SIR-C data quality and calibration results

Freeman, A.; Alves, Marcos Nopper; Chapman, B.; Cruz, João Carlos Ribeiro; Kim, Y.; Shaffer, S.; Sun, James; Turner, Earl; Sarabandi, Kamal

doi:10.1109/36.406671

Cited by 95 publications

(36 citation statements)

References 8 publications

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“…The absolute calibration of SIR-C data was found to be +2.3 and +2.2 dB for L-band and Cband, respectively, for SRL-1. SRL-2 calibration was reported to be +2.0 and +3.2 dB for C-band and L-band, respectively [Freeman et al, 1995]. XSAR calibration was very good and reported to be _+1 dB for both missions [Zink and Bamler, 1995].…”

Section: Study Area Descriptionmentioning

confidence: 93%

Mapping of boreal forest biomass from spaceborne synthetic aperture radar

Ranson¹,

Sun²,

Lang³

et al. 1997

J. Geophys. Res.

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Abstract. As part of the Boreal-Ecosystem Atmosphere Study (BOREAS), an investigation is being made of the use of satellite data including shuttle imaging radar-C (SIR-C), X-band synthetic aperture radar (XSAR), and Landsat-Thematic Mapper data for estimating total and component aboveground woody biomass in boreal forest study sites in Canada. The goal of this paper is to present progress in mapping above ground woody biomass over portions of the BOREAS southern study area using spaceborne sensor data. Relationships of backscatter to total biomass and total biomass to foliage, branch, and bole biomass are used to estimate biomass across the landscape. The procedure involves image classification with SAR and Landsat data and development of simple mapping techniques using combinations of SAR channels. The analysis uses measurements from forest stands representing a range of biomass and structures. Field measurements included plot level mensuration (species, stem diameter, height, density, and basal area) and tree geometry measurements (leaf, branch, bole size, and angle distributions). The results indicate that aboveground biomass can be estimated to within about 1.6 kg/m 2 and up to about 15 kg/m 2 across the SIR-C image evaluated. A general method produced equivalent results with those obtained by treating forest type (pine, spruce, and aspen) separately. The biomass mapping was extended to bole, branch, and foliage components from relationships with total aboveground biomass developed from detailed tree measurements. Average biomass within the imaged area was estimated to be about 7.3 kg/m 2 with biomass components of bole, branch, and foliage comprising 83, 12, and 5% of the total. Examination of the scaling of biomass estimates from remote sensing images of varying resolution shows that information at scales useful for ecosystem models can be obtained. In addition, the biomass estimation technique provides similar information at different image resolutions. IntroductionEstimates of regional and global forest biomass are important for understanding and monitoring ecosystem responses to climate change and human activities. Knowledge of the distribution and structure of aboveground woody biomass is important for assessing production and decomposition rates in forests. In addition, ecosystem model predictions of primary production rates could be improved by including the effect of woody plant tissue respiration which can be related to tree trunk biomass. Scientists interested in the fate of global carbon are using field measurements and remote sensing observations over diverse ecosystems to address these issues.A [1995a] reported on initial efforts to map cover type and estimate biomass over a portion of BOREAS southern study area. In the present paper, we discuss efforts to improve upon this earlier work and develop forest cover and biomass maps in a gridded format from SAR data suitable for use with ecosystem models. The method for developing the algorithm is discussed, including field measurements and im-29,599

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Section: Study Area Descriptionmentioning

confidence: 93%

Mapping of boreal forest biomass from spaceborne synthetic aperture radar

Ranson¹,

Sun²,

Lang³

et al. 1997

J. Geophys. Res.

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“…Indeed, a low level of cross-talk between H-and V-channels (−33 dB) was consistently measured during both SIR-C experiments day and night [4], which would not have been the case in the presence of Faraday rotation [see also (6), which shows that (second term of right-hand side of the equation) is not equal to (third term) when is nonzero]. In contrast, data acquired at 575 km altitude at L-band frequency by JERS-1 should be affected by Faraday rotation (Fig.…”

Section: Sir-c Jers Comparisonmentioning

confidence: 99%

“…If and are, respectively, the polarization vector of the receive and transmit antennas, the complex amplitude of the receive signal may be expressed as (3) If the signal is affected by Faraday rotation, the scattering matrix will be modified by Faraday rotation once downgoing and another time upgoing from the radar to become (4) where the Faraday rotation matrix is (5) The modified scattering matrix is (6) where we assumed that from the reciprocity principle. Equation (6) shows that a radar system operating at HH polarization above the ionosphere will in effect measure radar returns that are a mixture of H-polarized and V-polarized returns.…”

Section: Methodsmentioning

confidence: 99%

Effect of Faraday rotation on L-band interferometric and polarimetric synthetic-aperture radar data

Rignot

2000

IEEE Trans. Geosci. Remote Sensing

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Abstract-Electromagnetic waves traveling through the ionosphere undergo a Faraday rotation of the polarization vector, which modifies the polarization and phase characteristics of the electromagnetic signal. Using L-band ( = 24 cm), polarimetric synthetic aperture radar (SAR) data from the shuttle imaging radar C (SIR-C) acquired in 1994, we simulate the effect of a change in the Faraday rotation angle on spaceborne interferometric and polarimetric data. In one experiment, we find that phase coherence is reduced by up to 33% when changes between successive data acquisitions. If changes by more than 40 , a differential phase signal, which varies from field to field, appears in the interferogram and impairs the mapping of surface topography and/or the detection of ground deformation. This signal is caused by phase differences between horizontal-polarized and vertical-polarized radar signals from intermediate levels of vegetation canopy, similar to the phase difference measured between H-polarized and V-polarized signals on a single date. In a second experiment, data from the Japanese Earth Resources Satellite (JERS-1) L-band radar acquired in an area of active deforestation in Rondonia, Brazil, are compared with SIR-C L-band polarimetric data acquired at the same incidence, two weeks later, but from a lower orbiting altitude. Large differences in scattering behavior are recorded between the two datasets in the areas of slash and burn forest, which are difficult to reconcile with surface changes. A simulation with SIR-C polarimetric data, however, suggests that those differences are consistent with a Faraday rotation angle of about 30 ± 10 in the JERS-1 data and 0 in the SIR-C data. Based on these two experiments and on global positioning system (GPS) records of ionospheric activity, we conclude that Faraday rotation should not affect the analysis of L-band spaceborne data during periods of low ionospheric activity (solar minima). Yet during ionospheric storms or near solar maxima, the effects should become significant and impair data analysis. Corrections for Faraday rotation are impractical in the case of single-channel SAR data. SAR data must be acquired with the full polarimetry to recover from these effects.

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“…Another approach is based on internal calibration signal, which settles a special circuit in the system to test transmitting power, receiving gain, amplitude frequency error, phase frequency error, etc. [7][8][9] . However, this circuit is complicated.…”

Section: Introductionmentioning

confidence: 99%

Analysis and correction for systematic error of ionospheric monostatic system

Wang

Zhao

2009

Wuhan Univ. J. Nat. Sci.

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In the ionospheric monostatic system the echo is affected by systematic error. A real-time method using the special characters of direct wave existing in monostatic radar to correct systematic error is advanced. In the condition of large-amplitude direct wave, time delay of maximum amplitude of echo is considered as system time delay; in the condition of small-amplitude direct wave, the mathematical model of time delay error is built to approach after direct wave test. And a method using large-amplitude direct wave to correct phase distortion is advanced. It achieves good effect using this method in practice, which can improve the quality of sound result obviously.

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SIR-C data quality and calibration results

Cited by 95 publications

References 8 publications

Mapping of boreal forest biomass from spaceborne synthetic aperture radar

Mapping of boreal forest biomass from spaceborne synthetic aperture radar

Effect of Faraday rotation on L-band interferometric and polarimetric synthetic-aperture radar data

Analysis and correction for systematic error of ionospheric monostatic system

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