Using Dual-Polarization Interferograms to Correct Atmospheric Effects for InSAR Topographic Mapping

Zhiwei Liu,Tingying Zuo,Haiqiang Fu,Cui Zhou,Jianjun Zhu

doi:10.3390/rs10081310

Abstract

Atmospheric effect represents one of the major error sources for interferometric synthetic aperture radar (InSAR), particularly for the repeat-pass InSAR data. In order to further improve the practicability of InSAR technology, it is essential to study how to estimate and eliminate the undesired impact of atmospheric effects. In this paper, we propose the multi-resolution weighted correlation analysis (MRWCA) method between the dual-polarization InSAR data to estimate and correct atmospheric effects for InSAR topographic mapping. The study is based on the a priori knowledge that atmospheric effects is independent of the polarization. To find the identical atmospheric phase (ATP) signals of interferograms in different polarizations, we need to remove the other same or similar phase components. Using two different topographic data, differential interferometry was firstly performed so that the obtained differential interferograms (D-Infs) have different topographic error phases. A polynomial fitting method is then used to remove the orbit error phases. Thus, the ATP signals are the only identical components in the final obtained D-Infs. By using a forward wavelet transform, we break down the obtained D-Infs into building blocks based on their frequency properties. We then applied weighted correlation analysis to estimate the wavelet coefficients attributed to the atmospheric effects. Thus, the ATP signals can be obtained by the refined wavelet coefficients during inverse wavelet transform (IWT). Lastly, we tested the proposed method by the L-band Advanced Land Observing Satellite (ALOS)-1 PALSAR dual-polarization SAR data pairs covering the San Francisco (USA) and Moron (Mongolia) regions. By using Ice, Cloud, and land Elevation Satellite (ICESat) data as the reference data, we evaluated the vertical accuracy of the InSAR digital elevation models (DEMs) with and without atmospheric effects correction, which shows that, for the San Francisco test site, the corrected interferogram could provide a DEM with a root-mean-square error (RMSE) of 7.79 m, which is an improvement of 40.5% with respect to the DEM without atmospheric effects correction. For the Moron test site, the corrected interferogram could provide a DEM with an RMSE of 10.74 m, which is an improvement of 30.2% with respect to the DEM without atmospheric effects correction.

Highlights

Interferometric synthetic aperture radar (InSAR) is a powerful technology for Earth observations, which is noted for its all-weather and day-and-night working capability, wide spatial coverage, and fine resolution [1]
If common external digital elevation models (DEMs) is used to simulate the topographic phase for the dual-polarization interferograms, topographic error phase (TEP) φεpt1opo and φεpt2opo will be similar because they have the phase components caused by the identical ground elevation errors
A novel approach to correct the atmospheric effects in a repeat-pass interferogram has been presented, which combines wavelet multi-resolution analysis and weighted correlation analysis to identify the same atmospheric phase (ATP) signals from dual-polarization InSAR interferograms

Summary

Introduction

Interferometric synthetic aperture radar (InSAR) is a powerful technology for Earth observations, which is noted for its all-weather and day-and-night working capability, wide spatial coverage, and fine resolution [1]. The repeat-pass interferometric mode has been widely employed to acquire InSAR data [2]. For repeat-pass synthetic aperture radar (SAR) interferograms, different image acquisition times lead to different atmospheric delays for different SAR images, which result in significant atmospheric error in the interferometric phases. As an inevitable error source, the presence of atmospheric effects is a major problem in repeat-pass InSAR topographic mapping measurement [3]. It is difficult to achieve satisfactory results with the interferograms acquired over plain areas

Methods

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Discussion

Conclusion