Estimation of forest biomass density in Kalimantan Island using JERS-1 SAR data
Spaceborne SAR can obtain following data: 1) C band on the ERS-1 and RADARSAT, 2) L band on the JERS-1 and 3) C-band, L band and X band on the SIR-C. JERS-1 SAR data was used for analyzing because the data occur multiple scattering and volume scattering and the data is easily to be acquired.
Since JERS-1 was launched by NASDA in 1992, it had obtained very large quantify of valuable data up to 1998. Image are used in our research path 91 and raw 302 which are summarized below.
Backscatter model (Luckman, 1998) for the relationship between biomass density and microwave backscatter from vegetation can be described as:
s° (linear unit) = a-e -(bB+c) (1)
s° =calibrated normalized backscatter intensity (linear scale)
B=above-ground biomass density
s° (calibrated normalized backscatter intensity) is calculated by Normalized Radar Cross Section (NASDA, 1993).
Normalized Radar Cross Section (NRCS) of the target area in NASDA’s standard product, whose product level is 2.1, is calculated from the equation (2). This simple equation is obtained by the analysis of the point target response which are included in the NASDA’s standard area having several 2.4 and 2.0m trihedral corner reflectors, and active radar calibrators.
The dependency of the conversion factor on off nadir angle seems to a linear relationship with a small inclination. Because of the less confidence due to the smaller experimental points, the constant over all the off nadir angles has been obtained.
The processing parameters of the SAR processor has been improved , such as the antenna off nadir angle, AGC correction parameters. Then, the conversion parameters were listed in Table 1 as the function of the processed data.
||CF[dB] for JERS-1 SAR
|By feb. 14, 1993
|After Feb. 15, 1993
|After Nov. 1, 1997
Table 1 Processing parameters of NASDA JERS-1 products (NASDA, 1993)
Equation (1) is based on water cloud model, which essentially represents the extinction of microwave radiation as it passes through a layer of vegetation made up of elements containing water. Parameters a is that model corresponds exactly to the saturation value of s 0 in linear units. Parameter b represents the gradient of the low biomass density part of the curve while parameters c is related to the residual backscatter at zero biomass.
Three JERS-1 coverage of study area was analyzed by equation and validation of estimated biomass density accuracy used by field data (Toma, 1999).
The result of this validation will be shown at poster session on ACRS conference (Some materials will also be distributed).
We would like to acknowledge to Mr. T. Toma (Japan International Cooperation Agency ), Assistant Professor S. Tsuyuki and Mr. T. Yamaguchi (Graduate School of Agriculture and Life Sciences, the University of Tokyo) who provide field data and digital data and give information for this study.
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Luckman, A., Baker, J., Honzak, M., and Lucas, R., 1998. Tropical forest biomass density estimation using JERS-1 SAR: Seasonal variation, confidence limit, and application to image mosaics. Remote Sensing and Environment. 63, pp. 126-139.
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