A plea for radar brightness

Raney, R. K.; Freeman, Tony; Hawkins, R.; Bamler, Richard

doi:10.1109/igarss.1994.399352

Cited by 54 publications

(34 citation statements)

References 2 publications

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“…The first three are the common conventions [4], complemented here by two further terrain model-based options. In the following, we concentrate on the terrain corrected gamma radiometry (fifth option).…”

Section: Terrain-based Normalisationmentioning

confidence: 99%

“…The 0 convention provides the natural radar observable [4], normalising simply by the areal sample interval in the slant range plane -the contents of images conforming to its convention are not subjected to modifications based on ellipsoid or terrain Earth models. Typical 0 and 0 conventions normalise by a standard area calculated using an ellipsoidal Earth model.…”

Section: Ellipsoid-based Normalisationmentioning

confidence: 99%

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A revised radiometric normalisation standard for SAR

Small

Miranda

Meier

2009

2009 IEEE International Geoscience and Remote Sensing Symposium

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Improved geometric accuracy in SAR sensors implies that more complex models of the Earth may be used not only to geometrically rectify imagery, but also to more robustly calibrate their radiometry. Current beta, sigma, and gamma nought SAR radiometry conventions all assume a simple "flat as Kansas" Earth ellipsoid model. We complement these simple models with improved radiometric calibration that accounts for local terrain variations. In the era of ERS-1 and RADARSAT-1, image geolocation accuracy was in the order of multiple samples, and tiepointfree establishment of the relationship between radar and map geometries was not possible. Newer sensors such as ASAR, PALSAR, and TerraSAR-X all support accurate geolocation based on product annotations alone. We show that high geolocation accuracy, combined with availability of high-resolution accurate elevation models, enables a more robust radiometric calibration standard for modern SAR sensors that is based on gamma nought normalised using an Earth terrain-model. A REVISED RADIOMETRIC NORMALISATION STANDARD FOR SAR ABSTRACTImproved geometric accuracy in SAR sensors implies that more complex models of the Earth may be used not only to geometrically rectify imagery, but also to more robustly calibrate their radiometry. Current beta, sigma, and gamma nought SAR radiometry conventions all assume a simple "flat as Kansas" Earth ellipsoid model. We complement these simple models with improved radiometric calibration that accounts for local terrain variations. In the era of ERS-1 and RADARSAT-1, image geolocation accuracy was in the order of multiple samples, and tiepointfree establishment of the relationship between radar and map geometries was not possible. Newer sensors such as ASAR, PALSAR, and TerraSAR-X all support accurate geolocation based on product annotations alone. We show that high geolocation accuracy, combined with availability of high-resolution accurate elevation models, enables a more robust radiometric calibration standard for modern SAR sensors that is based on gamma nought normalised using an Earth terrain-model.

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Section: Terrain-based Normalisationmentioning

confidence: 99%

Section: Ellipsoid-based Normalisationmentioning

confidence: 99%

A revised radiometric normalisation standard for SAR

Small

Miranda

Meier

2009

2009 IEEE International Geoscience and Remote Sensing Symposium

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“…For distributed targets, radar brightness β 0 is defined as averaged backscatter ratio per unit area in the image plane (i.e., the slant range plane) [31]; backscatter coefficient σ 0 is defined as averaged backscatter ratio per unit ground area. For flat areas, the backscatter coefficient σ 0 can be retrieved using [17] incident angle θ…”

Section: Sar Radiometric Terrain Correctionmentioning

confidence: 99%

An Improved Sar Radiometric Terrain Correction Method and Its Application in Polarimetric Sar Terrain Effect Reduction

Chen¹

2013

PIER B

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Abstract-A new SAR radiometric terrain correction method was proposed to reduce the terrain effects in sloped regions. Based on this method, a procedure for polarimetric SAR terrain effect reduction was proposed, including geometric correction, shadow detection, radiometric terrain correction, and polarization orientation angle shift compensation. Experiments using RADARSAT-2 polarimetric SAR data of the Three Gorges Area, China demonstrated the effectiveness of the proposed radiometric terrain correction method. Both visual and quantitative analyses showed that after the proposed radiometric terrain correction method was applied, the contrast between different slopes that caused by local incidence angle differences, foreshortening, and layover was significantly reduced. The difference of backscattering intensity on slopes facing the radar sensor and facing away from the sensor was reduced from 12.5 dB before radiometric correction to 1.3 dB. The overall accuracy of land use/land cover classification was improved by 11.2 percent using the terrain corrected polarimetric SAR data.

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“…Using the energy rather than the peak intensity implies that, for a homogeneous distributed target, the ensemble average of the pixel intensity (i.e., for every pixel) equals the radar brightness divided by 4 . The radar brightness in turn equals sigma-naught divided by sine of the local incidence angle [22]. The above definition of radiometric calibration is related to the well-known integral method, [23].…”

Section: B Calibrationmentioning

confidence: 99%

EMISAR: an absolutely calibrated polarimetric L- and C-band SAR

Christensen

Skou

Dall

et al. 1998

IEEE Trans. Geosci. Remote Sensing

101

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Abstract-EMISAR is a high-resolution (2 2 2 2 2 m), fully polarimetric, dual-frequency (L-and C-band) synthetic aperture radar (SAR) system designed for remote-sensing applications. The SAR is operated at high altitudes on a Gulfstream G-3 jet aircraft. The system is very well calibrated and has low sidelobes and low cross-polar contamination. Digital technology has been utilized to realize a flexible and highly stable radar with variable resolution, swath width, and imaging geometry. Thermal control and several calibration loops have been built into the system to ensure system stability and absolute calibration. Accurately measured antenna gains and radiation patterns are included in the calibration. The processing system is developed to support data calibration, which is the key to most of the current applications. Recent interferometric enhancements are important for many scientific applications.

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A plea for radar brightness

Cited by 54 publications

References 2 publications

A revised radiometric normalisation standard for SAR

A revised radiometric normalisation standard for SAR

An Improved Sar Radiometric Terrain Correction Method and Its Application in Polarimetric Sar Terrain Effect Reduction

EMISAR: an absolutely calibrated polarimetric L- and C-band SAR

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