What is a Radar?
A radar is a sensor used for detecting, locating, tracking, and recognizing various kinds of objects at considerable distances. These may include aircraft, ships, spacecraft, automobiles, and astronomical bodies.
A radar operates by transmitting electromagnetic (radio) energy and then receiving echoes of the transmitted pulse. The time delay between the transmission and reception of the echo allows for calculations of the distance to a target.
Radars also determine the speed and direction of objects. They are commonly used to detect and track aircraft, ships, and other vehicles at sea level and to map the surface of the Earth from space.
Weather radars can resemble search radar, but use very short radio waves that reflect from the earth and stone rather than metal. They can rely on horizontal, dual (horizontal and vertical), or circular polarization to measure wind speed and type of precipitation. Some systems use Doppler shift to identify moving precipitation. They are commonly seen on commercial ships and long-distance airplanes.
How Does a Radar Work?
A radar uses the same principle that makes sound waves work: it sends out a focused pulse of microwave energy (think of a microwave oven or cell phone) and part of that beam bounces back. The echoes are picked up and converted into information that can be easily read on a screen, such as the location of the target or its direction.
Radars have been used for many years to detect targets on ships, aircraft and even in the sky. They are also useful for weather observation, remote sensing, aircraft and ship navigation, speed measurement for industrial applications and law enforcement.
Radars typically use a pulse repetition frequency and pulse form that matches the type of target they are trying to observe. For long range broadcasts, the pulses are longer with a delay between them, and for short range broadcasts they are shorter.
How Do I Use a Radar?
Radar operates on a radio frequency, sending out a beam of radio waves that reflect off targets. Some of the radio waves reflected back from a target change in frequency and are detected by the radar as Doppler shifts.
Police use radar in both stationary and moving modes. Generally, stationery radar is used from fixed locations such as patrol cars or motorcycles parked at a roadside.
Moving mode radar is used by officers operating their vehicles in the field (Pennsylvania is an exception). In most cases, the radar must be mounted inside of a police vehicle or on a portable hand held model that can be operated either from within a car or in front of the officer standing outside of his or her patrol vehicle.
The radar searches one angular search cell at a time, each angular cell covering a portion of the airspace. Each search task has a priority value, and the radar selects the next job based on the priority of the previous job.
What Are the Benefits of Using a Radar?
Radar can help predict upcoming storms and monitor rain, snow or hail. Meteorologists use radar to keep viewers informed so they can prepare to evacuate or stay safe.
Weather radars use pulsed electromagnetic waves to detect objects such as rain drops, hail, bugs or birds. When the pulses strike these objects, they reflect back to the radar, revealing information about the object’s size, shape and position.
The radar’s computers then use a doppler shift of the returned energy to determine whether it is moving toward or away from the radar. The radar displays this information in colors based on its direction and speed.
Unlike cameras, which struggle to detect objects in poor visibility or fog, radar can see well in rain or smoke. It also makes an inherent measurement of relative speed, which helps avoid collisions with other vessels.