Police traffic radar USES the theory of Doppler speed detection to measure the offset of the frequency.

雷达测速仪是利用多普勒测速原理，获得运动目标的频率偏移信号。

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Many people think that ATC consists of a row of controllers sitting in front of their radar screens at the nation's airports, telling arriving and departing traffic what to do.

许多人认为，空中交通管制系统是由一排坐在美国机场雷达屏幕前的管制员组成的，他们告诉到达和离开的航班该做什么。

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As Google explains it, its automated cars use video cameras, radar sensors and a laser range finder to "see" other traffic and detailed maps to navigate the road ahead.

如谷歌自己所解释的那样，谷歌最近出品的无人驾驶汽车使用了摄像机、雷达探测器和激光测距仪来“看”前后左右的交通情况，并通过详细的地图来指引汽车在路上行驶。

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Since then, there have been questions about the country's underfunded air traffic control systems, deficient radar system and the airlines' ability to cope with a surge in travelers.

NPR: Nearly 200 Feared Dead in Brazil Air Crash

Replacing outmoded radar-based air traffic control with more efficient systems has been possible for decades, but it has not happened.

FORBES: It's Time To Upgrade The Entire World's Infrastructure

Intersections will bristle with cameras, radar and sensors to control traffic flow and prevent collisions.

FORBES: Self-Driving Cars Will Take Over By 2040