TAILIEUCHUNG - Geoscience and Remote Sensing, New Achievements Part 15

Tham khảo tài liệu 'geoscience and remote sensing, new achievements part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Magnitude and Extent of Six Years of Land Subsidence in Shanghai Revealed by JERS-1 SAR Data 483 JERS-1 SAR data other than the C-band ERS-1 2 SAR data for this study. The critical baseline Bc is defined as Zebker and Villasenor 1992 Ảr c 2Ry cos2 e 2 where X is radar wavelength Ry is range resolution r is the distance between the sensor and the center of the resolution pixel and e is the incidence angle. Substituting individual sensor parameters . For ERS-1 2 9 23 Ry 25 m and r 853 km for JERS-1 9 39 Ry 18 m and r 693 km into equation 2 gives Bc of approximately 1150 m for ERS-1 2 SAR data and Bc of approximately 6750 m for the JERS-1 SAR data. Based on the above analyses we interpret that JERS-1 SAR enables us to extend the normal baseline and the temporal baseline further than the ERS-1 2 SAR to achieve satisfactory interferograms. This in fact is the advantage of longer wavelength SAR data over shorter ones for interferometric applications especially in areas where there are known problems of loss of coherence. A total of 19 L-band differential interferograms and 2 DEMs were generated to track the developmental stages of land subsidence in Shanghai. The data has minimum relative temporal baseline of 44 days maximum relative temporal baseline of 1056 days minimum relative normal baseline of 2 m and maximum relative normal baseline of 971 m. One of the DEMs was used to check the effectiveness of using the other to remove topographic phase from raw interferograms generated. Table 2 presents JERS-1 DInSAR pairs used for the qualitative mapping of land subsidence phenomenon in Shanghai. A major problem associated with using JERS-1 SAR data for interferometric applications is with precise orbit data to facilitate the removal of flat-earth phase from raw interferograms. Unlike the ERS-1 2 satellites which have very good orbit information to aid in interferogram flattening process the JERS-1 SAR system had inaccurate orbit data. It was therefore necessary to refine

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