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Compared with millimeter wave radar, laser radar has high resolution, good concealment, strong resistance to active interference, good low-altitude detection performance, small size and light weight. The disadvantage of laser radar is that it is affected by weather and atmosphere. In bad weather such as heavy rain, dense smoke, fog, etc., the attenuation increases sharply and the transmission distance is greatly affected.Secondly,due to the extremely narrow beam of laser radar, it is very difficult to collect targets in space, and can only collect and capture targets in a small area.
Comparison of Millimeter Wave Radar and Laser Radar Sensor Performance
Resolution: Highest for cameras,second for laser radar, lowest for millimeter-wave radar.
Weather Resistance: Millimeter-wave radar is the best, camera is the second best, and laser radar is the lowest.
Tracking object speed: Millimeter wave radar is the best, camera and laser radar are similar.
Ability to track object height: laser radar is the best, camera is the second best, millimeter wave radar is the lowest.
Trace distance: Laser radar and millimeter wave radar are very accurate, camera is the lowest.
Discrimination: Camera and radar are better, millimeter wave radar is lower.
Difference between millimeter wave radar (radar) and laser radar (Lidar)
1.Laser Radar
Lidar is a combination of laser and radar.In fact,it is not unfamiliar to all of us. When many unmanned vehicles conduct driving experiments on the road, there will be a small canister on the roof of the vehicle, which looks like a monitor, but it will rotate at a certain angle all the time.That's usually a laser radar.
Laser radar is an active detection method that uses light waves for measurement. Active detection means that the detection system receives its own signal echoes to make measurements, which is different from passive detection methods such as cameras that receive signals from ambient light. A laser radar calculates the distance to an obstacle by measuring the time it takes for the laser to be reflected from the source and received by the sensor.
Radar is generally categorized into pulsed and continuous wave types. Pulsed laser radar uses time intervals to calculate the distance to the vehicle, while continuous wave laser radar calculates the phase difference between the reflected light and the reflected light to obtain the target distance. Specifically, the technical key to laser radar is: Time of Flight (TOF). After the radar emits laser light, it turns back when it encounters an obstacle. The return beam is analyzed by the radar's internal receiver and finally processed by the processor through the time of return and the measurement signals to generate an accurate 3D map. The characteristics of the surrounding environment are recovered again.
As a simple example, a millimeter-wave radar can detect roadside obstacles but only “see” a vague shape, whereas a centimeter-accurate laser radar can clearly distinguish whether the obstacle is a shoulder or a slope in a very short period of time. After the driver determines that it is a slope, he or she can make a decision to safely enter the lane. This kind of accuracy is closer to 100% safety for fully automated vehicles on the road.
Such being the case, why don't we vigorously develop all-laser radar? The reason is simple: expensive! For example, Google uses a Velodyne laser radar from the United States. It costs 80,000 dollars for 64 lines and 40,000 dollars for 32 lines. This radar can even buy a GTR (in the US of course). It is also less effective in extreme weather, such as rain, snow, fog, etc., and does not work all day long. In this case, compared with millimeter wave radar, laser radar has both advantages and disadvantages.
Millimeter wave refers to electromagnetic waves with a wavelength between 1-10 millimeters, and millimeter wave radar refers to radar that operates in the millimeter wave band. The wavelength of millimeter wave is between the millimeter wave and the light wave, and this millimeter wave has the advantages of microwave guidance and optoelectronic guidance. When used in automobiles, it has strong anti-environmental interference ability and can meet the adaptability requirements of vehicles to all-weather climate. In addition, the characteristics of millimeter wave itself determines the millimeter wave radar sensor device size is small, light weight and other characteristics, to make up for the shortcomings of the monitor and other sensors, so that it has a great advantage in automotive applications.
At present, the mainstream vehicle-mounted millimeter-wave radar frequency band is 24GHz (for short- and medium-range radar, 15-30 meters) and 77GHz (for remote radar, 100-200 meters). This application has been popularized in automobiles in Europe, America and Japan. Nowadays, almost all cars in these fields are equipped with automotive millimeter wave radar sensors, including automotive collision avoidance radar, automotive blind spot detection radar and so on.
But even so, millimeter wave radar still has the characteristics of low precision and short visibility distance. These two defects in the automatic driving, but the difference is a thousand miles, it is easy to cause accidents. Against this background, an upgraded version of the laser radar was born.
Automatic driving is like a pedestrian walking. First, the eyes to observe and determine the route, and then the brain will give instructions to the body. For automobiles, all kinds of radar, monitors and other sensors are the eyes of the car, electronic circuits are the central nervous system, chips, algorithms and other control systems are the brain, and ultimately determine the direction and speed of the car. The “eyes” play a very crucial role: collecting first-hand information for analysis and judgment.
Among these “eyes”, the camera is relatively simple. Its advantages are outstanding: high precision, long distance, and convenient intuition; however, its disadvantages are also outstanding: it is too much affected by the weather. Vehicle-mounted radar has outstanding features and advantages. They have higher real-time performance, accuracy and reliability than ultrasonic detectors and computer vision devices. Among them, the main research directions are millimeter-wave radar and laser radar.
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Radar Coordinates
Step 2: Calculate the coordinates
Calculation of coordinate values