Learn speed gun: Shot without pain but losing money

Have you ever wondered how the traffic police can know exactly the speed of the car running?

Speed ​​gun is a specialized device of Traffic Police (Traffic Police) which is popularly used not only in Vietnam but also in many other countries. This device helps traffic police to know whether the moving vehicle is exceeding the permitted speed or not just once . shoot!

This is a specialized device of Traffic Police.

If you are a frequent traveler on the highways, you've probably seen speed guns. Perhaps this is the only gun that does not hurt but makes people lose money. Have you ever wondered how a speed rifle works to capture sharp images with accurate speed? This article will aggregate information to answer the above question.

Types of speed gun

First, we need to understand the speed guns and the operating principles of the Radio Detection and Ranging and laser guns.

Until the mid-70s of the last century, traffic police still use the X-Band radar gun (frequency of 10,535 GHz). However, it was removed due to being easily detected and replaced with K-Band in 1976, this device operates from 24.05 to 24.25 GHz. By 1989, the new device Ka-Band switched to operate at frequencies of 33.4 and 36.0 GHz. Later, the Laser Speed ​​Gun was also introduced.

Until the mid-70s of the last century, traffic police still used X-Band radar guns, then K-Band in 1976.

In fact, traffic police will not need to change the speed gun if the RD detector detector manufacturers (Radar Detector) do not upgrade their products. The chase between the traffic police and the speed gun and the product companies RD is like the chase between Tom & Jerry, even the traffic police have devices that detect the vehicle with RD or not.

How does the radar speed gun work?

Speed ​​gun is not too "divine" device , it is simply a radio signal receiver - transmitter. It will oscillate the current, causing the voltage at high to be low in a fixed frequency, thereby generating an electronic energy. When electricity flows, that energy will spread in space as an electromagnetic wave.

Handheld radar gun.

The transmitter usually has an amplifier to increase electromagnetic energy and an antenna to spread. Meanwhile the receiver will receive the signal from the antenna and convert the signal into an electrical current.

Radars using radio waves can detect and manage multiple objects, the simplest function is to announce the distance to a certain object. To do that, the radar device emits a focused radio wave and then analyzes the feedback. If there is an object blocking the radio, it will respond to some of the electromagnetic energy and radio waves will revert back to the radar device. Radio waves are transmitted in the air at a fixed speed, so this radar device can calculate the distance to an object based on the time required for the radio signal to return.

People can also use radar to measure the speed of an object based on the principle called Doppler shift.

Besides measuring distances, people can also use radar to measure the speed of an object based on the principle called Doppler shift. Simply understanding this principle is a radar gun that sends a microwave signal, when the signal meets a "shot" vehicle that will turn back to the gun. If your car moves, the signal sent out and returned will help the gun calculate the Doppler shift principle to know the vehicle is running at how many km / h.

Similar to sound waves, radio waves use certain frequencies and the number of vibrations in a unit of time. When both a speed gun and a car stand still, the received signal has the same frequency as the original signal. But when the car moves, each part of the radio signal will be reflected at a different point in space, thereby shifting the wavelength phase by changing the frequency.

In order to calculate a high accuracy, the sending signal must be strong enough so that when meeting a moving vehicle, it can turn back to the speed gun.

Speed ​​guns are used in Vietnam to ensure traffic safety is mostly static.

There are two types of radar: Static Radar and Dynamic Radar. Static radar needs to be used in a fixed position, either in a car or with a tripod. These cars are often parked on the roadside to shoot the speed of vehicles traveling on the route. Speed ​​gun is used in Vietnam to ensure traffic safety is mostly static, can take pictures by K band and Ka tape.

Mobile gun can shoot speed right on a vehicle moving with your car.

The second type is the mobile gun , which can fire speed right on a vehicle moving along with your vehicle. This type on American patrol vehicles is equipped. The way to calculate the speed of this type is slightly different that the mobile gun will connect to the speed measuring system on the patrol car and then compare with the speed obtained, thereby giving a calculation of the speed of the car being shot. .

How far is the "shot" distance?

The distance that the gun can measure the speed of the vehicle moving depends on the strong or weak microwave. However, due to the service of patrolling traffic control, the speed gun is often much weaker than the military radar system, because the stronger the gun, the greater the price.

The distance that the gun can measure the speed of the vehicle moving depends on the strong or weak microwave.

It is generally difficult to say exactly how far away the radar gun's firing range is, but we can understand it depends on a number of factors: The strength of the microwave wave and the vehicle's response ratio being shot. The feedback coefficient depends on the shape and size of the vehicle, so if the car is shot with a small size, the feedback coefficient is small, then the distance for the gun to shoot at speed and get a reduced response. .

That is also the reason that speed guns can sometimes measure the speed of container cars 1km away, but they cannot fire the speed of a passenger car 500m away.

Laser Gun (Lidar Gun - Light Detection And Ranging)

Laser speed gun.

The laser gun measures the speed based on the light response time instead of the Doppler shift principle. It automatically calculates the amount of time it takes for light to reach a moving vehicle and then turns back. The light from the shotgun laser speed moves much faster than the sound (about 30cm a nano-second).

The laser gun measures the speed based on the light response time instead of the Doppler shift principle.

When shooting, the gun will release a very short red laser and wait for a response from the car. Based on the number of nano-seconds required for the laser to go and return, then divide the found number by 2, the machine will know the distance from it to the vehicle. If the measuring gun performs this action 1000 times per second, it can calculate the distance between each measurement and then calculate the speed of the vehicle. By performing several hundred measurements in about 1/3 second, the accuracy will be very high.

Laser guns can fire through the steering glass of the patrol car.

The advantage of laser guns is that the size of the pyramid created by the light of the gun is very small, which allows the gun to aim directly at a specific vehicle. This laser gun is also very accurate. The downside of guns is that the traffic police will have to hold and aim instead of placing it in a fixed position, like a radar gun.

Is the exact shooting rate 100%?

Each speed-firing device is tested for accuracy and stamped by a competent authority, however guns and operators can make mistakes when done. When the range is blocked by a barrier, RFI, cosine or device interference may lead to false speed reporting.

Anyway the number of errors is still acceptable for a device used to ensure traffic safety. Some of today's state-of-the-art cameras also have the Same Lane feature that helps locate the same object on the road and Fastest Speed ​​helps to find the vehicle that moves at the fastest speed compared to other vehicles with it.