19-07-2013, 04:40 PM
Speed Detection of moving vehicle using speed cameras
Speed Detection.doc (Size: 150 KB / Downloads: 16)
INTRODUCTION
Although there is good road safety performance the number of people killed and injured on our roads remain unacceptably high. So the roads safety strategy was published or introduced to support the new casualty reduction targets. The road safety strategy includes all forms of invention based on the engineering and education and enforcement and recognizes that there are many different factors that lead to traffic collisions and casualties. The main reason is speed of vehicle. We use traffic lights and other traffic manager to reduce the speed. One among them is speed cameras.
Speed cameras on the side of urban and rural roads, usually placed to catch transgressors of the stipulated speed limit for that road. The speed cameras, the solely to identify and prosecute those drivers that pass by the them when exceed the stipulated speed limit. At first glance this seemed to be reasonable that the road users do not exceed the speed limit must be a good thing because it increases road safety, reduces accidents and protect other road users and pedestrians.
INTRODUCING THE DOPPLER EFFECT
The device that is the first generation RADAR is not capable of determining the speed of the detected object. This was limited to measuring the movement of echo on the screen, which gave a rather inaccurate result.
As an example consider the car that makes a sound with a fixed frequency. When you are in the car, you won't notice any variation in the frequency of the engine sound. However you stand at the side of the road and listen to the car when it drives past under identical condition you will notice that the frequency of the engines sound increases as the car comes nearer and then decreases as the car travels past you.
It is a matter of common experience that the pitch of the note appears to change when either source or observers or both are in motion relative to each other. Either the source or the observers or both move relative to and each other, the apparent pitch produced by the sounding body appears to be higher than actual pitch. In the same way, when the source moving towards the observers or the observers moving away from this source or both moving away from each other the apparent pitch will appear to be lower than the actual pitch of the sounding body.
FROM THEORY TO PRACTICE!
Now that we have seen how the Doppler Effect can be used to measure the speed of the vehicles, we will take a look at the commercial applications that are found at the side of the road. The basic of every speed camera is a SHF generator, which can transmit the beams in specific directions. From the previous section we know that the sensitivity of the device is directly of proportional to the frequency of the beams. The exact frequency depends on the manufacturer, which is generally between 2 GHz and 15 GHz. The power of oscillators is not very high (usually less than 10 mw), but the effect a power output is increased through the use of the directional aerials.
HOW WELL DOES IT WORKS
Now that we know how it all works. The may wonder how reliable the measurements made by these devices are. We will see the problem from a technical viewpoint to discover that what the limits of SHF speed cameras are.
Operating during the rain or mist:
In contrast the RADAR works perfectly well during a rain or mist. For example RADAR is used extensively to help the landing of airplanes in bad weather. In general, when it rains it comes down vertically which is right angles to the RADAR beam, bringing about a Doppler effect of zero (cos 90=0 soFm=0). Heavy rain that comes down at the angles due to strong gust of wind can't asset to the signal to noise ratio of the receiver and prevents its correct operation. In this case they processor will simply rejected the measurements.
ON THE WRONG SIDE OF THE LAW
Mankind, and especially homo automobiles, behave in such a way that when he comes across an obstacle he will try everything to get round of it. Speed cameras are no exception to this and numerous boffins have contributed to the development of counter measures.
There are two types of 'anti-radars'. Jamming devices and detectors. The jamming devices are simply is SHF oscillators, which are used to send ' take ' signal the to speed camera, causing the measurement to fail and preventing the logical analysis of the frequency. Besides the fact that these devices are relatively in effective, the electronic circuit in the radar can detect such the jamming signals and notify the police. A jamming device is therefore a sure fire way and to get caught.
CONCLUSION
Now we would like to believe that enforcement cameras are there for our on good and make our roads safer. In general speed camera are perceived to be good idea because they protect innocent road users and pedestrians. Although these cameras reduces accidents and protects the innocent road users, the way in which the speed cameras are currently used is not to make the driver slow down, obey the speed limit and make the road safe but to catch and penalize the transgressors who may otherwise have slowed down if they have seen as the cameras in advance .i.e. speed camera , as, currently deployed, are not so justifiable .
These cameras were highly visible then no one would travel by them exceeding the speed limit and they would do their job. Used as they hidden away, they are penalized and contribute little to road safety directly only generating revenue to pay for their installation and maintenance.
Speed Detection.doc (Size: 150 KB / Downloads: 16)
INTRODUCTION
Although there is good road safety performance the number of people killed and injured on our roads remain unacceptably high. So the roads safety strategy was published or introduced to support the new casualty reduction targets. The road safety strategy includes all forms of invention based on the engineering and education and enforcement and recognizes that there are many different factors that lead to traffic collisions and casualties. The main reason is speed of vehicle. We use traffic lights and other traffic manager to reduce the speed. One among them is speed cameras.
Speed cameras on the side of urban and rural roads, usually placed to catch transgressors of the stipulated speed limit for that road. The speed cameras, the solely to identify and prosecute those drivers that pass by the them when exceed the stipulated speed limit. At first glance this seemed to be reasonable that the road users do not exceed the speed limit must be a good thing because it increases road safety, reduces accidents and protect other road users and pedestrians.
INTRODUCING THE DOPPLER EFFECT
The device that is the first generation RADAR is not capable of determining the speed of the detected object. This was limited to measuring the movement of echo on the screen, which gave a rather inaccurate result.
As an example consider the car that makes a sound with a fixed frequency. When you are in the car, you won't notice any variation in the frequency of the engine sound. However you stand at the side of the road and listen to the car when it drives past under identical condition you will notice that the frequency of the engines sound increases as the car comes nearer and then decreases as the car travels past you.
It is a matter of common experience that the pitch of the note appears to change when either source or observers or both are in motion relative to each other. Either the source or the observers or both move relative to and each other, the apparent pitch produced by the sounding body appears to be higher than actual pitch. In the same way, when the source moving towards the observers or the observers moving away from this source or both moving away from each other the apparent pitch will appear to be lower than the actual pitch of the sounding body.
FROM THEORY TO PRACTICE!
Now that we have seen how the Doppler Effect can be used to measure the speed of the vehicles, we will take a look at the commercial applications that are found at the side of the road. The basic of every speed camera is a SHF generator, which can transmit the beams in specific directions. From the previous section we know that the sensitivity of the device is directly of proportional to the frequency of the beams. The exact frequency depends on the manufacturer, which is generally between 2 GHz and 15 GHz. The power of oscillators is not very high (usually less than 10 mw), but the effect a power output is increased through the use of the directional aerials.
HOW WELL DOES IT WORKS
Now that we know how it all works. The may wonder how reliable the measurements made by these devices are. We will see the problem from a technical viewpoint to discover that what the limits of SHF speed cameras are.
Operating during the rain or mist:
In contrast the RADAR works perfectly well during a rain or mist. For example RADAR is used extensively to help the landing of airplanes in bad weather. In general, when it rains it comes down vertically which is right angles to the RADAR beam, bringing about a Doppler effect of zero (cos 90=0 soFm=0). Heavy rain that comes down at the angles due to strong gust of wind can't asset to the signal to noise ratio of the receiver and prevents its correct operation. In this case they processor will simply rejected the measurements.
ON THE WRONG SIDE OF THE LAW
Mankind, and especially homo automobiles, behave in such a way that when he comes across an obstacle he will try everything to get round of it. Speed cameras are no exception to this and numerous boffins have contributed to the development of counter measures.
There are two types of 'anti-radars'. Jamming devices and detectors. The jamming devices are simply is SHF oscillators, which are used to send ' take ' signal the to speed camera, causing the measurement to fail and preventing the logical analysis of the frequency. Besides the fact that these devices are relatively in effective, the electronic circuit in the radar can detect such the jamming signals and notify the police. A jamming device is therefore a sure fire way and to get caught.
CONCLUSION
Now we would like to believe that enforcement cameras are there for our on good and make our roads safer. In general speed camera are perceived to be good idea because they protect innocent road users and pedestrians. Although these cameras reduces accidents and protects the innocent road users, the way in which the speed cameras are currently used is not to make the driver slow down, obey the speed limit and make the road safe but to catch and penalize the transgressors who may otherwise have slowed down if they have seen as the cameras in advance .i.e. speed camera , as, currently deployed, are not so justifiable .
These cameras were highly visible then no one would travel by them exceeding the speed limit and they would do their job. Used as they hidden away, they are penalized and contribute little to road safety directly only generating revenue to pay for their installation and maintenance.