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23.8.2017 : 13:43 : +0200

GAMMA Portable Radar Interferometer

Starting in 2005 GAMMA Remote Sensing developed and built a portable real aperture FMCW radar interferometer for displacement measurement and height mapping (Patent pending). The major technical characteristics of the instrument are:

 

Frequency: 17.2 GHz (wavelength: 0.0176 m)

Acquisition time: < 20 min for 70 degrees

Operational range: 0.1 to 4 km

Antenna aperture: 0.4 x 60 degrees

Range resolution (look direction): 0.75 m

Azimuth resolution (perpendicular to the look direction): 6.9 m at 1km, 13.9 m at 2km

Precision: < 2 mm along look direction

1 transmit and 2 receive antennas

 

 

The GAMMA portable radar interferometer (GPRI) is a real aperture FMCW radar using fan beam antennas to illuminate the target area. The antennas are mounted in parallel on a rotational scanner. The radar image is built up line by line by rotating the antennas in azimuth about the vertical axis. The range resolution of the radar is determined by the 200 MHz bandwidth and is equal to approximately 75 cm. The azimuth resolution is determined by the antenna beamwidth and slant range. In the case of the TRI, the azimuth beamwidth is 0.4 degree yielding an azimuth resolution of about 7m at a slant range of 1km. Each image line is acquired in approximately 2ms hence there is little or no movement of the scene to introduce decorrelation. Phase differences between successive images acquired from the same viewpoint are used to determine line-of-sight displacements from the differential phase. The instrument operates at 17.2 GHz with a displacement measurement sensitivity better than 1 mm.

 

Two receiving antennas form an interferometric baseline that can be used to precisely measure the look angle relative to the baseline thereby permitting derivation of the surface topography. Adjusting the baseline is used to tune the height sensitivity versus phase unwrapping complexity. For a detailed description it is referred to Werner et. al., 2008.