 degrees and converts
this into the speed of the vehicle. If the vehicles speed is greater than the
threshold speed set by the operator, a photograph is automatically taken of the
vehicle. A camera is capable of taking two photographs every second, and detects the
speed of vehicles travelling in either direction.
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Calculating the Speed of a Vehicle
Trigonometry can be used to calculate the speed of a vehicle travelling along a road,
detected by a radar beam transmitted across a road. Because the radar beam of the Gatso
Type 24 Unit is slanted across the road at 20 degrees, the Doppler frequency shift recorded
will indicate a speed that is slower than the targets true speed. In the radar unit there
is an automatic calculation for the slant angle so that the true speed in the direction of
travel is determined.
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