What is SAR range?

Resolution of ERS SAR The ground range resolution is about 25 m and the maximum azimuth resolution is 5 m. In practice, one averages several “looks” together to improve the quality of the amplitude (backscatter) image. In the case of ERS, one could average 5 looks to for a resolution cell of 25 m by 25 m.

How is synthetic aperture length calculated?

The synthetic aperture length is the beam width by range which a real aperture radar of the same length, can project in the azimuth direction. The resolution in the azimuth direction is given by half of real aperture radar as shown as follows.

What is range and azimuth resolution?

The range resolution (cross-track) is determined by the bandwidth and the nature of the modulation of the sent pulses, while the azimuth resolution (along-track) is achieved by Doppler shift frequencies detected in the along-track direction.

What is the azimuth resolution?

The angle or distance by which two targets at the same range must be separated in azimuth to be distinguished by a radar. Targets separated less than this distance appear as a single target on the display. See radar resolution.

What is SAR used for?

Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide finer spatial resolution than conventional stationary beam-scanning radars.

What type of aperture does SAR systems have?

Typically, Synthetic Aperture Radar (SAR) produces a two-dimensional (2-D) image. One dimension in the image is called range (or cross track) and is a measure of the “line-of-sight” distance from the radar to the target.

What is minimum range and pulse length?

The pulse width (H) determines the minimum range at which targets can be detected. This minimum range is approximately ½ the length of the wave burst. With a 1.57 µS pulse (as in the WSR-88D short-pulse mode) the minimum range would be about 235 meters.

What is resolution of antenna?

The most common resolution criterion states that the resolution capabil- ity of an antenna to distinguish between two sources is equal to half the first-null beamwidth (FNBW/2), which is usually used to approximate the HPBW.

What is real aperture radar?

real-aperture radar A radar system where the azimuth resolution is determined by the physical length of the antenna, wavelength, and range. Compare SYNTHETIC-APERTURE RADAR. A Dictionary of Earth Sciences.

Why it is called Synthetic Aperture Radar?

As transmission and reception occur at different times, they map to different positions. The well ordered combination of the received signals builds a virtual aperture that is much longer than the physical antenna width. That is the source of the term “synthetic aperture,” giving it the property of an imaging radar.

How does a SAR antenna work?

SAR uses the motion of the radar antenna over a target region to provide finer spatial resolution than conventional stationary beam-scanning radars. To create a SAR image, successive pulses of radio waves are transmitted to “illuminate” a target scene, and the echo of each pulse is received and recorded.

How big is the beam width of a SAR?

For example, with a signal wavelength of 10 centimeters and an antenna of 10 meters in diameter, the beam width is 1/100 radians (0.6 degrees). From an altitude of 1,000 kilometers, the resulting beam width on the ground becomes a very large 10 km, producing an image resolution which is insufficient for most applications.

Where does the synthetic aperture radar ( SAR ) come from?

SAR is typically mounted on a moving platform, such as an aircraft or spacecraft, and has its origins in an advanced form of side looking airborne radar (SLAR). The distance the SAR device travels over a target in the time taken for the radar pulses to return to the antenna creates the large synthetic antenna aperture (the size of the antenna).

How is SAR used to improve the resolution of radar?

SAR is the solution to this dilemma as it can vastly improve the resolution. SAR techniques take advantage of the fact that the radar is moving in orbit to synthesize a virtual 10-km-long antenna from the physical 10-m antenna in the direction of flight.

How are radio waves used to create SAR images?

To create a SAR image, successive pulses of radio waves are transmitted to “illuminate” a target scene, and the echo of each pulse is received and recorded. The pulses are transmitted and the echoes received using a single beam-forming antenna, with wavelengths of a meter down to several millimeters.