In 1935 the Scottish inventor Robert A Watson-Watt (1892-1973) illuminated the first radar in history. However, it took more than two decades, until 1958, to see the birth of the first radar connected to a photographic camera, the forerunner of the unpopular speed cameras on our roads.
The first speed control camera in history was called the Gatsometer or gatsometer, alluding to its prolific inventor -Maus Gatsonides, nicknamed Maus- who was also a race car driver.
Maus was obsessed with measuring speed, especially in the cornering sections, in order to improve his times. To determine it, he resorted to a device that worked thanks to the Doppler effect and that, in addition, was associated with an automatic shutter release.
This effect is based on an antenna that emits waves and is capable of measuring the time they take to return. If the car moves away from the radar, the time between the waves will increase, on the contrary, if it gets closer to the radar, it will decrease.
Kinemometers and speed
At this time, a radar that uses radio waves or lasers and is applied to movement is known as a kinemometer. These types of devices are used to measure the speed of an object in real time and are the instruments used by the DGT to enforce speed limits.
The laser kinemometer uses an infrared laser -with a frequency of 33 MHz and a wavelength of 904 nm- that reaches the vehicle and from which a pulse of light is reflected back to the kinemometer. Based on the time and the interval between pulses, it is able to determine the speed at which the car is traveling.
Optical kinemometers use light beams in the visible and infrared region of the electromagnetic spectrum and measure speed based on the reflection of light or the intervals between the interruptions of the beams that occur when being traversed by the vehicle.
In addition to these two types, there are sensor kinemometers, which use cables connected to piezoelectric bands that are placed on the asphalt. When the vehicle passes over it, it produces pressure on them, which emit impulses that determine the speed.
tolerance threshold
All these cinemometers have one characteristic in common –whether they are fixed or mobile-, they all have a margin of error, which means that for the radar to ‘jump’ it is necessary to exceed the maximum speed allowed.
At this time we know as the tolerance threshold the margin that exists between the speed limit of the road and the activation limitation of the kinemometer. In our legislation it is established that the margin of error follows the so-called ‘rule of 7’. This means that on a road with a speed limit of 90 km/h we would be fined at 97 km/h and on a road with a speed limit of 120 km/h they will inform us of speeding if we exceed 128.4 km/h.
So now you know, if you get lost and are penalized for speeding, remember that the fault lies with an eccentric car driver, who, by the way, won the Monte Carlo Rally in 1953.