ارائه الگوریتمی برای کاهش نوفه فاز تداخل‌سنجی راداری مورد استفاده در تعیین میزان جابه‌جاییهای پوسته زمین، بر اساس تبدیل موجک در حوزه مختلط

نوع مقاله: مقاله پژوهشی

نویسندگان

گروه مهندسی سنجش از دور دانشگاه صنعتی خواجه نصیرالدین طوسی، تهران، ایران

چکیده

     روش تداخل‌سنجی راداری با بهره‌گیری از اطلاعات فاز تصاویر مختلط SAR،  توانایی بالایی در تهیه مدل ارتفاعی زمین با دقت متر و اندازه‌گیری جابه‌جاییها و تغییرشکلهای پوسته زمین با دقت زیر سانتی‌متر در پوششی پیوسته و وسیع دارد. عوامل محدودکننده مختلفی چون عدم همبستگی هندسی و زمانی، تغییرات جوی و نوفه گرمایی سنجنده راداری موجب ایجاد نوفه در اینترفروگرام و ایجاد مشکل در عملیات بازیابی فاز و کاهش دقت نتایج می‌شود. در این پژوهش، از تبدیل موجک در حوزه مختلط برای کاهش نوفه اینترفروگرام استفاده شده است. بر خلاف روشهای دیگر چون روش چندمنظره و تبدیل فوریه در پنجره‌های کوچک اینترفروگرام، روش پیشنهاد شده در این پژوهش، نوفه را باوجود حفظ قدرت تفکیک مکانی و بدون نیاز به پنجره‌ای کردن اینترفروگرام، کاهش می‌دهد. نتایج اعمال این فیلتر بر داده‌های شبیه‌سازی شده و واقعی و مقایسه آن با فیلترهای موجود، نشان‌دهنده توانایی بالای تبدیل موجک در کاهش نوفه اینترفروگرام است.

کلیدواژه‌ها


عنوان مقاله [English]

Noise Reduction of the Radar Interferometric Phase Used for Surface Displacement Measurement Based on Wavelet Transform in the Complex Domain

نویسندگان [English]

  • H. Fattahi
  • M. J. Valadan Zouj
  • M. R. Mobasheri
  • M. Dehghani
Remote Sensing Department, Faculty of Geodesy and Geomatics Engineering, K.N.Toosi University of Technology, Tehran, Iran
چکیده [English]

      Interferometric Synthetic Aperture Radar (InSAR) technique using phase information has demonstrated its abilities in topographic mapping and measuring surface deformation with the precision of meter and sub-centimeter, respectively in a very high spatial resolution. However, various limiting factors such as spatial and temporal decorrelation, atmospheric effects and thermal noise of the radar sensor introduce different types of noise into the interferograms, which makes the phase unwrapping too difficult to obtain the accurate results. In this study, an algorithm for noise suppression is presented based on wavelet transform in the complex domain. The high-frequency data due to the phase jumps is not appeared in the complex domain. Therefore, the wavelet coefficients obtained in the complex domain include mostly the noise. The wavelet coefficients of the noisy interferogram are then filtered using the threshold computed from the related wavelet band. In comparison with the other noise reduction methods such as multi-look processing and those based on Fourier transform in small windows, the proposed algorithm can reduce the noise while keeping the spatial resolution without the need for windowing the interferogram. Quantitative and qualitative evaluations of the results obtained by the new method applied on the simulated and real noisy data show high performance of the wavelet transform in noise reduction.

کلیدواژه‌ها [English]

  • InSAR
  • Interferogram
  • Complex Domain
  • Noise Reduction
  • wavelet transform

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