LIDAR and radar
Radar
Radar stands for radio detection and ranging .Radar uses radio waves.you can find them in sysytem like adaptive cruise control,blind spot warning,collision warning and collision avoidance.Even though radar is a nature technology,it still gets improved all the time to make it even more powerful.while other sensors measure velocity.radar uses something called dopler effect to measure speed directly.The dopler effect measure the change in frequency of the radar waves based on whether the object is moving from you or toward you.This is kind of how a fire engine siren will differently depending on whether the fire engine is moving away from you or toward you.The dopler effect is important for sensor fusion because it give us the velocity as an independent measure parameter and it makes the fusion algorithm coverage much faster.Radar can also be used for localization by generating radar maps of the environment because Radar waves bounce the hard surface,they can provide the object without direct line of fight.Radar can see underneath object vehicle,and spot building and object that would be observed.Radar is the least affected by rain or fog and can have a wide feild of veiw,about 150 degree,or a long range,200plus meters.compare to lidar and camerw,radar have a low resolution.Epecially in the vehicle direction,the resolution is very limited.The lower resolution also means that reflection from static object can cause problems.
Radar stands for radio detection and ranging .Radar uses radio waves.you can find them in sysytem like adaptive cruise control,blind spot warning,collision warning and collision avoidance.Even though radar is a nature technology,it still gets improved all the time to make it even more powerful.while other sensors measure velocity.radar uses something called dopler effect to measure speed directly.The dopler effect measure the change in frequency of the radar waves based on whether the object is moving from you or toward you.This is kind of how a fire engine siren will differently depending on whether the fire engine is moving away from you or toward you.The dopler effect is important for sensor fusion because it give us the velocity as an independent measure parameter and it makes the fusion algorithm coverage much faster.Radar can also be used for localization by generating radar maps of the environment because Radar waves bounce the hard surface,they can provide the object without direct line of fight.Radar can see underneath object vehicle,and spot building and object that would be observed.Radar is the least affected by rain or fog and can have a wide feild of veiw,about 150 degree,or a long range,200plus meters.compare to lidar and camerw,radar have a low resolution.Epecially in the vehicle direction,the resolution is very limited.The lower resolution also means that reflection from static object can cause problems.
LIDAR
Lidar stand for light detection and ranging.It is uses as an infrared laser beam to determine the distance between the sensor and nearly object.Most current lidar use light in the 900 nm wavelength range , although some LiDARs use longer wavelength,which perform better in rain and fog.In current lidar,a rotating swivel scan the laser beam across the feild of veiw.The laser are pulsed, and the pulsed are reflected by object.These reflections return a point cloud that represent these object.lidar much higher spatial resolution than Radar because of more focussed laser beam, the larger number of scan layers in the vertical direction and the high density of lidar point per layers.The current generation of LIDAR can not measure the velocity of object directly.And have to reply on the different position between two or more Scans.lidarare also more affected by weather conditions and dirts on the sensor,which requires keeping then clean.They also bulkier than other sensors and therfore more difficult to integrate unless one just to mount a big scanner on the roof of the vehicle.
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