Speed radar guns

PowerPoint Presentation

SPEED RADAR GUNS

CONTENTSWhat is radarspeed radar gunPrinciple Doppler effectDoppler effect in radar gunLaser gunLaser v/s radar Radar detectorModifications Need

WHAT IS RADAR ?Acronym for radio detection and rangingUsed to remote-sense the position and velocity of targetsUsually uses energy in the microwave frequency bands roughly ranging from 0.5 to 100 GHz

-Detecting ground moving vehicles , such as tanks for defense purposes-Navigating aircraft and ships in bad weather or at night-Detecting, locating and identifying aircraft for air traffic control-Detecting and locating ships and land features for ship collision avoidance

-Measuring motor vehicle velocities for safety and automatic control-Controlling weapons , such as guns and missiles

3COMMONLY USED IN:Air traffic controlSub-marinesNASALaw-enforcement

WHAT IS SPEED RADAR GUN?measures the speed of moving objectsinvented by Bryce K Brown in 1954used in law-enforcement.

A device used to measure the speed of moving objects5may be

May be hand-held, vehicle-mounted or static

6

Vehicle mounted7

static8PRINCIPLE OF RADAR GUNUses Doppler Effect Emits high frequency radio wavescomputes time to receive the reflected wavescompute the change in position of vehicle Radio waves in GHzcomputes the amount of time it takes for those radio waves to travel to a vehicle, reflect back from the vehicle and return to the source. Uses the phenomenon of Doppler Effect Emits a burst of high frequency radio wavescomputes the amount of time to receive the reflected wavesDoing this many times per second will allow to compute the change in position of the vehicle per second.the frequency of the returned signal is increased in proportion to the object's speed approach if the object is approaching, and lowered if the object is receding

9

DOPPLER EFFECTDeals with change in frequency of a wave . To understand what happens, consider the following analogy. Someone throws one ball every second in a man's direction. Assume that balls travel with constant velocity. If the thrower is stationary, the man will receive one ball every second. However, if the thrower is moving towards the man, he will receive balls more frequently because the balls will be less spaced out. The inverse is true if the thrower is moving away from the man. So it is actually the wavelength which is affected; as a consequence, the received frequency is also affected. It may also be said that the velocity of the wave remains constant whereas wavelength changes; hence frequency also changes.10KEY POINTS:frequency is higher during the approach identical at the instant of passing by lower during the recession.It is the change in frequency of a wave for an observer moving relative to its sourcecommonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observerThe received frequency is higher compared to the emitted frequency during the approach It is identical at the instant of passing byIt is lower during the recession11Analysis:The frequency of the sounds that the source emits does not actually change

Frequency of the wave received when the source is moving and the observer is stationary is given by

With an observer stationary relative to the medium, if a moving source is emitting waves with an actual frequency, then the observer detects waves with a frequency given by

12

WITH SOURCE AT REST, RECEIVER IN MOTION

GENERALRELATION BETWEEN TRANSMITTED FREQUENCY AND RECEIVED FREQUENCY

A similar analysis for a moving observer and a stationary source (in this case, the wavelength keeps constant, but due to the motion, the rate at which the observer receives waves and hence the transmission velocity of the wave [with respect to the observer] is changed) yields the observed frequency13DOPPLER EFFECT IN RADAR GUNSA radar beam is fired at a moving targetEach successive wave travels fartherthe gap increases the wavelength.

A radar beam is fired at a moving targetEach successive radar wave has to travel farther to reach the carthe gap between each wave increases, increasing the wavelength.In some situations, the radar beam is fired at the moving car as it approaches, in which case each successive wave travels a lesser distance, decreasing the wavelength.14

.AN ANIMATION ILLUSTRATING DOPPLER EFFECTAn animation illustrating how the Doppler effect causes a car engine or siren to sound higher in pitch when it is approaching than when it is receding. The pink circles are sound waves. When the car is moving to the left, each successive wave is emitted from a position further to the left than the previous wave. So for an observer in front (left) of the car, each wave takes slightly less time to reach him than the previous wave. The waves "bunch together", so the time between arrival of successive wavefronts is reduced, giving them a higher frequency. For an observer in back (right) of the car, each wave takes a slightly longer time to reach him than the previous wave. The waves "stretch apart", so the time between the arrival of successive wave-fronts is increased slightly, giving them a lower frequency15

ASSOCIATED CAMERASradar triggers the camera.takes picture of the car's license plate The central office issues a ticket

When a speeding car is detected, the system triggers a small camera.It takes a picture of the car's license plate and the driver's face. The central office simply issues a ticket and sends it to the speeder in the mail.

Since the automated system has collected all of the evidence the police need, the 17LiDAR/LASER GUNsends infrared laser burstscollect multiple distancesSpeed calculated by comparing distances

sends out many infrared laser bursts in a short period of time to collect multiple distances.

By comparing these different distance samples, the system can calculate how fast the car is moving.

Takes several hundred samples in less than half a second.

The gun shines the laser beam at an angle across the road and registers the speed of any car that passes by.Police may use handheld lidar systems, just like conventional radar guns, but in many areas, the lidar system is completely automated18LASER GUN v/s RADAR GUNLASER GUNRADAR GUNShorter wavelengthMore accurate Less speed reading timeMore expensiveCant be used from a moving vehicle More accurate aiming is required

Longer wavelengthLess accurateMore speed reading timeLess expensiveCan be used from a moving vehicleLess accurate aiming is required

RADAR DETECTORHas a radio receiver Recognizes the presence of radar. Has a radio transmitterEmits a jamming signal.

Picks up Police Speed Guns using a simple radio receiver It recognizes the presence of radar. These devices have their own radio transmitterIt emits a jamming signal.The signal replicates the original signal from the police radar gunIt mixes it with additional radio noise. With this information added, the radar receiver gets aconfusing echo signal, and the police can't make an accurate speed reading.

20MODIFICATIONSDRS-3 radar units The 6F-2 systems The 9F systemsBasic radar guns to overcome the radar detectorsare modifiedDRS-3 radar units in the Ka band radar - 34.36GHz are mostly used as mobile traps that can be set up on highway bridges. The 6F-2 systems take 4 or 5 speed readings before taking the photo, and can take up to 3 photos a second using a fast motordrive camera system. The 9F systems extend this capability to being able to determine the vehicle types as either trucks or passenger cars. They are small, and from the front, look like miniature rocket launchers. They are shielded to prevent external interference, and because of the highly targeted radar beam ,are almost entirely undetectable by cheap radar detectors.

21

FEATURES :-small -look like miniature rocket launchers. -shielded to prevent external interference-entirely undetectable by cheap radar detectors.because of the highly targeted radar beam ,are almost entirely undetectable by cheap radar detectors22NEED FOR SPEED RADAR GUNSStrengthen the surveillance systemreduce Road accidents 2,22,659 speeding vehicle registered last year of which 1,308 were impounded.

About 66% of the total road accidents are a result of overspeeding According to statistics, 2,22,659 speeding vehicle were registered last year, of which 1,308 were impoundedHelps in saving lives by tracking overspeeding vehicles23

Booked 59,154 vehicles and impounded 51this year

This year, till April 30, the Traffic Police booked 59,154 vehicles for speeding and impounded 51.

24CONCLUSIONRADAR-remote-sense the position and velocity of targetsRADAR GUN-measures the speed of moving cars PRINCIPLE-Doppler effectWORKING-clicks picture of overspeeding vehiclesNEWER INSTRUMENT- LiDAR gunCOMPARISONRADAR DETECTOR-recognize the presence of radar

REFERENCEJump up ^ (Article: They Have Lasers! | Road & Track Magazine, Nov. 1991, Page 106)Jump up ^ "How Police Laser Guns Work". Jump up ^ http://solutions.3m.com/wps/portal/3M/en_US/NA_MVSS/Motor_Vehicle/Resources/Programs/License_Plate_Reissue/Jump up ^ "Range Testing by www.digitalallyinc.com". Jump up ^ "Mobile Speed Cameras". Jump up ^ "How Laser Jammers Work"Hyperphysics - technical info and calculators for police RADARCalibration of Speed Enforcement Down-The-Road RadarsTHANK YOU